Kinesin heavy chain (KINH_DORPE) is the conventional kinesin-1 heavy chain from the longfin inshore squid Doryteuthis pealeii. It is a plus-end-directed microtubule motor protein that powers anterograde axonal transport of organelles, vesicles, and other cargo along microtubules. The protein was among the first kinesins to be cloned and characterized at the molecular level (Kosik et al. 1990). It forms a heterotetramer composed of two heavy chains and two light chains. The N-terminal globular motor domain hydrolyzes ATP and walks processively along microtubules, the central coiled-coil mediates dimerization, and the C-terminal tail interacts with light chains and cargo. In the squid giant axon, kinesin-1 drives fast anterograde transport of synaptic vesicle precursors, mitochondria, and amyloid precursor protein (APP)-containing vesicles. Kinesin-1 mRNA is a major target of A-to-I RNA editing in cephalopods, where temperature-dependent and tissue-specific recoding of the motor domain tunes transport velocity, run length, and microtubule landing rate (Rangan and Reck-Peterson 2023; Birk et al. 2023). Squid stellate ganglion-specific kinesin variants display enhanced velocity, potentially supporting rapid long-distance transport in the giant axon system.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003774 cytoskeletal motor activity | IEA GO_REF:0000117 | ACCEPT | Summary: Kinesin heavy chain is definitively a cytoskeletal motor. This term is correct but less specific than GO:0003777 (microtubule motor activity), which is already annotated. Since both are IEA, it is acceptable to keep the broader term alongside the more specific one. Reason: Kinesin-1 is a microtubule-based cytoskeletal motor. The term is correct and consistent with the protein's established function as a force-producing mechanochemical enzyme. The more specific child term microtubule motor activity is also present. Supporting Evidence: PMID:2137456 We report the cDNA sequence of the squid kinesin heavy chain...A comparison of the sequences from the two species reveals the head, stalk, and tail domains |
| GO:0003777 microtubule motor activity | IEA GO_REF:0000002 | MODIFY | Summary: Kinesin-1 is the prototypical plus-end-directed microtubule motor. This annotation is correct but could be made more specific as GO:0008574 (plus-end-directed microtubule motor activity), since kinesin-1 exclusively moves toward microtubule plus ends. Reason: Kinesin-1 is specifically a plus-end-directed motor. The term microtubule motor activity is correct but less precise than plus-end-directed microtubule motor activity. Single-molecule assays confirm processive plus-end-directed movement of squid kinesin along microtubules (Rangan and Reck-Peterson 2023). Proposed replacements: plus-end-directed microtubule motor activity Supporting Evidence: PMID:37295401 kinesin variants generated in cold seawater displayed enhanced motile properties in single-molecule experiments conducted in the cold. We also identified tissue-specific recoded squid kinesin variants that displayed distinct motile properties. |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | ACCEPT | Summary: Kinesin heavy chain has a well-characterized ATP-binding site in the motor domain (residues 85-92 per UniProt). ATP hydrolysis is essential for the mechanochemical cycle that generates force and movement along microtubules. Reason: ATP binding is fundamental to kinesin function. The UniProt entry identifies the ATP binding site at residues 85-92, and the protein belongs to the TRAFAC class myosin-kinesin ATPase superfamily. The kinesin motor domain hydrolyzes ATP to produce force. Supporting Evidence: PMID:2137456 We report the cDNA sequence of the squid kinesin heavy chain |
| GO:0005737 cytoplasm | IEA GO_REF:0000117 | ACCEPT | Summary: Kinesin heavy chain is a cytoplasmic protein. UniProt subcellular location confirms cytoplasm, cytoskeleton. This is correct but very broad; more specific CC terms (axon, microtubule cytoskeleton) are also annotated. Reason: Cytoplasmic localization is accurate for kinesin-1. The soluble pool of kinesin in axoplasm is well documented from squid giant axon studies. Supporting Evidence: PMID:23011729 The kinesins have long been known to drive microtubule-based transport of sub-cellular components |
| GO:0005856 cytoskeleton | IEA GO_REF:0000044 | ACCEPT | Summary: Kinesin associates with the microtubule cytoskeleton during its motor activity. UniProt subcellular location explicitly states "Cytoplasm, cytoskeleton." This term is correct but broad; the more specific microtubule cytoskeleton term is also present. Reason: Kinesin is a microtubule-associated protein and thus localized to the cytoskeleton. This is consistent with the UniProt subcellular location annotation. |
