SCAMP3 (Secretory carrier-associated membrane protein 3) is a tetraspanning integral membrane protein that functions as a key regulator of endosomal trafficking and multivesicular body (MVB) biogenesis. The protein contains an N-terminal cytoplasmic domain with functionally critical motifs including a PPAY motif that binds WW-domain E3 ubiquitin ligases (NEDD4 family) and a PSAP motif that mediates interaction with the ESCRT-I component TSG101. SCAMP3 localizes to the Golgi apparatus, early endosomes, and a subset of late endosomes. It plays a central role in regulating epidermal growth factor receptor (EGFR) trafficking fate, balancing receptor recycling versus lysosomal degradation through ESCRT-dependent sorting into intralumenal vesicles. SCAMP3 is multi-monoubiquitinated and is itself phosphorylated by EGFR at Tyr86, which promotes EGFR-SCAMP3 interaction and EGFR degradation. SCAMP3 is essential for WW domain-activated extracellular vesicle (WAEV) budding, positioning it as a critical factor in exosome/EV biogenesis.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0006887 exocytosis | IBA GO_REF:0000033 | MODIFY | Summary: This IBA annotation derives from phylogenetic inference across the SCAMP family. While SCAMP3 is involved in vesicular trafficking pathways, the primary experimental evidence supports its role in endosomal sorting and MVB biogenesis rather than classical exocytosis. The original SCAMP1/2 literature focused on post-Golgi recycling carriers, but SCAMP3-specific studies emphasize EGFR trafficking and intralumenal vesicle formation (PMID:19158374). Reason: The term 'exocytosis' is too general and does not capture the specific role of SCAMP3. The deep research indicates SCAMP3 functions primarily in endosomal sorting, MVB biogenesis, and regulation of receptor recycling vs degradation rather than classical exocytosis. A more appropriate term would be 'post-Golgi vesicle-mediated transport' (which already exists as another annotation) or 'endosomal transport'. Proposed replacements: endosomal transport Supporting Evidence: PMID:19158374 SCAMP3 negatively regulates epidermal growth factor receptor degradation and promotes receptor recycling file:human/SCAMP3/SCAMP3-deep-research-falcon.md model: Edison Scientific Literature |
| GO:0032588 trans-Golgi network membrane | IBA GO_REF:0000033 | ACCEPT | Summary: This IBA annotation is consistent with experimental findings. The deep research indicates SCAMP3 localizes to the Golgi apparatus, and the original 1997 paper (PMID:9378760) showed SCAMPs have similar subcellular distributions including Golgi-associated compartments. The 2012 Traffic paper confirmed SCAMP3 localization to Golgi and endosomal compartments. Reason: The annotation accurately reflects SCAMP3 localization. Literature demonstrates SCAMP3 presence at Golgi and trans-Golgi network membranes consistent with its role in post-Golgi trafficking. Supporting Evidence: PMID:9378760 Examination of the codistribution of the three forms within individual cells using double label immunofluorescence indicates extensive colocalization of SCAMP2 and SCAMP3 with endogenous SCAMP1 |
| GO:0055038 recycling endosome membrane | IBA GO_REF:0000033 | ACCEPT | Summary: This IBA annotation is well-supported by experimental evidence. SCAMP3 promotes receptor recycling and localizes to endosomal compartments including recycling endosomes. The 2009 Mol Biol Cell paper demonstrated that SCAMP3 promotes EGFR recycling rather than degradation (PMID:19158374). Reason: The annotation accurately reflects SCAMP3 localization and function. SCAMP3 functions as a recycling carrier and promotes receptor recycling from endosomal compartments back to the plasma membrane. Supporting Evidence: PMID:19158374 SCAMP3 negatively regulates epidermal growth factor receptor degradation and promotes receptor recycling |
| GO:0015031 protein transport | IEA GO_REF:0000120 | ACCEPT | Summary: This IEA annotation inferred from InterPro domain and UniProtKB keywords is accurate but very general. SCAMP3 is indeed involved in protein transport through its role in vesicular trafficking, EGFR sorting, and MVB pathway regulation. Reason: The annotation is correct but represents a high-level term. More specific annotations like post-Golgi vesicle-mediated transport and endosomal transport better capture SCAMP3 function. However, this IEA annotation is not incorrect and provides appropriate coverage. Supporting Evidence: PMID:9378760 The SCAMPs may largely function at the same sites during vesicular transport rather than in separate post-Golgi recycling pathways |
| GO:0016020 membrane | IEA GO_REF:0000120 | ACCEPT | Summary: This IEA annotation is correct. SCAMP3 is a tetraspanning integral membrane protein with four transmembrane helices (residues 171-191, 197-217, 247-267, 277-297) according to UniProt annotation. Reason: The annotation is accurate. SCAMP3 is clearly a membrane protein with four transmembrane domains. More specific membrane localizations (trans-Golgi network membrane, recycling endosome membrane) are captured in other annotations. Supporting Evidence: PMID:9378760 SCAMPs are highly related products of distinct genes |
