Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cysteine residues play important roles in the control of tubulin function. To determine which of the six cysteine residues in beta-tubulin are critical to tubulin function, we mutated the cysteines in Saccharomyces cerevisiae beta-tubulin individually to alanine and serine residues. Of the twelve mutations, only three produced significant effects: C12S, C354A, and C354S. The C12S mutation was lethal in the haploid, but the C12A mutation had no observable phenotype. Based on interactive views of the electron crystallographic structure of tubulin, we suggest that substitution of serine for cysteine at this position has a destabilizing effect on the interaction of tubulin with the exchangeable GTP. The two C354 mutations, although not lethal, produced dramatic effects on microtubules and cellular processes that require microtubules. The C354 mutant cells had decreased growth rates, a slowed mitosis, increased resistance to benomyl, and impaired nuclear migration and spindle assembly. The C354A mutation produced a more severe phenotype than the C354S mutation: the haploid cells had chromosome segregation defects, only 50% of cells in a culture were viable, and a significant percentage of the cells were misshapened. Cytoplasmic microtubules in the C354S and C354A cells were longer than in the control strain and spindle structures appeared shorter and thicker. Both cytoplasmic and spindle microtubules in the two C354 mutants were extremely stable to cold temperature. After 24 h at 4 degrees C, the microtubules were still present and, in fact, very long and thick tubulin polymers had formed. Evidence exists to indicate that the C354 residue in mammalian tubulin is near the colchicine binding site and the electron crystal structure of tubulin places the residue at the interface between the alpha- and beta-subunits. The sulfhydryl group is situated in a polar environment, which may explain why the alanine mutation is more severe than the serine mutation. When the C12S and the two C354 mutations were made in a diploid strain, the mutated tubulin was incorporated into microtubules and the resulting heterozygotes had phenotypes that were intermediate between those of the mutated haploids and the wild-type strains. The results suggest that the C12 and C354 residues play important roles in the structure and function of tubulin.
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PMID:Mutagenesis of beta-tubulin cysteine residues in Saccharomyces cerevisiae: mutation of cysteine 354 results in cold-stable microtubules. 1144 37

Laulimalide is a cytotoxic natural product that stabilizes microtubules. The compound enhances tubulin assembly, and laulimalide is quantitatively comparable to paclitaxel in its effects on the reaction. Laulimalide is also active in P-glycoprotein overexpressing cells, while isolaulimalide, a congener without the drug's epoxide moiety, was reported to have negligible cytotoxic and biochemical activity [Mooberry et al. (1999) Cancer Res. 59, 653-660]. We report here that laulimalide binds at a site on tubulin polymer that is distinct from the taxoid site. We found that laulimalide, while as active as paclitaxel, epothilone A, and eleutherobin in promoting the assembly of cold-stable microtubules, was unable to inhibit the binding of radiolabeled paclitaxel or of 7-O-[N-(2,7-difluoro-4'-fluoresceincarbonyl)-L-alanyl]paclitaxel, a fluorescent paclitaxel derivative, to tubulin. Confirming this observation, we demonstrated that microtubules formed in the presence of both laulimalide and paclitaxel contained near-molar quantities, relative to tubulin, of both drugs. Laulimalide was active against cell lines resistant to paclitaxel or epothilones A and B on the basis of mutations in the M40 human beta-tubulin gene. We also report that a laulimalide analogue lacking the epoxide moiety, while less active than laulimalide in biochemical and cellular systems, is probably more active than isolaulimalide. Further exploration of the role of the epoxide in the interaction of laulimalide with tubulin is therefore justified.
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PMID:The microtubule stabilizing agent laulimalide does not bind in the taxoid site, kills cells resistant to paclitaxel and epothilones, and may not require its epoxide moiety for activity. 1211 25

Epothilones are naturally occurring 16-membered macrolides with the ability to promote tubulin polymerization in vitro and to stabilize preformed microtubules against Ca(2+)- or cold-induced depolymerization. In contrast to paclitaxel (Taxol((R))) epothilones are also active in vitro against multidrug-resistant cancer cell lines as well as cell lines whose paclitaxel-resistance is derived from specific beta-tubulin mutations. Based on their attractive in vitro biological profile epothilones have turned into important lead structures in anticancer drug discovery and hundreds of analogs and derivatives of epothilone A and B have been prepared and biologically characterized over the past four years. A number of compounds, including natural epothilone B, deoxyepothilone B, and epothilone B lactam (BMS-247550) have also been reported to exhibit profound in vivo antitumor activity in animal models. Apart from providing a brief summary of the SAR that has emerged from the above in vitro studies, this minireview will largely focus on the biology and chemistry of those analogs for which in vivo antitumor activity has been reported in the literature. Two of these compounds, natural epothilone B and epothilone B lactam (BMS-247550) have advanced to clinical studies in humans.
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PMID:Epothilone B and its analogs - a new family of anticancer agents. 1257 Aug 48

