SPCC4F11.04c (SPCC4F11.04c; imt2; UniProt Q9UT67) encodes one of three redundant Golgi inositol phosphoceramide mannosyltransferases (imt1-imt3; SUR1/CSH1 homologues) that mannosylate IPC to MIPC, the terminal and most abundant complex sphingolipid of fission yeast. Single imt mutants are viable, but the triple disruptant lacks MIPC and accumulates IPC. It then shows defects in cell and vacuole morphology, ergosterol distribution and endocytic sorting of a plasma-membrane amino acid transporter.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000030 mannosyltransferase activity | IBA GO_REF:0000033 | MODIFY | Summary: PAINT inference of generic mannosyltransferase activity; the specific IPC mannosyltransferase activity is the role. Reason: Changed from KEEP_AS_NON_CORE because the term is correct but general, and GO has the specific descendant GO:0103064 (inositol phosphorylceramide mannosyltransferase activity, is_a GO:0000030). In S. pombe, the triple imt1 imt2 imt3 disruptant lacks MIPC and accumulates IPC (PMID:20388730), and UniProt curates the IPC mannosylation from that paper (ECO:0000269). The evidence is genetic and shared by three redundant paralogs, not an enzyme assay of Imt2 alone. Family membership (PANTHER PTHR32385, mannosyl phosphorylinositol ceramide synthase; S. cerevisiae SUR1/CSH1 homologue) agrees. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN001285482 SUPPORTS TRANSFER The mannosyltransferase activity transfers correctly; the term is only less specific than the IPC mannosyltransferase activity (GO:0103064) supported for the imt1-3 family. Proposed replacements: inositol phosphorylceramide mannosyltransferase activity Supporting Evidence: file:SCHPO/SPCC4F11.04c/SPCC4F11.04c-uniprot.txt Catalyzes the addition of mannosyl to phosphorylinositol ceramide (IPC). PMID:20388730 MIPC was not detected and IPC levels were increased in the triple disruptant, indicating that the three SUR1 homologues are involved in the synthesis of MIPC. file:SCHPO/SPCC4F11.04c/SPCC4F11.04c-uniprot.txt PANTHER; PTHR32385; MANNOSYL PHOSPHORYLINOSITOL CERAMIDE SYNTHASE; 1. |
| GO:0005794 Golgi apparatus | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | ACCEPT | Summary: ORFeome screen: Golgi. Supporting Evidence: PMID:16823372 we determined the localization of 4,431 proteins |
| GO:0005794 Golgi apparatus | IEA GO_REF:0000044 | ACCEPT | Summary: Mapping. Reason: Root organelle term. GFP-Imt2 (with Imt1 and Imt3) localises to Golgi membranes (PMID:20388730), and the UniProt SUBCELLULAR LOCATION comment places it in Golgi cis- and trans-network membranes. The organelle claim holds. Supporting Evidence: PMID:20388730 GFP-tagged Imt1p, Imt2p and Imt3p localized to Golgi apparatus membranes. file:SCHPO/SPCC4F11.04c/SPCC4F11.04c-uniprot.txt SUBCELLULAR LOCATION: Golgi apparatus, cis-Golgi network membrane |
| GO:0005802 trans-Golgi network | IDA PMID:20388730 Mannosylinositol phosphorylceramide is a major sphingolipid ... | ACCEPT | Summary: GFP-Imt proteins localise to Golgi membranes. Supporting Evidence: PMID:20388730 GFP-tagged Imt1p, Imt2p and Imt3p localized to Golgi apparatus membranes. |
| GO:0032588 trans-Golgi network membrane | IDA PMID:20388730 Mannosylinositol phosphorylceramide is a major sphingolipid ... | ACCEPT | Summary: Golgi membrane localisation of GFP-Imt. Supporting Evidence: PMID:20388730 GFP-tagged Imt1p, Imt2p and Imt3p localized to Golgi apparatus membranes. |
