G protein beta subunit is closely associated with microtubules.
Previously, we have identified the association of G protein beta subunit (Gbeta) with mitotic spindles in various mammalian cells. Since microtubules are the main component of mitotic spindles, here we have isolated bovine brain microtubules and purified Gbeta subunit to identify the close association of Gbeta subunit with purified brain microtubules and have shown the direct incorporation of Gbeta subunit into the microtubules both in vitro and in vivo. It was found that: (1) microtubular fraction isolated from bovine brain contained Gbeta subunit, (2) coimmunoprecipitation demonstrated that Gbeta subunit could be coprecipitated with tubulin, (3) addition of purified Gbeta subunit into cytosolic extract for microtubule assembly caused direct incorporation of Gbeta subunit into assembled microtubules and increased the association of microtubule-associated proteins with microtubules, and (4) incubation of exogenous Gbeta subunit with detergent-permeabilized cells resulted in direct incorporation of Gbeta subunit into microtubule fibers and depolymerized tubulin molecules. We conclude that G protein beta subunit is closely associated with microtubules and may play an important role in the regulation of microtubule formation in addition to its regulatory role in cellular signal transduction.
Institute of Pathology, College of Medicine, National Taiwan University, Taipei.
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Wu
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Huang
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Lin
D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D002474:Cell-Free System; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D019204:GTP-Binding Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*
D019204:GTP-Binding Proteins