Alpha-sarcoglycan is a critical transmembrane glycoprotein component of the dystrophin-glycoprotein complex that maintains muscle fiber membrane integrity through mechanical linkage between the cytoskeleton and extracellular matrix, possesses ATP-hydrolyzing enzymatic activity, and participates in mechanotransduction signaling. Mutations cause limb-girdle muscular dystrophy type 2D/LGMDR3.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0016012 sarcoglycan complex | IBA GO_REF:0000033 | ACCEPT | Summary: IBA annotation for sarcoglycan complex membership is strongly supported by phylogenetic analysis and extensive experimental evidence. Alpha-sarcoglycan is a core structural component of the tetrameric sarcoglycan complex comprising alpha, beta, gamma, and delta subunits that forms a subcomplex within the dystrophin-glycoprotein complex. Reason: This annotation accurately reflects the primary structural role of SGCA. Multiple lines of evidence support this assignment including UniProt annotation, the deep research report describing the sarcoglycan complex as a critical subcomplex of the DGC, recent cryoEM structural data showing the tower-like architecture, and the fact that loss of any single sarcoglycan destabilizes the entire complex. This is a core cellular component annotation representing the fundamental structural context of the protein. Supporting Evidence: file:human/SGCA/SGCA-deep-research-perplexity.md The sarcoglycan complex, of which alpha-sarcoglycan is a component, functions as a critical subcomplex within the larger dystrophin-glycoprotein complex file:human/SGCA/SGCA-uniprot.txt Component of the sarcoglycan complex, a subcomplex of the dystrophin-glycoprotein complex file:human/SGCA/SGCA-deep-research-falcon.md Ξ±-SG is one of four core transmembrane glycoproteins (Ξ±, Ξ², Ξ³, Ξ΄) that form a tetrameric sarcoglycan complex embedded in the DGC at the skeletal muscle sarcolemma file:human/SGCA/SGCA-deep-research-falcon.md Ξ±-SG is one of four core sarcoglycans (Ξ±, Ξ², Ξ³, Ξ΄) in the sarcoglycan complex, associated with sarcospan, dystroglycan, dystrophin, and adaptor/signaling proteins such as Ξ±-dystrobrevin/syntrophin/nNOS within the DGC |
| GO:0005509 calcium ion binding | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation for calcium ion binding based on InterPro domain mapping to cadherin-like superfamily. The extracellular domain contains calcium-binding pockets conserved with alpha-dystroglycan, and the ATP-hydrolyzing enzymatic activity is calcium and magnesium dependent. Reason: Multiple lines of evidence support calcium binding capability. The deep research describes calcium-binding pockets in the cadherin-like domain and the ATP-hydrolysing activity requiring both Ca2+ and Mg2+. UniProt features include predicted calcium-binding regions. While this is IEA, the inference is well-supported by structural and biochemical data. Supporting Evidence: file:human/SGCA/SGCA-deep-research-perplexity.md Within the N-terminal extracellular region, alpha-sarcoglycan contains a cadherin-like domain and calcium-binding pockets that are also found in alpha-dystroglycan file:human/SGCA/SGCA-deep-research-perplexity.md alpha-sarcoglycan is a calcium and magnesium-dependent ecto-ATPase that hydrolyzes extracellular ATP and ADP file:human/SGCA/SGCA-deep-research-falcon.md reviews describe extracellular cadherin/EGF-like features and CaΒ²βΊ-binding motifs, consistent with a membrane receptor/adhesion-support role rather than a classic enzyme file:human/SGCA/SGCA-deep-research-falcon.md Some literature additionally reports an extracellular ATP-binding domain and Ca2+/Mg2+-dependent ecto-ATPase activity associated with Ξ±-SG |
| GO:0005856 cytoskeleton | IEA GO_REF:0000044 | MODIFY | Summary: IEA annotation based on subcellular location mapping is overly general. While SGCA is part of the DGC that links to the actin cytoskeleton, the protein itself is a transmembrane component at the sarcolemma, not a cytoskeletal protein per se. Reason: This annotation is too general and somewhat misleading. SGCA is not itself a cytoskeletal component but rather a sarcolemmal membrane protein that indirectly associates with the cytoskeleton through the dystrophin-glycoprotein complex. More specific annotations like sarcolemma, sarcoglycan complex, or dystrophin-associated glycoprotein complex better capture its actual localization and function. The term cytoskeleton suggests the protein is part of the cytoskeletal framework itself, which is inaccurate. Proposed replacements: sarcolemma dystrophin-associated glycoprotein complex |