| GO:0032588 trans-Golgi network membrane | IEA GO_REF:0000117 | ACCEPT | Summary: Mapping. Reason: The cached abstract of PMID:20388730 supports Golgi membrane localisation of GFP-Imt2 but does not resolve cis versus trans; the UniProt curated SUBCELLULAR LOCATION comment (no evidence tag) lists the trans-Golgi network membrane, and PomBase curators made an IDA annotation to this term from the full text. Kept consistent with that IDA row. Supporting Evidence: PMID:20388730 GFP-tagged Imt1p, Imt2p and Imt3p localized to Golgi apparatus membranes. file:SCHPO/SPCC4F11.04c/SPCC4F11.04c-uniprot.txt Golgi apparatus, trans-Golgi network |
| GO:0033106 cis-Golgi network membrane | IDA PMID:20388730 Mannosylinositol phosphorylceramide is a major sphingolipid ... | ACCEPT | Summary: Golgi membrane localisation of GFP-Imt. Supporting Evidence: PMID:20388730 GFP-tagged Imt1p, Imt2p and Imt3p localized to Golgi apparatus membranes. |
| GO:0033106 cis-Golgi network membrane | IEA GO_REF:0000117 | ACCEPT | Summary: Mapping. Reason: The cached abstract of PMID:20388730 supports Golgi membrane localisation of GFP-Imt2 but does not resolve cis versus trans; the UniProt curated SUBCELLULAR LOCATION comment (no evidence tag) lists the cis-Golgi network membrane, and PomBase curators made an IDA annotation to this term from the full text. Kept consistent with that IDA row. Supporting Evidence: PMID:20388730 GFP-tagged Imt1p, Imt2p and Imt3p localized to Golgi apparatus membranes. file:SCHPO/SPCC4F11.04c/SPCC4F11.04c-uniprot.txt SUBCELLULAR LOCATION: Golgi apparatus, cis-Golgi network membrane |
| GO:0051999 mannosyl-inositol phosphorylceramide biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT inference. Reason: The imt1 imt2 imt3 triple disruptant lacks MIPC and accumulates IPC (PMID:20388730), and UniProt records from that study (ECO:0000269|PubMed:20388730) that the protein, with imt1 and imt3, is required for MIPC synthesis and catalyses mannosyl addition to IPC. The genetic evidence is for the redundant trio; catalysis by Imt2 itself is inferred from SUR1/CSH1 homology. Supporting Evidence: PMID:20388730 MIPC was not detected and IPC levels were increased in the triple disruptant, indicating that the three SUR1 homologues are involved in the synthesis of MIPC. file:SCHPO/SPCC4F11.04c/SPCC4F11.04c-uniprot.txt Catalyzes the addition of mannosyl |
| GO:0051999 mannosyl-inositol phosphorylceramide biosynthetic process | IEA GO_REF:0000117 | ACCEPT | Summary: Mapping. Reason: The imt1 imt2 imt3 triple disruptant lacks MIPC and accumulates IPC (PMID:20388730), and UniProt records from that study (ECO:0000269|PubMed:20388730) that the protein, with imt1 and imt3, is required for MIPC synthesis and catalyses mannosyl addition to IPC. The genetic evidence is for the redundant trio; catalysis by Imt2 itself is inferred from SUR1/CSH1 homology. Supporting Evidence: PMID:20388730 MIPC was not detected and IPC levels were increased in the triple disruptant, indicating that the three SUR1 homologues are involved in the synthesis of MIPC. file:SCHPO/SPCC4F11.04c/SPCC4F11.04c-uniprot.txt Catalyzes the addition of mannosyl |
| GO:0051999 mannosyl-inositol phosphorylceramide biosynthetic process | IGI PMID:20388730 Mannosylinositol phosphorylceramide is a major sphingolipid ... | ACCEPT | Summary: The imt1 imt2 imt3 triple disruptant lacks MIPC and accumulates IPC. Supporting Evidence: PMID:20388730 MIPC was not detected and IPC levels were increased in the triple disruptant, indicating that the three SUR1 homologues are involved in the synthesis of MIPC. |
| GO:0051999 mannosyl-inositol phosphorylceramide biosynthetic process | IMP PMID:20388730 Mannosylinositol phosphorylceramide is a major sphingolipid ... | ACCEPT | Summary: As above. Supporting Evidence: PMID:20388730 MIPC was not detected and IPC levels were increased in the triple disruptant, indicating that the three SUR1 homologues are involved in the synthesis of MIPC. |
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