BBS-1 is a core component of the BBSome complex in C. elegans, an octameric coat complex essential for cilium biogenesis and intraflagellar transport (IFT). BBS-1 is required for proper BBSome assembly and its ciliary localization. The protein functions in assembling IFT particles at the ciliary base and regulating IFT turnaround at the ciliary tip, enabling the recycling of IFT-B components for retrograde transport. BBS-1 localizes to ciliated sensory neurons, including amphid and labial neurons in the head and phasmid neurons in the tail. Loss of BBS-1 function results in defective cilia structure, compromised IFT, and accumulation of IFT-B at the ciliary tip.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0034464 BBSome | IBA GO_REF:0000033 | ACCEPT | Summary: BBS-1 is a well-established component of the BBSome complex in C. elegans. The BBSome contains bbs-1, bbs-2, bbs-4, bbs-5, osm-12, bbs-8/ttc-8, and bbs-9. BiFC analyses in PMID:22922713 directly demonstrate that BBS-1 associates with BBS-7 and BBS-9 in the same complex. Reason: This is a core function of BBS-1 strongly supported by experimental evidence. UniProt states "Part of BBSome complex" and PMID:22922713 demonstrated BBSome complex formation using BiFC assays showing BBS-1-BBS-7 and BBS-1-BBS-9 fluorescence complementation. Supporting Evidence: PMID:22922713 In wild-type animals, fluorescence complementation can be observed in BBS-1–BBS-7 and BBS-1–BBS-9 pair, indicative of the coexistence of these three BBS proteins in the same complex file:worm/bbs-1/bbs-1-deep-research-falcon.md model: Edison Scientific Literature |
| GO:0005813 centrosome | IBA GO_REF:0000033 | MODIFY | Summary: The centrosome annotation is inferred from mammalian BBS1 localization. While BBS-1 localizes to the ciliary base (basal body) in C. elegans, which derives from the centriole, the direct evidence is for basal body localization rather than centrosome per se. Reason: In C. elegans, BBS-1 localizes predominantly to the ciliary base/basal body rather than a classical centrosome structure. The more accurate term would be ciliary basal body (GO:0036064), which is already annotated with direct evidence. The centrosome annotation is technically acceptable as basal bodies derive from centrioles, but is less precise for this organism. Proposed replacements: ciliary basal body |
| GO:0061512 protein localization to cilium | IBA GO_REF:0000033 | ACCEPT | Summary: The BBSome functions as a coat complex required for sorting membrane proteins to primary cilia. This is a core function conserved across species including C. elegans. Reason: This represents a core function of the BBSome. PMID:22922713 demonstrates that BBS-1 is required for proper localization of IFT components to cilia, and the BBSome is thought to function as a coat complex for targeting proteins to cilia. Supporting Evidence: PMID:22922713 The BBSome also shares the common structural features with COPI, COPII, and clathrin coats, and can directly recognize IFT cargos |
| GO:1905515 non-motile cilium assembly | IBA GO_REF:0000033 | ACCEPT | Summary: C. elegans sensory cilia are non-motile (primary-type) cilia. BBS-1 is required for cilia biogenesis in these neurons. Reason: BBS-1 is required for cilia biogenesis in C. elegans, and worm sensory cilia are non-motile. PMID:15231740 demonstrates BBS proteins are required for cilia biogenesis and maintenance, and PMID:22922713 shows BBS-1 is essential for IFT assembly required for ciliogenesis. Supporting Evidence: PMID:15231740 mutations in the Caenorhabditis elegans bbs-7 and bbs-8 genes cause structural and functional defects in cilia PMID:22922713 Phylogenetically conserved IFT machinery mediates the bidirectional movement of IFT cargos that are required for the biogenesis, maintenance, and signaling of cilia |
| GO:0005113 patched binding | IBA GO_REF:0000033 | REMOVE | Summary: This annotation is transferred from mammalian BBS1 which binds Patched in the context of Hedgehog signaling. However, C. elegans lacks canonical Hedgehog signaling - the worm genome encodes Patched homologs (PTC-1, PTC-3) but these function independently of Smoothened, which is absent in C. elegans. Reason: C. elegans lacks Smoothened and canonical Hedgehog signaling. While C. elegans has Patched homologs (PTC-1, PTC-3), these have diverged functionally and do not participate in Hedgehog signaling as in mammals. There is no evidence that C. elegans BBS-1 binds Patched proteins. The IBA transfer from mammalian data is inappropriate for this organism. |
| GO:0005119 smoothened binding | IBA GO_REF:0000033 | REMOVE | Summary: This annotation is transferred from mammalian BBS1, where the BBSome binds Smoothened as a ciliary cargo. However, C. elegans completely lacks Smoothened - this gene is absent from the worm genome. Reason: C. elegans lacks Smoothened entirely - the gene is absent from the genome. This is a well-documented evolutionary divergence of the Hedgehog signaling pathway in nematodes. The IBA annotation cannot be valid for an organism that lacks the binding partner. |