| GO:0016010 dystrophin-associated glycoprotein complex | IEA GO_REF:0000117 | ACCEPT | Summary: IEA annotation for DGC membership based on ARBA machine learning model is well-supported. The sarcoglycan complex is a core subcomplex of the DGC, and SGCA participates in the full transmembrane architecture linking cytoskeleton to extracellular matrix. Reason: This is accurate and represents a key aspect of SGCA function. The sarcoglycan complex is an integral subcomplex of the larger DGC. Recent cryoEM data reveals that sarcoglycans flank and stabilize dystroglycan in the transmembrane region and engage with dystrophin-dystrobrevin on the intracellular side. This annotation is supported by extensive structural and biochemical evidence. Supporting Evidence: file:human/SGCA/SGCA-deep-research-perplexity.md The sarcoglycan complex, of which alpha-sarcoglycan is a component, functions as a critical subcomplex within the larger dystrophin-glycoprotein complex that links the intracellular actin cytoskeleton to the extracellular matrix file:human/SGCA/SGCA-uniprot.txt Component of the sarcoglycan complex, a subcomplex of the dystrophin-glycoprotein complex which forms a link between the F-actin cytoskeleton and the extracellular matrix file:human/SGCA/SGCA-deep-research-falcon.md the DGC links intracellular cytoskeleton (via dystrophin) to the extracellular matrix and stabilizes the sarcolemma during contraction |
| GO:0016012 sarcoglycan complex | IEA GO_REF:0000120 | ACCEPT | Summary: Duplicate IEA annotation for sarcoglycan complex from combined automated methods. This is the same GO term as the IBA annotation already reviewed. Reason: This is a duplicate annotation of the same GO term annotated above with IBA evidence. Both are correct. The IEA is based on orthology to mouse and domain mapping while the IBA is based on phylogenetic inference. Both support the same accurate annotation. |
| GO:0016020 membrane | IEA GO_REF:0000002 | MODIFY | Summary: IEA annotation for membrane localization based on InterPro domain mapping. While technically correct (SGCA is a transmembrane protein), this is too general and uninformative. Reason: The term membrane is overly broad and does not capture the specific sarcolemmal/plasma membrane localization of SGCA. More specific terms like plasma membrane, sarcolemma, or cell membrane are available and provide more biological information about where the protein actually functions. Generic membrane annotations should be replaced with more specific cellular component terms. Proposed replacements: plasma membrane sarcolemma |
| GO:0042383 sarcolemma | IEA GO_REF:0000120 | ACCEPT | Summary: IEA annotation for sarcolemma localization based on orthology and UniProt subcellular location. This is the most specific and accurate cellular component term for SGCA, representing the muscle fiber plasma membrane where the DGC functions. Reason: Sarcolemma is the correct and most specific cellular component term for SGCA. The protein localizes exclusively to the plasma membrane of muscle fibers, which is termed the sarcolemma. UniProt states Cell membrane, sarcolemma and the deep research extensively describes sarcolemmal localization and enrichment at costameres and the neuromuscular junction. This is a core annotation. Supporting Evidence: file:human/SGCA/SGCA-uniprot.txt Cell membrane, sarcolemma; Single-pass type I membrane protein file:human/SGCA/SGCA-deep-research-perplexity.md Alpha-sarcoglycan is localized exclusively to the plasma membrane (sarcolemma) of muscle fibers where it functions as a transmembrane component of the dystrophin-glycoprotein complex file:human/SGCA/SGCA-deep-research-falcon.md Ξ±-SG is described as a single-pass transmembrane protein with an extracellularly oriented domain and is targeted to the plasma membrane (sarcolemma) after maturation through the ERβGolgi secretory pathway |
