title: Cytosolic carboxypeptidase 1 is involved in processing α- and β-tubulin.
abstract: The Purkinje cell degeneration (pcd) mouse has a disruption in the gene encoding cytosolic carboxypeptidase 1 (CCP1). This study tested two proposed functions of CCP1: degradation of intracellular peptides and processing of tubulin. Overexpression (2-3-fold) or knockdown (80-90%) of CCP1 in human embryonic kidney 293T cells (HEK293T) did not affect the levels of most intracellular peptides but altered the levels of α-tubulin lacking two C-terminal amino acids (delta2-tubulin) ≥ 5-fold, suggesting that tubulin processing is the primary function of CCP1, not peptide degradation. Purified CCP1 produced delta2-tubulin from purified porcine brain α-tubulin or polymerized HEK293T microtubules. In addition, CCP1 removed Glu residues from the polyglutamyl side chains of porcine brain α- and β-tubulin and also generated a form of α-tubulin with two C-terminal Glu residues removed (delta3-tubulin). Consistent with this, pcd mouse brain showed hyperglutamylation of both α- and β-tubulin. The hyperglutamylation of α- and β-tubulin and subsequent death of Purkinje cells in pcd mice was counteracted by the knock-out of the gene encoding tubulin tyrosine ligase-like-1, indicating that this enzyme hyperglutamylates α- and β-tubulin. Taken together, these results demonstrate a role for CCP1 in the processing of Glu residues from β- as well as α-tubulin in vitro and in vivo.
authors.affiliation: Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
authors.forename: Iryna
authors.initials: I
authors.lastname: Berezniuk
authors.forename: Hang T
authors.initials: HT
authors.lastname: Vu
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Lyons
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Sironi
authors.forename: Hui
authors.initials: H
authors.lastname: Xiao
authors.forename: Berta
authors.initials: B
authors.lastname: Burd
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Setou
authors.forename: Ruth H
authors.initials: RH
authors.lastname: Angeletti
authors.forename: Koji
authors.initials: K
authors.lastname: Ikegami
authors.forename: Lloyd D
authors.initials: LD
authors.lastname: Fricker
mesh_terms: D000818:Animals; D001943:Breast Neoplasms; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms; D003600:Cytosol / Q000201:enzymology; D005260:Female; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008817:Mice, Mutant Strains; D009410:Nerve Degeneration / Q000235:genetics / Q000378:metabolism*; D010453:Peptide Synthases / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011689:Purkinje Cells / Q000201:enzymology / Q000473:pathology; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase / Q000235:genetics / Q000378:metabolism*; D013552:Swine; D014404:Tubulin / Q000737:chemistry / Q000378:metabolism*
chemical_list: D014404:Tubulin; D018698:Glutamic Acid; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase; C420042:Agtpbp1 protein, mouse; D019204:GTP-Binding Proteins; D010453:Peptide Synthases; C112698:tubulin polyglutamylase