GMFG encodes glia maturation factor gamma, an ADF-H/cofilin-like GMF-family actin regulator that binds the Arp2/3 complex and remodels branched actin networks. The strongest current evidence supports Arp2/3 binding, inhibition of Arp2/3-mediated nucleation, and actin filament debranching at cortical and immune-cell actin structures, with downstream roles in leukocyte migration, integrin trafficking, immune synapse remodeling, and BCR signaling.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0071933 Arp2/3 complex binding | IBA GO_REF:0000033 | ACCEPT | Summary: This IBA annotation captures the best-supported molecular function of GMFG as an Arp2/3 complex-binding GMF-family actin network remodeling factor. Reason: Falcon research, InterPro/UniProt domain context, and phylogenetic annotation converge on GMFG functioning through Arp2/3 binding rather than as a generic glial growth factor. Supporting Evidence: file:human/GMFG/GMFG-deep-research-falcon.md GMFG is an ADF-H family protein that binds the Arp2/3 complex rather than actin itself; it inhibits Arp2/3-dependent nucleation and catalyzes debranching/pruning of daughter filaments at branch junctions. |
| GO:0030864 cortical actin cytoskeleton | IBA GO_REF:0000033 | ACCEPT | Summary: Cortical actin cytoskeleton is an appropriate active site for GMFG's Arp2/3-dependent branched actin remodeling function. Reason: GMFG is discussed as cytosolic and enriched at actin remodeling sites such as leading edges, immune synapses, and focal adhesions; cortical actin cytoskeleton is the most specific existing GOA location. Supporting Evidence: file:human/GMFG/GMFG-deep-research-falcon.md Across experimental contexts, GMFgamma is primarily discussed as a cytosolic protein enriched at actin remodeling sites |
| GO:0071846 actin filament debranching | IBA GO_REF:0000033 | ACCEPT | Summary: Actin filament debranching is a core biological process for GMFG/GMF family proteins acting on Arp2/3-branched actin networks. Reason: This term is specific and mechanistically aligned with GMFG's conserved Arp2/3-regulatory activity. Supporting Evidence: file:human/GMFG/GMFG-deep-research-falcon.md Debranching: removal/dissociation of the daughter filament at an Arp2/3-mediated branch junction, which contributes to turnover of branched actin arrays and recycling of Arp2/3. |
| GO:0034316 negative regulation of Arp2/3 complex-mediated actin nucleation | IBA GO_REF:0000033 | ACCEPT | Summary: This annotation captures the inhibitory arm of GMFG function toward Arp2/3-mediated nucleation. Reason: The term is mechanistically specific and complements the debranching annotation; both are part of GMF-family remodeling of branched actin arrays. Supporting Evidence: file:human/GMFG/GMFG-deep-research-falcon.md A central concept is that branched actin networks (e.g., lamellipodia) are nucleated by Arp2/3 complex, and GMF proteins can both (i) inhibit Arp2/3-mediated nucleation and (ii) catalyze debranching/pruning |
| GO:0007165 signal transduction | IEA GO_REF:0000108 | MARK AS OVER ANNOTATED | Summary: This broad IEA appears to derive from the legacy "growth factor" view of GMF proteins rather than from GMFG's current mechanistic annotation. Reason: GMFG can affect immune signaling through actin remodeling, but signal transduction is too broad and indirect for the protein's core molecular role. Supporting Evidence: file:human/GMFG/GMFG-deep-research-falcon.md Human GMFG (GMFgamma) is an ADF-H/cofilin-like Arp2/3-binding regulator that remodels branched actin networks |
| GO:0003779 actin binding | IEA GO_REF:0000002 | MODIFY | Summary: The ADF-H domain supports a relationship to actin-network regulation, but Falcon research indicates that the more precise molecular target for GMFG is the Arp2/3 complex rather than generic actin binding. Reason: Replace this generic term with the more informative Arp2/3 complex binding term, which is already present in GOA and better describes GMFG's core molecular function. Proposed replacements: Arp2/3 complex binding Supporting Evidence: file:human/GMFG/GMFG-deep-research-falcon.md GMFG is an ADF-H family protein that binds the Arp2/3 complex rather than actin itself |
| GO:0008083 growth factor activity | IEA GO_REF:0000043 | REMOVE | Summary: The growth factor activity annotation reflects the historical protein name rather than current mechanistic evidence for human GMFG. Reason: GMFG lacks evidence for secreted growth factor molecular activity in the current review context; its supported role is intracellular Arp2/3 and actin-network remodeling. Supporting Evidence: file:human/GMFG/GMFG-deep-research-falcon.md GMFG is best positioned as a mechanistic node and candidate biomarker rather than a validated therapeutic target. |
| GO:0071846 actin filament debranching | IEA GO_REF:0000002 | ACCEPT | Summary: The InterPro2GO IEA agrees with the IBA annotation and with the GMF-family mechanistic literature. Reason: Actin filament debranching is a specific, core biological process for GMFG and is supported by family/domain evidence. Supporting Evidence: file:human/GMFG/GMFG-deep-research-falcon.md Human GMFG (GMFgamma) is an ADF-H/cofilin-like Arp2/3-binding regulator that remodels branched actin networks by inhibiting Arp2/3-dependent nucleation and catalyzing debranching |
| GO:0071933 Arp2/3 complex binding | IEA GO_REF:0000002 | ACCEPT | Summary: The InterPro2GO Arp2/3 complex binding annotation is consistent with the stronger IBA annotation and the falcon-summarized literature. Reason: This is the most informative molecular-function annotation currently in GMFG GOA. Supporting Evidence: file:human/GMFG/GMFG-deep-research-falcon.md Biochemical and structural work summarized in an authoritative review indicates that GMF binds the Arp2/3 complex at two sites |