| GO:0005515 protein binding | IPI PMID:21516116 Next-generation sequencing to generate interactome datasets. | MODIFY | Summary: IPI annotation for protein binding from high-throughput interactome study. While true, protein binding is uninformative and should be replaced with more specific molecular function terms describing SGCA actual activities. Reason: Protein binding is too generic and does not provide useful information about SGCA function. Per curation guidelines, this term should be avoided in favor of more informative molecular function terms. SGCA primary molecular functions are structural constituent of muscle and ATPase activity. These generic protein binding annotations from high-throughput studies should be replaced. Proposed replacements: structural constituent of muscle Supporting Evidence: PMID:21516116 Next-generation sequencing to generate interactome datasets. |
| GO:0005515 protein binding | IPI PMID:25416956 A proteome-scale map of the human interactome network. | MODIFY | Summary: IPI annotation for protein binding from proteome-scale interactome mapping. Generic and uninformative. Reason: Same as above - protein binding provides no useful functional information about SGCA. The structural role in the sarcoglycan and DGC complexes is better captured by structural constituent terms. Proposed replacements: structural constituent of muscle Supporting Evidence: PMID:25416956 A proteome-scale map of the human interactome network. |
| GO:0005515 protein binding | IPI PMID:25910212 Widespread macromolecular interaction perturbations in human... | MODIFY | Summary: IPI annotation from genetic disorder protein interaction study. Generic and uninformative. Reason: Generic protein binding term should be replaced with more specific molecular function. Proposed replacements: structural constituent of muscle Supporting Evidence: PMID:25910212 Widespread macromolecular interaction perturbations in human genetic disorders. |
| GO:0005515 protein binding | IPI PMID:26871637 Widespread Expansion of Protein Interaction Capabilities by ... | MODIFY | Summary: IPI annotation from alternative splicing interactome study. Generic and uninformative. Reason: Generic protein binding term should be replaced with more specific molecular function. Proposed replacements: structural constituent of muscle Supporting Evidence: PMID:26871637 Widespread Expansion of Protein Interaction Capabilities by Alternative Splicing. |
| GO:0005515 protein binding | IPI Q16586-2 PMID:26871637 Widespread Expansion of Protein Interaction Capabilities by ... | MODIFY | Summary: IPI annotation for protein binding from alternative splicing interactome study, specifically for isoform SGCA-2 (Q16586-2). This isoform lacks residues 196-319 including the transmembrane domain and produces a shorter non-transmembrane protein. Generic protein binding annotation is uninformative. Reason: Generic protein binding term should be replaced with more specific molecular function. The isoform Q16586-2 represents a splice variant lacking the transmembrane domain, predicting a 35-kDa non-transmembrane form. Its specific function may differ from the full-length protein. Proposed replacements: structural constituent of muscle Supporting Evidence: PMID:26871637 Widespread Expansion of Protein Interaction Capabilities by Alternative Splicing. PMID:7937874 Additionally, a splice form of adhalin message was found that predicts a 35-kDa nontransmembrane adhalin. |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | MODIFY | Summary: IPI annotation from reference human binary protein interactome. Generic and uninformative. Reason: Generic protein binding term should be replaced with more specific molecular function. Proposed replacements: structural constituent of muscle Supporting Evidence: PMID:32296183 Apr 8. A reference map of the human binary protein interactome. |
| GO:0005515 protein binding | IPI PMID:32814053 Interactome Mapping Provides a Network of Neurodegenerative ... | MODIFY | Summary: IPI annotation from neurodegenerative disease protein interactome study. Generic and uninformative. Reason: Generic protein binding term should be replaced with more specific molecular function describing actual SGCA activities. Proposed replacements: structural constituent of muscle Supporting Evidence: PMID:32814053 Interactome Mapping Provides a Network of Neurodegenerative Disease Proteins and Uncovers Widespread Protein Aggregation in Affected Brains. |