| GO:0031625 ubiquitin protein ligase binding | IPI PMID:23418353 The E3 ubiquitin ligases RNF126 and Rabring7 regulate endoso... | ACCEPT | Summary: This IPI annotation is well-supported. SCAMP3 contains a PPAY motif that binds WW-domain E3 ubiquitin ligases including NEDD4 and NEDD4L. The UniProt entry confirms interactions with NEDD4, NEDD4L, TSG101, and RNF126. The cited paper (PMID:23418353) demonstrates SCAMP3 interaction with RNF126 E3 ubiquitin ligase. Reason: The annotation accurately reflects SCAMP3's molecular function. The PPAY motif mediates binding to WW-domain containing E3 ubiquitin ligases. This interaction is functionally important for SCAMP3's role in endosomal sorting and receptor trafficking. Supporting Evidence: PMID:23418353 We also show that the depletion of Rabring7 attenuates the degradation of MET and that both RNF126 and Rabring7 regulate the sorting of CXCR4 from an early endocytic compartment PMID:19158374 SCAMP3 is multimonoubiquitylated and is able to associate with Nedd4 HECT ubiquitin ligases and the ESCRT-I subunit Tsg101 via its PY and PSAP motifs, respectively |
| GO:0070062 extracellular exosome | HDA PMID:20458337 MHC class II-associated proteins in B-cell exosomes and pote... | ACCEPT | Summary: This HDA annotation from high-throughput proteomics is strongly supported by recent functional studies. The 2023 Science Advances paper demonstrated that SCAMP3 is essential for WW domain-activated extracellular vesicle (WAEV) budding. SCAMP3 knockout nearly abolishes EV production measured by NanoSight, and only wild-type (not PPAY mutant) SCAMP3 can rescue this phenotype. Reason: The annotation is experimentally validated by multiple studies. SCAMP3 was identified in B-cell exosome proteomics and later shown to be functionally required for extracellular vesicle biogenesis through its PPAY-WW domain interactions. Supporting Evidence: PMID:20458337 We first analyzed the total proteome of highly purified B cell-derived exosomes using sensitive and accurate mass spectrometry (MS), and identified 539 proteins |
| GO:0006892 post-Golgi vesicle-mediated transport | TAS PMID:9378760 Three mammalian SCAMPs (secretory carrier membrane proteins)... | ACCEPT | Summary: This TAS annotation from the original SCAMP characterization paper is well-supported. The 1997 paper established that SCAMPs function in post-Golgi recycling pathways, and subsequent studies have confirmed SCAMP3's role in trafficking from Golgi through endosomal compartments. Reason: The annotation accurately reflects a core function of SCAMP3. The protein functions in post-Golgi vesicular transport, mediating carrier function between Golgi, endosomal compartments, and plasma membrane. Supporting Evidence: PMID:9378760 These findings suggest that the SCAMPs may largely function at the same sites during vesicular transport rather than in separate post-Golgi recycling pathways |
| GO:0070676 intralumenal vesicle formation | IDA file:human/SCAMP3/SCAMP3-deep-research-falcon.md | NEW | Summary: NEW annotation supported by direct experimental evidence. The 2012 Traffic paper demonstrated that SCAMP3 knockdown significantly reduces intralumenal vesicle (ILV) formation in multivesicular bodies (stereological analysis, p<0.0001). SCAMP3 is required for cargo sorting into ILVs and MVB biogenesis. Reason: Strong experimental evidence supports this annotation. SCAMP3 is required for ILV formation through its interaction with ESCRT machinery via the PSAP-TSG101 and PPAY-WW domain interactions. Supporting Evidence: PMID:19158374 SCAMP3, its modification with ubiquitin, and its interactions with ESCRTs coordinately regulate endosomal pathways and affect the efficiency of receptor down-regulation |
| GO:0005770 late endosome | IDA file:human/SCAMP3/SCAMP3-deep-research-falcon.md | NEW | Summary: NEW annotation supported by experimental evidence. The 2012 Traffic paper demonstrated that approximately 30% of late endosomes contain SCAMP3 based on quantitative image analysis. SCAMP3 localizes to a subset of late endosomes/MVBs. Reason: Direct evidence from immunofluorescence and EM studies shows SCAMP3 localization to late endosomal compartments where it functions in cargo sorting and ILV formation. Supporting Evidence: PMID:19158374 SCAMP3 depletion appeared to sustain the incidence of EGFR-containing MVBs detected by immunoelectron microscopy |
| GO:0001881 receptor recycling | IMP PMID:19158374 SCAMP3 negatively regulates epidermal growth factor receptor... | NEW | Summary: NEW annotation supported by experimental evidence. The 2009 Mol Biol Cell paper demonstrated that SCAMP3 promotes EGFR recycling. SCAMP3 overexpression enhanced EGFR recycling while knockdown accelerated degradation and impaired recycling. Reason: Strong experimental evidence from mutant analysis shows SCAMP3 functions in promoting receptor recycling, balancing recycling vs degradation fate. Supporting Evidence: PMID:19158374 Depletion of SCAMP3 in HeLa cells by inhibitory RNA accelerated degradation of EGFR and EGF while inhibiting recycling |
| GO:0032585 multivesicular body membrane | IDA file:human/SCAMP3/SCAMP3-deep-research-falcon.md | NEW | Summary: NEW annotation supported by experimental evidence. SCAMP3 localizes to and functions at MVB membranes, where it is required for ILV formation and cargo sorting. Reason: SCAMP3 localization to MVB membranes is demonstrated through its role in MVB biogenesis and ESCRT-dependent sorting. Supporting Evidence: PMID:19158374 SCAMP3 depletion appeared to sustain the incidence of EGFR-containing MVBs detected by immunoelectron microscopy |
Loading supporting content…
Download this section (compressed HTML)Q: How does SCAMP3 ubiquitination state regulate the balance between receptor recycling and degradation?
Q: What is the precise mechanism by which SCAMP3 coordinates with ESCRT-0 (HRS) in addition to ESCRT-I (TSG101)?
Experiment: Structure-function analysis of SCAMP3 using site-directed mutagenesis of the ubiquitination sites to determine how ubiquitination state affects recycling vs degradation outcomes. This could resolve the apparent discrepancy between SCAMP3's role in promoting recycling versus driving lysosomal degradation.
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)