title: Calpain 6 is involved in microtubule stabilization and cytoskeletal organization.
abstract: The calpains are a family of Ca(2+)-dependent cysteine proteases implicated in various biological processes. In this family, calpain 6 (Capn6) is unique in that it lacks the active-site cysteine residues requisite for protease activity. During the search for genes downstream of the endothelin 1 (ET-1) signaling in pharyngeal-arch development, we identified Capn6. After confirming that the expression of Capn6 in pharyngeal arches is downregulated in ET-1-null embryos by in situ hybridization, we investigated its function. In Capn6-transfected cells, cytokinesis was retarded and was often aborted to yield multinucleated cells. Capn6 overexpression also caused the formation of microtubule bundles rich in acetylated alpha-tubulin and resistant to the depolymerizing activity of nocodazole. Green fluorescent protein-Capn6 overexpression, immunostaining for endogenous Capn6, and biochemical analysis demonstrated interaction between Capn6 and microtubules, which appeared to be mainly mediated by domain III. Furthermore, RNA interference-mediated Capn6 inactivation caused microtubule instability with a loss of acetylated alpha-tubulin and induced actin reorganization, resulting in lamellipodium formation with membrane ruffling. Taken together, these results indicate that Capn6 is a microtubule-stabilizing protein expressed in embryonic tissues that may be involved in the regulation of microtubule dynamics and cytoskeletal organization.
authors.affiliation: Department of Physiological Chemistry and Metabolism, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tonami
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kurihara
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Aburatani
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Uchijima
authors.forename: Tomoichiro
authors.initials: T
authors.lastname: Asano
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kurihara
mesh_terms: D000107:Acetylation; D000818:Animals; D002154:Calpain / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D048749:Cytokinesis; D003599:Cytoskeleton / Q000502:physiology* / Q000648:ultrastructure; D004622:Embryo, Mammalian / Q000166:cytology; D019332:Endothelin-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008334:Mandible / Q000166:cytology; D051379:Mice; D018345:Mice, Knockout; D008870:Microtubules / Q000502:physiology / Q000648:ultrastructure; D020411:Oligonucleotide Array Sequence Analysis; D011554:Pseudopodia / Q000502:physiology; D034622:RNA Interference; D015398:Signal Transduction
chemical_list: D019332:Endothelin-1; D002154:Calpain; C403234:Capn6 protein, mouse