Identification, Characterization, and Localization of a Novel Kidney Polycystin-1-Polycystin-2 Complex

Abstract

The functions of the two proteins defective in autosomal dominant polycystic kidney disease, polycystin-1 and polycystin-2, have not been fully clarified, but it has been hypothesized that they may heterodimerize to form a "polycystin complex" involved in cell adhesion. In this paper, we demonstrate for the first time the existence of a native polycystin complex in mouse kidney tubular cells transgenic for PKD1, non-transgenic kidney cells, and normal adult human kidney. Polycystin-1 is heavily N-glycosylated, and several glycosylated forms of polycystin-1 differing in their sensitivity to endoglycosidase H (Endo H) were found; in contrast, native polycystin-2 was fully Endo H-sensitive. Using highly specific antibodies to both proteins, we show that polycystin-2 associates selectively with two species of full-length polycystin-1, one Endo H-sensitive and the other Endo H-resistant; importantly, the latter could be further enriched in plasma membrane fractions and coimmunoprecipitated with polycystin-2. Finally, a subpopulation of this complex co-localized to the lateral cell borders of PKD1 transgenic kidney cells. These results demonstrate that polycystin-1 and polycystin-2 interact in vivo to form a stable heterodimeric complex and suggest that disruption of this complex is likely to be of primary relevance to the pathogenesis of cyst formation in autosomal dominant polycystic kidney disease.

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]).…”

Polycystin-1 Interacts with Inositol 1,4,5-Trisphosphate Receptor to Modulate Intracellular Ca2+ Signaling with Implications for Polycystic Kidney Disease

“…PC1 is also expressed in the adherens junction and focal adhesions of the plasma membrane (25,26). Interestingly, significant amounts of polycystins have also been found in the endoplasmic reticulum (ER) (27)(28)(29)(30)(31). Although various studies have focused on the C-terminal tail of PC1 targeted to the plasma membrane and reported that it participates in several important signaling pathways (28,(32)(33)(34)(35)(36), the physiological significance of ER-localized PC1 has not been addressed in the literature.…”

Drosophila Pkd2 Is Haploid-insufficient for Mediating Optimal Smooth Muscle Contractility

“…Our observation of the strong genetic interaction between Pkd2 and the ryanodine receptor mutation suggests that cooperation between PKD2 and the ryanodine receptor also occurs in the SMCs. PKD2 has been shown to localize on the endoplasmic reticulum membrane and the plasma membrane as well as on primary cilia (15,17,18,23,37,38). In both mammalian and fly SMCs, PKD2 appears to be predominantly cytoplasmic (23).…”