| GO:0005886 plasma membrane | IEA GO_REF:0000107 | ACCEPT | Summary: IEA annotation for plasma membrane based on Ensembl orthology mapping to mouse. Accurate but less specific than sarcolemma for muscle context. Reason: This annotation is correct - SGCA is indeed localized to the plasma membrane. While sarcolemma is more specific for the muscle context, plasma membrane is also accurate and appropriate. Both terms can coexist as sarcolemma is a child term of plasma membrane. Supporting Evidence: file:human/SGCA/SGCA-uniprot.txt Cell membrane, sarcolemma |
| GO:0005911 cell-cell junction | IEA GO_REF:0000107 | REMOVE | Summary: IEA annotation for cell-cell junction based on Ensembl orthology. This is somewhat questionable for SGCA as it localizes to the sarcolemma but not specifically to intercellular junctions between myocytes. Reason: This annotation appears to be an over-annotation from orthology mapping. While the DGC may have some role at specialized membrane domains, SGCA is not specifically enriched at cell-cell junctions between muscle fibers. The primary localization is to the sarcolemma broadly and to specialized regions like costameres and the neuromuscular junction, which is a neuron-muscle synapse not a cell-cell junction per se. No evidence in the literature supports specific cell-cell junction localization. |
| GO:0016011 dystroglycan complex | IEA GO_REF:0000107 | MODIFY | Summary: IEA annotation for dystroglycan complex membership. This is technically incorrect - SGCA is part of the sarcoglycan complex which associates with dystroglycan, but is not itself part of the dystroglycan complex per se. Reason: This annotation conflates the sarcoglycan complex with the dystroglycan complex. Recent cryoEM structural data shows that sarcoglycans flank and stabilize dystroglycan transmembrane domain but form a distinct subcomplex. The more accurate term is dystrophin-associated glycoprotein complex or sarcoglycan complex. Dystroglycan complex typically refers to the alpha/beta dystroglycan heterodimer. Proposed replacements: sarcoglycan complex dystrophin-associated glycoprotein complex |
| GO:0045121 membrane raft | IEA GO_REF:0000107 | REMOVE | Summary: IEA annotation for membrane raft localization based on Ensembl orthology. While lipid rafts may exist in the sarcolemma, there is insufficient evidence that SGCA specifically localizes to or functions in membrane rafts. Reason: This appears to be an over-annotation from computational transfer. There is no specific experimental evidence in the literature that SGCA localizes to membrane rafts or lipid raft microdomains. The primary localizations are sarcolemma, costameres, and neuromuscular junction - none of which are necessarily membrane raft domains. Without specific experimental evidence, this annotation should be removed. |
| GO:0031594 neuromuscular junction | NAS PMID:19899002 The roles of the dystrophin-associated glycoprotein complex ... | ACCEPT | Summary: NAS annotation for neuromuscular junction localization from ComplexPortal based on review of DGC roles at synapses. Recent detailed studies confirm sarcoglycan enrichment at the NMJ. Reason: This annotation is well-supported. PMID:19899002 is a comprehensive review on DGC roles at synapses and describes sarcoglycan localization at the NMJ. The deep research report specifically states that sarcoglycans including alpha-sarcoglycan exhibit enrichment at the neuromuscular junction in an nerve signal-dependent manner, with colocalization with acetylcholine receptor clusters. This is an important specialized localization beyond general sarcolemma. Supporting Evidence: PMID:19899002 The dystrophin protein is part of the highly conserved dystrophin-associated glycoprotein complex (DGC) which accumulates at the neuromuscular junction (NMJ) and at a variety of synapses in the peripheral and central nervous systems file:human/SGCA/SGCA-deep-research-perplexity.md Beyond costameres, alpha-sarcoglycan exhibits enrichment at a second specialized membrane domainβthe neuromuscular junction (NMJ). Recent detailed immunofluorescence studies have demonstrated for the first time that the entire sarcoglycan complex, including alpha-sarcoglycan, accumulates at postsynaptic regions of the NMJ in an enriched manner |
