dyf-5 encodes a ciliary serine/threonine protein kinase of the CMGC-group, MAK/RCK (ICK/CILK1-related) subfamily. It is expressed in ciliated sensory neurons of the head (amphid and labial) and tail (phasmid), where its protein is enriched at the dendrite-cilium transition zone and distributed from the tip of the ciliary middle segment through the distal segment to the ciliary tip. DYF-5 is a master regulator of sensory-cilium length, morphology and intraflagellar transport (IFT). In worm cilia, anterograde IFT is driven by two kinesin-2 motors (heterotrimeric kinesin-II, KLP-11/KLP-20/KAP-1, in the middle segment and homodimeric OSM-3 in the distal segment); DYF-5 coordinates their handover, promoting undocking of kinesin-II from IFT trains at the end of the middle segment and docking of OSM-3 onto IFT particles. Two direct in-vitro substrates are established: the IFT-B subunit IFT-74, whose N-terminal tubulin-binding module DYF-5 phosphorylates at multiple sites to lower IFT-74/81 tubulin affinity and release tubulin at the ciliary tip, and the OSM-3 kinesin C-terminal region. Loss of dyf-5 produces abnormally long, misaligned cilia with accumulation of IFT components, whereas altered IFT-74 phosphorylation lengthens or shortens cilia, consistent with a balance-point model of tubulin delivery and axoneme length control. The kinase acts with the substrate consensus motif (R)PX[S/T].
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004674 protein serine/threonine kinase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic (IBA) inference of the core molecular function. DYF-5 is a bona fide protein serine/threonine kinase and this is directly demonstrated experimentally (see the IDA annotations from PMID:35969738 and PMID:38806659), so this term represents the core function of the gene. Supporting Evidence: PMID:35969738 the ciliary kinase DYF-5/MAK phosphorylates multiple sites within the tubulin-binding module of IFT-74, reducing the tubulin-binding affinity of IFT-74/81 approximately sixfold |
| GO:0005634 nucleus | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: Nuclear localization is inferred phylogenetically from the broader MAPK/CMGC family (many canonical MAPKs are nuclear), but there is no experimental evidence that C. elegans DYF-5 acts in the nucleus. The experimentally established sites of action are the cilium, dendrite, axon and neuronal cell body; a ciliary IFT-regulating kinase in the nucleus is not supported. Treated as an over-propagated family inference. Propagation Review Root cause: PROPAGATION BAD Failure modes: COMPARTMENT OR COMPLEX MISMATCH FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN000622075 · MAPK/CMGC family node SUPPORTS SOURCE BUT NOT TARGET Nuclear localization is a property of canonical MAPKs in the family tree, not of the divergent ciliary MAK/RCK member DYF-5, which localizes to the cilium, dendrite, axon and cell body with no nuclear evidence. |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Broadly correct but non-informative. DYF-5 is present in the neuronal cell body/cytoplasm, but its characterized site of action is the cilium. Retained as a general, non-core location. |
| GO:0035556 intracellular signal transduction | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: Generic biological-process term propagated from the MAPK/CMGC family. DYF-5's actual, well-characterized role is regulation of intraflagellar transport and cilium length, not canonical intracellular signal transduction. The specific ciliary/IFT process terms capture the biology far better. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: FUNCTIONAL DIVERGENCE GRANULARITY MISMATCH Sources checked: PANTHER:PTN000622075 · MAPK/CMGC family node SUPPORTS SOURCE BUT NOT TARGET The signal-transduction role is a family-level generalization; the MAK/RCK member DYF-5 acts as a ciliary IFT/length regulator, so the specific IFT and cilium-assembly process terms are the informative annotations. |
| GO:0005929 cilium | IBA GO_REF:0000033 | ACCEPT | Summary: Core cellular location. DYF-5 is a ciliary kinase; it acts within sensory cilia along the axoneme and is enriched at the dendrite-cilium transition zone. Supporting Evidence: PMID:35969738 the ciliary kinase DYF-5/MAK |
| GO:0060271 cilium assembly | IBA GO_REF:0000033 | ACCEPT | Summary: Core biological process. DYF-5 is required for normal ciliogenesis; loss of function yields abnormally long, misshapen sensory cilia. Supported both by phylogeny and by direct C. elegans experiments. Supporting Evidence: PMID:35969738 Ablation or constitutive activation of IFT-74 phosphorylation abnormally elongates or shortens sensory cilia in Caenorhabditis elegans neurons |
| GO:0042073 intraciliary transport | IBA GO_REF:0000033 | ACCEPT | Summary: Core biological process. DYF-5 regulates IFT; in dyf-5 mutants IFT proteins accumulate abnormally in cilia and IFT motor behavior is disrupted. Supporting Evidence: PMID:17420466 six IFT proteins accumulate in the cilia of dyf-5(lf) mutants |
