FIG 1.

MT organization and regulation. (A) A primary fibroblast fixed and stained for EB1 and dynamic (tyrosinated) MTs. The nucleus is stained with Hoechst stain. 1, focal point of MTs emanating from the centrosome. 2, EB1 forms a “comet-like” staining pattern as it tracks growing MT plus ends. (B) Schematic overview of core features of MT nucleation at the centrosome. γ-TuSCs are organized into γ-TuRCs surrounded by pericentriolar material. γ-Tubulin binds α-tubulin at the minus end, while plus ends grow through the addition of new α/β-tubulin dimers loaded with GTP, which is rapidly hydrolyzed as the filament polymerizes. MAPs associate with the MT lattice and regulate stability. +TIPs can bind MTs but accumulate at MT plus ends through interactions with EB family members (EB1 to -3) that recognize GTP-tubulin. (C) Illustration showing how cells contain a mix of growing and depolymerizing MTs that can nucleate from multiple MTOCs, including the centrosome, Golgi apparatus, plasma membrane, and nucleus. Polarization of the MT array involves the stabilization of MT subsets captured at the plasma membrane in response to localized environmental signals. Stable MTs serve as specialized tracks that sort organelles and vesicles to specific regions of the cell.