Cardiac sodium channel Na v1.5 interacts with and is regulated by the protein tyrosine phosphatase PTPH1

Abstract

In order to identify proteins interacting with the cardiac voltage-gated sodium channel Na v1.5, we used the last 66 amino acids of the C-terminus of the channel as bait to screen a human cardiac cDNA library. We identified the protein tyrosine phosphatase PTPH1 as an interacting protein. Pull-down experiments confirmed the interaction, and indicated that it depends on the PDZ-domain binding motif of Na v1.5. Co-expression experiments in HEK293 cells showed that PTPH1 shifts the Na v1.5 availability relationship toward hyperpolarized potentials, whereas an inactive PTPH1 or the tyrosine kinase Fyn does the opposite. The results of this study suggest that tyrosine phosphorylation destabilizes the inactivated state of Na v1.5.