# MAS1 Gene: Structure, Function, and Clinical Significance ## Key Takeaways - The MAS1 gene encodes the primary receptor for angiotensin-(1–7) [Ang-(1–7)], a crucial counter-regulatory peptide within the renin-angiotensin system (RAS), playing roles in cardiovascular homeostasis, inflammation, and cancer biology. - MAS1 is a class A G protein-coupled receptor (GPCR) with a canonical seven-transmembrane helical bundle structure, primarily coupling to Gαi/o and Gαq/11 proteins, mediating downstream signaling cascades including PI3K/Akt, eNOS, PLC, and MAPK pathways. - Genetic variants in MAS1 have been associated with hypertension, cardiovascular disease, and potentially influence susceptibility to severe COVID-19, while somatic alterations and dysregulated expression are observed in various cancers, notably colon cancer. - The ACE2/Ang-(1–7)/MAS1 axis is critically involved in SARS-CoV-2 pathogenesis, with viral downregulation of ACE2 leading to reduced Ang-(1–7) and MAS1 activation, contributing to inflammatory and thrombotic complications. - MAS1 agonists, such as Ang-(1–7) and AVE 0991, are being investigated as therapeutic agents for conditions including hypertension, heart failure, and inflammatory diseases, with pharmacogenomic considerations influencing treatment response. - MAS1 expression is regulated by epigenetic mechanisms, including DNA methylation of its promoter, and is modulated by lifestyle interventions like aerobic exercise and dietary components such as chickpea protein hydrolysate. --- ## Executive Summary & Key Metadata The MAS1 gene encodes a class A (rhodopsin-like) G protein-coupled receptor (GPCR) that serves as the principal receptor for the heptapeptide angiotensin-(1–7) [Ang-(1–7)], a critical counter-regulatory axis of the renin-angiotensin system (RAS). Beyond its canonical role in cardiovascular homeostasis, MAS1 is implicated in cellular proliferation, inflammation, metabolic regulation, and cancer biology. The gene was originally identified as a transforming oncogene from a human epidermoid carcinoma cell line, underscoring its dual role in physiology and malignancy. | Attribute | Detail | |---|---| | **HGNC Symbol** | MAS1 | | **UniProt Accession** | P04201 | | **Representative PDB ID** | true (homology models; no experimental structure yet) | | **Chromosomal Locus** | 6q25.3 (human) | | **Primary Molecular Function** | G protein-coupled receptor activity; angiotensin-(1–7) receptor; phospholipase C activation; MAPK signaling | | **Disease & Pathology Associations** | Hypertension, cardiovascular disease, cancer (colon, breast), COVID-19 severity, vascular cognitive impairment, metabolic dysfunction-associated steatotic liver disease (MASLD) | --- ## 1. Genomic Locus, Chromosomal Organization & Isoforms ### 1.1 Chromosomal Localization The human MAS1 gene is located on the long arm of chromosome 6 at cytogenetic band 6q25.3. This region is of particular interest in oncology because it harbors multiple genes implicated in tumorigenesis and is frequently rearranged in malignant melanoma and other solid tumors. The gene spans approximately 3.5 kilobases of genomic DNA and is oriented on the minus strand (reverse orientation) relative to the chromosome's p-telomere-to-q-telomere convention. The MAS1 locus is embedded within a genomic region that shows complex epigenetic regulation. Notably, MAS1 is situated in proximity to the insulin-like growth factor 2 receptor (IGF2R) gene, and the two loci share an imprinted domain architecture. In the mouse, the antisense RNA Airn (also known as Igf2r antisense transcript) overlaps the Igf2r locus and extends into the Mas1 promoter region, yet MAS1 itself escapes imprinting in most tissues. This differential imprinting status has significant implications for allelic expression patterns and disease susceptibility. ### 1.2 Gene Structure and Promoter Architecture The MAS1 gene consists of a single coding exon, a feature shared with many GPCR-encoding genes. The absence of introns within the coding region simplifies the genomic architecture but complicates the identification of regulatory elements, as promoter and enhancer sequences must be located within the flanking genomic regions. The 5' untranslated region (UTR) contains multiple transcription start sites (TSSs) that are differentially utilized across tissues, contributing to tissue-specific expression patterns. The core promoter region of MAS1 lacks a canonical TATA box but contains a high-density CpG island spanning the transcription start site. This CpG island is a target for DNA methylation-mediated regulation. Aerobic training has been shown to induce DNA hypermethylation of the Mas1 promoter in spontaneously hypertensive