Abstract 1227: Tid1 Interacts With Trpc6 And Negatively Regulates Calcium Entry In Cardiomyocytes
Transient receptor potential channels C6 (TRPC6) are non-selective cation channels that have been implicated in disease states involving the heart (cardiac hypertrophy) and the kidneys (focal segmental glomerulosclerosis). In fact, mutations within the human TRPC6 gene (P112Q) highlight the importance of the ankyrin repeats (ANK) to TRPC6 function. ANK repeats are common motifs and function in protein-protein interactions. To identify binding partners for TRPC6 ANK repeats we conducted a bacterial two hybrid screen and identified tumorous imaginal disc 1 (TID1) as a binding Partner. This interaction was confirmed by co-immunoprecipitation and GST-pull down studies. Both TID1 and TRPC6 are found in cultured cardiomyoctyes. Silencing of TID1 in cultured cardiomyocytes and HEK293 cells led to a large increase in receptor operated calcium entry by fura-2 calcium measurements indicating that TID1l negatively regulates TRPC6 calcium entry. However silencing of TID1 did not change the surface expression of TRPC6 as assessed by surface biotinylation studies. Live cell imaging of cardiomyocytes found that TRPC6-YFP was expressed on the surface and in a perinuclear region that overlapped with mitotracker staining suggesting TRPC6 compartmentalized in mitochondria. In cardiomyocytes in which TID1 was silenced, TRPC6-YFP could be found throughout the cytosol in a pattern excluding the mitochondria. These findings indicate that TRPC6 internalization and compartmentalization to the mitochondria is dependent on the TID1l interaction. Interestingly, mice with a cardiac specific deletion of TID1 die from a dilated cardiomyopathy. Moreover, both cardiac hypertrophy and FSGS are common manifestations of inherited mitochondrial disorders. These results indicate that TRPC6 trafficking to the mitochondria mediated by TID1l may play an important cellular function disruption of which leads to cell death and cardiac failure.