Cd79a encodes Ig-alpha, the ITAM-bearing signaling chain of the B-cell antigen receptor. It pairs with Ig-beta and membrane immunoglobulin at the plasma membrane, supporting receptor assembly and phosphorylation-dependent recruitment of intracellular effectors. Its cytoplasmic ITAM and non-ITAM tyrosines connect receptor engagement to Syk and BLNK-dependent signaling. Mouse developmental and activation phenotypes depend on the mutated site and the availability of the Ig-beta tail. Activated receptor also enters raft-associated and multivesicular antigen-processing compartments.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004888 transmembrane signaling receptor activity | IBA GO_REF:0000033 | ACCEPT | Summary: The CD79 chain contributes transmembrane signaling within the assembled B-cell receptor. Reason: Membrane immunoglobulin supplies antigen recognition, and the Ig-alpha/Ig-beta heterodimer couples receptor engagement to intracellular effectors. Reconstitution in mouse AtT20 cells demonstrates several signaling outputs after Syk expression, without sufficiency for the entire native B-cell network. Any contributes_to flag is retained and assessed as a complex contribution. |
| GO:0004888 transmembrane signaling receptor activity | IDA PMID:1439759 The B cell antigen receptor complex: association of Ig-alpha... | ACCEPT | Summary: The CD79 chain contributes transmembrane signaling within the assembled B-cell receptor. Reason: Membrane immunoglobulin supplies antigen recognition, and the Ig-alpha/Ig-beta heterodimer couples receptor engagement to intracellular effectors. Reconstitution in mouse AtT20 cells demonstrates several signaling outputs after Syk expression, without sufficiency for the entire native B-cell network. Any contributes_to flag is retained and assessed as a complex contribution. |
| GO:0004888 transmembrane signaling receptor activity | IDA PMID:8626447 Reconstitution of B cell antigen receptor-induced signaling ... | ACCEPT | Summary: The CD79 chain contributes transmembrane signaling within the assembled B-cell receptor. Reason: Membrane immunoglobulin supplies antigen recognition, and the Ig-alpha/Ig-beta heterodimer couples receptor engagement to intracellular effectors. Reconstitution in mouse AtT20 cells demonstrates several signaling outputs after Syk expression, without sufficiency for the entire native B-cell network. Any contributes_to flag is retained and assessed as a complex contribution. |
| GO:0004888 transmembrane signaling receptor activity | IDA PMID:8626447 Reconstitution of B cell antigen receptor-induced signaling ... | ACCEPT | Summary: The CD79 chain contributes transmembrane signaling within the assembled B-cell receptor. Reason: Membrane immunoglobulin supplies antigen recognition, and the Ig-alpha/Ig-beta heterodimer couples receptor engagement to intracellular effectors. Reconstitution in mouse AtT20 cells demonstrates several signaling outputs after Syk expression, without sufficiency for the entire native B-cell network. Any contributes_to flag is retained and assessed as a complex contribution. |
| GO:0004888 transmembrane signaling receptor activity | IEA GO_REF:0000002 | ACCEPT | Summary: The CD79 chain contributes transmembrane signaling within the assembled B-cell receptor. Reason: Membrane immunoglobulin supplies antigen recognition, and the Ig-alpha/Ig-beta heterodimer couples receptor engagement to intracellular effectors. Reconstitution in mouse AtT20 cells demonstrates several signaling outputs after Syk expression, without sufficiency for the entire native B-cell network. Any contributes_to flag is retained and assessed as a complex contribution. |
| GO:0005515 protein binding | IPI PMID:1373499 The membrane IgM-associated proteins MB-1 and Ig-beta are su... | MODIFY | Summary: The CD79 chains heterodimerize to form the receptor signaling module. Reason: Coexpression and assembly experiments establish the Ig-alpha/Ig-beta pair, so the more informative protein heterodimerization activity captures the reported partner interaction. This does not assign antigen recognition to either isolated chain. Proposed replacements: protein heterodimerization activity |
| GO:0005515 protein binding | IPI PMID:8626447 Reconstitution of B cell antigen receptor-induced signaling ... | MODIFY | Summary: The CD79 chains heterodimerize to form the receptor signaling module. Reason: Coexpression and assembly experiments establish the Ig-alpha/Ig-beta pair, so the more informative protein heterodimerization activity captures the reported partner interaction. This does not assign antigen recognition to either isolated chain. Proposed replacements: protein heterodimerization activity |
| GO:0005515 protein binding | IPI PMID:8626447 Reconstitution of B cell antigen receptor-induced signaling ... | MODIFY | Summary: Ig-alpha provides a phosphorylation-dependent docking platform for the receptor-associated Syk kinase. Reason: The source reconstitutes Syk association and downstream signaling in BCR-expressing mouse AtT20 cells. Ig-alpha is a signaling adaptor rather than a kinase. The specific adaptor activity describes this role more informatively than bare binding; the reconstitution does not recover every B-cell pathway, notably inositol-phosphate production. Proposed replacements: signaling receptor complex adaptor activity |