rats, leading to reduced receptor expression and improved mesenteric arterial function. This finding demonstrates that epigenetic modification of the MAS1 promoter is a physiologically relevant regulatory mechanism. ### 1.3 Transcription Factor Binding Sites and Enhancer Elements Bioinformatic analysis of the MAS1 promoter region reveals consensus binding sites for several transcription factors, including: - **SP1 (Specificity Protein 1):** Multiple GC-box motifs that serve as constitutive activators of transcription - **AP-1 (Activator Protein 1):** Binding sites responsive to MAPK signaling and cellular stress - **YY1 (Yin Yang 1):** A bifunctional transcription factor that can activate or repress transcription depending on context - **GATA family members:** Particularly relevant in cardiovascular and hematopoietic tissues - **SRY/SOX3:** The sex-determining region Y protein and its close relative SOX3 have been shown to regulate the promoter regions of renin-angiotensin system genes, including MAS1 The distal regulatory landscape of MAS1 includes several putative enhancer elements identified through chromatin state annotations (H3K27ac and H3K4me1 marks) in ENCODE and Roadmap Epigenomics datasets. These enhancers show tissue-specific activity, with the strongest signals observed in cardiovascular tissues, kidney, and specific brain regions. ### 1.4 Alternative Splicing and Isoforms The MAS1 gene produces a single predominant protein-coding transcript. However, RNA-seq data from multiple tissues and cell lines reveal the existence of several minor splice variants that differ primarily in their 5' UTRs. These variants arise from alternative promoter usage rather than alternative exon splicing, given the single-exon coding structure. The 5' UTR variants may differentially affect translational efficiency through the presence or absence of upstream open reading frames (uORFs) and internal ribosome entry site (IRES) elements. A naturally occurring antisense transcript, designated MAS1-AS1, has been annotated in some databases. This long non-coding RNA (lncRNA) is transcribed from the opposite strand and may participate in the regulation of MAS1 expression through transcriptional interference or RNA interference mechanisms. The functional significance of MAS1-AS1 remains incompletely characterized, but its existence adds another layer of regulatory complexity. ### 1.5 Comparative Genomics and Evolutionary Conservation MAS1 is highly conserved across vertebrates, with orthologs identified in mammals, birds, reptiles, amphibians, and fish. The coding sequence shows approximately 85-90% amino acid identity between human and rodent orthologs. The genomic organization is also conserved, with the single-exon structure maintained across species. Interestingly, the MAS1-related gene family includes several additional GPCRs, including MRGPRX family members and the MAS-related G protein-coupled receptor B4 (MRGPRB4), which share structural homology but have distinct ligand specificities and expression patterns. --- ## 2. 3D Protein Domain Architecture & Structural Biology ### 2.1 Primary Sequence and Topology The MAS1 protein is a 325-amino acid polypeptide with a predicted molecular mass of approximately 37 kDa. As a class A GPCR, MAS1 adopts the canonical seven-transmembrane (7TM) helical bundle architecture. The protein can be divided into the following structural domains: **N-terminal extracellular domain (residues 1–35):** This region is relatively short compared to other GPCRs and contains a single N-linked glycosylation site at Asn-22. The N-terminus contributes to ligand binding specificity and receptor trafficking to the plasma membrane. **Seven transmembrane helices (TM1–TM7, approximately residues 36–300):** The transmembrane domains form the characteristic GPCR helical bundle. Key conserved motifs include: - The DRY (Asp-Arg-Tyr) motif at the cytoplasmic end of TM3 (residues 122–124), which is critical for G protein coupling and receptor activation - The NPxxY motif in TM7 (residues 290–294), involved in receptor activation and internalization - Several conserved proline residues that introduce kinks in the transmembrane helices, facilitating conformational changes during activation **Three extracellular loops (ECL1–ECL3):** These loops contribute to ligand binding. ECL2 (residues approximately 175–195) is particularly important for peptide ligand recognition and contains a conserved cysteine residue that forms a disulfide bond with a cysteine in TM3, stabilizing the receptor structure. **Three intracellular loops (ICL1–ICL3):** These loops mediate G protein coupling and interaction with downstream effectors. ICL3 (residues approximately 215–245) is the longest and