| GO:0000165 MAPK cascade | IEA GO_REF:0000108 | MARK AS OVER ANNOTATED | Summary: Electronic inference (GO_REF:0000108) triggered by the MAP-kinase-activity term. DYF-5 belongs to the MAK/RCK (ICK/CILK1) subfamily; despite the historical "MAP kinase" name it is not a component of a canonical three-tiered MAP3K-MAP2K-MAPK signaling cascade, and no such cascade role is documented for DYF-5. Over-annotation driven by nomenclature. |
| GO:0004672 protein kinase activity | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Correct but a general parent of the specific, experimentally supported term protein serine/threonine kinase activity (GO:0004674). Retained as non-core. |
| GO:0004674 protein serine/threonine kinase activity | IEA GO_REF:0000003 | ACCEPT | Summary: EC-based electronic inference of the core molecular function; consistent with the experimental IDA evidence. |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Standard active-site feature of a protein kinase (ATP-binding loop residues 17-25 and Lys40). Correct but a generic molecular-detail term; non-core. |
| GO:0005929 cilium | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt SubCell-derived ciliary localization; consistent with experimental data. Duplicates the IBA cilium annotation; correct core location. |
| GO:0030424 axon | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: SubCell-derived; consistent with the experimental IDA axon annotation (PMID:17420466). Real but non-core neuronal localization. |
| GO:0030425 dendrite | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: SubCell-derived; consistent with the experimental IDA dendrite annotation (PMID:17420466). Real but non-core neuronal localization. |
| GO:0043204 perikaryon | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: SubCell-derived; consistent with the experimental (EXP/IDA) perikaryon annotation from PMID:17420466. Real but non-core. |
| GO:0106310 protein serine kinase activity | IEA GO_REF:0000116 | KEEP AS NON CORE | Summary: RHEA-derived; a valid subtype of the kinase activity. DYF-5 phosphorylates both Ser and Thr residues, so protein serine/threonine kinase activity (GO:0004674) is the most complete descriptor; retained as non-core. |
| GO:0004674 protein serine/threonine kinase activity | IDA PMID:38806659 Neurons dispose of hyperactive kinesin into glial cells for ... | ACCEPT | Summary: Direct experimental demonstration of kinase activity. In this study dyf-5 kinase-domain mutations were recovered as intergenic suppressors of a hyperactive OSM-3, and in-vitro protein kinase assays show DYF-5 directly phosphorylates the C-terminal fragment of the OSM-3 kinesin (residues 444-699), identifying OSM-3 as a direct substrate and supporting the core molecular function. Supporting Evidence: PMID:38806659 mutations inhibiting the ciliary kinase DYF-5, both of which restored normal cilia in OSM-3CA-expressing animals |
| GO:0043204 perikaryon | EXP PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | KEEP AS NON CORE | Summary: Experimentally observed localization to the neuronal cell body (perikaryon). Real but non-core relative to the ciliary site of action. |
| GO:0106310 protein serine kinase activity | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Sequence-similarity transfer of a valid kinase-activity subtype. Consistent with the demonstrated Ser/Thr kinase activity; non-core relative to GO:0004674. |
| GO:0004674 protein serine/threonine kinase activity | IDA PMID:35969738 DYF-5/MAK-dependent phosphorylation promotes ciliary tubulin... | ACCEPT | Summary: Direct experimental demonstration of kinase activity. DYF-5 phosphorylates the tubulin-binding module of IFT-74 at multiple Ser/Thr sites in vitro, reducing IFT-74/81 tubulin affinity ~sixfold. Establishes the core molecular function and a direct substrate (IFT-74). Supporting Evidence: PMID:35969738 the ciliary kinase DYF-5/MAK phosphorylates multiple sites within the tubulin-binding module of IFT-74, reducing the tubulin-binding affinity of IFT-74/81 approximately sixfold |
| GO:0035720 intraciliary anterograde transport | IMP PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | ACCEPT | Summary: Core biological process. Mutant-phenotype analysis shows DYF-5 is required for correct anterograde IFT: it restricts kinesin-II to the middle segment and is needed for OSM-3 to remain attached to and move IFT particles at normal speed. Supporting Evidence: PMID:17420466 dyf-5 is required to restrict kinesin II to the cilia middle segments |
| GO:0035720 intraciliary anterograde transport | IGI PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | ACCEPT | Summary: Genetic-interaction evidence (with osm-3/kinesin-II components) for the same core anterograde-IFT regulatory role. In dyf-5 mutants OSM-3 detaches from IFT particles and slows. Supporting Evidence: PMID:17420466 OSM-3 moves at a reduced speed and is not attached to IFT particles |
