Effects of α-tubulin acetylation on microtubule structure and stability

Abstract

28Acetylation of K40 in α-tubulin is the sole post-translational modification to mark the 29 luminal surface of microtubules. It is still controversial whether its relationship with 30 microtubule stabilization is correlative or causative. We have obtained high-resolution 31 cryo-electron microscopy reconstructions of pure samples of αTAT1-acetylated and 32 SIRT2-deacetylated microtubules to visualize the structural consequences of this 33 modification and reveal its potential for influencing the larger assembly properties of 34 microtubules. We modeled the conformational ensembles of the unmodified and 35 acetylated states by using the experimental cryo-EM density as the structural restraint in 36 molecular dynamics simulations. We found that acetylation alters the conformational 37 landscape of the flexible loop that contains αK40. Modification of αK40 reduces the 38 disorder of the loop and restricts the states that it samples. We propose that the change 39 in conformational sampling that we describe, at a location very close to the lateral contacts 40 site, is likely to affect microtubule stability and function. 41 42 ABBREVIATIONS 43 MT, microtubule; PF, protofilament; PTM, post-translational modification; MAP, 44 microtubule-associated protein; αTAT1, acetyltransferase TAT1 for α-tubulin; SIRT2 45 deacetylase SIRT2. 46 47 131 cryo-EM samples as previously described 2,26 of Ac 96 and Ac 0 MTs in the presence of end-132 binding protein 3 (EB3). EB3 served as a fiducial marker of the dimer that facilitated 133 alignment of MT segments during image processing 27 . Table S1 summarizes the data 134

ARMC9 and TOGARAM1 define a Joubert syndrome-associated protein module that regulates axonemal post-translational modifications and cilium stability

“…It has been long observed that the hyperstabilized ciliary microtubules are acetylated, but until recently it was not known if the modification confers stability or if long-lived stable microtubules accumulate this modification. Recent work using cryo-EM confirmed that acetylation causes a stabilizing conformational change (68). This is in line with our findings of decreased axonemal microtubule acetylation and stability with ARMC9 and TOGARAM1 dysfunction, as well as previously published findings with Kif7 dysfunction (57).…”

NC1‐peptide regulates spermatogenesis through changes in cytoskeletal organization mediated by EB1

“…But co-overexpression of EB1 was found to block the NC1-peptide mediated disruptive organization of MTs in Sertoli cells. Overexpression of EB1 also blocked the NC1-peptide induced disruptive organization of acetylated α-tubulin (the stabilized form of MTs53,86 ) and tyrosinated α-tubulin (which confers MTs to become more dynamic54 as noted herein. B, Based on a biochemical assay to quantify the relative amount of polymerized MTs, overexpression of NC1-peptide reduced the ability of Sertoli cells to polymerize MTs, which was also blocked following overexpression of EB1.…”

“…As shown in Figure 9A, overexpression of EB1 was capable of blocking NC1-peptide-induced disruptive organization of MTs, possibly through changes in distribution of the acetylated α-tubulin (the modified form of α-tubulin known to induce MT stabilization 53,54 ) and tyrosinated α-tubulin (the modified form of α-tubulin known to induce MT dynamic, making MTs less stable 54 ). For instance, following NC1peptide overexpression, MTs no longer stretched across the F I G U R E 6 NC1-peptide-induced disruptive cytoskeletal organization of MTs is mediated through disruptive spatial expression of dynein 1 and Dvl3.…”

The inner junction complex of the cilia is an interaction hub that involves tubulin post-translational modifications

“…S3D-G). When there is no interacting protein, this loop is flexible consistent with previous literature (29). However, we were able visualize the loop in several places in both Chlamydomonas and Tetrahymena where there is an interacting protein (Fig.…”