Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Microtubules are built of tubulin subunits assembled into hollow cylinders which consist of parallel protofilaments. Thus, motor molecules interacting with a microtubule could do so either with one or several tubulin subunits. This makes it difficult to determine the structural requirements for the interaction. One way to approach the problem is to alter the surface lattice. This can be done in several ways. Proto-filaments can be exposed on their inside (C-tubules or "sheets"), they can be made antiparallel (zinc sheets), or they can be rolled up (duplex tubules). We have exploited this polymorphism to study how the motor protein kinesin attached to a glass surface interacts and moves the various tubulin assemblies. Microtubules glide over the surface along straight paths and with uniform velocities. In the case of C-tubules, approximately 40% glide similarly to microtubules, but a major fraction do not glide at all. This indicates (a) that a full cylindrical closure is not necessary for movement, and (b) that the inside surface of microtubules does not support gliding. With zinc sheets, up to 70% of the polymers move, but the movement is discontinuous, has a reduced speed, and follows along a curved path. Since zinc sheets have protofilaments alternating in orientation and polarity, this result suggests that in principle a single protofilament can produce movement, even when its neighbors cannot. Duplex microtubules do not move because they are covered with protofilaments coiled inside out, thus preventing the interaction with kinesin. The data can be explained by assuming that the outside of one protofilament represents the minimal track for kinesin, but smooth gliding requires several parallel protofilaments. Finally, we followed the motion of kinesin-coated microbeads on sea-urchin sperm flagella, from the flagellar outer doublet microtubules to the singlet microtubule tips extending from the A-tubules. No change in behavior was detected during the transition. This indicates that even if these microtubules differ in surface lattice, this does not affect the motility.
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PMID:Tubulin protofilaments and kinesin-dependent motility. 150 Apr 29

Moving along a microtubule, kinesin follows a course parallel to the protofilaments; but it is not known whether kinesin binds exclusively on a single protofilament. The presence of zinc during tubulin polymerization induces sheets where neighboring protofilaments are antiparallel. If kinesin could support the motility of these zinc-sheets, then the binding site for a kinesin molecule would be limited to a single protofilament. Kamimura and Mandelkow [1992: J. Cell Biol. 118:865-75] reported that kinesin moves along zinc-sheets. We found that zinc-sheets grown under their conditions often had a microtubule-like structure along one edge. We confirmed the possibility that the motility observed by Kamimura and Mandelkow [1992: J. Cell Biol. 118:865-75] is attributed to the microtubule-like structure rather than the zinc-sheet. To resolve the question of whether kinesin can recognize an antiparallel protofilament lattice, we investigated the kinesin-mediated motility of zinc-macrotubes. At higher free zinc concentrations, zinc-sheets roll up as macrotubes, free of edges. In the presence of 10 microM taxol and 100 nM free Zn2+ at pH 6.8, the samples were shown by electron microscopy to contain only macrotubes. Under these buffer conditions, kinesin could bind strongly to axonemal doublets in the presence of AMP-PNP, and generate motility in the presence of ATP, but kinesin did not bind to nor move the macrotubes. This shows that kinesin cannot bind efficiently to nor move on the anti-parallel lattice; it is possible (though not necessary) that the groove between two parallel protofilaments is required for kinesin's motility.
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PMID:Kinesin does not support the motility of zinc-macrotubes. 760 7

We present a three-dimensional (3D) map, reconstructed from electron microscope (EM) images of naturally occurring 16-protofilament (PF) microtubules (MTs) in ice. We compare it with the tubulin in six 3D maps of MTs decorated with motor domains, three from frozen MTs decorated with kinesin or ncd in the tightly bound AMP-PNP state, and three from negatively stained MTs decorated with kinesin in different nucleotide states. The comparison confirms that kinesin and ncd bind to identical sites and interact with both monomers of a tubulin dimer. Maps of specimens in negative stain and in ice are similar except that the protein in the top half of a motor domain appears denser in negative stain. The interactions have only a small effect on tubulin structure; the outward appearance is unchanged, but there seems to be a small internal rearrangement. The relative polarity of undecorated and decorated MTs is evident from their 3D structures. This agrees with the absolute polarities indicated by the orientations of motors in decorated specimens and by polar superposition patterns calculated for undecorated MTs. An image of tubulin PFs in zinc-induced sheets has been tentatively oriented by similar criteria.
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PMID:Three-dimensional cryoelectron microscopy of 16-protofilament microtubules: structure, polarity, and interaction with motor proteins. 912 39

