HSPA8 regulates microtubule detyrosination through direct interaction with the VASH1-SVBP complex

Detyrosination is one of the most well-studied post-translational modifications of microtubules (MTs), significantly impacting cell growth, differentiation, division, and intracellular traffic. The VASH1/2-SVBP complex is the first identified carboxypeptidase that specifically catalyzes the detyrosination modification of microtubules. While the structure and mechanisms of the VASH1/2-SVBP complex in mediating this modification are well studied, the regulatory mechanisms governing the catalytic activity of this enzyme remain elusive. Here, we identify a highly conserved five-residue motif located at the C-terminus of VASH1, demonstrating that this motif is crucial for the in vivo detyrosination activity of VASH1. Through peptide pull-down assays combined with mass spectrometry analysis, we identified the chaperone protein HSPA8 as a binding partner of VASH1. The structural model of the HSPA8-VASH1-SVBP ternary complex, predicted by AlphaFold, indicates that HSPA8 interacts with VASH1 through two distinct interaction surfaces. The subsequent biochemical analysis with mutagenesis assays was performed to validate the binding model of HSPA8 to VASH1. Furthermore, in vivo detyrosination assays in HeLa cells reveal that HSPA8 promotes the detyrosination modification of microtubules through direct binding to VASH1. Thus, our study identifies the HSPA8-regulated pathway of microtubule detyrosination, providing a potential target for the diagnosis and therapy of human diseases associated with abnormal microtubule detyrosination.