Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.4.4 (kinesin)
 5,033 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Melanophores move pigment organelles (melanosomes) from the cell center to the periphery and vice-versa. These bidirectional movements require cytoplasmic microtubules and microfilaments and depend on the function of microtubule motors and a myosin. Earlier we found that melanosomes purified from Xenopus melanophores contain the plus end microtubule motor kinesin II, indicating that it may be involved in dispersion (Rogers, S.L., I.S. Tint, P.C. Fanapour, and V.I. Gelfand. 1997. Proc. Natl. Acad. Sci. USA. 94: 3720-3725). Here, we generated a dominant-negative construct encoding green fluorescent protein fused to the stalk-tail region of Xenopus kinesin-like protein 3 (Xklp3), the 95-kD motor subunit of Xenopus kinesin II, and introduced it into melanophores. Overexpression of the fusion protein inhibited pigment dispersion but had no effect on aggregation. To control for the specificity of this effect, we studied the kinesin-dependent movement of lysosomes. Neither dispersion of lysosomes in acidic conditions nor their clustering under alkaline conditions was affected by the mutant Xklp3. Furthermore, microinjection of melanophores with SUK4, a function-blocking kinesin antibody, inhibited dispersion of lysosomes but had no effect on melanosome transport. We conclude that melanosome dispersion is powered by kinesin II and not by conventional kinesin. This paper demonstrates that kinesin II moves membrane-bound organelles.
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PMID:Heterotrimeric kinesin II is the microtubule motor protein responsible for pigment dispersion in Xenopus melanophores. 985 50

Conventional kinesin is a motor protein that moves stepwise along microtubules carrying membrane-bound organelles toward the periphery of cells. The steps are of amplitude 8.1 nm, the distance between adjacent tubulin binding sites, and are powered by the hydrolysis of ATP. We have asked: how many steps does kinesin take for each molecule of ATP that it hydrolyzes? To answer this question, the motility and ATP hydrolysis of recombinant, heterotetrameric and homodimeric conventional Drosophila kinesins adsorbed to 200-nm-diameter casein-coated silica beads were assayed under identical, single-molecule conditions. Division of the speed by the maximum microtubule-activated ATPase rate gave a stoichiometry of 1. 08 +/- 0.09 steps for each ATP hydrolyzed at 1 mM ATP. Therefore, under low loads in which the drag force << 1 pN, coupling between the chemical and mechanical cycles of kinesin is tight, consistent with conventional power stroke models. Our results rule out models that require two or more ATPs/step, such as some thermal ratchet models, or that propose multiple steps powered by single ATPs.
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PMID:Kinesin takes one 8-nm step for each ATP that it hydrolyzes. 992 Sep 16

We examined cytoskeleton-associated forms of NF proteins during axonal neuritogenesis in cultured dorsal root ganglion (DRG) neurons and NB2a/d1 neuroblastoma. In addition to filamentous immunoreactivity, we observed punctate NF immunoreactivity throughout perikarya and neurites. Immuno-electron microscopy revealed this punctate immunoreactivity to consist of non-membrane-bound 75 nm round/ovoid structures consisting of amorphous, fibrous material. Endogenous and microinjected NF subunits incorporated into dots prior to their accumulation within filaments. A transfected GFP-conjugated NF-M incorporated into dots and translocated at a rate consistent with slow axonal transport in real-time video analyses. Some dots converted into a filamentous form or exuded filamentous material during transport. Dots contained conventional kinesin immunoreactivity, associated with microtubules, and their transport into axons was blocked by anti-kinesin antibodies and nocodazole. These oligomeric structures apparently represent one form in which NF subunits are transported in growing axons and may utilize kinesin as a transport motor.
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PMID:Kinesin-mediated transport of neurofilament protein oligomers in growing axons. 1052 15

