The Centrosomal Kinase Plk1 Localizes to the Transition Zone of Primary Cilia and Induces Phosphorylation of Nephrocystin-1

Abstract

Polo-like kinase (Plk1) plays a central role in regulating the cell cycle. Plk1-mediated phosphorylation is essential for centrosome maturation, and for numerous mitotic events. Although Plk1 localizes to multiple subcellular sites, a major site of action is the centrosomes, which supports mitotic functions in control of bipolar spindle formation. In G0 or G1 untransformed cells, the centriolar core of the centrosome differentiates into the basal body of the primary cilium. Primary cilia are antenna-like sensory organelles dynamically regulated during the cell cycle. Whether Plk1 has a role in ciliary biology has never been studied. Nephrocystin-1 (NPHP1) is a ciliary protein; loss of NPHP1 in humans causes nephronophthisis (NPH), an autosomal-recessive cystic kidney disease. We here demonstrate that Plk1 colocalizes with nephrocystin-1 to the transition zone of primary cilia in epithelial cells. Plk1 co-immunoprecipitates with NPHP1, suggesting it is part of the nephrocystin protein complex. We identified a candidate Plk1 phosphorylation motif (D/E-X-S/T-φ-X-D/E) in nephrocystin-1, and demonstrated in vitro that Plk1 phosphorylates the nephrocystin N-terminus, which includes the specific PLK1 phosphorylation motif. Further, induced disassembly of primary cilia rapidly evoked Plk1 kinase activity, while small molecule inhibition of Plk1 activity or RNAi-mediated downregulation of Plk1 limited the first and second phase of ciliary disassembly. These data identify Plk1 as a novel transition zone signaling protein, suggest a function of Plk1 in cilia dynamics, and link Plk1 to the pathogenesis of NPH and potentially other cystic kidney diseases.

PCM1 Recruits Plk1 to Pericentriolar Matrix to Promote Primary Cilia Disassembly before Mitotic Entry

“…Previous work suggests that PCM1 is important in the formation of primary cilia by associating with CEP290 and BBSome during the ciliogenesis (Kim et al, 2008;Nachury et al, 2007), indicating that PCM1 may play dual role in regulating primary cilia dynamics: When cells exit cell cycle and enter quiescence, PCM1 maintains steady state for primary cilia assembly independent of Plk1; whereas in proliferating cells, PCM1 is needed to recruit Plk1 to induce ciliary resorption before mitotic entry. During the preparation of this manuscript, two reports were published online and showed that the kinase activity of Plk1 is required for primary cilia disassembly (Lee et al, 2012;Seeger-Nukpezah et al, 2012). Lee and co-workers showed that Plk1 interacts with Dishevelled 2 (Dvl2) and promotes cilia disassembly; and Schermer and co-workers showed that Plk1 induces the phosphorylation of nephrocystin-1.…”

Cilia and coordination of signaling networks during heart development

“…By these means, primary cilia control cellular processes during development and in the adult organism. 20,[27][28][29][30][31][32][33][34][35][36] In addition, specialized non-motile sensory cilia are present on neurons in the olfactory epithelium of the nasal Table 1. Common types of congenital heart defects Congenital heart defect Abbreviation Characteristics…”

Cilia and cilia-associated proteins in cancer

“…The AURKA-activating interaction with NEDD9 is stimulated by the binding of Ca 2+ -liganded calmodulin to AURKA [15,16]. AURKA-NEDD9 interactions are also stabilized by an interacting PLK1-DVL2 complex at the basal body [11] and the adjacent ciliary transition zone [17]; in the normal initiation of ciliogenesis after mitosis, BUBR1 restrains DVL2 expression [18]. …”