title: Centrobin-mediated regulation of the centrosomal protein 4.1-associated protein (CPAP) level limits centriole length during elongation stage.
abstract: Microtubule-based centrioles in the centrosome mediate accurate bipolar cell division, spindle orientation, and primary cilia formation. Cellular checkpoints ensure that the centrioles duplicate only once in every cell cycle and achieve precise dimensions, dysregulation of which results in genetic instability and neuro- and ciliopathies. The normal cellular level of centrosomal protein 4.1-associated protein (CPAP), achieved by its degradation at mitosis, is considered as one of the major mechanisms that limits centriole growth at a predetermined length. Here we show that CPAP levels and centriole elongation are regulated by centrobin. Exogenous expression of centrobin causes abnormal elongation of centrioles due to massive accumulation of CPAP in the cell. Conversely, CPAP was undetectable in centrobin-depleted cells, suggesting that it undergoes degradation in the absence of centrobin. Only the reintroduction of full-length centrobin, but not its mutant form that lacks the CPAP binding site, could restore cellular CPAP levels in centrobin-depleted cells, indicating that persistence of CPAP requires its interaction with centrobin. Interestingly, inhibition of the proteasome in centrobin-depleted cells restored the cellular and centriolar CPAP expression, suggesting its ubiquitination and proteasome-mediated degradation when centrobin is absent. Intriguingly, however, centrobin-overexpressing cells also showed proteasome-independent accumulation of ubiquitinated CPAP and abnormal, ubiquitin-positive, elongated centrioles. Overall, our results show that centrobin interacts with ubiquitinated CPAP and prevents its degradation for normal centriole elongation function. Therefore, it appears that loss of centrobin expression destabilizes CPAP and triggers its degradation to restrict the centriole length during biogenesis.
authors.affiliation: From the Department of Microbiology and Immunology, gudi@musc.edu.
authors.forename: Radhika
authors.initials: R
authors.lastname: Gudi
authors.affiliation: Department of Oral Health Sciences.
authors.forename: Courtney J
authors.initials: CJ
authors.lastname: Haycraft
authors.affiliation: Department of Medicine, and.
authors.forename: P Darwin
authors.initials: PD
authors.lastname: Bell
authors.affiliation: From the Department of Microbiology and Immunology.
authors.forename: Zihai
authors.initials: Z
authors.lastname: Li
authors.affiliation: From the Department of Microbiology and Immunology, Department of Surgery, Medical University of South Carolina, Charleston, South Carolina 29425.
authors.forename: Chenthamarakshan
authors.initials: C
authors.lastname: Vasu
mesh_terms: D018797:Cell Cycle Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002502:Centrioles / Q000378:metabolism* / Q000648:ultrastructure; D017353:Gene Deletion; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000032:analysis / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D059748:Proteolysis; D054875:Ubiquitination; D015854:Up-Regulation
chemical_list: C414735:CENPJ protein, human; C507203:CNTROB protein, human; D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D046988:Proteasome Endopeptidase Complex
keywords: Centriole; Centrosome; Confocal Microscopy; Proteasome; Ubiquitin