Host: The Japanese Pharmacological Society, The Japanese Society of Clinical Pharmacology
Name : WCP2018 (18th World Congress of Basic and Clinical Pharmacology)
Location : Kyoto
Date : July 01, 2018 - July 06, 2018
The ubiquitin-proteasome system (UPS) and autophagy/lysosome pathways play an essential regulatory role for intracellular protein degradation and protein homeostasis. The von Hippel-Lindau (VHL) is an E3 ubiquitin ligase, which negatively regulates the hypoxia-inducible factor-1a (HIF-1a) by promoting its polyubiquitination. Although the protein VHL (pVHL) was reported to be involved in the heart function, the underlying mechanism remains unclear. In the heart, phospholamban (PLN) plays an important role in the regulateon of Ca2+ flux across the sarcoplasmic reticulum (SR) by inhibiting the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA2a). Although PLN has been reported to be ubiquitinated at Lys3 prior to the induction of its degradation, the E3 ubiquitin ligase that targets PLN remains unknown. This study was conducted to investing whether the VHL is involved in the ubiquitination of PLN to induce PLN degradation, lead to dilated cardiomyopathy (DCM).
First of all, the pVHL expression and its interaction with PLN in heart tissues from DCM mice (TgPLNR9C, transgenic mouse expressing an Arg9 to Cys point mutation in PLN, and NHE1-Tg, transgenic mouse with activated form of sodium/hydrogen exchanger 1) were examined by western blotting and co-immunoprecipitation experiments. Also, we assessed whether pVHL was involved in the ubiquitination of PLN using VHL-silenced HEK293 cells.
As a results, pVHL expression level was upregulated in the heart of DCM mice. Also, PLN was co-immunoprecipitated with pVHL in both PLN-overexpressing HEK293 cells and mouse hearts with DCM. Furthermore, the overexpression of VHL into HEK293 cells decreased PLN expression levels under the H2O2 stress, whereas knockdown of VHL by transfection with VHL-siRNA increased PLN expression levels both under the normal and the H2O2 stress.
In conclusion, we propose that the increase in the oxidative stress results in the upregulation of pVHL expression, and pVHL binding with PLN induces ubiquitination-mediated PLN degradation in failing hearts.