| GO:1902856 negative regulation of non-motile cilium assembly | IGI PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | ACCEPT | Summary: Core regulatory role. Loss of dyf-5 elongates sensory cilia, indicating that DYF-5 normally restrains cilium elongation/assembly. Mechanistically consistent with DYF-5 driving ciliary-tip tubulin unloading. Supporting Evidence: PMID:17420466 the cilia of dyf-5 loss-of-function (lf) animals are elongated and are not properly aligned into the amphid channel |
| GO:1902857 positive regulation of non-motile cilium assembly | IGI PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | KEEP AS NON CORE | Summary: Context-dependent genetic-interaction annotation from the same study, made against a different set of partner genes. It reflects the composite genetic requirement of dyf-5 for normal ciliogenesis (e.g. in sensitized kinesin backgrounds cilia fail to form), opposite in sign to the negative-regulation annotation. Retained as non-core; the dominant, mechanistically supported role is restraint of cilium elongation (GO:1902856). |
| GO:0097730 non-motile cilium | IDA PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | ACCEPT | Summary: Precise core location: C. elegans sensory cilia are non-motile, and DYF-5 localizes to and acts within them. More specific and preferable to the general cilium term. Supporting Evidence: PMID:35969738 the ciliary kinase DYF-5/MAK |
| GO:0004674 protein serine/threonine kinase activity | ISS PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | ACCEPT | Summary: Sequence-similarity transfer of the core kinase function from the human MAK/ICK-family orthologue. Now directly confirmed experimentally in worm. |
| GO:0004707 MAP kinase activity | ISS PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | MODIFY | Summary: Name-driven over-specification. DYF-5 was historically called a "MAP kinase", but molecularly it is a MAK/RCK (ICK/CILK1) CMGC kinase, not a mitogen-activated protein kinase activated by dual TXY phosphorylation within a MAPK cascade. Its demonstrated activity is general protein serine/threonine phosphorylation. The accurate term is protein serine/threonine kinase activity (GO:0004674). Proposed replacements: protein serine/threonine kinase activity Supporting Evidence: PMID:17420466 we identify DYF-5, a conserved MAP kinase that plays a role in these processes |
| GO:0005524 ATP binding | ISS PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | KEEP AS NON CORE | Summary: Sequence-similarity transfer of the standard kinase ATP-binding feature. Correct but a generic molecular-detail term; non-core. |
| GO:0008104 intracellular protein localization | IMP PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | KEEP AS NON CORE | Summary: Reflects the dyf-5 mutant phenotype in which IFT components are mislocalized and accumulate within cilia. This is a generic term for what is more precisely the regulation of intraciliary transport and of ciliary protein distribution; retained as non-core, with the specific IFT process terms preferred. Supporting Evidence: PMID:17420466 six IFT proteins accumulate in the cilia of dyf-5(lf) mutants |
| GO:0030424 axon | IDA PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | KEEP AS NON CORE | Summary: Experimentally observed neuronal localization. Real but non-core relative to the ciliary site of action. |
| GO:0030425 dendrite | IDA PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | KEEP AS NON CORE | Summary: Experimentally observed neuronal localization; DYF-5 is enriched at the dendrite-cilium transition zone. Real but non-core. |
| GO:0042073 intraciliary transport | IDA PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | ACCEPT | Summary: Direct experimental evidence for a role in IFT: live imaging of IFT-component motility and accumulation in dyf-5 mutants. Core process. Supporting Evidence: PMID:17420466 six IFT proteins accumulate in the cilia of dyf-5(lf) mutants |
| GO:0043025 neuronal cell body | IDA PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | KEEP AS NON CORE | Summary: Experimentally observed localization to the neuronal cell body. Real but non-core relative to the ciliary site of action. |
| GO:1905515 non-motile cilium assembly | IMP PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | ACCEPT | Summary: Core biological process, precise to the non-motile sensory cilia of C. elegans. dyf-5 loss-of-function mutants have abnormally long, misshapen cilia, showing a requirement for normal non-motile cilium assembly/morphogenesis. Supporting Evidence: PMID:17420466 the cilia of dyf-5 loss-of-function (lf) animals are elongated and are not properly aligned into the amphid channel |
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Download this section (compressed HTML)Q: Beyond IFT-74 and OSM-3, what are the physiological DYF-5 substrates in the cilium, and which one executes kinesin-II undocking?
