Nephrocystin-1 and nephrocystin-4 are required for epithelial morphogenesis and associate with PALS1/PATJ and Par6

Abstract

Nephronophthisis (NPH) is an autosomal recessive disorder characterized by renal fibrosis, tubular basement membrane disruption and corticomedullary cyst formation leading to end-stage renal failure. The disease is caused by mutations in NPHP1-9 genes, which encode the nephrocystins, proteins localized to cell–cell junctions and centrosome/primary cilia. Here, we show that nephrocystin mRNA expression is dramatically increased during cell polarization, and shRNA-mediated knockdown of either NPHP1 or NPHP4 in MDCK cells resulted in delayed tight junction (TJ) formation, abnormal cilia formation and disorganized multi-lumen structures when grown in a three-dimensional collagen matrix. Some of these phenotypes are similar to those reported for cells depleted of the TJ proteins PALS1 or Par3, and interestingly, we demonstrate a physical interaction between these nephrocystins and PALS1 as well as their partners PATJ and Par6 and show their partial co-localization in human renal tubules. Taken together, these results demonstrate that the nephrocystins play an essential role in epithelial cell organization, suggesting a plausible mechanism by which the in vivo histopathologic features of NPH might develop.

Casein Kinase 1 α Phosphorylates the Wnt Regulator Jade-1 and Modulates Its Activity

“…In subconfluent cells, NPHP4 is dispersed throughout the cytoplasm and could play an earlier role during this time in enhancing Jade-1 nuclear translocation. Of note, NPHP4 mRNA is up-regulated after injury (56). Because Jade-1 can also ubiquitinate non-phosphorylated ␤-catenin (26), the ability of cytosolic NPHP4 to enhance this might be particularly important during injury repair.…”

The Joubert Syndrome-associated Missense Mutation (V443D) in the Abelson-helper Integration Site 1 (AHI1) Protein Alters Its Localization and Protein-Protein Interactions

“…Mutations in NPHP1 are often associated with JBTS accompanied with renal dysfunction (1), and also account for a majority of cases of nephronophthisis (NPHP; a recessive renal cystic disease) (21). Although the function of NPHP1 is not well understood, the interaction of NPHP1 with other NPHP disease proteins at cell junctions and its highly regulated mRNA expression during cell polarization, suggest a role of NPHP1 in cellular organization (22,23). An interaction of AHI1 and NPHP1 was demonstrated by yeast two-hybrid analysis in which the SH3 domain of NPHP1 bound the WD40 repeats in AHI1 (15).…”

Phosphorylation‐dependent Akt–Inversin interaction at the basal body of primary cilia

“…We postulate that loss of INVS phosphorylation possibly underlies the distorted lumen formation observed in NPHP2, perhaps due to disorientation of the spindle axis during metaphase. Abnormal cilia formation and disorganized multi‐lumen structures were linked to the pathogenesis of NPHP2, an autosomal recessive renal disorder (Delous et al , 2009). However, since the spindle axis can be oriented in the apico‐basal or planar directions, the measurement of the baso‐apical angle of the spindle axis in the experimental system may not fully address the pathological nature of the cystogenic formation.…”