Differential Binding Regulation of Microtubule-associated Proteins MAP1A, MAP1B, and MAP2 by Tubulin Polyglutamylation

Abstract

The major neuronal post-translational modification of tubulin, polyglutamylation, can act as a molecular potentiometer to modulate microtubule-associated proteins (MAPs) binding as a function of the polyglutamyl chain length. The relative affinity of Tau, MAP2, and kinesin has been shown to be optimal for tubulin modified by ϳ3 glutamyl units. Using blot overlay assays, we have tested the ability of polyglutamylation to modulate the interaction of two other structural MAPs, MAP1A and MAP1B, with tubulin. MAP1A and MAP2 display distinct behavior in terms of tubulin binding; they do not compete with each other, even when the polyglutamyl chains of tubulin are removed, indicating that they have distinct binding sites on tubulin. Binding of MAP1A and MAP1B to tubulin is also controlled by polyglutamylation and, although the modulation of MAP1B binding resembles that of MAP2, we found that polyglutamylation can exert a different mode of regulation toward MAP1A. Interestingly, although the affinity of the other MAPs tested so far decreases sharply for tubulins carrying long polyglutamyl chains, the affinity of MAP1A for these tubulins is maintained at a significant level. This differential regulation exerted by polyglutamylation toward different MAPs might facilitate their selective recruitment into distinct microtubule populations, hence modulating their functional properties. Microtubules (MTs)1 are dynamic polymers, which are essential for a large variety of cellular functions such as cell morphology and polarity, cell motility, intracellular trafficking, and cell division. They are made up of ␣-and ␤-tubulin heterodimers, the two related subunits displaying a large isoform polymorphism due to the expression of multiple genes whose products are substrates for several post-translational modifications (for review, see Refs.

Protein 4.1R, a Microtubule-associated Protein Involved in Microtubule Aster Assembly in Mammalian Mitotic Extract

“…In contrast to the interaction of 4.1R isoforms with interphase T-cell tubulin (13), an interaction that requires only the MBD, we found that both the MBD and the CTD of 4.1R contribute to its binding to tubulin in HeLa mitotic extracts. Post-translational modifications of tubulin have been shown to regulate its association with microtubule-associated proteins (43). Polyglutamylated tubulin was detected in proliferating cells of different origins (HeLa, KE37, and NIH 3T3), where it associates with the centrioles, the spindle, and the midbody (44).…”

Correlated break at PARK2/FRA6E and loss of AF-6/Afadin protein expression are associated with poor outcome in breast cancer

“…TTLL2 (Tubulin Tyrosine Ligase-like 2) encodes a member of the TTL homology domain protein family, which catalyses the ligation of glutamic acid to tubulin. In neuronal systems, tubulin polyglutamination could regulate the organization of microtubule network (Bonnet et al, 2001) thus controlling centriole stability and mitosis (Bobinnec et al, 1998a, b). KIF25 encodes a protein of the kinesin superfamily, KIF25, which is involved in molecular transport away from the centrosome (Miki et al, 2005).…”

The Tubulin Code

“…75 In vitro, Tau, MAP1B, and MAP2 bind preferentially to tubulins with moderate levels of polyglutamylation (~3 glutamyl units) whereas MAP1A shows optimal affinity for highly modified tubulins (~6 glutamyl units). [76][77][78] As a-tubulin glutamylation is abundant in very young neurons whereas b-tubulin glutamylation increases during post-natal development, 50 glutamylation could control transitions in MAP binding during neuronal development. 78 Lys 40 a-tubulin acetylation may also influence MAP binding as overexpression of HDAC6 delocalized p58, a MAP involved in the association of Golgi membranes with microtubules.…”

“…[76][77][78] As a-tubulin glutamylation is abundant in very young neurons whereas b-tubulin glutamylation increases during post-natal development, 50 glutamylation could control transitions in MAP binding during neuronal development. 78 Lys 40 a-tubulin acetylation may also influence MAP binding as overexpression of HDAC6 delocalized p58, a MAP involved in the association of Golgi membranes with microtubules. 79 +TIPs.…”