The nature of kinesin interactions with membrane-bound organelles and mechanisms for regulation of kinesin-based motility have both been surprisingly difficult to define. Most kinesin is recovered in supernatants with standard protocols for purification of motor proteins, but kinesin recovered on membrane-bound organelles is tightly bound. Partitioning of kinesin between vesicle and cytosolic fractions is highly sensitive to buffer composition. Addition of either N-ethylmaleimide or EDTA to homogenization buffers significantly increased the fraction of kinesin bound to organelles. Given that an antibody against kinesin light chain tandem repeats also releases kinesin from vesicles, these observations indicated that specific cytoplasmic factors may regulate kinesin release from membranes. Kinesin light tandem repeats contain DnaJ-like motifs, so the effects of hsp70 chaperones were evaluated. Hsc70 released kinesin from vesicles in an MgATP-dependent and N-ethylmaleimide-sensitive manner. Recombinant kinesin light chains inhibited kinesin release by hsc70 and stimulated the hsc70 ATPase. Hsc70 actions may provide a mechanism to regulate kinesin function by releasing kinesin from cargo in specific subcellular domains, thereby effecting delivery of axonally transported materials.
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PMID:Release of kinesin from vesicles by hsc70 and regulation of fast axonal transport. 1084 36

The parasitic protist Giardia lamblia lacks mitochondria and peroxisomes, as well as many typical membrane-bound organella characteristics of higher eukaryotic cells, together with extremely economized usage of DNA sequence, as demonstrated by the lack of introns. We describe here the presence of overlapping genes in G. lamblia, in which a part of the protein coding sequence of one mRNA exists in a region corresponding to the 3'-noncoding region of another mRNA transcribed from a gene on the opposite strand. Recently we isolated 13 kinesin-related cDNAs from G. lamblia. Nine of these cDNAs contain long 3'-noncoding sequences in which long open reading frames (ORFs) exist (in the remaining four cDNAs, the lengths of the 3'-noncoding sequences are very short). The predicted amino acid sequences of these ORFs were subjected to a search for homologies with sequences in databases. The amino acid sequences of the six ORFs exhibited significant sequence similarities with known sequences. These lines of evidence suggest the frequent occurrence of gene overlap in Giardial genome.
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PMID:Overlapping genes in parasitic protist Giardia lamblia. 1173 29

Rapid organelle transport is required for process growth and establishment of specialized structures during neuronal development. Furthermore, maintenance of mature neuronal architecture and function depends on the proper delivery of materials to specialized domains within axons, such as nodes of Ranvier and synaptic terminals. Kinesin is the most abundant member of the kinesin superfamily of microtubule-based motors. Kinesins are responsible for anterograde transport of an assortment of membrane-bound organelles in all cell types. Kinesin is enriched in neurons, but relatively little is known about the developmental regulation of its expression, localization, and function in nervous tissue. By examining kinesin expression in developing brain and in cultures of cortical neurons, we found that kinesin is enriched in elongating neurites, including their growing tips, the growth cones. To gain understanding of mechanisms that underlie the delivery of proteins to specific cellular subcompartments, we focused on studying modifications on kinesin that lead to its dissociation from membranes. Since kinesin is a phosphoprotein in vivo, we evaluated the correlation between kinesin phosphorylation and its membrane association and identified a number of kinases which phosphorylate kinesin and alter its function.
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PMID:Regulation of kinesin: implications for neuronal development. 1175 52

The elucidation of physical and molecular mechanisms by which a membrane tube is generated from a membrane reservoir is central to the understanding of the structure and dynamics of intracellular organelles and of transport intermediates in eukaryotic cells. Compelling evidence exists that molecular motors of the dynein and kinesin families are involved in the tubulation of organelles. Here, we show that lipid giant unilamellar vesicles (GUVs), to which kinesin molecules have been attached by means of small polystyrene beads, give rise to membrane tubes and to complex tubular networks when incubated in vitro with microtubules and ATP. Similar tubes and networks are obtained with GUVs made of purified Golgi lipids, as well as with Golgi membranes. No tube formation was observed when kinesins were directly bound to the GUV membrane, suggesting that it is critical to distribute the load on both lipids and motors by means of beads. A kinetic analysis shows that network growth occurs in two phases: a phase in which membrane-bound beads move at the same velocity than free beads, followed by a phase in which the tube growth rate decreases and strongly fluctuates. Our work demonstrates that the action of motors bound to a lipid bilayer is sufficient to generate membrane tubes and opens the way to well controlled experiments aimed at the understanding of basic mechanisms in intracellular transport.
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PMID:A minimal system allowing tubulation with molecular motors pulling on giant liposomes. 1195 94

