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.
Highlights
Cilia are microtubule-based sensory organelles projecting from the surface of almost all mammalian cells [1]
Plk1 usually co-localizes with c-tubulin at centrosomes in cycling cells [29] (Fig. S1), the Plk1 signal did not overlap with the c-tubulin signal marking the basal bodies, but was consistently slightly displaced into the region between the basal body and the ciliary shaft, which reflects the transition zone [30]
Plk1 strikingly colocalized with the transition zone protein nephrocystin-1 (NPHP1) in both cell lines (Fig. 1B)
Summary
Cilia are microtubule-based sensory organelles projecting from the surface of almost all mammalian cells [1]. Covered by a specialized plasma membrane compartment, cilia play a major role in cell signaling during chemosensation and mechanosensation [2]. Ciliary assembly occurs in the G1 or G0 phases of the cell cycle, as the mother centriole converges to the plasma membrane and forms a basal body. This provides an anchor point for extension of the microtubule core of the cilium and positions the cilium at the apical membrane of the cell. Through signaling and sequestration of the mother centriole in the basal body, primary cilia influence cell cycle progression [4]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
