Tumor suppressor RARRES1 interacts with cytoplasmic carboxypeptidase AGBL2 to regulate the α-tubulin tyrosination cycle

Even though it is among the most commonly methylated loci in multiple cancers, the retinoic acid-induced tumor suppressor retinoic acid receptor responder 1 (RARRES1) has no known function. We now show that RARRES1 is lost in many Cancer cells, particularly those with a mesenchymal phenotype, and is a transmembrane Carboxypeptidase Inhibitor that interacts with ATP/GTP binding protein-like 2 (AGBL2), a cytoplasmic Carboxypeptidase. Knockdown of AGBL2 results in a failure of the cell to detyrosinate the C-terminal EEY region of α-tubulin and indicates that it is a candidate for the long sought-after tubulin tyrosine Carboxypeptidase important in the regulation of microtubule dynamics. In contrast, knockdown of RARRES1 increases the level of detyrosinated α-tubulin consistent with a role as the cognate inhibitor of AGBL2. We conclude that RARRES1, its interacting partners AGBL2, Eg5/KIF11, another EEY-bearing protein (EB1), and the microtubule tyrosination cycle are important in tumorigenesis and identify a novel area for therapeutic intervention.