The Kidney Foundation of Canada

Dr Xing-Zhen Chen 

Dr. Xing-Zhen Chen

University of Alberta, AB

Regulation of PKD2 function and associated disease via the S4-S5 linker to C-terminus interaction

2018-2020:  $100,000 |  Biomedical Research Grants  |  Category: Kidney biology

Lay Summary

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in the PKD1 or PKD2 protein.
It affects 0.2% of adults worldwide and has no effective cure. Recent clinical trials targeted to known regulatory
pathways but only Tolvaptan was approved as the first ADPKD drug in Canada. However, effectiveness of this drug is marginal and the US FDA has not approved it because it has an unclear risk-benefit ratio. There is thus a pressing need for alternative routes to therapies for ADPKD. Because these tested drugs all act on regulatory pathways rather than on PKD1 or PKD2 itself, the drug efficacy and specificity are questionable. Our goal is to identify molecules that directly act on PKD2 to compensate for pathogenic PKD2 function.

PKD2 has 6 membrane spans (S1-S6) and an intracellular N- and C-terminus. Our preliminary experiments revealed the interaction of the intracellular S4-S5 linker with the C-terminus (termed L-C interaction) in PKD2 and its close homologue PKD2L1, and that the interaction is required for channel function. We also found that phospholipid PIP2 inhibits the PKD2L1 L-C interaction. We hypothesize that PIP2 binds to the PKD2 linker, which undermines the L-C interaction and thus inhibits PKD2 function.

In this project, using mutagenesis, molecular biology, protein-protein interaction, electrophysiology, and cellular models we will determine: 1) that the intra-molecular L-C interaction in PKD2 is functionally critical and is inhibited by PIP2, and 2) that PKD2 peptides that disrupt the L-C or PIP2-PKD2 interaction can compensate for PKD2 pathogenic mutants function. Further, using zebrafish models that mimic human loss-offunction
PKD2 pathogenic mutants, we will identify PKD2 peptide modulators (as candidate drugs) that regulate disease phenotypes through inhibiting the L-C or PIP2-PKD2 binding.

This research will give us new insights into how PIP2 regulates the PKD2 L-C binding and channel function and determine how cystic diseases can be treated by PKD2 peptide modulators that directly act on the PIP2/L-C
binding axis.