Microtubule-associated protein autophosphorylation alters in vitro microtubule dynamic instability.
While phosphorylation of high-molecular-weight microtubule-associated proteins (MAPs) alters the assembly properties of microtubules in vitro, virtually nothing is known about the influence of MAP phosphorylation on the time-scale of microtubule polymer length redistribution. The latter has been used as an index of microtubule assembly/disassembly turnover as predicted by the dynamic instability model (Mitchison, T.M. and Kirschner, M.W. (1984) Nature 312, 237-242). We have now determined that under conditions leading to the incorporation of 8-10 mol phosphoryl groups per mol MAP-2 (and about 0.2 mol phosphoryl groups per mol MAP-1 and tau), we can reproducibly observe significant acceleration in the polymer length redistribution process in a manner consistent with greater microtubule dynamic instability. We have also found that MAP phosphorylation resulted in more extensive release of MAPs from microtubules as a function of increasing salt concentration. These results are consistent with a weakening of MAP-microtubule interactions upon phosphorylation.
Raffaelli
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Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville 32610-0245.
Yamauchi
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PS
Purich
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D000242:Cyclic AMP / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D017239:Paclitaxel; D010766:Phosphorylation; D016875:tau Proteins / Q000378:metabolism
D000470:Alkaloids; D008869:Microtubule-Associated Proteins; D016875:tau Proteins; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D017239:Paclitaxel