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that cleave and degrade a wide spectrum of extracellular matrix components. By enhancing turnover of extracellular matrix, MMP activity is also known to play a key role in tumor cell invasion. Because extracellular protease activity requires efficient release of these proteases to the cellular surface, we investigated storage, transport, and exocytosis of MMP-2 and MMP-9 in human melanoma cells using immunofluorescence, electrical, and biochemical techniques. Immunolabeling of melanoma cells with antibodies specific for MMP-2 and MMP-9 led to the identification of two distinct populations of small cytoplasmatic vesicles containing MMP-2 or MMP-9, respectively. In combination with alpha-tubulin-specific antibodies, both vesicle populations were found to be aligned along the microtubular network. Moreover, the molecular motor protein kinesin is shown to be localized on most of these vesicles, providing evidence that the identified vesicles are actively propelled along microtubules toward the plasma membrane. The functional relevance of these findings is demonstrated using low dosage (5.9 nmol/L) of paclitaxel to affect the microtubular function of melanoma cells. Although cell proliferation is not altered, paclitaxel treatment impairs secretion of MMP-2/MMP-9 and significantly reduces invasive activity in our new cell invasion assay. In conclusion, we demonstrate in melanoma cells that microtubule-dependent traffic of MMP-containing vesicles and exocytosis are critical steps for invasive behavior and therefore are potential targets for specific antitumor drugs.
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PMID:Microtubule-dependent matrix metalloproteinase-2/matrix metalloproteinase-9 exocytosis: prerequisite in human melanoma cell invasion. 1560 54

Orthologues of nearly all of the core components of the Hedgehog signalling pathway, defined originally through genetic analysis in Drosophila, have now been discovered in vertebrates and shown to have highly conserved functions. The one striking exception to this rule is the kinesin-like protein Costal2, which plays a central role in controlling the activity of the zinc-finger-containing transcriptional regulator, Cubitus interruptus that modulates all Hedgehog-dependent target gene expression, but whose involvement in Hedgehog signalling has not been demonstrated in vertebrates. We report the cloning of a kinesin-related gene from the zebrafish that in structure as well as function, appears to represent the first vertebrate orthologue of costal2. Using a combination of genetic and biochemical analysis, we provide evidence that as in Drosophila, zebrafish Costal2 acts principally as an intracellular repressor of signal transduction, in conjunction with Suppressor of Fused, another protein that negatively regulates signalling in Hedgehog-responsive cells.
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PMID:A homologue of the Drosophila kinesin-like protein Costal2 regulates Hedgehog signal transduction in the vertebrate embryo. 1564 23

The amyloid precursor protein (APP) was initially detected in cells of the central nervous system where it is considered to be involved in the pathogenesis of Alzheimer's disease. However, APP is also found in peripheral organs with exceptionally strong expression in the mammalian epidermis where it fulfils a variety of distinct biological roles. Full length APP appears to facilitate keratinocyte adhesion due to its ability to interact with the extracellular matrix. The C-terminus of APP also serves as adapter protein for binding the motor protein kinesin thereby mediating the centripetal transport of melanosomes in epidermal melanocytes. By the action of alpha-secretase sAPPalpha, the soluble N-terminal portion of APP, is released. sAPPalpha has been shown to be a potent epidermal growth factor thus stimulating proliferation and migration of keratinocytes as well as the exocytic release of melanin by melanocytes. The release of sAPPalpha can be almost completely blocked by inhibiting alpha-secretase with hydroxamic acid-based zinc metalloproteinase inhibitors. In hyperproliferative keratinocytes from psoriatic skin this inhibition results in normalized growth.
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PMID:Biological roles of APP in the epidermis. 1567 6