The early Caenorhabditis elegans embryo contains abundant transcripts for two alpha- and two beta-tubulins, raising the question of whether each isoform performs specialized functions or simply contributes to total tubulin levels. Our identification of two recessive, complementing alleles of a beta-tubulin that disrupt nuclear-centrosome centration and rotation in the early embryo originally suggested that this tubulin, tbb-2, has specialized functions. However, embryos from tbb-2 deletion worms do not have defects in nuclear-centrosome centration and rotation suggesting that the complementing alleles are not null mutations. Both complementing alleles have distinct effects on microtubule dynamics and show allele-specific interactions with the two embryonically expressed alpha-tubulins: One of the alleles causes microtubules to be cold stable and resistant to the microtubule-depolymerizing drug benomyl, whereas the other causes cell cycle-specific defects in microtubule polymerization. Gene-specific RNA interference targeting all four embryonically expressed tubulin genes singly and in all double combinations showed that the tubulin isoforms in the early embryo are largely functionally redundant with the exception of tbb-2. tbb-2 is required for centrosome stabilization during anaphase of the first cell division, suggesting that tbb-2 may be specialized for interactions with the cell cortex.
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PMID:Mutations in a beta-tubulin disrupt spindle orientation and microtubule dynamics in the early Caenorhabditis elegans embryo. 1293 70

The effects of exogenous abscisic acid (ABA), low temperature, and seedling age on the content of tubulin, actin, and phosphorylated proteins and the structural organization of microtubules (MTs) in cells of different tissues and organs of winter wheat cultivars contrasting in cold hardiness were studied by immunocytochemical methods using monoclonal (against alpha- and beta-tubulin and actin) and polyclonal (phosphothreonine) antibodies. The leaves and roots of five- and nine-day-old seedlings of three cultivars were characterized by unequal proportion of actin/tubulin proteins. ABA decreased the content of the cytoskeleton and the 60-kD phosphorylated proteins, thus promoting a decrease in the number of MTs and occurrence of a less branched network of weakly fluorescent tubulin components in the cells of the root differentiating zone (which is most responsible for the development of cold hardiness in wheat). Although the cold acclimation of plants (3 degrees C, 7 days) did not change the level of tubulin and actin proteins, it evoked the spatial aggregation of MT, leading to formation of a dense network of tubulin cytoskeleton comprised of thick bundles of intensively fluorescent MTs. In the case of a combined action of the studied factors, low temperatures abolished the hormone effect described above, evoking an increase in the content of the cytoskeletal and 60-kD phosphorylated proteins and MT structures. We suggest that the ABA-induced decrease in the levels of proteins and MTs occurs at the initial stages of plant cold acclimation (3 degrees C, 2-3 days). It may be the signal that triggers the processes of low-temperature adaptation. As the duration of cold acclimation increased (3 degrees C, 7 days), the role of ABA in the formation of plant tolerance decreased. Apparently, in this case other hormone-independent mechanisms of frost hardiness development are triggered, in which the role of the cytoskeleton components and cytoskeleton-associated proteins increases.
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PMID:Effects of abscisic acid, low temperature, and plant age on cytoskeleton and phosphorylated proteins. 1294 13

The microtubule cytoskeleton is involved in regulation of cell morphology, differentiation, and cell cycle progression. Precisely controlled dynamic properties are required for these microtubule functions. To better understand how tubulin's dynamics are embedded in its primary sequence, we investigated in vivo the consequences of altering a single, highly conserved residue in beta-tubulin that lies at the interface between two structural domains. The residue differs between the cold-adapted Antarctic fish and temperate animals in a manner that suggests a role in microtubule stability. Fungi, like the Antarctic fish, have a phenylalanine in this position, whereas essentially all other animals have tyrosine. We mutated the corresponding residue in fission yeast to tyrosine. Temperature effects were subtle, but time-lapse microscopy of microtubule dynamics revealed reduced depolymerization rates and increased stability. Mitotic exit signaled by breakdown of the mitotic spindle was delayed. In meiosis, microtubules displayed prolonged contact to the cell cortex during horsetail movement, followed by completion of meiosis I but frequent asymmetric failure of meiosis II spindle formation. Our results indicate that depolymerization dynamics modulated through interdomain motion may be important for regulating a subset of plus-end microtubule complexes in Schizosaccharomyces pombe.
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PMID:Meiosis-specific failure of cell cycle progression in fission yeast by mutation of a conserved beta-tubulin residue. 1465 51

