Role of anti-adhesin, podocalyxin and adaptor proteins in glomerular injury

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We have previously demonstrated that anti-adhesin molecule, podocalyxin binds to the second PDZ domain of NHERF2 and ezrin in vitro and in vivo and that the interaction is important to maintain the unique organization of podocyte structure. In this research project, we investigated how the adaptor proteins interact with podocalyxin in glomerular injury.1. We found that phosphrylation status of podocalyxin/NHERF2/ezrin comlex linked to the golmerular injury.2. We identified the protein which interacted with first PDZ domain of NHERF2 by yeast two-hybrid system. Surprisingly, it was NHERF2 itself. This self-interaction was confirmed by GST pull-down assay and co-immunoprecipitation and was disrupted in severe injured glomeruli.3. We analyzed the endocytic function of mouse immortalized glomerular epithlial cells that was established by Dr. Mundel like as in vivo millue.4. We also found that the interaction between podocalyxin and adaptor proteins of above cell line was reduced in propotion to the angioteinsin II concentration.5. When highly polarized MDCK cells were transfected to express podocalyxin, the adaptor proteins were re-localized to the apical submembranous domain and small G-protein, Rho A was activated. These results suggest podocalyxin may lead the adaptor proteins re-locate to the apical domain through the activation of Rho A.