| GO:0005930 axoneme | IBA GO_REF:0000033 | ACCEPT | Summary: BBS-1 localizes to the ciliary axoneme where it participates in IFT transport along the axonemal microtubules. Reason: Direct evidence from PMID:15231740 confirms axoneme localization, and PMID:22922713 shows BBS-1 moves along the axoneme with IFT particles. This IBA is consistent with experimental data in C. elegans. Supporting Evidence: PMID:15231740 C. elegans BBS proteins localize predominantly at the base of cilia, and like proteins involved in intraflagellar transport (IFT), a process necessary for cilia biogenesis and maintenance, move bidirectionally along the ciliary axoneme |
| GO:0005929 cilium | IEA GO_REF:0000044 | ACCEPT | Summary: BBS-1 localizes to cilia as confirmed by direct experimental evidence. Reason: This IEA annotation is correct and supported by experimental data. BBS-1 is expressed exclusively in ciliated neurons and localizes to cilia (PMID:15231740). Supporting Evidence: PMID:15231740 C. elegans BBS proteins localize predominantly at the base of cilia, and like proteins involved in intraflagellar transport (IFT), a process necessary for cilia biogenesis and maintenance, move bidirectionally along the ciliary axoneme |
| GO:0005930 axoneme | IEA GO_REF:0000044 | ACCEPT | Summary: This IEA annotation for axoneme localization is supported by experimental evidence. Reason: This annotation is consistent with direct experimental evidence showing axoneme localization (PMID:15231740, PMID:22922713). The IEA provides redundant support. |
| GO:0015031 protein transport | IEA GO_REF:0000043 | ACCEPT | Summary: BBS-1/BBSome functions in protein transport to and within cilia as part of IFT. Reason: This is a general term that captures the BBSome role in transporting proteins to cilia. While more specific terms exist (protein localization to cilium), this annotation is not wrong. The BBSome transports cargo proteins and regulates IFT assembly. Supporting Evidence: PMID:22922713 The BBSome also shares the common structural features with COPI, COPII, and clathrin coats, and can directly recognize IFT cargos |
| GO:0030030 cell projection organization | IEA GO_REF:0000043 | ACCEPT | Summary: Cilia are a type of cell projection, and BBS-1 is involved in cilium organization. Reason: This is a broad parent term that encompasses cilium organization. While more specific terms are preferred, this annotation captures the involvement of BBS-1 in organizing ciliary cell projections. |
| GO:0034464 BBSome | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro-based annotation for BBSome component. Redundant with IBA annotation. Reason: Correct annotation supported by domain architecture and experimental evidence. InterPro domain IPR028784 (BBS1) correctly identifies this as a BBSome component. |
| GO:1905515 non-motile cilium assembly | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro-based annotation for cilium assembly role. Redundant with IBA annotation. Reason: Correct annotation consistent with experimental evidence showing BBS-1 is required for cilia biogenesis. |
| GO:0005929 cilium | NAS PMID:22922713 The BBSome controls IFT assembly and turnaround in cilia. | ACCEPT | Summary: ComplexPortal annotation for cilium localization based on PMID:22922713. Reason: PMID:22922713 directly demonstrates BBS-1 localization to cilia using GFP-tagged constructs and shows BBS-1 undergoes IFT transport within cilia. Supporting Evidence: PMID:22922713 Compared to the strong ciliary targeting of wild-type BBS-1 protein, GFP-tagged BBS-1G207D only accumulated around the ciliary base |
| GO:0060271 cilium assembly | NAS PMID:22922713 The BBSome controls IFT assembly and turnaround in cilia. | ACCEPT | Summary: ComplexPortal annotation for cilium assembly based on BBSome function. Reason: BBS-1 is required for proper ciliogenesis. The BBSome regulates IFT assembly which is essential for cilium formation. Supporting Evidence: PMID:22922713 Phylogenetically conserved IFT machinery mediates the bidirectional movement of IFT cargos that are required for the biogenesis, maintenance, and signaling of cilia |
| GO:0003674 molecular_function | ND GO_REF:0000015 | REMOVE | Summary: ND (No Data) annotation indicating no specific molecular function was assigned at time of curation. Reason: This ND annotation is outdated. The gene now has IBA molecular function annotations (though the patched/smoothened binding ones are not valid for C. elegans). A more appropriate molecular function might be protein-containing complex binding or structural molecule activity given the BBSome coat function. |