| GO:0005771 multivesicular body | IDA PMID:11854359 Dynamics of major histocompatibility complex class II compar... | KEEP AS NON CORE | Summary: Stimulated native mouse Ig-alpha accumulates in multivesicular antigen-processing compartments. Reason: PMID11854359 Fig. 5C directly detects Ig-alpha by immunogold in multivesicular MHC-II compartments of stimulated IIA1.6 cells. This is a conditional receptor-trafficking location, not a claim of constitutive residence or vesicle-biogenesis activity. Supporting Evidence: PMID:11854359 The multivesicular MIICs also contain Ig Ξ± |
| GO:0005886 plasma membrane | IEA GO_REF:0000120 | ACCEPT | Summary: The assembled receptor is expressed at the plasma membrane. Reason: Reconstitution establishes surface expression of the membrane-IgM/Ig-alpha/Ig-beta complex. Independent receptor-assembly evidence corroborates the orthology or curated pathway assignment; intracellular receptor trafficking does not contradict cell-surface residence. Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC48876/ |
| GO:0005886 plasma membrane | ISO GO_REF:0000119 | ACCEPT | Summary: The assembled receptor is expressed at the plasma membrane. Reason: Reconstitution establishes surface expression of the membrane-IgM/Ig-alpha/Ig-beta complex. Independent receptor-assembly evidence corroborates the orthology or curated pathway assignment; intracellular receptor trafficking does not contradict cell-surface residence. Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC48876/ |
| GO:0005886 plasma membrane | TAS Reactome:R-MMU-983702 | ACCEPT | Summary: The assembled receptor is expressed at the plasma membrane. Reason: Reconstitution establishes surface expression of the membrane-IgM/Ig-alpha/Ig-beta complex. Independent receptor-assembly evidence corroborates the orthology or curated pathway assignment; intracellular receptor trafficking does not contradict cell-surface residence. Supporting Evidence: Reactome:R-MMU-983702 url:https://pmc.ncbi.nlm.nih.gov/articles/PMC48876/ |
| GO:0007166 cell surface receptor signaling pathway | IEA GO_REF:0000002 | MODIFY | Summary: The broad process can be specified as B-cell receptor signaling. Reason: The chain performs receptor assembly and ITAM-dependent signal transmission in this specific pathway; the refinement assigns neither kinase catalysis nor a generic function to all immune processes. Proposed replacements: B cell receptor signaling pathway Supporting Evidence: |
| GO:0009897 external side of plasma membrane | IBA GO_REF:0000033 | ACCEPT | Summary: The extracellular CD79 domain is exposed on the outside of the plasma membrane. Reason: Surface receptor assembly and the extracellular Ig-domain structure establish this topology. The same protein has a transmembrane segment and cytoplasmic ITAM; the annotation concerns its exposed extracellular region and does not move signaling chemistry outside the cell. |
| GO:0009897 external side of plasma membrane | IDA PMID:1373499 The membrane IgM-associated proteins MB-1 and Ig-beta are su... | ACCEPT | Summary: The extracellular CD79 domain is exposed on the outside of the plasma membrane. Reason: Surface receptor assembly and the extracellular Ig-domain structure establish this topology. The same protein has a transmembrane segment and cytoplasmic ITAM; the annotation concerns its exposed extracellular region and does not move signaling chemistry outside the cell. |
| GO:0016020 membrane | IEA GO_REF:0000002 | MODIFY | Summary: Specify the established plasma-membrane location. Reason: The protein is a single-pass component of the surface BCR, so a specific supported location is available. Proposed replacements: plasma membrane Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC48876/ |
| GO:0019815 B cell receptor complex | IBA GO_REF:0000033 | ACCEPT | Summary: The CD79 chain is an integral signaling component of the BCR. Reason: Mouse receptor reconstitution directly establishes association with membrane IgM and the other CD79 chain. Human/murine ectodomain work independently supports the assembly interface. This is complex membership, not autonomous antigen binding or a claim that all BCRs use the IgM isotype. |
| GO:0019815 B cell receptor complex | IDA PMID:1373499 The membrane IgM-associated proteins MB-1 and Ig-beta are su... | ACCEPT | Summary: The CD79 chain is an integral signaling component of the BCR. Reason: Mouse receptor reconstitution directly establishes association with membrane IgM and the other CD79 chain. Human/murine ectodomain work independently supports the assembly interface. This is complex membership, not autonomous antigen binding or a claim that all BCRs use the IgM isotype. |
