title: Sticky/Citron kinase maintains proper RhoA localization at the cleavage site during cytokinesis.
abstract: In many organisms, the small guanosine triphosphatase RhoA controls assembly and contraction of the actomyosin ring during cytokinesis by activating different effectors. Although the role of some RhoA effectors like formins and Rho kinase is reasonably understood, the functions of another putative effector, Citron kinase (CIT-K), are still debated. In this paper, we show that, contrary to previous models, the Drosophila melanogaster CIT-K orthologue Sticky (Sti) does not require interaction with RhoA to localize to the cleavage site. Instead, RhoA fails to form a compact ring in late cytokinesis after Sti depletion, and this function requires Sti kinase activity. Moreover, we found that the Sti Citron-Nik1 homology domain interacts with RhoA regardless of its status, indicating that Sti is not a canonical RhoA effector. Finally, Sti depletion caused an increase of phosphorylated myosin regulatory light chain at the cleavage site in late cytokinesis. We propose that Sti/CIT-K maintains correct RhoA localization at the cleavage site, which is necessary for proper RhoA activity and contractile ring dynamics.
authors.affiliation: Department of Pathology, Cell Cycle Genetics Research Group, Department of Genetics, University of Cambridge, Cambridge CB2 1QP, England, UK.
authors.forename: Zuni I
authors.initials: ZI
authors.lastname: Bassi
authors.forename: Koen J
authors.initials: KJ
authors.lastname: Verbrugghe
authors.forename: Luisa
authors.initials: L
authors.lastname: Capalbo
authors.forename: Stephen
authors.initials: S
authors.lastname: Gregory
authors.forename: Emilie
authors.initials: E
authors.lastname: Montembault
authors.forename: David M
authors.initials: DM
authors.lastname: Glover
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: D'Avino
mesh_terms: D000818:Animals; D048749:Cytokinesis; D004330:Drosophila / Q000166:cytology* / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; C115635:citron-kinase; D017346:Protein Serine-Threonine Kinases; C511153:Rho1 protein, Drosophila; D020741:rho GTP-Binding Proteins
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