MTs in cytoplasmic extensions including axons, dendrites and axonemes serve as polarized tracks for vectorial intracellular transport driven by MT-based motor proteins. Although axons and axonemes serve very different functions, increasing evidence suggests that the transport events, MT organization and the motors involved in their formation and function are conserved. Thus, there are obvious similarities in the mechanisms of axonal transport and IFT. The MT arrays of axons and axonemes are parallel, whereas those of dendrites are anti-parallel, but the functional significance of this difference and its consequences for mechanisms of transport along these processes are unclear. MT-based motor proteins of the dynein and kinesin superfamilies transport a variety of cargos including membrane-bound vesicles and macromolecular complexes along MTs of axons, dendrites and axonemes, and thus contribute to the formation, maintenance and function of these cytoplasmic extensions. Chemosensory neurons in the nematode C. elegans represent an appealing system for studying transport events along dendrites and axonemes that occur sequentially in a single cell.
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PMID:Microtubule-based transport along axons, dendrites and axonemes. 1247 92

Several lines of evidence indicate that alterations in axonal transport play a critical role in Alzheimer's disease (AD) neuropathology, but the molecular mechanisms that control this process are not understood fully. Recent work indicates that presenilin 1 (PS1) interacts with glycogen synthase kinase 3beta (GSK3beta). In vivo, GSK3beta phosphorylates kinesin light chains (KLC) and causes the release of kinesin-I from membrane-bound organelles (MBOs), leading to a reduction in kinesin-I driven motility (Morfini et al., 2002b). To characterize a potential role for PS1 in the regulation of kinesin-based axonal transport, we used PS1-/- and PS1 knock-inM146V (KIM146V) mice and cultured cells. We show that relative levels of GSK3beta activity were increased in cells either in the presence of mutant PS1 or in the absence of PS1 (PS1-/-). Concomitant with increased GSK3beta activity, relative levels of KLC phosphorylation were increased, and the amount of kinesin-I bound to MBOs was reduced. Consistent with a deficit in kinesin-I-mediated fast axonal transport, densities of synaptophysin- and syntaxin-I-containing vesicles and mitochondria were reduced in neuritic processes of KIM146V hippocampal neurons. Similarly, we found reduced levels of PS1, amyloid precursor protein, and synaptophysin in sciatic nerves of KIM146V mice. Thus PS1 appears to modulate GSK3beta activity and the release of kinesin-I from MBOs at sites of vesicle delivery and membrane insertion. These findings suggest that mutations in PS1 may compromise neuronal function by affecting GSK-3 activity and kinesin-I-based motility.
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PMID:Alzheimer's presenilin 1 mutations impair kinesin-based axonal transport. 1280 90

Chlamydiae are pathogenic obligate intracellular bacteria with a biphasic developmental cycle that involves cell types adapted for extracellular survival (elementary bodies, EBs) and intracellular multiplication (reticulate bodies, RBs). The intracellular development of chlamydiae occurs entirely within a membrane-bound vacuole termed an inclusion. Within 2 hours after entry into host cells, Chlamydia trachomatis EBs are trafficked to the perinuclear region of the host cell and remain in close proximity to the Golgi apparatus, where they begin to fuse with a subset of host vesicles containing sphingomyelin. Here, we provide evidence that chlamydial migration from the cell periphery to the peri-Golgi region resembles host cell vesicular trafficking. Chlamydiae move towards the minus end of microtubules and aggregate at the microtubule-organizing center (MTOC). In mammalian cells the most important minus-end-directed microtubule motor is cytoplasmic dynein. Microinjection of antibodies to a subunit of cytoplasmic dynein inhibited movement of chlamydiae to the MTOC, whereas microinjection of antibodies to the plus-directed microtubule motor, kinesin, had no effect. Surprisingly, overexpression of the protein p50 dynamitin, a subunit of the dynactin complex that links vesicular cargo to the dynein motor in minus directed vesicle trafficking, did not abrogate chlamydial migration even though host vesicle transport was inhibited. Nascent chlamydial inclusions did, however, colocalize with the p150(Glued) dynactin subunit, which suggests that p150(Glued) may be required for dynein activation or processivity but that the cargo-binding activity of dynactin, supplied by p50 dynamitin subunits and possibly other subunits, is not. Because chlamydial transcription and translation were required for this intracellular trafficking, chlamydial proteins modifying the cytoplasmic face of the inclusion membrane are probable candidates for proteins fulfilling this function.
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PMID:Chlamydia trachomatis uses host cell dynein to traffic to the microtubule-organizing center in a p50 dynamitin-independent process. 1290 5


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