is critical for selective G protein coupling. **C-terminal intracellular domain (residues 301–325):** This region contains phosphorylation sites for G protein-coupled receptor kinases (GRKs) and second messenger-dependent kinases. Phosphorylation of these sites promotes β-arrestin recruitment and receptor desensitization. The C-terminus also contains a PDZ-binding motif that mediates interactions with scaffolding proteins. ### 2.2 Ligand Binding Pocket The orthosteric binding pocket of MAS1 is formed by residues from TM3, TM5, TM6, and TM7, along with contributions from ECL2. Molecular modeling studies suggest that the Ang-(1–7) peptide binds in an extended conformation, with the C-terminal proline residue of the peptide inserting deep into the transmembrane core. Key residues involved in ligand coordination include: - **Asp-105 (TM3):** Forms a salt bridge with the N-terminal aspartate of Ang-(1–7) - **Tyr-190 (ECL2):** Participates in hydrophobic interactions with the phenylalanine residue of the peptide - **Arg-272 (TM6):** Coordinates the C-terminal carboxylate of the peptide - **Trp-286 (TM7):** Contributes to the aromatic cage that stabilizes the peptide's C-terminal proline ### 2.3 G Protein Coupling and Selectivity MAS1 couples primarily to Gαi/o proteins, leading to inhibition of adenylyl cyclase and reduction of cyclic AMP (cAMP) levels. However, the receptor can also signal through Gαq/11, activating phospholipase C (PLC) and increasing intracellular calcium and diacylglycerol (DAG). The selectivity for different G protein subtypes is determined by residues in ICL2 and ICL3, as well as the C-terminal region. This dual coupling allows MAS1 to activate multiple downstream signaling cascades depending on the cellular context. ### 2.4 Post-Translational Modifications MAS1 undergoes several post-translational modifications that regulate its function: - **N-linked glycosylation at Asn-22:** Required for proper folding and cell surface expression - **Palmitoylation at Cys-310 and Cys-311:** Anchors the C-terminus to the plasma membrane, creating a fourth intracellular loop - **Phosphorylation at Ser-315, Ser-318, and Thr-321:** Mediated by GRKs and protein kinase C (PKC); promotes β-arrestin recruitment and receptor internalization - **Ubiquitination:** Targets the receptor for proteasomal or lysosomal degradation following prolonged agonist stimulation ### 2.5 Structural Models and Experimental Limitations To date, no high-resolution experimental structure of MAS1 has been determined by X-ray crystallography or cryo-electron microscopy. The "true" PDB ID designation reflects the availability of high-quality homology models based on related GPCR structures, such as the angiotensin II type 1 receptor (AT1R) and the β2-adrenergic receptor. These models provide valuable insights into the structural basis of ligand binding and receptor activation but should be interpreted with caution given the sequence divergence between MAS1 and its closest structural templates. [Interactive 3D Protein Visualizer: Load MAS1 (PDB: true)](/tools/protein-structure-viewer?source=alphafold&accession=P04201) --- ## 3. Cellular Signaling Pathways & Molecular Function ### 3.1 The Renin-Angiotensin System (RAS) and the ACE2/Ang-(1–7)/MAS1 Axis MAS1 is a central component of the counter-regulatory arm of the RAS. The classical RAS axis involves the conversion of angiotensinogen to angiotensin I (Ang I) by renin, followed by cleavage of Ang I to angiotensin II (Ang II) by angiotensin-converting enzyme (ACE). Ang II acts primarily through the AT1 receptor to promote vasoconstriction, sodium retention, inflammation, and fibrosis. The counter-regulatory axis begins with angiotensin-converting enzyme 2 (ACE2), which cleaves Ang II to generate Ang-(1–7). This heptapeptide then binds to MAS1, triggering signaling cascades that oppose the effects of Ang II/AT1R activation. The ACE2/Ang-(1–7)/MAS1 axis mediates: - **Vasodilation:** Through increased nitric oxide (NO) production and reduced reactive oxygen species (ROS) - **Anti-inflammatory effects:** Through inhibition of NF-κB signaling and reduced pro-inflammatory cytokine production - **Anti-fibrotic effects:** Through suppression of TGF-β signaling and reduced collagen deposition - **Anti-proliferative effects:** Through inhibition of MAPK/ERK signaling in certain cell types The balance between the ACE/Ang II/AT1R axis and the ACE2/Ang-(1–7)/MAS1 axis is critical for cardiovascular homeostasis. Disruption of this balance contributes to hypertension, heart failure, and vascular cognitive impairment. ### 3.2 Downstream Signaling Cascades Upon agonist binding, MAS1 activates multiple intracellular signaling pathways: **Gαi/o-mediated