Modification of the composition of polycystin-1 multiprotein complexes by calcium and tyrosine phosphorylation

Abstract

Mutations in the PKD1 gene are responsible for >85% of autosomal dominant polycystic kidney disease (ADPKD). The protein product of PKD1, polycystin-1, is a large, modular membrane protein, with putative ligand-binding motifs in the extracelluar N-terminal portion, 9-11 transmembrane domains and an intracellular C-terminal portion with phosphorylation sites. A role for polycystin-1 as a cell surface receptor involved in cell-matrix and cell-cell interactions has been proposed. In this study, we have analyzed polycystin-1 and associated protein distribution in normal human epithelial cells and examined the role of cell-matrix versus cell-cell interactions in regulation of the assembly of polycystin-1 multiprotein complexes. Immunocytochemistry, sucrose density gradient sedimentation, co-immunoprecipitation analyses and in vitro binding assays have shown that polycystin-1 associates with the focal adhesion proteins talin, vinculin, p130Cas, FAK, alpha-actinin, paxillin and pp60c-src in subconfluent normal human fetal collecting tubule (HFCT) epithelia when cell-matrix interactions predominate. Polycystin-1 also forms higher S value complexes with the cell-cell adherens junction proteins E-cadherin, beta- and gamma-catenins in confluent cultures when cell-cell interactions are predominant. Polycystin-1 multiprotein complexes can be disrupted by cytochalasin D but not by colchicine, suggesting involvement of the actin cytoskeleton. Although inhibition of tyrosine phosphorylation by tyrphostin inhibits polycystin-1-FAK interactions, E-cadherin interactions are enhanced. High calcium treatment also increases polycystin-1-E-cadherin interactions.

A polycystin multiprotein complex constitutes a cholesterol-containing signalling microdomain in human kidney epithelia

“…Polycystin-1 contains numerous sites in its C-terminus that are targets for regulatory phosphorylation by Src kinase and PKA [47,48]. Opposing activities of tyrosine kinases (Src and PKC, among others) and, as we show here, closely associated tyrosine phosphatases control the dephosphorylation of polycystin-1.…”

HEF1-Aurora A Interactions: Points of Dialog between the Cell Cycle and Cell Attachment Signaling Networks

“…Mutations in these proteins are associated with a variety of polycystic kidney disorders; 120,121 studies of their orthologs in lower eukaryotes such as C. elegans indicate the defects may involve sensing or response of external chemical or physical signals. 121,122 p130Cas has been identified as an interactor for cilia-associated proteins, including nephrocystin 121,122 and polycystin-1, 123 providing functional coupling between the cilium and proteins including FAK, paxillin, and other focal adhesion components. 122,123 HEF1 mRNA is particularly abundant in kidney tissue: 71 specific localization of HEF1 to cilia, and in renal cells, is currently under investigation.…”

“…121,122 p130Cas has been identified as an interactor for cilia-associated proteins, including nephrocystin 121,122 and polycystin-1, 123 providing functional coupling between the cilium and proteins including FAK, paxillin, and other focal adhesion components. 122,123 HEF1 mRNA is particularly abundant in kidney tissue: 71 specific localization of HEF1 to cilia, and in renal cells, is currently under investigation. An exciting recent study has also implicated specific Pak kinase activity at the cilium in quiescent cells, where it has been proposed to contribute to environmental sensing and tissue homeostasis.…”

Cilia-like Structures and Polycystin-1 in Osteoblasts/Osteocytes and Associated Abnormalities in Skeletogenesis and Runx2 Expression

“…PC1 is a 4303-amino acid cell-surfaceexpressed protein that has a multidomain extracellular region, an 11 transmembrane region (10), and an ϳ200 amino acid cytoplasmic C-terminal tail (3), whereas PC2 is a Ca 2ϩ -permeable cation channel belonging to the transient receptor potential family (11)(12)(13). There is compelling evidence that PC1 forms heterodimers with PC2 to create a polycystin complex that localizes with Tg737, Kif3a, and Cpk in cilium and may be involved in cell-matrix interfaces and cell-cell contacts (1,5,9,14). The polycystin complex, either through its association with cilium or cell-to-cell or cell-to-matrix interactions, has been implicated as a mechano-sensor in renal epithelial cells (15)(16)(17).…”