title: A polymer-dependent increase in phosphorylation of beta-tubulin accompanies differentiation of a mouse neuroblastoma cell line.
abstract: We have examined the phosphorylation of cellular microtubule proteins during differentiation and neurite outgrowth in N115 mouse neuroblastoma cells. N115 differentiation, induced by serum withdrawal, is accompanied by a fourfold increase in phosphorylation of a 54,000-mol-wt protein identified as a specific isoform of beta-tubulin by SDS PAGE, two-dimensional isoelectric focusing/SDS PAGE, and immunoprecipitation with a specific monoclonal antiserum. Isoelectric focusing/SDS PAGE of [35S]methionine-labeled cell extracts revealed that the phosphorylated isoform of beta-tubulin, termed beta 2, is one of three isoforms detected in differentiated N115 cells, and is diminished in amounts in the undifferentiated cells. Taxol, a drug which promotes microtubule assembly, stimulates phosphorylation of beta-tubulin in both differentiated and undifferentiated N115 cells. In contrast, treatment of differentiated cells with either colcemid or nocodazole causes a rapid decrease in beta-tubulin phosphorylation. Thus, the phosphorylation of beta-tubulin in N115 cells is coupled to the levels of cellular microtubules. The observed increase in beta-tubulin phosphorylation during differentiation then reflects developmental regulation of microtubule assembly during neurite outgrowth, rather than developmental regulation of a tubulin kinase activity.
authors.forename: D L
authors.initials: DL
authors.lastname: Gard
authors.forename: M W
authors.initials: MW
authors.lastname: Kirschner
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D003703:Demecolcine / Q000494:pharmacology; D051379:Mice; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D009447:Neuroblastoma / Q000378:metabolism*; D017239:Paclitaxel; D010766:Phosphorylation; D014404:Tubulin / Q000378:metabolism*
chemical_list: D000470:Alkaloids; D014404:Tubulin; D017239:Paclitaxel; D003703:Demecolcine