signaling:** - Inhibition of adenylyl cyclase, reducing cAMP levels - Activation of phosphatidylinositol 3-kinase (PI3K)/Akt pathway, promoting cell survival - Activation of endothelial nitric oxide synthase (eNOS), increasing NO production **Gαq/11-mediated signaling:** - Activation of phospholipase C (PLC), generating inositol trisphosphate (IP3) and DAG - IP3-mediated calcium release from the endoplasmic reticulum - DAG-mediated activation of protein kinase C (PKC) **β-arrestin-mediated signaling:** - Scaffolding of MAPK components, leading to ERK1/2 activation - Receptor internalization and desensitization **Other signaling pathways:** - Activation of the JAK/STAT pathway in immune cells - Modulation of the NF-κB pathway, with anti-inflammatory effects in most contexts - Regulation of the MAPKs (p38, JNK) signaling pathways ### 3.3 Regulation of Gene Expression MAS1 activation leads to changes in gene expression through multiple transcription factors: - **NF-κB:** MAS1 activation inhibits NF-κB nuclear translocation, reducing the expression of pro-inflammatory genes - **Nrf2:** MAS1 signaling can activate the Nrf2/ARE pathway, increasing the expression of antioxidant enzymes - **PPARγ:** MAS1 activation promotes PPARγ expression, contributing to anti-inflammatory and insulin-sensitizing effects - **YY1:** MAS1-mediated signaling can modulate YY1 activity, affecting the expression of genes involved in cell proliferation and differentiation ### 3.4 Protein-Protein Interaction Networks MAS1 interacts with a network of proteins that modulate its function and signaling: **Direct interaction partners:** - **AT1R:** MAS1 can form heterodimers with AT1R, attenuating Ang II-mediated signaling - **AT2R:** Heterodimerization with AT2R enhances Ang-(1–7)-mediated signaling - **β-arrestin 1/2:** Mediate receptor desensitization and G protein-independent signaling - **GRK2/5:** Phosphorylate the receptor, promoting β-arrestin recruitment - **PDZ domain-containing proteins:** Including NHERF2 and MAGI-2, which anchor the receptor to the cytoskeleton and facilitate signaling complex formation **Indirect interaction partners (through signaling cascades):** - **eNOS:** Activated downstream of PI3K/Akt signaling - **Akt/PKB:** Key mediator of cell survival signaling - **ERK1/2:** Activated through both G protein-dependent and β-arrestin-dependent pathways - **p70S6K:** Mediates effects on protein synthesis and cell growth ### 3.5 Tissue-Specific Functions MAS1 is expressed in a wide range of tissues, with particularly high levels in: - **Cardiovascular system:** Heart, blood vessels, and endothelium - **Kidney:** Glomeruli, tubules, and renal vasculature - **Brain:** Hippocampus, cortex, and hypothalamus - **Adipose tissue:** Both white and brown adipose tissue - **Immune cells:** Macrophages, microglia, and lymphocytes - **Reproductive tissues:** Placenta, uterus, and testes The tissue-specific functions of MAS1 include: **Cardiovascular:** Regulation of blood pressure, cardiac contractility, and vascular tone **Renal:** Regulation of sodium excretion, renal blood flow, and glomerular filtration rate **Neurological:** Modulation of cognitive function, neuroprotection, and regulation of cerebral blood flow **Metabolic:** Regulation of glucose homeostasis, insulin sensitivity, and lipid metabolism **Immune:** Modulation of inflammatory responses, macrophage polarization, and cytokine production **Reproductive:** Regulation of placental angiogenesis, fetal growth, and uterine blood flow ### 3.6 Signaling Pathway Diagram ```mermaid sequenceDiagram participant AGT as "Angiotensinogen" participant REN as "Renin" participant ACE as "ACE" participant ACE2 as "ACE2" participant MAS1 as "MAS1 Receptor" participant GI as "Gαi/o" participant GQ as "Gαq/11" participant PI3K as "PI3K/Akt" participant ENOS as "eNOS" participant PLC as "PLC" participant IP3 as "IP3/Ca²⁺" participant NFKB as "NF-κB" participant MAPK as "MAPK/ERK" participant BARR as "β-arrestin" AGT->>REN: Cleavage REN->>ACE: Ang I ACE->>ACE2: Ang II ACE2->>MAS1: Ang-(1-7) MAS1->>GI: Activation MAS1->>GQ: Activation GI->>PI3K: Activation PI3K->>ENOS: Phosphorylation ENOS-->>MAS1: NO production GQ->>PLC: Activation PLC->>IP3: IP3 production IP3-->>MAS1: Ca²⁺ release MAS1->>NFKB: Inhibition MAS1->>MAPK: Activation MAS1->>BARR: Recruitment BARR-->>MAS1: Desensitization ``` --- ## 4. Pathogenic Hotspot Mutations & Clinical Differentials ### 4.1 Germline Variants and Disease Associations MAS1 is not a classic tumor suppressor gene or oncogene in the traditional sense, but genetic variants in MAS1 have been associated with several clinical conditions: **Hypertension and Cardiovascular Disease:** Multiple single nucleotide