The Cytoplasmic C-terminal Fragment of Polycystin-1 Regulates a Ca2+-permeable Cation Channel

Abstract

The cytoplasmic C-terminal portion of the polycystin-1 polypeptide (PKD1(1-226)) regulates several important cell signaling pathways, and its deletion suffices to cause autosomal dominant polycystic kidney disease. However, a functional link between PKD1 and the ion transport processes required to drive renal cyst enlargement has remained elusive. We report here that expression at the Xenopus oocyte surface of a transmembrane fusion protein encoding the C-terminal portion of the PKD1 cytoplasmic tail, PKD1 (115-226

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

“…In parallel, several efforts have been made to study the function of PC1 through investigation of a fusion protein that fused the PC1-C-terminal tail with the CD7 transmembrane or other transmembrane domains to locate it into the plasma membrane (28,(32)(33)(34)(35)(36). The overexpression of the plasma membrane-targeted C-terminal tail of PC1 stimulates GPCR to increase Ca 2ϩ release (32).…”

“…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.…”

Human ADPKD primary cyst epithelial cells with a novel, single codon deletion in the PKD1 gene exhibit defective ciliary polycystin localization and loss of flow-induced Ca2+ signaling

“…Anti-PC2 antibody (64) raised against a GST-PC2 fusion protein encoding the PC2 COOH-terminal cytoplasmic aa 687-968 was originally obtained from Dr. Oxana Beskrovnaya-Ibraghimova (Genzyme). Anti-CD16 monoclonal antibody (mAb) 3G8 was used as an Ig fraction as described (64,65). Anti-N-acetylated-␣-tubulin was obtained from Sigma, anti-calnexin from Stressgen, and anti-GM130 from BD Biosciences Pharmingen.…”

“…The PKD1 polypeptide gene product, polycystin-1 (PC1/TRPP1), is a 4,302-amino acid (aa) polypeptide with an NH 2 -terminal extracellular domain of ϳ3,000 aa, ϳ11 transmembrane domains, and a ϳ200-aa COOH-terminal cytoplasmic domain interacting with polycystin-2 (PC2/TRPP2) (46, 63), heterotrimeric G proteins, and the regulator of G protein signaling RGS7, among many other proteins. The COOH-terminal tail of PC1 also upregulates several transcriptional pathways, in part by regulated proteolysis (24), and activates endogenous Ca 2ϩ -permeable cation channels of 20 -30 pS in Xenopus laevis oocytes and HEK-293 cells (64,65). The PKD2 gene product, PC2, is a 968-aa polypeptide believed to function as a Ca 2ϩ -permeable cation channel in the endoplasmic reticulum and/or at the plasma membrane, independently or in complex with PC1 (11,26,33) or other proteins.…”

Novel PKD1 deletions and missense variants in a cohort of Hellenic polycystic kidney disease families

“…At the present time, only the last 112 C-terminal residues of polycystin-1 have been convincingly shown to be involved in the regulation of a calcium channel, most probably through interaction with polycystin-2. This explains why mutations as far C-terminal as C4086X and others, 19,31,42 which result in removing the crucial polycystin-1 fragment that is implicated in regulating a cation channel, 12 result also in cyst formation and disease development.…”