Regulation of microtubule detyrosination by Ca2+ and conventional calpains

• DOI: 10.1242/jcs.259108
• Publication Date: 2022-04-04T07:55:17Z
• Authors: Julia Bär; Yannes Popp; Tomas Koudelka; Andreas Tholey; Marina Mikhaylova
• Keywords: 0301 basic medicine; 03 medical and health sciences; HEK293 Cells; Calpain; Tubulin; Humans; Calcium; Cell Cycle Proteins; Angiogenic Proteins; Carrier Proteins; Microtubules

ABSTRACT Detyrosination is a major post-translational modification of microtubules (MTs), which has significant impact on MT function in cell division, differentiation, growth, migration and intracellular trafficking. Detyrosination of α-tubulin occurs mostly via the recently identified complex of vasohibin 1 or 2 (VASH1 and VASH2, respectively) with small vasohibin binding protein (SVBP). However, there is still remaining detyrosinating activity in the absence of VASH1 and/or VASH2 and SVBP, and little is known about the regulation of detyrosination. Here, we found that intracellular Ca2+ is required for efficient MT detyrosination. Furthermore, we show that the Ca2+-dependent proteases calpains 1 and 2 (CAPN1 and CAPN2, respectively) regulate MT detyrosination in VASH1- and SVBP-overexpressing human embryonic kidney (HEK293T) cells. We identified new calpain cleavage sites in the N-terminal disordered region of VASH1. However, this cleavage did not affect the enzymatic activity of vasohibins. In conclusion, we suggest that the regulation of VASH1-mediated MT detyrosination by calpains could occur independently of vasohibin catalytic activity or via another yet unknown tubulin carboxypeptidase. Importantly, the Ca2+ dependency of calpains could allow a fine regulation of MT detyrosination. Thus, identifying the calpain-regulated pathway of MT detyrosination can be of major importance for basic and clinical research.