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Ectopic A-lattice seams destabilize microtubules.

ABSTRACT: Natural microtubules typically include one A-lattice seam within an otherwise helically symmetric B-lattice tube. It is currently unclear how A-lattice seams influence microtubule dynamic instability. Here we find that including extra A-lattice seams in GMPCPP microtubules, structural analogues of the GTP caps of dynamic microtubules, destabilizes them, enhancing their median shrinkage rate by >20-fold. Dynamic microtubules nucleated by seeds containing extra A-lattice seams have growth rates similar to microtubules nucleated by B-lattice seeds, yet have increased catastrophe frequencies at both ends. Furthermore, binding B-lattice GDP microtubules to a rigor kinesin surface stabilizes them against shrinkage, whereas microtubules with extra A-lattice seams are stabilized only slightly. Our data suggest that introducing extra A-lattice seams into dynamic microtubules destabilizes them by destabilizing their GTP caps. On this basis, we propose that the single A-lattice seam of natural B-lattice MTs may act as a trigger point, and potentially a regulation point, for catastrophe.

SUBMITTER: Katsuki M

PROVIDER: S-EPMC3921467 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Ectopic A-lattice seams destabilize microtubules.

Katsuki Miho M Drummond Douglas R DR Cross Robert A RA

Nature communications 20140101

Natural microtubules typically include one A-lattice seam within an otherwise helically symmetric B-lattice tube. It is currently unclear how A-lattice seams influence microtubule dynamic instability. Here we find that including extra A-lattice seams in GMPCPP microtubules, structural analogues of the GTP caps of dynamic microtubules, destabilizes them, enhancing their median shrinkage rate by >20-fold. Dynamic microtubules nucleated by seeds containing extra A-lattice seams have growth rates si ...[more]

PMID: 24463734

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Project description:Adenosine triphosphate (ATP) synthase is located on the inner membrane of mitochondria which generate ATP for various cellular processes. Our previous studies showed that ATP synthases existed on plasma membrane of several types of cancer cells, which was defined as ectopic ATP synthase. However, the trafficking pathway of ectopic ATP synthase is still unclear. To investigate how ATP synthase subunits are involved in the trafficking process, we performed shot-gun proteomic analysis to reveal the plasma membrane proteins of A549 lung cancer cells and identified four subunits of ATP synthases, ATP5A1, ATP5B, ATP5H, and MT-ATP6. With the results of gene set enrichment analysis, we inferred that ectopic ATP synthase subunits are assembled as complex consistently and then translocated to cell surface through the trafficking of mitochondria. On the other hand, microtubules are involved in many intracellular transport. During protein trafficking, mitochondria and vesicles are transported to their final destination along microtubules by motor proteins such as kinesins and dyneins. To explore the function of microtubules in the trafficking of ectopic ATP synthase, we treated MCF-7 breast and A549 lung cancer cells with nocodazole, a microtubule depolymerization agent, and found that the expression level of ectopic ATP synthase decreased using both immunocytochemistry and flow cytometry. Besides, since kinesin family member 5B (KIF5B) is an important motor proteins involved in the transport of mitochondria, we further performed the immunoprecipitation of KIF5B followed by liquid chromatography−tandem mass spectrometry (LC−MS/MS). The result revealed that one of the mitochondrial outer membrane proteins, dynamin-1 like proteins (Drp1), was able to associate to KIF5B. From our recent research results and other reports show that Drp1 is a mediator of mitochondrial dynamic through regulation of mitochondrial fission. Taken together, our findings suggested that Drp1-KIF5B complex-mediated mitochondrial trafficking along microtubules may play a critical role in the transport of ectopic ATP synthase

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Ectopic A-lattice seams destabilize microtubules.

Publications

Ectopic A-lattice seams destabilize microtubules.

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