Analysis of cardiac-specific mutations of the cell-cell adhesion protein Plakophilin-2

PAC Gym

Human cells are held together by specialized protein complexes called desmosomes that form junctions between cells. Desmosomes are especially prevalent in tissues that undergo high degrees of mechanical stress, such as skin or heart tissue, and mutations in desmosomal proteins can lead to diseases in these tissues. Arrhythmogenic cardiomyopathy (AC) is one such disease that has been linked to various mutations in the desmosomal protein Plakophilin-2 (PKP2) and is characterized by arrhythmia and loss of myocytes in the heart wall. The primary objective of this research was to determine the localization and expression of PKP2 in cardiomyocytes transfected with PKP2 mutations linked to AC. The localization of other desmosomal proteins such as desmoplakin (DP) and plakoglobin (PG) in response to mutant PKP2 was explored as well. In cells that had been transfected with PKP2 mutations, we expected to see PKP2 localize in areas other than the borders of the cells, which is where PKP2 is located in wild type cardiomyocytes. Any change in PKP2 localization would indicate that specific mutation is likely pathogenic. Our data suggests that for mutants 7, 8, 11, 12, 13, 15, 16, 18, and 19, PKP2 localizes in the cytoplasm instead of at the borders of transfected cells. Additionally, our data suggests that mutant 14 PKP2 localizes at the borders of transfected cells, but the borders are irregular compared to the borders of the wild type cardiomyocytes. Total expression of all PKP2 mutants were confirmed by western blot. These results detail cellular changes caused by the mutations of desmosomal proteins that are associated with AC. The mislocalization of PKP2 results in less PKP2 at the borders of the cells, which may result in weakened desmosome proteins complexes holding the cardiomyocytes together. Since one of the defining features of AC is the loss of cardiomyocytes from the walls of the heart, a reduction of PKP2 at cell borders could contribute to detachment of cardiomyocytes from the other heart tissue. By contributing to the understanding of the mechanism of AC, it is plausible that our results can also help contribute to better strategies to regulate or treat AC in the future.