Regulation of microtubule motors by tubulin isotypes and post-translational modifications

Abstract

The ‘tubulin-code’ hypothesis proposes that different tubulin genes or posttranslational modifications (PTMs), which mainly confer variation in the carboxy-terminal tail (CTT), result in unique interactions with microtubule-associated proteins for specific cellular functions. However, the inability to isolate distinct and homogenous tubulin species has hindered biochemical testing of this hypothesis. Here, we have engineered 25 α/β tubulin heterodimers with distinct CTTs and PTMs and tested their interactions with four different molecular motors using single molecule assays. Our results show that tubulin isotypes and PTMs can govern motor velocity, processivity and microtubule depolymerization rates, with substantial changes conferred by even single amino acid variation. Revealing the importance and specificity of PTMs, we show that kinesin-1 motility on neuronal β-tubulin (TUBB3) is increased by polyglutamylation and that robust kinesin-2 motility requires detyrosination of α-tubulin. Our results also show that different molecular motors recognize distinctive tubulin “signatures”, which supports the premise of tubulin-code hypothesis.

Tubulin Tail Sequences and Post-translational Modifications Regulate Closure of Mitochondrial Voltage-dependent Anion Channel (VDAC)

“…The CTT are also a major focus of post-translational modifications that comprise the "tubulin code" (8). In the microtubule, these tails form a charged brush surrounding the microtubule (9 -12) and, in this context, the post-translational modifications are recognized to regulate binding of other proteins (13).…”

“…This evolutionarily ancient post-translational modification of tubulin is usually related to microtubule stability and binding of other proteins to the microtubule (13), although also implicated in rapid shifts during cellular signaling (20,21).…”

Increased Spinal Cord Na+-K+-2Cl− Cotransporter-1 (NKCC1) Activity Contributes to Impairment of Synaptic Inhibition in Paclitaxel-induced Neuropathic Pain

“…Microtubule motors, including cytoplasmic dynein and kinesin-5, move along microtubules by interacting with tubulins (47,(55)(56)(57). There are two basic types of microtubule motors: plus-end motors and minus-end motors, depending on the direction in which they move along the microtubule track within the cell.…”

Microtubule Organization and Microtubule-Associated Proteins (MAPs)

“…For instance, kinesin-1 has been reported to prefer stable (acetylated/detyrosinated) MTs (Dunn et al 2008;Konishi and Setou 2009;Reed et al 2006). Additional in vitro studies showed that kinesin-1 motility is increased by polyglutamylation and that detyrosination of α-tubulin promotes kinesin-2 motility (Sirajuddin et al 2014). It has been hypothesized that posttranslational modifications, together with specific MAP patterns, form a "tubulin code" that can be "read" by factors that interact with MTs, such as motor proteins (Janke and Bulinski 2011;Tischfield and Engle 2010;Verhey and Gaertig 2007).…”