PIGEA-14, a Novel Coiled-coil Protein Affecting the Intracellular Distribution of Polycystin-2

Abstract

Employing a yeast two-hybrid screen with the COOH terminus of polycystin-2, one of the proteins mutated in patients with polycystic kidney disease, we were able to isolate a novel protein that we call PIGEA-14 (polycystin-2 interactor, Golgi-and endoplasmic reticulum-associated protein with a molecular mass of 14 kDa). Molecular modeling only predicts a coiled-coil motif, but no other functional domains, in PIGEA-14. In a subsequent two-hybrid screen using PIGEA-14 as a bait, we found GM130, a component of the cis-compartment of the Golgi apparatus. Co-expression of the PIGEA-14 and PKD2 cDNAs in LLC-PK 1 and HeLa cells resulted in a redistribution of PIGEA-14 and polycystin-2 to the trans-Golgi network, which suggests that PIGEA-14 plays an important role in regulating the intracellular location of polycystin-2 and possibly other intracellular proteins. Our results also indicate that the intracellular trafficking of polycystin-2 is regulated both at the level of the endoplasmic reticulum and that of the trans-Golgi network.

Cell biology of polycystin-2

“…It is now accepted that PKD2 can function at the plasma membrane, but its activity there is under complex regulation involving shuttling between ER and plasma membrane, protein-protein interactions, and modes of activation. Specifically, it has been shown that the amount of PKD2 in the plasma membrane is dynamically regulated by interacting proteins (PKD1 [29,35], Polycystin-2 interactor, Golgi-and ER-associated protein-14 (PIGEA-14) [37]), posttranslational modifications (serine phosphorylation by casein kinase 2 (CK2) [38] and glycogen synthase kinase 3 (GSK3) [39]), interaction with other channel subunits in the plasma membrane (PKD1 [29,35,[40][41][42], TRPC1 [11], TRPV4 [43]) (Fig. 2), and finally, activation secondary to cell surface receptor activation (epidermal growth factor receptor (EGFR) [36]).…”

“…It would be interesting to know whether the S76/S80 mutation affected PKD2 channel function in the ER. In a separate study, Hidaka et al [37] identified PIGEA-14 as an interacting protein with PKD2 and proposed that binding to PIGEA-14 facilitated the movement of PKD2 from the ER to the Golgi (Fig. 2).…”

Ciliary dysfunction in polycystic kidney disease: an emerging model with polarizing potential

“…The details of how polycystin-2 traffics to the cilium are limited, but current data suggests that there is a specific ciliary signal sequence, which allows polycystin-2 to exit the endoplasmic reticulum and enter the ciliary plasma membrane (106,107). Interestingly, the localization of the polycystins appears to be partially dependent on one another.…”

The NBPF Gene Family

“…It was shown that the coiled-coil region in the N-terminal domain of NBPF interacts with the coiled-coil region in the C-terminal domain of Cby. This C-terminal portion of Cby harbours not only the binding site for NBPF, but also the binding site for most other known interaction partners of Cby, such as β-catenin (Takemaru et al, 2003), polycystin-2 (Hidaka et al, 2004) and TC1 (Jung et al, 2006). Functional analysis of the interaction showed that NBPF did not influence Cby-mediated Wnt signalling, nor did it compete with β-catenin binding to Cby.…”

“…Cby also plays a role in other processes. Reports on the binding of Cby to polycystin-2 (Hidaka et al, 2004) and on the Cby knockout mouse (Voronina et al, 2009;Love et al, 2010) implicate Cby in the development of motile airway cilia. Germline inactivation of Cby resulted in complete absence of mucociliary transport due to scarcity of motile cilia in the nasal epithelium (Voronina et al, 2009).…”