| GO:0005886 plasma membrane | NAS PMID:19899002 The roles of the dystrophin-associated glycoprotein complex ... | ACCEPT | Summary: Duplicate NAS annotation for plasma membrane from same reference as IEA annotation. Correct but redundant. Reason: This is a duplicate of the IEA plasma membrane annotation reviewed above. Both are correct. The NAS is from ComplexPortal curated information while IEA is from orthology transfer. Having multiple evidence codes for the same correct annotation is acceptable. Supporting Evidence: PMID:19899002 Nov 9. The roles of the dystrophin-associated glycoprotein complex at the synapse. |
| GO:0016010 dystrophin-associated glycoprotein complex | NAS PMID:19899002 The roles of the dystrophin-associated glycoprotein complex ... | ACCEPT | Summary: Duplicate NAS annotation for DGC from same reference as IEA annotation. Well-supported by literature. Reason: This is a duplicate of the IEA DGC annotation reviewed above. Both are correct and represent core SGCA function as part of the DGC. Multiple evidence codes for this critical annotation are appropriate. Supporting Evidence: PMID:19899002 Nov 9. The roles of the dystrophin-associated glycoprotein complex at the synapse. |
| GO:0043010 camera-type eye development | NAS PMID:19899002 The roles of the dystrophin-associated glycoprotein complex ... | KEEP AS NON CORE | Summary: NAS annotation for camera-type eye development based on DGC review discussing retinal roles. While DGC components are present in retina, SGCA expression is restricted to striated muscle and this developmental annotation seems like over-annotation. Reason: This annotation is peripheral to SGCA primary function. While PMID:19899002 discusses DGC roles in multiple tissues including retina, and some sarcoglycans are expressed in retinal tissue, SGCA itself is described as restricted to striated muscle in the deep research report and UniProt. The primary function is muscle membrane stabilization. Eye development may be affected in some sarcoglycanopathies but this is not a core function of SGCA. This should be marked as non-core or potentially removed entirely. Supporting Evidence: file:human/SGCA/SGCA-deep-research-perplexity.md SGCA exhibits relatively confined expression, being primarily restricted to striated muscle tissue including skeletal and cardiac muscle fibers PMID:19899002 Nov 9. The roles of the dystrophin-associated glycoprotein complex at the synapse. |
| GO:0000139 Golgi membrane | TAS Reactome:R-HSA-9913332 | KEEP AS NON CORE | Summary: TAS annotation for Golgi membrane based on Reactome pathway showing sarcoglycan complex assembly and trafficking through Golgi. This represents a transient biosynthetic localization, not the functional localization. Reason: While technically accurate that SGCA traffics through the Golgi during biosynthesis and complex assembly, this is not a functionally relevant localization. The Reactome pathways describe the assembly and trafficking process. The functional location is the sarcolemma. Golgi localization is transient and biosynthetic, not where the protein carries out its biological role. This should be kept as non-core or potentially removed. |
| GO:0000139 Golgi membrane | TAS Reactome:R-HSA-9913336 | KEEP AS NON CORE | Summary: Duplicate TAS annotation for Golgi membrane from different Reactome pathway (translocation to plasma membrane). Represents biosynthetic trafficking. Reason: Same as above - this reflects biosynthetic trafficking through the secretory pathway, not functional localization. |
| GO:0000139 Golgi membrane | TAS Reactome:R-HSA-9913338 | KEEP AS NON CORE | Summary: Third duplicate TAS annotation for Golgi from Reactome pathway on sarcoglycan complex translocation. Biosynthetic only. Reason: Same as above - transient biosynthetic localization, not functionally relevant. |
| GO:0005789 endoplasmic reticulum membrane | TAS Reactome:R-HSA-9913330 | KEEP AS NON CORE | Summary: TAS annotation for ER membrane from Reactome pathway on sarcoglycan complex assembly. Represents biosynthetic/co-translational insertion and folding in ER, not functional localization. Reason: Like the Golgi annotations, this represents transient biosynthetic localization. The deep research extensively describes ER quality control, co-translational insertion, N-glycosylation, and chaperone-mediated folding in the ER. However, this is not where SGCA functions - it is where the protein is synthesized and undergoes quality control before trafficking to the sarcolemma. Non-core annotation. Supporting Evidence: file:human/SGCA/SGCA-deep-research-perplexity.md Nascent alpha-sarcoglycan molecules are cotranslationally inserted into the endoplasmic reticulum where they encounter the ER quality control system file:human/SGCA/SGCA-deep-research-falcon.md many pathogenic missense SGCA variants lead to misfolding, ER retention, and premature degradation (e.g., via proteasome/ER-associated degradation), preventing normal sarcolemmal delivery and causing secondary loss of other sarcoglycan complex members at the membrane |