Astrocytes play an active role in the central nervous system and are critically involved in astrogliosis, a homotypic response of these cells to disease, injury, and associated neuroinflammation. Among the numerous molecules involved in these processes are the matrix metalloproteinases (MMPs), a family of zinc-dependent endopeptidases, secreted or membrane-bound, that regulate by proteolytic cleavage the extracellular matrix, cytokines, chemokines, cell adhesion molecules, and plasma membrane receptors. MMP activity is tightly regulated by the tissue inhibitors of MMPs (TIMPs), a family of secreted multifunctional proteins. Astrogliosis in vivo and astrocyte reactivity induced in vitro by proinflammatory cues are associated with modulation of expression and/or activity of members of the MMP/TIMP system. However, nothing is known concerning the intracellular distribution and secretory pathways of MMPs and TIMPs in astrocytes. Using a combination of cell biology, biochemistry, fluorescence and electron microscopy approaches, we investigated in cultured reactive astrocytes the intracellular distribution, transport, and secretion of MMP-2, MMP-9, TIMP-1, and TIMP-2. MMP-2 and MMP-9 demonstrate nuclear localization, differential intracellular vesicular distribution relative to the myosin V and kinesin molecular motors, and LAMP-2-labeled lysosomal compartment, and we show vesicular secretion for MMP-2, MMP-9, and their inhibitors. Our results suggest that these proteinases and their inhibitors use different pathways for trafficking and secretion for distinct astrocytic functions.
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PMID:Differential vesicular distribution and trafficking of MMP-2, MMP-9, and their inhibitors in astrocytes. 1978 Feb 1

Extracellular Hedgehog (Hh) proteins alter cellular behaviours from flies to man by regulating the activities of Gli/Ci family transcription factors. A major component of this response in Drosophila is the inhibition of proteolytic processing of the latent transcriptional activator Ci-155 to a shorter Ci-75 repressor form. Processing is thought to rely on binding of the kinesin-family protein Cos2 directly to Ci-155 domains known as CDN and CORD, allowing Cos2-associated protein kinases to phosphorylate Ci-155 efficiently and create a binding site for an E3 ubiquitin ligase complex. Here we show that the last three zinc fingers of Ci-155 also bind Cos2 in vitro and that the zinc finger region, rather than the CDN domain, functions redundantly with the CORD domain to promote Hh-regulated Ci-155 proteolysis in wing discs. We also find evidence for a unique function of Cos2 binding to CORD. Cos2 binding to CORD, but not to other regions of Ci, is potentiated by nucleotides and abrogated by the nucleotide binding variant Cos2 S182N. Removal of the CORD region alone enhances processing under a variety of conditions. Most strikingly, CORD region deletion allows Cos2 S182N to stimulate efficient Ci processing. We deduce that the CORD region has a second function distinct from Cos2 binding that inhibits Ci processing, and that Cos2 binding to CORD relieves this inhibition. We suggest that this regulatory activity of Cos2 depends on a specific nucleotide-bound conformation that may be regulated by Hh.
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PMID:Costal 2 interactions with Cubitus interruptus (Ci) underlying Hedgehog-regulated Ci processing. 2085 Apr 29

Cytoplasmic dynein and kinesin are two-headed microtubule motor proteins that move in opposite directions on microtubules. It is known that kinesin steps by a 'hand-over-hand' mechanism, but it is unclear by which mechanism dynein steps. Because dynein has a completely different structure from that of kinesin and its head is massive, it is suspected that dynein uses multiple protofilaments of microtubules for walking. One way to test this is to ask whether dynein can step along a single protofilament. Here, we examined dynein and kinesin motility on zinc-induced tubulin sheets (zinc-sheets) which have only one protofilament available as a track for motor proteins. Single molecules of both dynein and kinesin moved at similar velocities on zinc-sheets compared to microtubules, clearly demonstrating that dynein and kinesin can walk on a single protofilament and multiple rows of parallel protofilaments are not essential for their motility. Considering the size and the motile properties of dynein, we suggest that dynein may step by an inchworm mechanism rather than a hand-over-hand mechanism.
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PMID:A single protofilament is sufficient to support unidirectional walking of dynein and kinesin. 2290 78

In healthy organisms the metabolism of the trace element zinc is well balanced. If this balance becomes destroyed the free zinc level might increase and cause toxic effects. The present study demonstrates that under definite conditions zinc ions are able to inhibit the ATPase activity of neuron-specific KIF5A (kinesin-1). Correspondingly, the motility activity of KIF5A also decreased. The inhibition rates have been found to depend on the magnesium ion concentration. Lowering the magnesium concentration weakens the inhibition. In addition, also decreases of temperature or increasing the ATP concentration result in reduced inhibition. Zinc ion-mediated inhibition of KIF5A activity might be one molecular cause contributing to impaired transport processes within brain and other organs in cases of zinc dyshomeostasis.
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PMID:Toxic effects of zinc ions on kinesin - Potential molecular cause of impaired intracellular transport. 2812 63


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