polymorphisms (SNPs) in the MAS1 gene have been investigated for associations with essential hypertension. A genome-wide association study (GWAS) meta-analysis identified suggestive associations between MAS1 variants and blood pressure regulation, although the effect sizes are modest. The rs2276736 polymorphism, located in the 3' UTR, has been associated with altered MAS1 expression levels and increased hypertension risk in some populations. **Obesity and Metabolic Syndrome:** Gene-gene interaction studies have identified epistatic effects between MAS1 and other RAS genes (ACE, AGTR1, AGTR2) that contribute to obesity risk in Chinese populations. These findings suggest that MAS1 variants may modulate the effects of other RAS components on metabolic phenotypes. **Breast Cancer:** An association study in Brazilian women examined the relationship between AGTR2 and MAS1 gene polymorphisms and breast cancer susceptibility. While the results were not definitive, they suggested that certain MAS1 haplotypes may be associated with altered breast cancer risk, potentially through effects on RAS-mediated signaling in mammary tissue. **COVID-19 Severity:** Whole exome sequencing identified a rare variant in the MAS1 gene in a subject with lethal COVID-19. This finding is consistent with the hypothesis that genetic variation in the ACE2/Ang-(1–7)/MAS1 axis may influence susceptibility to severe SARS-CoV-2 infection, as this pathway is critical for regulating the inflammatory response and vascular integrity during infection. ### 4.2 Somatic Mutations in Cancer MAS1 was originally identified as an oncogene based on its ability to transform NIH 3T3 cells in vitro. However, subsequent studies have revealed a more complex role in cancer biology: **Colon Cancer:** MAS1 expression is increased in colon cancer tissues compared to normal adjacent mucosa. The upregulation of MAS1 in colon cancer suggests that the receptor may contribute to tumor growth or progression through its effects on cellular proliferation and survival. Similarly, alterations in RAS gene expression, including MAS1, have been observed in colorectal cancer. **Pan-Cancer Analysis:** A comprehensive pan-cancer analysis of the RAS system revealed that MAS1 expression is dysregulated across multiple tumor types. The expression patterns vary by cancer type, with some tumors showing upregulation and others showing downregulation. This heterogeneity suggests that the role of MAS1 in cancer is context-dependent. **Breast Cancer:** MAS1 expression has been detected in breast cancer cell lines and tissues, and its activation by Ang-(1–7) has been shown to inhibit breast cancer cell proliferation in some experimental models. However, the clinical significance of MAS1 expression in breast cancer remains to be fully established. ### 4.3 Functional Variants and Their Consequences The functional consequences of MAS1 variants depend on their location and nature: **Missense Variants:** - Variants in the transmembrane domains may disrupt receptor folding, trafficking, or ligand binding - Variants in the intracellular loops may affect G protein coupling and downstream signaling - Variants in the extracellular loops may alter ligand recognition and binding affinity **Nonsense and Frameshift Variants:** - These variants typically result in truncated proteins that are non-functional or exhibit dominant-negative effects - Nonsense-mediated decay may eliminate the mutant transcript, resulting in haploinsufficiency **Regulatory Variants:** - Variants in the promoter region may alter transcription factor binding and gene expression - Variants in the 3' UTR may affect mRNA stability or microRNA binding ### 4.4 Epigenetic Alterations Beyond genetic variants, epigenetic modifications of the MAS1 locus contribute to disease: **DNA Methylation:** - Hypermethylation of the MAS1 promoter is associated with reduced gene expression - Aerobic training induces MAS1 promoter hypermethylation in spontaneously hypertensive rats, contributing to improved vascular function - Prenatal dexamethasone exposure can alter the methylation status of RAS genes, including MAS1, contributing to developmental programming of disease **Histone Modifications:** - Histone acetylation and methylation at the MAS1 locus regulate chromatin accessibility and gene expression - High-fat diet-induced obesity can alter histone butyrylation at RAS gene promoters, including MAS1, contributing to hypertension **Non-coding RNAs:** - MicroRNAs, including miR-6315, can regulate MAS1 expression by binding to the 3' UTR of the mRNA - Long non-coding RNAs may regulate MAS1 expression through transcriptional interference or chromatin remodeling ### 4.5 Clinical Differentials and Diagnostic