Specific association of the gene product of PKD2 with the TRPC1 channel

Abstract

The function(s) of the genes (PKD1 and PKD2) responsible for the majority of cases of autosomal dominant polycystic kidney disease is unknown. While PKD1 encodes a large integral membrane protein containing several structural motifs found in known proteins involved in cell-cell or cell-matrix interactions, PKD2 has homology to PKD1 and the major subunit of the voltage-activated Ca 2؉ channels. We now describe sequence homology between PKD2 and various members of the mammalian transient receptor potential channel (TRPC) proteins, thought to be activated by G protein-coupled receptor activation and͞or depletion of internal Ca 2؉ stores. We show that PKD2 can directly associate with TRPC1 but not TRPC3 in transfected cells and in vitro. This association is mediated by two distinct domains in PKD2. One domain involves a minimal region of 73 amino acids in the C-terminal cytoplasmic tail of PKD2 shown previously to constitute an interacting domain with PKD1. However, distinct residues within this region mediate specific interactions with TRPC1 or PKD1. The C-terminal domain is sufficient but not necessary for the PKD2-TRPC1 association. A more N-terminal domain located within transmembrane segments S2 and S5, including a putative pore helical region between S5 and S6, is also responsible for the association. Given the ability of the TRPC to form functional homo-and heteromultimeric complexes, these data provide evidence that PKD2 may be functionally related to TRPC proteins and suggest a possible role of PKD2 in modulating Ca 2؉ entry in response to G protein-coupled receptor activation and͞or store depletion.

Cell biology of polycystin-2

“…This concept was originally proposed by Ma et al [92]. In this study, a yeast two hybrid screen using the C-terminal cytosolic fragment of TRPC1, an interacting protein with PKD2 [11], resulted in the identification of the "a" isoform of the myogenic family (Imfa). I-mfa is a known inhibitor of a subset of bHLHs such as myogenin [93], MyoD [93], and other bHLHs [94].…”

“…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]).…”

“…PKD2 or TRPP2 (its current name) structurally belongs to the transient receptor potential (TRP) superfamily of ion channels [11]. TRP channels are predicted to span the plasma membrane six times with their N-and C-termini located inside the cell [12].…”

The Transient Receptor Potential Superfamily of Ion Channels

“…However, expression of PKD2 with or without PKD1 in cultured cells produces surface membrane whole-cell currents with nearly linear current-voltage relationships (85,86). It has been shown that PKD2 protein can physically associate with TRPC1 (40). The molecular composition of pore-forming protein(s) underlying the whole-cell currents in PKD2-expressing cells versus the single-channel activity recorded in lipid bilayer deserves further investigation (87).…”

“…PKD2 (also called TRPP2) was discovered as one of the gene products mutated in autosomal dominant polycystic kidney disease (39). PKD2 is a six-TM protein that shares~25% amino acid identity with the closely related TRPC3 and TRPC6 over the region spanning TM segments IV through VI (40). Mammalian PKD2 is a Ca 2ϩ -permeable, nonselective cation channel (41).…”