Homophilic and heterophilic polycystin 1 interactions regulate E-cadherin recruitment and junction assembly in MDCK cells

Abstract

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited human renal disease and is caused by mutations in two genes, PKD1 (85%) and PKD2 (15%). Cyst epithelial cells are characterised by a complex cellular phenotype including changes in proliferation, apoptosis, basement membrane composition and apicobasal polarity. Since polycystin 1 (PC1), the PKD1 protein, has been located in the basolateral membrane of kidney epithelial cells, we hypothesised that it might have a key role in mediating or stabilising cell-cell interactions. In non-ciliated L929 cells, stable or transient surface expression of the PC1 extracellular domain was sufficient to confer an adhesive phenotype and stimulate junction formation. In MDCK cells, we found that PC1 was recruited to the lateral membranes coincident with E-cadherin within 30 minutes after a `calcium switch'. Recruitment of both proteins was significantly delayed when cells were treated with a PC1 blocking antibody raised to the PKD domains. Finally, PC1 and E-cadherin could be coimmunoprecipitated together from MDCK cells. We conclude that PC1 has a key role in initiating junction formation via initial homophilic interactions and facilitates junction assembly and the establishment of apicobasal polarity by E-cadherin recruitment.

Polycystin-2 Activity Is Controlled by Transcriptional Coactivator with PDZ Binding Motif and PALS1-associated Tight Junction Protein

“…Several abnormalities in the polarized distribution of membrane proteins and cell-cell contact proteins such as E-cadherin have been reported in ADPKD in cyst-lining epithelia (29). Recently, the polycystin complex has been implicated in junction formation and establishment of apicobasal polarity (31). In addition, it has been shown that PATJ, among other polarity proteins such as PALS1 and PAR6, interacts with nephrocystins, suggesting a link between tight junction formation and cystic kidney disease (32).…”

Polycystin-1 Protein Level Determines Activity of the Gα12/JNK Apoptosis Pathway

“…There are numerous examples of G proteins regulating transmembrane proteins, especially ion channels (reviewed in Ref. 35), and PC1 was recently shown to function as an adhesion molecule (15). We recently identified G␣ 12 regulation of integrins through an inside-out signaling mechanism (23).…”

“…In addition, there are other potential overlapping pathways between G␣ 12 and PC1. For example, PC1 regulates junction assembly in MDCK cells (15), and G␣ 12 interacts with ZO-1 in the tight junction and with E-cadherin to regulate tight junctions and cell adhesion (16,17). Finally, the G␣ 12 family regulates stress fiber formation and numerous other fundamental cellular processes, including proliferation, transformation, and cell migration (reviewed in Ref.…”

Gα12 is required for renal cystogenesis induced by Pkd1 inactivation

“…E-cadherin is one of the most important components in the PC1 complex. The association of E-cadherin molecules is very important for maintaining the integrity of E-cadherin-mediated adherens junctions in MDCK cells (Streets et al, 2009). N-cadherin and E-cadherin can also form heterodimers in adherens junctions through heterophilic binding (Prakasam et al, 2006), which suggests that their association might be very important for cystic epithelial cell-cell contacts, and also for contacts between cystic and surrounding normal epithelial cells.…”