Figure 1.

PCs and cilia. (A) Renal tubular epithelium depicted as cuboidal cells with apical primary cilia projections subjected to luminal flow. (B) Schematic of 9 + 0 primary cilia. As a microtubule-based structure that imports proteins via anterograde IFT and returns proteins to the cell body via retrograde IFT transport. PC1 and PC2 reside in the cilium membrane and are hypothesized to subsume a local calcium signaling process that may be modulated by mechanical or ligand stimuli. (C) Schematic representations of PC1 and PC2 showing their respective topologies and interaction via coiled coil domains in their carboxy termini. PC1 has the properties of a receptor and undergoes cleavage at the indicated (red letters) GPS sites.

GPS site, whereas PC2 is a calcium channel of the TRP family. GPS, G protein coupled receptor proteolytic site; IFT, intraflagellar transport; PC, polycystin; TRP, transient receptor potential. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)