Cap-Gly Proteins at Microtubule Plus Ends: Is EB1 Detyrosination Involved?

Localization of CAP-Gly proteins such as CLIP170 at microtubule+ends results from their dual interaction with alpha-tubulin and EB1 through their C-terminal amino acids -EEY. Detyrosination (cleavage of the terminal tyrosine) of alpha-tubulin by tubulin-carboxypeptidase abolishes CLIP170 binding. Can detyrosination affect EB1 and thus regulate the presence of CLIP170 at microtubule+ends as well? We developed specific antibodies to discriminate tyrosinated vs detyrosinated forms of EB1 and detected only tyrosinated EB1 in fibroblasts, astrocytes, and total brain tissue. Over-expressed EB1 was not detyrosinated in cells and chimeric EB1 with the eight C-terminal amino acids of alpha-tubulin was only barely detyrosinated. Our results indicate that detyrosination regulates CLIPs interaction with alpha-tubulin, but not with EB1. They highlight the specificity of carboxypeptidase toward tubulin.