Revisiting the tubulin cofactors and Arl2 in the regulation of soluble αβ-tubulin pools and their effect on microtubule dynamics.

Soluble αβ-tubulin heterodimers are maintained at high concentration inside eukaryotic cells, forming pools that fundamentally drive microtubule dynamics. Five conserved tubulin cofactors and ADP ribosylation factor-like 2 regulate the biogenesis and degradation of αβ-tubulins to maintain concentrated soluble pools. Here I describe a revised model for the function of three tubulin cofactors and Arl2 as a multisubunit GTP-hydrolyzing catalytic chaperone that cycles to promote αβ-tubulin biogenesis and degradation. This model helps explain old and new data indicating these activities enhance microtubule dynamics in vivo via repair or removal of αβ-tubulins from the soluble pools.