| GO:0005789 endoplasmic reticulum membrane | TAS Reactome:R-HSA-9913338 | KEEP AS NON CORE | Summary: Duplicate TAS annotation for ER membrane from different Reactome pathway. Biosynthetic localization only. Reason: Same as above - represents biosynthetic processing, not functional localization. |
| GO:0005886 plasma membrane | TAS Reactome:R-HSA-9913333 | ACCEPT | Summary: TAS annotation for plasma membrane from Reactome pathway on DGC binding to laminins. This is the functional localization. Reason: Multiple Reactome pathways correctly annotate SGCA to plasma membrane, which is the functional localization. These TAS annotations complement the IEA and NAS plasma membrane annotations and all are correct. |
| GO:0005886 plasma membrane | TAS Reactome:R-HSA-9913336 | ACCEPT | Summary: Duplicate TAS for plasma membrane from Reactome translocation pathway. Reason: Correct annotation, duplicate evidence. |
| GO:0005886 plasma membrane | TAS Reactome:R-HSA-9913339 | ACCEPT | Summary: Third TAS for plasma membrane from Reactome pathway on recruitment of dystrophin complex. Reason: Correct annotation, duplicate evidence. |
| GO:0005886 plasma membrane | TAS Reactome:R-HSA-9914537 | ACCEPT | Summary: Fourth TAS for plasma membrane from Reactome pathway on DGC binding to agrin and perlecan. Reason: Correct annotation, duplicate evidence. |
| GO:0006936 muscle contraction | TAS PMID:8069911 Missense mutations in the adhalin gene linked to autosomal r... | MODIFY | Summary: TAS annotation for muscle contraction from seminal paper identifying SGCA mutations causing muscular dystrophy. While SGCA is essential for muscle integrity during contraction, it does not directly participate in the contractile process itself. Reason: This annotation is somewhat imprecise. SGCA does not directly participate in muscle contraction - it is not part of the contractile apparatus. Rather, it maintains sarcolemmal integrity during contraction and protects against contraction-induced membrane damage. More accurate terms would be muscle structure development, sarcomere organization, or maintenance of muscle cell membrane integrity. The primary role is structural stabilization, not the contractile process per se. Proposed replacements: muscle structure development muscle system process Supporting Evidence: file:human/SGCA/SGCA-deep-research-perplexity.md The primary structural function of alpha-sarcoglycan centers on maintaining mechanical stability of the sarcolemma during the intense forces generated by muscle contraction PMID:8069911 Missense mutations in the adhalin gene linked to autosomal recessive muscular dystrophy file:human/SGCA/SGCA-deep-research-falcon.md The dominant functional model is that Ξ±-SG is a structural/mechanoprotective component of the DGC: the sarcoglycan complex strengthens the dystrophinβdystroglycan axis and helps protect the sarcolemma from contraction-induced injury |
| GO:0007517 muscle organ development | TAS PMID:7663524 Primary adhalinopathy: a common cause of autosomal recessive... | ACCEPT | Summary: TAS annotation for muscle organ development from paper on SGCA mutations and variable disease severity. This is appropriate as SGCA is essential for proper muscle development and maintenance. Reason: This annotation is appropriate. SGCA is required for proper muscle organ development and maintenance. Loss of SGCA causes progressive muscular dystrophy with muscle degeneration starting in childhood, demonstrating its essential role in muscle development and homeostasis. While the primary molecular function is structural, the biological process of muscle organ development accurately captures the physiological role. This is supported by the disease phenotype and tissue-specific expression. Supporting Evidence: PMID:7663524 Primary adhalinopathy: a common cause of autosomal recessive muscular dystrophy of variable severity file:human/SGCA/SGCA-deep-research-perplexity.md Mutations in SGCA cause autosomal recessive limb-girdle muscular dystrophy type 2D (LGMD2D), also designated LGMDR3 according to newer nomenclature file:human/SGCA/SGCA-deep-research-falcon.md In the sgca-null mouse model, lack of Ξ±-SG causes typical dystrophic features (necrosis/fibrosis, elevated serum CK, reduced muscle force, impaired locomotion) |
