Melanocortin-1 Receptor-Stimulation and its Downstream Effector Mechanisms in Podocytes

Abstract

Abstract Degree Project thesis, Programme in Medicine, 2015. Sara Elofsson, Department of Molecular and Clinical Medicine, Institute of Medicine, University of Gothenburg, Sweden. Börje Haraldsson and Johannes Elvin, supervisors. Previous clinical studies and in vitro experiments have confirmed that treatment with adrenocorticotropic hormone (ACTH) have ameliorating effects on nephrotic syndrome. This action is believed to be mediated by stimulation of Melanocortin-1 Receptor (MC1R) in podocytes. The full extent of MC1R signalling in podocytes is still unknown, but the anti-oxidative enzyme catalase has been found to be one of the downstream effectors. We have studied in what ways catalase is regulated to exert its action and what effect this activity has in podocytes. In addition, we studied the human constitutively active MC1R-mutant, E94K. Cultured differentiated mouse podocytes were transduced with different lentivirus to overexpress MC1R or the constitutively active MC1R-mutant. The podocytes were subjected to different concentrations of a nephrotoxic agent, puromycin, and/or the known MC1R agonist BMS-470539. In addition, a catalase specific inhibitor, 3- amino-1, 2, 4-triazole, was used to elucidate whether the protective effects of MC1R stimulation is dependent on catalase. The effects due to different treatments on the podocytes were assessed with diverse analytical assays. The human constitutive MC1R-mutant did not show an effect in the range we expected and the mouse mutant will be tested hereafter. The inhibitor gave a dosedependent inhibition but had an unsuspected interaction with puromycin. In summary, catalase still seems to have a possible role in the ameliorating effects of MC1R-stimulation in nephrotic syndrome and these experiments have given new strategies and developed better implements to future experiments.