Q: Do the two dyf-5 splice isoforms (a and b), which differ in the C-terminal tail that governs ciliary targeting, have distinct functions or localizations?
Q: What kinase activates DYF-5 and how is its activity spatially restricted to the distal ciliary segment?
Experiment: Comparative in-vivo ciliary phosphoproteomics of wild-type versus dyf-5(mn400) null sensory neurons to enumerate DYF-5-dependent phosphosites on IFT and motor proteins.
Experiment: CRISPR phospho-dead and phospho-mimic knock-ins at DYF-5-dependent OSM-3 and kinesin-II phosphosites, scored for cilium length, IFT velocity and motor docking/undocking behavior.
Experiment: Structure-function dissection of the DYF-5 C-terminus (truncations/point mutants) to separate kinase activation from ciliary-tip targeting, with live imaging of tagged DYF-5.
What is not known — curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: The complete set of in-vivo DYF-5 substrates that execute cilium-length and IFT control, and how their phosphorylation drives ciliary-tip cargo (tubulin) unloading, is undetermined. Only two direct substrates (IFT-74 and the OSM-3 C-terminus) have been demonstrated biochemically in vitro; which substrates are phosphorylated in the intact cilium, at which residues, and with what functional consequence, remains open.
OPEN BIOLOGY RESIDUAL_SUBGAP
What is known: DYF-5 is an established ciliary Ser/Thr kinase with a defined substrate consensus motif ((R)PX[S/T]); IFT-74 (11 N-terminal phosphosites reducing IFT-74/81 tubulin affinity) and the OSM-3 kinesin C-terminal fragment (444-699) are proven in-vitro substrates.
Significance: Identifying the full substrate set would explain how a single kinase coordinately controls tubulin unloading, motor handover and axoneme length, and would clarify the conserved MAK/ICK/CILK1 pathway relevant to human retinal ciliopathies.
What would resolve it: In-vivo phosphoproteomics of dyf-5(+) versus dyf-5(null) cilia; targeted phospho-site mapping on candidate IFT/motor substrates; separation-of-function phospho-dead/phospho-mimic alleles tested for ciliary length and IFT phenotypes.
Provenance (the field's own admissions):
Gap: The molecular mechanism by which DYF-5 switches anterograde IFT from heterotrimeric kinesin-II to homodimeric OSM-3 at the end of the middle segment is not resolved. It is unknown whether DYF-5 triggers the handover directly by phosphorylating a motor or an adaptor (e.g. OSM-3, kinesin-II subunits, or IFT linkers) or indirectly by remodeling IFT-train architecture, and which phosphosite(s) on OSM-3 are functionally required in vivo.
OPEN BIOLOGY MF_DARK
What is known: Genetics and imaging show DYF-5 is required for undocking of kinesin-II from IFT particles and docking of OSM-3, and DYF-5 phosphorylates the OSM-3 C-terminus in vitro and suppresses OSM-3 hyperactivity; the causal phosphorylation event that executes the handover is not identified.
Significance: The kinesin-II to OSM-3 handoff is the paradigm for how two anterograde motors are coordinated on a shared IFT train to build compartmentalized cilia; resolving it would define a general principle of IFT regulation conserved to vertebrate KIF3/KIF17.
What would resolve it: Map and mutate DYF-5-dependent OSM-3 phosphosites in vivo; test whether phospho-dead/phospho-mimic OSM-3 (or kinesin-II subunits) recapitulate dyf-5 handover defects; reconstitute motor docking/undocking on IFT trains with and without DYF-5 phosphorylation.
Provenance (the field's own admissions):
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