Mechanistic Analysis of CCP1 in Generating ΔC2 α-Tubulin in Mammalian Cells and Photoreceptor Neurons

Biomolecules. 2023 Feb 12;13(2):357. doi: 10.3390/biom13020357.

Abstract

An important post-translational modification (PTM) of α-tubulin is the removal of amino acids from its C-terminus. Removal of the C-terminal tyrosine residue yields detyrosinated α-tubulin, and subsequent removal of the penultimate glutamate residue produces ΔC2-α-tubulin. These PTMs alter the ability of the α-tubulin C-terminal tail to interact with effector proteins and are thereby thought to change microtubule dynamics, stability, and organization. The peptidase(s) that produces ΔC2-α-tubulin in a physiological context remains unclear. Here, we take advantage of the observation that ΔC2-α-tubulin accumulates to high levels in cells lacking tubulin tyrosine ligase (TTL) to screen for cytosolic carboxypeptidases (CCPs) that generate ΔC2-α-tubulin. We identify CCP1 as the sole peptidase that produces ΔC2-α-tubulin in TTLΔ HeLa cells. Interestingly, we find that the levels of ΔC2-α-tubulin are only modestly reduced in photoreceptors of ccp1-/- mice, indicating that other peptidases act synergistically with CCP1 to produce ΔC2-α-tubulin in post-mitotic cells. Moreover, the production of ΔC2-α-tubulin appears to be under tight spatial control in the photoreceptor cilium: ΔC2-α-tubulin persists in the connecting cilium of ccp1-/- but is depleted in the distal portion of the photoreceptor. This work establishes the groundwork to pinpoint the function of ΔC2-α-tubulin in proliferating and post-mitotic mammalian cells.

Keywords: VASOHIBIN; cytosolic carboxypeptidase (CCP); detyrosination; tubulin; ΔC2-tubulin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • HeLa Cells
  • Humans
  • Mammals / metabolism
  • Mice
  • Microtubules / metabolism
  • Neurons* / metabolism
  • Peptide Hydrolases / metabolism
  • Protein Processing, Post-Translational
  • Tubulin* / metabolism
  • Tyrosine / metabolism

Substances

  • Tubulin
  • Peptide Hydrolases
  • Tyrosine