| GO:0016010 dystrophin-associated glycoprotein complex | TAS PMID:7937874 Human adhalin is alternatively spliced and the gene is locat... | ACCEPT | Summary: TAS annotation for DGC from paper on SGCA alternative splicing and chromosomal localization. This is a duplicate of earlier DGC annotations with different evidence codes. Reason: This is another correct annotation for DGC membership, now with TAS evidence from an early characterization paper. Multiple evidence codes for this core annotation are appropriate. Supporting Evidence: PMID:7937874 Human adhalin is alternatively spliced and the gene is located on chromosome 17q21. |
| GO:0030899 calcium-dependent ATPase activity | IDA PMID:15032752 Characterization of the ATP-hydrolysing activity of alpha-sa... | NEW | Summary: Proposed new annotation for calcium-dependent ATPase activity based on experimental biochemical evidence from PMID:15032752 and PMID:10075685. Alpha-sarcoglycan is a Ca2+/Mg2+-dependent ecto-ATPase that hydrolyzes extracellular ATP and ADP. Transfection of HEK293 cells with SGCA resulted in increased ATP-hydrolyzing activity that was completely abolished by anti-alpha-sarcoglycan antibodies. Reason: Alpha-sarcoglycan has been experimentally demonstrated to possess intrinsic ATP-hydrolyzing enzymatic activity that requires both calcium and magnesium ions. The enzyme has a substrate specificity for ATP and ADP, does not hydrolyze other triphosphonucleosides, and has an affinity for ATP in the low mM range. The ATPase activity was completely inhibited by suramin and reactive blue-2. This ecto-ATPase activity represents a distinct molecular function of SGCA beyond its structural role. The falcon deep research corroborates this biochemical activity but cautions that it is a specialized/less universally emphasized aspect of Ξ±-SG biology compared to its core structural DGC role; it should therefore be retained as a NEW molecular function annotation but is non-core relative to the structural role. Supporting Evidence: PMID:15032752 The enzyme had a substrate specificity for ATP and ADP, did not hydrolyse other triphosphonucleosides, and the affinity for ATP was in the low mM range. The ATPase activity strictly required the presence of both Mg2+ and Ca2+ and was completely inhibited by suramin and reactive blue-2. PMID:10075685 we provide evidence for an ecto-ATPase activity of alpha-sarcoglycan file:human/SGCA/SGCA-deep-research-falcon.md Some literature additionally reports an extracellular ATP-binding domain and Ca2+/Mg2+-dependent ecto-ATPase activity associated with Ξ±-SG; this enzymatic-like activity is not the primary framing in most modern functional summaries (which emphasize structural DGC roles), but it remains a recurring observation in authoritative reviews/workshop material |
| GO:0070371 ERK1 and ERK2 cascade | IDA | NEW | Summary: Proposed new annotation for involvement in ERK1/2 signaling cascade based on mechanotransduction studies. The sarcoglycan complex including SGCA participates in mechanical signal transduction through ERK1/2 phosphorylation. Reason: Studies demonstrate that the sarcoglycan complex functions as a mechanoreceptor that activates ERK1/2 signaling in response to mechanical loading. During eccentric contractions, the sarcoglycan complex undergoes rapid phosphorylation with concomitant activation of ERK1/2. Muscles lacking sarcoglycans show altered ERK1/2 phosphorylation responses to mechanical stimulation. This annotation captures an important signaling function beyond the structural role. Supporting Evidence: file:human/SGCA/SGCA-deep-research-perplexity.md The sarcoglycan complex functions as a mechanoreceptor capable of detecting and transducing mechanical perturbations. When muscles experience dynamic mechanical loading such as eccentric contractions, the sarcoglycan complex undergoes rapid phosphorylation events with concomitant activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) |
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