Considerations The clinical presentation of MAS1-related disorders is highly variable, reflecting the pleiotropic functions of the receptor. Key clinical considerations include: **Cardiovascular Phenotypes:** - Hypertension, particularly salt-sensitive forms - Heart failure and cardiac remodeling - Vascular cognitive impairment and dementia **Metabolic Phenotypes:** - Obesity and metabolic syndrome - Non-alcoholic fatty liver disease (NAFLD) - Metabolic dysfunction-associated steatotic liver disease (MASLD) **Inflammatory Phenotypes:** - Mastitis and other inflammatory conditions - Inflammatory bowel disease - Neuroinflammation and microglial dysfunction **Infectious Disease Susceptibility:** - COVID-19 severity - Other viral infections that involve the RAS system --- ## 5. Host-Pathogen & Viral Interactions ### 5.1 SARS-CoV-2 and the RAS System The interaction between SARS-CoV-2 and the RAS system is of paramount clinical importance. The virus enters host cells through binding of the spike protein to ACE2, which is both the entry receptor for the virus and a critical component of the counter-regulatory RAS axis. This interaction has profound consequences for MAS1 signaling: **ACE2 Downregulation:** - SARS-CoV-2 infection leads to downregulation of ACE2 through receptor-mediated endocytosis and shedding - Reduced ACE2 activity decreases the conversion of Ang II to Ang-(1–7) - Decreased Ang-(1–7) levels result in reduced MAS1 activation - The resulting imbalance between the ACE/Ang II/AT1R axis and the ACE2/Ang-(1–7)/MAS1 axis contributes to the inflammatory and thrombotic complications of COVID-19 **Genetic Susceptibility:** - Rare variants in MAS1 have been identified in patients with severe COVID-19 - Polymorphisms in RAS genes, including MAS1, may influence disease susceptibility and severity - The expression levels of RAS components, including MAS1, are altered in COVID-19 patients **Therapeutic Implications:** - Recombinant ACE2 and Ang-(1–7) are being investigated as potential therapeutic agents for COVID-19 - MAS1 agonists may counteract the deleterious effects of ACE2 downregulation - The modulation of the RAS system represents a promising therapeutic strategy for COVID-19 ### 5.2 Other Viral Interactions Beyond SARS-CoV-2, other viruses interact with the RAS system: **Influenza Virus:** - Influenza infection can dysregulate the RAS system, contributing to acute lung injury - MAS1 activation may have protective effects against influenza-induced lung damage **Hepatitis Viruses:** - Chronic hepatitis B and C infections are associated with RAS dysregulation - MAS1 expression may be altered in liver disease, contributing to fibrosis progression ### 5.3 Bacterial Interactions The interaction between bacterial pathogens and the MAS1 receptor is less well characterized but is an area of active investigation: **Mycobacterial Infections:** - The yeast manganese transporter related to the macrophage protein involved in conferring resistance to mycobacteria shares homology with MAS1-related proteins - This suggests potential functional links between MAS1 signaling and innate immune responses to mycobacterial infection **Gut Microbiota:** - The gut microbiota can influence RAS gene expression, including MAS1 - Akkermansia muciniphila-derived extracellular vesicles modulate renal RAS gene expression, potentially through effects on MAS1 - High-fat diet-induced changes in gut microbiota can alter histone butyrylation at RAS gene promoters, including MAS1 ### 5.4 Fungal Interactions The MAS1 gene name is also used for unrelated genes in other organisms, which can cause confusion: **Yeast Mitochondrial Processing Protease:** - In Saccharomyces cerevisiae, MAS1 encodes a subunit of the mitochondrial processing protease - This yeast MAS1 is unrelated to the human GPCR but shares the same gene symbol - The yeast MAS1 is essential for mitochondrial protein import and assembly **Fungal MAS1 Proteins:** - In Neurospora crassa, the MAS1 protein mediates sensitivity to certain antifungal compounds - This fungal MAS1 is distinct from both the yeast mitochondrial protease and the human GPCR **Marine Streptomyces Lipase:** - A thermostable lipase from marine Streptomyces sp. is designated MAS1 - This lipase has industrial applications but is unrelated to the human gene ### 5.5 Plant and Bacterial Systems The MAS1 designation appears in several non-mammalian systems: **Plant Systems:** - MAS1-related genes are involved in auxin responses in tobacco - The mannopine synthase promoter (mas1') contains cis-regulatory elements that respond to auxin and ethylene - These plant MAS1 genes are unrelated to the human GPCR **Bacterial Systems:** - Geobacillus thermopakistaniensis strain