| GO:0007018 microtubule-based movement | IEA GO_REF:0000002 | ACCEPT | Summary: Kinesin-1 drives microtubule-based movement, specifically anterograde axonal transport. This is a correct annotation at a general level. The more specific term anterograde axonal transport (GO:0008089) would better capture the primary biological role of this protein in squid neurons. Reason: Microtubule-based movement is the core process enabled by kinesin-1. This is well established from decades of squid axoplasm transport studies. While anterograde axonal transport is the more precise process, this broader term is also appropriate. Supporting Evidence: PMID:37295401 We investigated the function of cephalopod RNA recoding in the microtubule motor proteins kinesin and dynein. We found that squid rapidly employ RNA recoding in response to changes in ocean temperature |
| GO:0007097 nuclear migration | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: Nuclear migration is a known function of kinesin-1 family members in some organisms (e.g., filamentous fungi, developing neurons). However, there is no direct evidence for squid kinesin-1 involvement in nuclear migration. This ARBA annotation likely derives from transfer from other kinesin-1 orthologs. Reason: While kinesin-1 does participate in nuclear migration in some organisms, this function has not been demonstrated for the squid kinesin heavy chain. The available literature on squid kinesin focuses on axonal transport, not nuclear positioning. This appears to be an over-extension from other kinesin-1 family members. |
| GO:0007292 female gamete generation | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: Female gamete generation (oogenesis) involves intracellular transport, and kinesin-1 plays roles in oocyte development in Drosophila and other organisms. However, there is no direct evidence for squid kinesin-1 in oogenesis. This ARBA annotation appears to be transferred from studies in other species. Reason: There is no published evidence linking squid kinesin heavy chain P21613 to female gamete generation. The annotation likely derives from ARBA rules built on kinesin-1 function in Drosophila oogenesis. While plausible, it is an unsupported extrapolation for this particular protein. |
| GO:0008017 microtubule binding | IEA GO_REF:0000002 | ACCEPT | Summary: Kinesin heavy chain binds microtubules via its motor domain. The microtubule-binding region is mapped to residues 173-314 in the UniProt entry. This is a core molecular function of kinesin. Reason: Microtubule binding is fundamental to kinesin motor function. The UniProt entry identifies a specific microtubule-binding region (residues 173-314). Single-molecule studies of squid kinesin directly demonstrate microtubule binding and processive movement along microtubules (Rangan and Reck-Peterson 2023). Supporting Evidence: PMID:2137456 We report the cDNA sequence of the squid kinesin heavy chain PMID:37295401 We investigated the function of cephalopod RNA recoding in the microtubule motor proteins kinesin and dynein |
| GO:0015630 microtubule cytoskeleton | IEA GO_REF:0000117 | ACCEPT | Summary: Kinesin associates with the microtubule cytoskeleton during transport. This is a correct cellular component term for a microtubule motor protein. Reason: As a microtubule motor, kinesin-1 is inherently localized to the microtubule cytoskeleton during its active transport function. This is well established. |
| GO:0030424 axon | IEA GO_REF:0000044 | ACCEPT | Summary: Kinesin heavy chain localizes to the axon. This is strongly supported by direct experimental evidence from the squid giant axon. The UniProt entry states "Cell projection, axon" with experimental evidence from Seamster et al. 2012. Reason: Axonal localization is one of the most strongly supported annotations for this protein. Squid kinesin was studied extensively in the giant axon, and its axonal localization is confirmed by multiple experimental approaches including injection of exogenous cargo into the giant axon. Supporting Evidence: PMID:23011729 After injection into the squid giant axon, particle movements are imaged by laser-scanning confocal time-lapse microscopy |
