TAOK2 is an ER-localized Kinase that Catalyzes the Dynamic Tethering of ER to Microtubules

Abstract

The endoplasmic reticulum (ER) depends on extensive association with the microtubule cytoskeleton for its structure, function and mitotic inheritance. The identity of molecular tethers that mediate ER-microtubule coupling, and mechanisms through which dynamic tethering is regulated are poorly understood. Here, we identify, Thousand And One amino acid Kinase 2 (TAOK2) as a pleiotropic protein kinase that mediates tethering of ER to microtubules. We show that TAOK2 is a unique multipass membrane spanning serine/threonine kinase localized in distinct ER domains via four transmembrane and amphipathic helices. Using in vitro and cellular assays, we find that TAOK2 directly binds microtubules with high affinity. We define the minimal TAOK2 determinants that induce ER-microtubule tethering, and delineate the mechanism for its autoregulation. While ER membrane dynamics are increased in TAOK2 knockout cells, the movement of ER along growing microtubule plus-ends is disrupted. We show that ER-microtubule tethering is tightly regulated by catalytic activity of TAOK2 in both interphase and mitotic cells, perturbation of which leads to profound defects in ER morphology and cell division. Our study identifies TAOK2 as an ER-microtubule tether, and reveals a kinase-regulated mechanism for control of ER dynamics critical for cell growth and division.