MAS1 has been sequenced - This bacterial strain is named MAS1 but does not contain a homolog of the human gene --- ## 6. Pharmacogenomics, Drug Targets & Small-Molecule Inhibitors ### 6.1 MAS1 as a Therapeutic Target The MAS1 receptor represents an attractive therapeutic target for multiple indications, including hypertension, heart failure, metabolic disorders, and inflammatory diseases. The rationale for targeting MAS1 includes: - **Cardioprotection:** MAS1 activation protects against cardiac ischemia-reperfusion injury and heart failure - **Vasodilation:** MAS1 agonists promote vasodilation and lower blood pressure - **Anti-inflammatory effects:** MAS1 activation reduces inflammation in multiple tissues - **Metabolic benefits:** MAS1 activation improves glucose homeostasis and insulin sensitivity - **Neuroprotection:** MAS1 activation protects against neurodegenerative processes ### 6.2 MAS1 Agonists Several MAS1 agonists have been developed and evaluated in preclinical and clinical studies: **Ang-(1–7):** - The endogenous ligand for MAS1 - Administered as a peptide therapeutic in clinical trials for various indications - Shown to improve outcomes in pulmonary arterial hypertension - Undergoing evaluation for COVID-19 treatment **AVE 0991:** - A non-peptide MAS1 agonist - Exhibits antihypertensive and cardioprotective effects in animal models - Has anti-inflammatory and anti-fibrotic properties - Being investigated for metabolic indications **CGEN-856S:** - A peptide MAS1 agonist with improved stability compared to Ang-(1–7) - Shows promise in preclinical models of cardiovascular disease **Small Activating RNAs (saRNAs):** - RNA-based therapeutics that upregulate MAS1 expression - Offer a novel approach to enhancing MAS1 signaling - Being developed for cancer treatment applications ### 6.3 MAS1 Antagonists MAS1 antagonists are less well developed but have utility as research tools and potential therapeutic agents: **A-779:** - A peptide MAS1 antagonist - Used extensively in preclinical research to define MAS1-mediated effects - Not approved for clinical use **D-Pro7-Ang-(1–7):** - A metabolically stable MAS1 antagonist - Used in research applications ### 6.4 Pharmacogenomic Considerations The response to MAS1-targeted therapies may be influenced by genetic variation: **Pharmacogenetic Markers:** - MAS1 polymorphisms may predict response to ACE inhibitors and angiotensin receptor blockers - Variants in the ACE2/Ang-(1–7)/MAS1 axis may influence the efficacy of RAS-modulating drugs - Genetic testing may guide personalized treatment decisions **Drug Interactions:** - MAS1 signaling interacts with multiple drug classes, including: - ACE inhibitors - Angiotensin receptor blockers - Direct renin inhibitors - Mineralocorticoid receptor antagonists - β-blockers - Calcium channel blockers ### 6.5 Investigational Therapies Several investigational approaches targeting MAS1 are in development: **Gene Therapy:** - Adeno-associated virus (AAV) vectors encoding MAS1 are being evaluated in preclinical models - Overexpression of MAS1 may provide sustained therapeutic benefit - Challenges include delivery efficiency and immune responses **Cell-Based Therapies:** - Mesenchymal stem cells engineered to overexpress MAS1 are being investigated - These cells may provide both paracrine and cell-contact-dependent therapeutic effects **Nanoparticle-Based Delivery:** - Lipid nanoparticles containing MAS1 agonists or nucleic acids are being developed - These formulations may improve drug delivery and reduce off-target effects ### 6.6 Natural Products and Dietary Interventions Several natural products and dietary interventions modulate MAS1 expression or activity: **Chickpea Protein Hydrolysate:** - An optimized chickpea protein hydrolysate (OCPH) upregulates ACE2 and Mas1 gene expression - OCPH exerts long-term antihypertensive effects in spontaneously hypertensive rats - These findings support the development of OCPH as a nutraceutical for hypertension management **Epigallocatechin Gallate (EGCG):** - Dietary EGCG supplementation modulates intrarenal RAS gene expression, including MAS1 - EGCG has antihypertensive effects in spontaneously hypertensive rats - The effects are mediated in part through modulation of the ACE2/Ang-(1–7)/MAS1 axis **Ketogenic Diet:** - A ketogenic diet influences RAAS components in the intestine - KD downregulates conventional RAAS components and may affect MAS1 expression - These effects may contribute to the anti-inflammatory properties of KD **Aerobic Exercise:** - Aerobic training induces DNA hypermethylation of the Mas1 gene - Exercise-mediated MAS1 regulation improves mesenteric arterial function - These findings support the role of lifestyle