| GO:0030951 establishment or maintenance of microtubule cytoskeleton polarity | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: Kinesin-1 is a plus-end-directed motor and its movement along microtubules is polarity-dependent, but kinesin-1 does not establish or maintain microtubule polarity. Microtubule polarity is determined by tubulin polymerization dynamics and microtubule-organizing centers, not by motor proteins walking along them. Reason: This annotation confuses kinesin's dependence on microtubule polarity for directional transport with a role in establishing or maintaining that polarity. Kinesin-1 reads microtubule polarity but does not set it. There is no evidence that squid kinesin heavy chain is involved in establishing or maintaining microtubule polarity. |
| GO:0032991 protein-containing complex | IEA GO_REF:0000117 | MODIFY | Summary: Kinesin-1 functions as a heterotetramer of two heavy chains and two light chains. The generic term protein-containing complex is correct but uninformative. The specific term kinesin I complex (GO:0016938) would be more appropriate. Reason: The UniProt entry states kinesin is an "oligomer composed of two heavy chains and two light chains," which is the kinesin-1 holoenzyme. The generic protein-containing complex term should be replaced with the specific kinesin I complex term. Proposed replacements: kinesin I complex Supporting Evidence: PMID:2137456 We report the cDNA sequence of the squid kinesin heavy chain |
| GO:0043005 neuron projection | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: Kinesin-1 localizes to neuron projections, specifically the axon. The axon is a type of neuron projection, and the more specific term GO:0030424 (axon) is already annotated. This broader term is redundant but not wrong. Reason: Neuron projection is a parent term of axon, which is already annotated. While technically correct, the axon annotation is more informative. This is kept as non-core since it adds no information beyond the axon annotation. |
| GO:0048489 synaptic vesicle transport | IEA GO_REF:0000117 | ACCEPT | Summary: Kinesin-1 is involved in anterograde transport of synaptic vesicle precursors. In squid axon studies, kinesin-1 drives transport of membranous organelles including vesicles toward the synapse. The Seamster et al. 2012 study directly examined cargo-motor interactions during fast transport in the squid giant axon. Reason: Synaptic vesicle transport is well supported by the squid giant axon literature. Kinesin-1 transports vesicle cargo anterogradely toward presynaptic terminals. The Seamster et al. study quantified cargo-motor interactions during fast axonal transport of vesicle-like cargo in the living squid axon. Supporting Evidence: PMID:23011729 The results reveal that negatively charged beads differ from APP-C beads in velocity and dispersion, and predict that at long time points APP-C will achieve greater progress towards the presynaptic terminal. |
| GO:0098957 anterograde axonal transport of mitochondrion | IEA GO_REF:0000117 | MODIFY | Summary: Kinesin-1 is known to transport mitochondria anterogradely in axons in mammalian systems. This is a plausible function for squid kinesin-1 given the conservation of the transport machinery, but there is no direct experimental evidence specifically for mitochondrial transport by squid kinesin. The broader term anterograde axonal transport (GO:0008089) would be more appropriate given the available evidence. Reason: While kinesin-1-dependent anterograde mitochondrial transport is well established in mammals, the specific cargo (mitochondria) has not been demonstrated for squid kinesin. The squid giant axon studies focus on general organelle and vesicle transport. The broader term anterograde axonal transport better reflects the directly supported biology. Proposed replacements: anterograde axonal transport Supporting Evidence: PMID:37295402 For kinesin-1, a motor protein driving axonal transport, editing regulates transport velocity down microtubules |
| GO:0120544 polypeptide conformation or assembly isomerase activity | IEA GO_REF:0000117 | REMOVE | Summary: This annotation appears to be erroneous for kinesin heavy chain. Kinesin-1 is a motor protein, not a chaperone or isomerase. There is no evidence that squid kinesin has polypeptide conformation or assembly isomerase activity. This appears to be a mis-assignment by the ARBA machine learning model. Reason: Kinesin-1 is a microtubule motor protein. It does not have any known chaperone, foldase, or isomerase activity. This annotation is likely a false positive from the ARBA automated annotation pipeline and should be removed. No literature supports this function for any kinesin-1 family member. |
