Polycystins 1 and 2 mediate mechanosensation in the primary cilium of kidney cells

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Several proteins implicated in the pathogenesis of polycystic kidney disease (PKD) localize to cilia. Furthermore, cilia are malformed in mice with PKD with mutations in TgN737Rpw (encoding polaris). It is not known, however, whether ciliary dysfunction occurs or is relevant to cyst formation in PKD. Here, we show that polycystin-1 (PC1) and polycystin-2 (PC2), proteins respectively encoded by Pkd1 and Pkd2, mouse orthologs of genes mutated in human autosomal dominant PKD, co-distribute in the primary cilia of kidney epithelium. Cells isolated from transgenic mice that lack functional PC1 formed cilia but did not increase Ca2+ influx in response to physiological fluid flow. Blocking antibodies directed against PC2 similarly abolished the flow response in wild-type cells as did inhibitors of the ryanodine receptor, whereas inhibitors of G-proteins, phospholipase C and InsP3 receptors had no effect. These data suggest that PC1 and PC2 contribute to fluid-flow sensation by the primary cilium in renal epithelium and that they both function in the same mechanotransduction pathway. Loss or dysfunction of PC1 or PC2 may therefore lead to PKD owing to the inability of cells to sense mechanical cues that normally regulate tissue morphogenesis.

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Figure 1: Polycystin-1 was detected in the cilia of wild-type (wt) mouse embryonic kidney and collecting duct–derived epithelial cells.
Figure 2: Polycystin-1 mediated mechanical flow-induced extracellular Ca2+ influx.
Figure 3: Responses to mechanical flow stimulation require fully developed cilia.
Figure 4: Polycystin-2 was detected in the cilia of wild-type (wt) collecting duct–derived epithelial cells.
Figure 5: Polycystin-2 in flow-induced Ca2+ signaling.
Figure 6: Specificity of antibodies against polycystins.
Figure 7: Ca2+-induced Ca2+ release was required for flow-induced Ca2+ responses.
Figure 8: Schematic diagram of mechanisms of fluid shear stress and Ca2+ signaling in mouse embryonic kidney cells.


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We thank K.R. Spring, G.J. Pazour, M. Logman and G.B. Witman for discussions and Q. Xi and A.P. Wiebe for technical assistance. This work was supported by grants from the US National Institutes of Health (J.Z.), the US National Aeronautics and Space Administration (D.E.I.), a Howard Hughes Predoctoral Fellowship (F.J.A.) and a Polycystic Kidney Disease Foundation Postdoctoral Fellowship (S.M.N.).

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Correspondence to Jing Zhou.

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