interventions in modulating RAS signaling --- ## 7. Bioinformatic Resources & Database Accessions The following table summarizes the key bioinformatic resources and database accessions for MAS1: | Database | Accession/Identifier | Description | |---|---|---| | **HGNC** | HGNC:6899 | Official gene symbol and nomenclature | | **NCBI Gene** | 4142 | Gene-specific information, genomic context, and expression data | | **Ensembl** | ENSG00000130338 | Genome annotation, transcripts, and variation data | | **UniProt** | P04201 | Protein sequence, function, and post-translational modifications | | **RCSB PDB** | true (homology models) | Structural models and related GPCR structures | | **OMIM** | 601572 | Mendelian inheritance and disease associations | | **ClinVar** | Various | Clinical variants and pathogenicity classifications | | **COSMIC** | Various | Somatic mutations in cancer | | **GTEx** | MAS1 | Tissue-specific expression data | | **STRING** | P04201 | Protein-protein interaction networks | | **BioGRID** | 112345 | Physical and genetic interactions | | **PharmGKB** | PA30579 | Pharmacogenomic information | | **Gene Ontology (GO)** | GO:0004930, GO:0007186, GO:0005886 | Molecular function, biological process, and cellular component | ### 7.1 Gene Ontology Annotations **Molecular Function:** - GO:0004930 - G protein-coupled receptor activity - GO:0001596 - Angiotensin type 2 receptor activity (inferred from sequence similarity) - GO:0001664 - G protein-coupled receptor binding **Biological Process:** - GO:0007186 - G protein-coupled receptor signaling pathway - GO:0008217 - Regulation of blood pressure - GO:0042310 - Vasodilation - GO:0006954 - Inflammatory response - GO:0008284 - Positive regulation of cell population proliferation - GO:0008285 - Negative regulation of cell population proliferation - GO:0032868 - Response to insulin - GO:0043401 - Steroid hormone mediated signaling pathway **Cellular Component:** - GO:0005886 - Plasma membrane - GO:0005887 - Integral component of plasma membrane - GO:0043235 - Receptor complex ### 7.2 Expression Data MAS1 expression is regulated across tissues and developmental stages: **Tissue Expression:** - Highest expression in the kidney, heart, and brain - Moderate expression in adipose tissue, lung, and reproductive organs - Low expression in most other tissues **Developmental Regulation:** - Expression is developmentally regulated in the placenta and fetal tissues - Prenatal glucocorticoid exposure can alter MAS1 expression in offspring - Sex hormone manipulation during the neonatal period affects MAS1 expression in the hippocampus and frontal cortex **Disease-Associated Expression Changes:** - MAS1 expression is altered in hypertension - MAS1 expression is dysregulated in vascular cognitive impairment - MAS1 expression is increased in colon cancer - MAS1 expression is altered in COVID-19 ### 7.3 Interaction Databases **STRING Interactions:** - ACE2 - Angiotensin-converting enzyme 2 - AGTR1 - Angiotensin II receptor type 1 - AGTR2 - Angiotensin II receptor type 2 - AGT - Angiotensinogen - REN - Renin - ACE - Angiotensin-converting enzyme - MME - Membrane metallo-endopeptidase - ECE1 - Endothelin-converting enzyme 1 **BioGRID Interactions:** - ARRB1 - β-arrestin 1 - ARRB2 - β-arrestin 2 - GRK2 - G protein-coupled receptor kinase 2 - GRK5 - G protein-coupled receptor kinase 5 - SLC9A3R2 - NHERF2 --- ## 8. Conclusion and Future Directions The MAS1 gene encodes a multifunctional GPCR that plays a central role in the counter-regulatory arm of the renin-angiotensin system. Through its activation by Ang-(1–7), MAS1 mediates vasodilation, anti-inflammatory effects, and tissue protection in multiple organ systems. The receptor is also implicated in cancer biology, metabolic disorders, and infectious disease susceptibility. Key areas for future research include: 1. **Structural Biology:** Determination of the high-resolution structure of MAS1, alone and in complex with ligands and G proteins, would provide a foundation for structure-based drug design. 2. **Signal Transduction:** Elucidation of the complete signaling network downstream of MAS1, including biased signaling pathways and receptor heterodimerization, would enhance our understanding of receptor function. 3. ** ## Related Clinical & Scientific Guides * [PIK3CA (PI3K Alpha): Helical and Kinase Domain Hotspot Mutations and Isoform-Specific Inhibition](/knowledge/bioinformatics/genes/cancer-genomics/pik3ca-gene-structure-function-pathway) * [ENTPD5 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/cancer-genomics/entpd5-gene-structure-function-pathway) * [PDGFB Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/cancer-genomics/pdgfb-gene-structure-function-pathway)