It's not all in the cilium, but on the road to it: Genetic interaction network in polycystic kidney and liver diseases and how trafficking and quality control matter

Autosomal dominant polycystic liver disease results from mutations in PRKCSH or SEC63. The respective gene products, glucosidase II beta and SEC63p, function in protein translocation and quality control pathways in the endoplasmic reticulum. Here we show that glucosidase II beta and SEC63p are required in mice for adequate expression of a functional complex of the polycystic kidney disease gene products, polycystin-1 and polycystin-2. We find that polycystin-1 is the rate-limiting component of this complex and that there is a dose-response relationship between cystic dilation and levels of functional polycystin-1 following mutation of Prkcsh or Sec63. Reduced expression of polycystin-1 also serves to sensitize the kidney to cyst formation resulting from mutations in Pkhd1, the recessive polycystic kidney disease gene. Finally, we show that proteasome inhibition increases steady-state levels of polycystin-1 in cells lacking glucosidase II beta and that treatment with a proteasome inhibitor reduces cystic disease in orthologous gene models of human autosomal dominant polycystic liver. (C) 2011 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.