| GO:0005576 extracellular region | TAS Reactome:R-HSA-6798748 | KEEP AS NON CORE | Summary: Reactome links GMFG to neutrophil degranulation/exocytosis datasets, where proteins can be released or detected extracellularly. Reason: This may reflect immune-cell granule/exocytosis context, but the core functional location for GMFG is intracellular actin-remodeling sites. Supporting Evidence: file:human/GMFG/GMFG-uniprot.txt Reactome; R-HSA-6798695; Neutrophil degranulation. |
| GO:0005576 extracellular region | TAS Reactome:R-HSA-6800434 | KEEP AS NON CORE | Summary: Duplicate Reactome extracellular-region annotation from ficolin-rich granule exocytosis context. Reason: Retain as non-core Reactome localization evidence; it should not displace the intracellular cortical actin cytoskeleton as the functional site. Supporting Evidence: file:human/GMFG/GMFG-uniprot.txt Reactome; R-HSA-6798695; Neutrophil degranulation. |
| GO:0034774 secretory granule lumen | TAS Reactome:R-HSA-6798748 | KEEP AS NON CORE | Summary: This Reactome location may reflect detection in neutrophil granule contents rather than the site of GMFG's actin-remodeling activity. Reason: GMFG is relevant to immune cells, but its core function remains intracellular Arp2/3/actin network regulation. Supporting Evidence: file:human/GMFG/GMFG-uniprot.txt Reactome; R-HSA-6798695; Neutrophil degranulation. |
| GO:1904813 ficolin-1-rich granule lumen | TAS Reactome:R-HSA-6800434 | KEEP AS NON CORE | Summary: Ficolin-1-rich granule lumen is plausible as Reactome immune-cell context but is not the primary functional site for GMFG. Reason: Retain as non-core granule-context annotation while emphasizing cortical actin cytoskeleton and cytosolic actin-remodeling locations as core. Supporting Evidence: file:human/GMFG/GMFG-uniprot.txt Reactome; R-HSA-6798695; Neutrophil degranulation. |
| GO:0004860 protein kinase inhibitor activity | TAS PMID:8639570 In vitro inhibition of MAP kinase (ERK1/ERK2) activity by ph... | REMOVE | Summary: The cited study tested phosphorylated GMF as an in vitro ERK inhibitor, but it predates GMFG-specific isolation and does not establish this as a human GMFG molecular function. Reason: This annotation is not transferable to GMFG: the cited in vitro work used recombinant GMF described as a brain protein, consistent with the brain-expressed GMFB isoform rather than immune-cell-expressed GMFG. Current GMFG evidence supports Arp2/3/actin-network remodeling instead. Supporting Evidence: PMID:8639570 recombinant glia maturation factor (GMF), a 17-kDa brain protein, inhibits the activity of mitogen-activated protein (MAP) kinase in the test tube assay |
| GO:0006468 protein phosphorylation | TAS PMID:7598724 Phorbol ester stimulates rapid intracellular phosphorylation... | REMOVE | Summary: This is a substrate/process misannotation: the cited paper describes GMF being phosphorylated by kinases, not GMFG catalyzing protein phosphorylation. Reason: GMFG is not a kinase. The cited evidence supports post-translational regulation of GMF proteins, not assignment of the phosphorylation biological process to GMFG as an actor. Supporting Evidence: PMID:7598724 recombinant glia maturation factor (GMF), a 17-kD brain protein, can be phosphorylated in vitro at the serine residue by protein kinase C (PKC), protein kinase A (PKA), and casein kinase II (CKII) |
| GO:0008047 enzyme activator activity | TAS PMID:8798479 In vitro enhancement of p38 mitogen-activated protein kinase... | REMOVE | Summary: The cited work reports in vitro activation of p38 MAP kinase by phosphorylated GMF, but does not support enzyme activator activity as a current core function for GMFG. Reason: This legacy activity is not transferable to GMFG: the cited phosphorylated-GMF experiments reflect brain-derived/brain-expressed GMF biology, which is most consistent with GMFB rather than immune-cell-expressed GMFG. Current GMFG evidence supports Arp2/3-dependent actin network remodeling. Supporting Evidence: PMID:8798479 PKA-phosphorylated GMF strongly enhances the activity of a related but distinct subfamily of MAP kinase, the p38 MAP kinase |
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Download this section (compressed HTML)Q: Which human immune-cell contexts require GMFG's Arp2/3 debranching activity directly, rather than indirect effects on integrin trafficking?
Q: Are the Reactome granule/extracellular annotations true GMFG localization states or proteomics carryover from neutrophil degranulation datasets?
Q: Do historical MAPK inhibitor/activator findings apply to GMFG specifically, or only to GMFB/undifferentiated GMF preparations?
Experiment: Endogenous GMFG tagging in primary monocytes and B cells followed by live imaging of Arp2/3, F-actin, and integrin recycling during chemotaxis or immune synapse formation.
Hypothesis: GMFG localizes to cortical actin remodeling sites where Arp2/3-dependent debranching supports immune-cell migration and synapse dynamics.
Type: live-cell imaging/genome editing
Experiment: Biochemical reconstitution comparing purified human GMFG and GMFB for Arp2/3 binding, nucleation inhibition, and branch deassembly using TIRF microscopy.
Hypothesis: GMFG has direct Arp2/3-regulatory activity comparable to other GMF-family proteins and does not require legacy MAPK-modulatory activity to explain its core function.
Type: biochemical reconstitution
Experiment: Proteomic reanalysis of neutrophil granule/extracellular fractions with endogenous GMFG controls and cytosolic contamination markers.
Hypothesis: Reactome granule/extracellular annotations reflect immune-cell degranulation datasets rather than the primary functional location of GMFG.
Type: proteomics/localization validation
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