| GO:1904115 axon cytoplasm | IEA GO_REF:0000108 | ACCEPT | Summary: Axon cytoplasm (axoplasm) is the correct and specific compartment where kinesin-1 resides and functions in the squid giant axon. This annotation was inferred from the anterograde axonal transport of mitochondrion annotation via logical reasoning. Reason: Kinesin-1 is abundantly present in squid axoplasm, where it was originally discovered and characterized. This is one of the most directly supported annotations for this protein. Kinesin was first purified from squid axoplasm. Supporting Evidence: PMID:23011729 After injection into the squid giant axon, particle movements are imaged by laser-scanning confocal time-lapse microscopy |
| GO:0008089 anterograde axonal transport | IDA PMID:37295402 Temperature-dependent RNA editing in octopus extensively rec... | NEW | Summary: Kinesin-1 is the primary motor for anterograde axonal transport. This function is extensively documented in squid giant axon studies and confirmed by single-molecule assays of squid kinesin constructs. Reason: Anterograde axonal transport is the core biological process for kinesin-1 in neurons. Birk et al. 2023 directly state that kinesin-1 is "the primary molecular motor responsible for moving cargo in the anterograde direction down microtubules in axons." Rangan and Reck-Peterson 2023 demonstrate processive plus-end-directed movement of squid kinesin in single-molecule assays. Supporting Evidence: PMID:37295402 For kinesin-1, a motor protein driving axonal transport, editing regulates transport velocity down microtubules PMID:37295401 We found that squid rapidly employ RNA recoding in response to changes in ocean temperature, and kinesin variants generated in cold seawater displayed enhanced motile properties in single-molecule experiments conducted in the cold. |
| GO:0008574 plus-end-directed microtubule motor activity | IDA PMID:37295401 RNA recoding in cephalopods tailors microtubule motor protei... | NEW | Summary: Kinesin-1 is specifically a plus-end-directed microtubule motor. Single-molecule assays of recombinant squid kinesin confirm processive plus-end-directed movement along taxol-stabilized microtubules. Reason: This is the most specific and accurate MF term for the motor activity of kinesin-1. All kinesin-1 family members are plus-end-directed. Rangan and Reck-Peterson 2023 performed single-molecule motility assays of squid kinesin that directly demonstrate processive plus-end-directed movement. Supporting Evidence: PMID:37295401 We also identified tissue-specific recoded squid kinesin variants that displayed distinct motile properties |
| GO:0005874 microtubule | IDA PMID:37295401 RNA recoding in cephalopods tailors microtubule motor protei... | NEW | Summary: Kinesin-1 binds to and walks along microtubules. The UniProt entry lists microtubule (GO:0005874) as a GO term. This CC annotation reflects that kinesin is found associated with microtubules during its motor cycle. Reason: Microtubule is listed in the UniProt Swiss-Prot entry under GO terms (IEA:UniProtKB-KW) but was absent from the GOA file. Kinesin-1 associates with microtubules as its track, and the microtubule-binding region is well characterized (residues 173-314). Supporting Evidence: PMID:2137456 We report the cDNA sequence of the squid kinesin heavy chain |
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Download this section (compressed HTML)Q: How do the multiple RNA editing sites in squid kinesin-1 interact epistatically to tune transport properties? The Birk et al. 2023 paper notes 17 recoding sites in kinesin-1 mRNA, 8 temperature-sensitive, but most studies examine single sites.
Q: Does squid kinesin-1 have cargo-specific roles beyond general anterograde transport? The APP interaction is documented, but whether kinesin-1 vs other kinesins partition different cargo types in squid is unclear.
Q: Is there evidence for kinesin-1 involvement in nuclear migration or oogenesis specifically in cephalopods, or are those annotations solely transferred from other organisms?
Experiment: Proteomics of squid axoplasm to identify specific cargoes of kinesin-1 vs other kinesin family members in the giant axon.
Hypothesis: Different kinesin family members partition distinct cargo types in squid neurons.
Type: proteomics
Experiment: In vivo single-particle tracking of kinesin-1 variants (edited vs unedited) in intact squid giant axons to validate single-molecule findings in a physiological context.
Hypothesis: RNA editing-generated kinesin variants display altered transport dynamics in intact axons, not just in vitro single-molecule assays.
Type: live imaging
Experiment: Characterization of combinatorial RNA editing effects on kinesin-1 motility using multiply-edited recombinant constructs.
Hypothesis: Multiple editing sites interact epistatically to produce transport properties not predicted by individual site effects.
Type: single-molecule motility assay
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