| GO:0019815 B cell receptor complex | IDA PMID:8626447 Reconstitution of B cell antigen receptor-induced signaling ... | ACCEPT | Summary: The CD79 chain is an integral signaling component of the BCR. Reason: Mouse receptor reconstitution directly establishes association with membrane IgM and the other CD79 chain. Human/murine ectodomain work independently supports the assembly interface. This is complex membership, not autonomous antigen binding or a claim that all BCRs use the IgM isotype. |
| GO:0019815 B cell receptor complex | IEA GO_REF:0000107 | ACCEPT | Summary: The CD79 chain is an integral signaling component of the BCR. Reason: Mouse receptor reconstitution directly establishes association with membrane IgM and the other CD79 chain. Human/murine ectodomain work independently supports the assembly interface. This is complex membership, not autonomous antigen binding or a claim that all BCRs use the IgM isotype. |
| GO:0019815 B cell receptor complex | ISO GO_REF:0000119 | ACCEPT | Summary: The CD79 chain is an integral signaling component of the BCR. Reason: Mouse receptor reconstitution directly establishes association with membrane IgM and the other CD79 chain. Human/murine ectodomain work independently supports the assembly interface. This is complex membership, not autonomous antigen binding or a claim that all BCRs use the IgM isotype. |
| GO:0030183 B cell differentiation | IBA GO_REF:0000033 | ACCEPT | Summary: Receptor-associated signaling supports B-cell developmental checkpoints. Reason: Native mouse deficiency arrests maturation at the progenitor stage while preserving V(D)J recombination. Ig-alpha ITAM mutation and Ig-beta-tail truncation show context-dependent compensation, not dispensability of the receptor signaling module. The proteins do developmental signaling work, not DNA recombination. |
| GO:0030183 B cell differentiation | IMP PMID:11514602 Interference with immunoglobulin (Ig)alpha immunoreceptor ty... | ACCEPT | Summary: Receptor-associated signaling supports B-cell developmental checkpoints. Reason: Native mouse deficiency arrests maturation at the progenitor stage while preserving V(D)J recombination. Ig-alpha ITAM mutation and Ig-beta-tail truncation show context-dependent compensation, not dispensability of the receptor signaling module. The proteins do developmental signaling work, not DNA recombination. |
| GO:0030183 B cell differentiation | IMP PMID:12097390 B cell progenitors are arrested in maturation but have intac... | ACCEPT | Summary: Receptor-associated signaling supports B-cell developmental checkpoints. Reason: Native mouse deficiency arrests maturation at the progenitor stage while preserving V(D)J recombination. Ig-alpha ITAM mutation and Ig-beta-tail truncation show context-dependent compensation, not dispensability of the receptor signaling module. The proteins do developmental signaling work, not DNA recombination. |
| GO:0042100 B cell proliferation | IMP PMID:16860757 The B cell receptor promotes B cell activation and prolifera... | KEEP AS NON CORE | Summary: The Ig-alpha non-ITAM Y204 site supports activation and proliferation in a defined immune context. Reason: Targeted Y204 mutation in mice selectively impairs T-independent BCR-driven activation, proliferation and antibody responses, with normal B-cell numbers and several T-dependent functions. The activation role is central; proliferation is a downstream physiological output rather than cell-cycle catalysis. These results are not generalized to every activation stimulus. Supporting Evidence: |
| GO:0042113 B cell activation | IMP PMID:16860757 The B cell receptor promotes B cell activation and prolifera... | ACCEPT | Summary: The Ig-alpha non-ITAM Y204 site supports activation and proliferation in a defined immune context. Reason: Targeted Y204 mutation in mice selectively impairs T-independent BCR-driven activation, proliferation and antibody responses, with normal B-cell numbers and several T-dependent functions. The activation role is central; proliferation is a downstream physiological output rather than cell-cycle catalysis. These results are not generalized to every activation stimulus. Supporting Evidence: |
| GO:0042802 identical protein binding | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Self-association is supported in purified CD79-domain experiments. Reason: Purified cytoplasmic Ig-alpha/Ig-beta domains oligomerize in PMID14967045; PMID20696394 additionally resolves murine and human Ig-beta ectodomain homodimers. These experiments support the biochemical binding capacity, without replacing the physiological Ig-alpha/Ig-beta signaling heterodimer with an obligatory homomer. |
| GO:0042802 identical protein binding | ISO GO_REF:0000119 | KEEP AS NON CORE | Summary: Self-association is supported in purified CD79-domain experiments. Reason: Purified cytoplasmic Ig-alpha/Ig-beta domains oligomerize in PMID14967045; PMID20696394 additionally resolves murine and human Ig-beta ectodomain homodimers. These experiments support the biochemical binding capacity, without replacing the physiological Ig-alpha/Ig-beta signaling heterodimer with an obligatory homomer. |