| GO:0035721 intraciliary retrograde transport | IMP PMID:22922713 The BBSome controls IFT assembly and turnaround in cilia. | ACCEPT | Summary: PMID:22922713 demonstrates that bbs-1 mutants have defective retrograde IFT, specifically the turnaround of IFT particles at the ciliary tip. Reason: This is a core function experimentally demonstrated in C. elegans. The bbs-1(jhu598) mutant shows defective IFT-B recycling at the ciliary tip, with IFT-B components accumulating there due to failed reassembly into retrograde transport machinery. Supporting Evidence: PMID:22922713 we identified two hypomorphic mutations in dyf-2 and bbs-1 as the only mutants showing normal anterograde IFT transport but defective IFT turnaround at the ciliary tip PMID:22922713 the defects of bbs-1(jhu598) animals completely phenocopy the observations in dyf-2(jhu616): IFT-A and IFT-B associate in anterograde but not retrograde IFT and IFT-B accumulates at the ciliary tip |
| GO:0036064 ciliary basal body | IDA PMID:22922713 The BBSome controls IFT assembly and turnaround in cilia. | ACCEPT | Summary: BBS-1 localizes to the ciliary basal body region as shown by fluorescence microscopy. Reason: Direct localization to ciliary base/basal body is well documented. In wild-type, BBS-1 localizes to ciliary base before moving along axoneme; in bbs-1(jhu598) mutants, BBSome proteins accumulate at ciliary base. Supporting Evidence: PMID:22922713 all BBS proteins examined strongly accumulated around the ciliary base. Some of them (BBS-1, BBS-4) totally lost the ciliary localization PMID:15231740 C. elegans BBS proteins localize predominantly at the base of cilia |
| GO:0061512 protein localization to cilium | IMP PMID:22922713 The BBSome controls IFT assembly and turnaround in cilia. | ACCEPT | Summary: BBS-1 mutants show defects in localizing proteins (including IFT components) to and within cilia. Reason: This is a key function demonstrated by mutant phenotypes. BBS-1 is required for proper localization of BBSome and cargo proteins to cilia. Supporting Evidence: PMID:22922713 the BBSome is required for assembling IFT particles at both ciliary base and tip |
| GO:0043005 neuron projection | IDA PMID:14520415 Basal body dysfunction is a likely cause of pleiotropic Bard... | KEEP AS NON CORE | Summary: BBS-1 is expressed in ciliated sensory neurons in C. elegans, which are projecting neurons. Reason: While technically correct that BBS-1 localizes to neuronal projections (specifically ciliated dendrites of sensory neurons), the more informative annotation is cilium. This annotation reflects the tissue expression pattern rather than core function. Supporting Evidence: PMID:14520415 all available Caenorhabditis elegans BBS homologues are expressed exclusively in ciliated neurons |
| GO:1905515 non-motile cilium assembly | IEP PMID:14520415 Basal body dysfunction is a likely cause of pleiotropic Bard... | ACCEPT | Summary: Expression pattern evidence showing bbs-1 is expressed in ciliated neurons during cilium assembly. Reason: The expression pattern of bbs-1 in ciliated neurons is consistent with a role in cilium assembly. This IEP complements stronger IMP and IBA evidence for this function. Supporting Evidence: PMID:14520415 all available Caenorhabditis elegans BBS homologues are expressed exclusively in ciliated neurons, and contain regulatory elements for RFX, a transcription factor that modulates the expression of genes associated with ciliogenesis and intraflagellar transport |
| GO:0005930 axoneme | IDA PMID:15231740 Loss of C. elegans BBS-7 and BBS-8 protein function results ... | ACCEPT | Summary: Direct visualization of BBS proteins moving along the ciliary axoneme in C. elegans. Reason: This is well-supported experimental evidence. BBS proteins, including BBS-1, localize to and move along the axoneme as part of IFT. Supporting Evidence: PMID:15231740 C. elegans BBS proteins localize predominantly at the base of cilia, and like proteins involved in intraflagellar transport (IFT), a process necessary for cilia biogenesis and maintenance, move bidirectionally along the ciliary axoneme |
| GO:0005198 structural molecule activity | NAS | NEW | Summary: Added to align core_functions with existing annotations. Reason: Core function term not present in existing_annotations. |
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Download this section (compressed HTML)Q: What specific cargo proteins does the C. elegans BBSome transport?
Q: Does BBS-1 have functions outside of cilia as suggested for the mammalian BBSome?
Q: What is the precise molecular function of BBS-1 within the BBSome complex?
Experiment: Identify direct cargo proteins of the C. elegans BBSome using proteomics
Hypothesis: The C. elegans BBSome transports specific membrane receptors and signaling molecules to cilia
Experiment: Test for cilia-independent functions of BBS-1 using daf-19 mutant background
Hypothesis: BBS-1 may have additional functions outside of cilia as reported for mammalian BBSome
Experiment: Determine if BBS-1 has specific binding partners among C. elegans membrane proteins
Hypothesis: BBS-1 directly binds to specific cargo proteins for ciliary transport
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