title: Tissue-specific control of midbody microtubule stability by Citron kinase through modulation of TUBB3 phosphorylation.
abstract: Cytokinesis, the physical separation of daughter cells at the end of cell cycle, is commonly considered a highly stereotyped phenomenon. However, in some specialized cells this process may involve specific molecular events that are still largely unknown. In mammals, loss of Citron-kinase (CIT-K) leads to massive cytokinesis failure and apoptosis only in neuronal progenitors and in male germ cells, resulting in severe microcephaly and testicular hypoplasia, but the reasons for this specificity are unknown. In this report we show that CIT-K modulates the stability of midbody microtubules and that the expression of tubulin β-III (TUBB3) is crucial for this phenotype. We observed that TUBB3 is expressed in proliferating CNS progenitors, with a pattern correlating with the susceptibility to CIT-K loss. More importantly, depletion of TUBB3 in CIT-K-dependent cells makes them resistant to CIT-K loss, whereas TUBB3 overexpression increases their sensitivity to CIT-K knockdown. The loss of CIT-K leads to a strong decrease in the phosphorylation of S444 on TUBB3, a post-translational modification associated with microtubule stabilization. CIT-K may promote this event by interacting with TUBB3 and by recruiting at the midbody casein kinase-2α (CK2α) that has previously been reported to phosphorylate the S444 residue. Indeed, CK2α is lost from the midbody in CIT-K-depleted cells. Moreover, expression of the nonphosphorylatable TUBB3 mutant S444A induces cytokinesis failure, whereas expression of the phospho-mimetic mutant S444D rescues the cytokinesis failure induced by both CIT-K and CK2α loss. Altogether, our findings reveal that expression of relatively low levels of TUBB3 in mitotic cells can be detrimental for their cytokinesis and underscore the importance of CIT-K in counteracting this event.
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Sgrò
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors.forename: F T
authors.initials: FT
authors.lastname: Bianchi
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Falcone
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Pallavicini
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Gai
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors.forename: A M A
authors.initials: AM
authors.lastname: Chiotto
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors.forename: G E
authors.initials: GE
authors.lastname: Berto
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Turco
authors.affiliation: Max-Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Chang
authors.affiliation: Max-Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
authors.forename: W B
authors.initials: WB
authors.lastname: Huttner
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.|Neuroscience Institute of Turin, Turin, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Di Cunto
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008297:Male; D051379:Mice; D008870:Microtubules / Q000737:chemistry / Q000378:metabolism*; D009928:Organ Specificity; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C498585:TUBB3 protein, human; C000592703:Tubb3 protein, mouse; D014404:Tubulin; C115635:citron-kinase; D017346:Protein Serine-Threonine Kinases