| GO:0045121 membrane raft | IDA PMID:10587346 A role for lipid rafts in B cell antigen receptor signaling ... | KEEP AS NON CORE | Summary: Activated BCR redistributes into raft-associated fractions. Reason: The mouse B-cell studies identify Ig-alpha in stimulated GM1-enriched raft fractions. BCR translocation can precede signaling and does not require the Ig-alpha/Ig-beta complex in the tested constructs (PMID11238609), so raft localization is conditional rather than proof that Ig-alpha drives raft formation or signals only there. Supporting Evidence: |
| GO:0045121 membrane raft | IDA PMID:11238609 Translocation of the B cell antigen receptor into lipid raft... | KEEP AS NON CORE | Summary: Activated BCR redistributes into raft-associated fractions. Reason: The mouse B-cell studies identify Ig-alpha in stimulated GM1-enriched raft fractions. BCR translocation can precede signaling and does not require the Ig-alpha/Ig-beta complex in the tested constructs (PMID11238609), so raft localization is conditional rather than proof that Ig-alpha drives raft formation or signals only there. |
| GO:0050853 B cell receptor signaling pathway | IBA GO_REF:0000033 | ACCEPT | Summary: Ig-alpha/Ig-beta supplies the receptor-proximal signaling module. Reason: Reconstitution and effector-association studies show that the cytoplasmic tails transmit antigen-receptor signals. The 1996 AtT20 experiment required active Syk for several outputs and did not reconstitute phosphoinositide signaling; the existing pathway assignment does not assert sufficiency for all downstream branches. |
| GO:0050853 B cell receptor signaling pathway | IDA PMID:1373499 The membrane IgM-associated proteins MB-1 and Ig-beta are su... | ACCEPT | Summary: Ig-alpha/Ig-beta supplies the receptor-proximal signaling module. Reason: Reconstitution and effector-association studies show that the cytoplasmic tails transmit antigen-receptor signals. The 1996 AtT20 experiment required active Syk for several outputs and did not reconstitute phosphoinositide signaling; the existing pathway assignment does not assert sufficiency for all downstream branches. |
| GO:0050853 B cell receptor signaling pathway | IDA PMID:1439759 The B cell antigen receptor complex: association of Ig-alpha... | ACCEPT | Summary: Ig-alpha/Ig-beta supplies the receptor-proximal signaling module. Reason: Reconstitution and effector-association studies show that the cytoplasmic tails transmit antigen-receptor signals. The 1996 AtT20 experiment required active Syk for several outputs and did not reconstitute phosphoinositide signaling; the existing pathway assignment does not assert sufficiency for all downstream branches. |
| GO:0050853 B cell receptor signaling pathway | IDA PMID:8626447 Reconstitution of B cell antigen receptor-induced signaling ... | ACCEPT | Summary: Ig-alpha/Ig-beta supplies the receptor-proximal signaling module. Reason: Reconstitution and effector-association studies show that the cytoplasmic tails transmit antigen-receptor signals. The 1996 AtT20 experiment required active Syk for several outputs and did not reconstitute phosphoinositide signaling; the existing pathway assignment does not assert sufficiency for all downstream branches. |
| GO:0050853 B cell receptor signaling pathway | IDA PMID:8626447 Reconstitution of B cell antigen receptor-induced signaling ... | ACCEPT | Summary: Ig-alpha/Ig-beta supplies the receptor-proximal signaling module. Reason: Reconstitution and effector-association studies show that the cytoplasmic tails transmit antigen-receptor signals. The 1996 AtT20 experiment required active Syk for several outputs and did not reconstitute phosphoinositide signaling; the existing pathway assignment does not assert sufficiency for all downstream branches. |
| GO:0071755 IgM B cell receptor complex | IEA GO_REF:0000107 | ACCEPT | Summary: The CD79 chain is an integral signaling component of the BCR containing membrane IgM. Reason: Mouse receptor reconstitution directly establishes association with membrane IgM and the other CD79 chain. Human/murine ectodomain work independently supports the assembly interface. This is complex membership, not autonomous antigen binding or a claim that all BCRs use the IgM isotype. |
| GO:0071755 IgM B cell receptor complex | ISO GO_REF:0000119 | ACCEPT | Summary: The CD79 chain is an integral signaling component of the BCR containing membrane IgM. Reason: Mouse receptor reconstitution directly establishes association with membrane IgM and the other CD79 chain. Human/murine ectodomain work independently supports the assembly interface. This is complex membership, not autonomous antigen binding or a claim that all BCRs use the IgM isotype. |
| GO:0071755 IgM B cell receptor complex | ISS GO_REF:0000024 | ACCEPT | Summary: The CD79 chain is an integral signaling component of the BCR containing membrane IgM. Reason: Mouse receptor reconstitution directly establishes association with membrane IgM and the other CD79 chain. Human/murine ectodomain work independently supports the assembly interface. This is complex membership, not autonomous antigen binding or a claim that all BCRs use the IgM isotype. |
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