Low and high levels of resistance to the benzimidazole fungicides benomyl and thiophanate-methyl were observed in field isolates of Monilinia fructicola, which is the causative agent of brown rot of stone fruit. Isolates that had low levels of resistance (hereafter referred to as LR isolates) and high levels of resistance (hereafter referred to as HR isolates) were also cold and heat sensitive, respectively. Results from microsatellite DNA fingerprints showed that genetic identities among the populations of sensitive (S), LR, and HR isolates were very high (>0.96). Analysis of DNA sequences of the beta-tubulin gene showed that the LR isolates had a point mutation at codon 6, causing a replacement of the amino acid histidine by tyrosine. Codon 198, which encodes a glutamic acid in S and LR isolates, was converted to a codon for alanine in HR isolates. Based on these point mutations in the beta-tubulin gene, allele-specific PCR assays were developed for rapid detection of benzimidazole-resistant isolates of M. fructicola from stone fruit.
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PMID:Identification and characterization of benzimidazole resistance in Monilinia fructicola from stone fruit orchards in California. 1466 Mar 60

We have shown previously that the tubulins of Antarctic fish assemble into microtubules efficiently at low temperatures (-2 to +2 degrees C) due to adaptations intrinsic to the tubulin subunits. To determine whether changes in posttranslational glutamylation of the fish tubulins may contribute to cold adaptation of microtubule assembly, we have characterized C-terminal peptides from alpha- and beta-tubulin chains from brains of adult specimens of the Antarctic rockcod Notothenia coriiceps by MALDI-TOF mass spectrometry and by Edman degradation amino acid sequencing. Of the four fish beta-tubulin isotypes, nonglutamylated isoforms were more abundant than glutamylated isoforms. In addition, maximal glutamyl side-chain length was shorter than that observed for mammalian brain beta tubulins. For the nine fish alpha-tubulin isotypes, nonglutamylated isoforms were also generally more abundant than glutamylated isoforms. When glutamylated, however, the maximal side-chain lengths of the fish alpha tubulins were generally longer than those of adult rat brain alpha chains. Thus, Antarctic fish adult brain tubulins are glutamylated differently than mammalian brain tubulins, resulting in a more heterogeneous population of alpha isoforms and a reduction in the number of beta isoforms. By contrast, neonatal rat brain tubulin possesses low levels of glutamylation that are similar to that of the adult fish brain tubulins. We suggest that unique residue substitutions in the primary structures of Antarctic fish tubulin isotypes and quantitative changes in isoform glutamylation act synergistically to adapt microtubule assembly to low temperatures.
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PMID:Posttranslational modification of brain tubulins from the Antarctic fish Notothenia coriiceps: reduced C-terminal glutamylation correlates with efficient microtubule assembly at low temperature. 1537 65

Novel C2-C3'N-linked macrocyclic taxoids 4 bearing an aromatic ring at position C2 were synthesized. These compounds, tethered between N3' and the C2-aromatic ring at the ortho, meta, or para position, were constructed by ring-closing metathesis. The para-substituted derivatives were unable to stabilize microtubules, whereas the ortho- and meta-substituted compounds show significant activity in cold-induced microtubule disassembly assay. The meta derivative 4c is the first C2-C3'-linked cyclic analogue to be equipotent to paclitaxel in this assay and to show significant cytotoxicity. Computational studies of the conformational behavior of these compounds indicate that they can adopt several conformations including mainly the "T-shaped" forms. Docking experiments have shown that the "T-shaped" form is preferred for a good interaction of these compounds with the beta-tubulin binding pocket.
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PMID:Synthesis of C2-C3'N-linked macrocyclic taxoids. Novel docetaxel analogues with high tubulin activity. 1553 48

Wild-type Saccharomyces cerevisiae tubulin does not bind the anti-mitotic microtubule stabilizing agent paclitaxel. Previously, we introduced mutations into the S. cerevisiae gene for beta-tubulin that imparted paclitaxel binding to the protein, but the mutant strain was not sensitive to paclitaxel and other microtubule-stabilizing agents, due to the multiple ABC transporters in the membranes of budding yeast. Here, we introduced the mutated beta-tubulin gene into a S. cerevisiae strain with diminished transporter activity and developed the first paclitaxel-sensitive budding yeast strain. In the presence of paclitaxel, cytoplasmic microtubules were stable to cold depolymerization. Paclitaxel-treated cells showed evidence of a mitotic block, with an increase in large-budded cells and cells with a 2N DNA content and DNA fragmentation, identified by FACS analysis and the TUNEL assay. In the presence of paclitaxel, the number of dead cells in cultures increased three-fold and cells containing reactive oxygen species were present. We conclude that paclitaxel blocks mitosis in this strain, leading to an apoptotic-like cell death. This strain will also be useful in further studies of the effect of microtubule dynamics on various cellular processes in S. cerevisiae.
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PMID:Paclitaxel-induced microtubule stabilization causes mitotic block and apoptotic-like cell death in a paclitaxel-sensitive strain of Saccharomyces cerevisiae. 1613 17


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