Tyrosine-phosphorylated sodium channel beta1 subunits colocalize with connexin-43, N-cadherin, and Nav1.5 at intercalated disks in mouse ventricular myocytes, but not at t-tubules.
Tyrosine phosphorylation of sodium channel beta1 subunits regulates their subcellular localization to intercalated disks in ventricular myocytes, where they associate with N-cadherin and connexin-43.
Voltage-gated sodium channel alpha and beta subunits expressed in mammalian heart are differentially localized to t-tubules and intercalated disks. Sodium channel beta subunits are multifunctional molecules that participate in channel modulation and cell adhesion. Reversible, receptor-mediated changes in beta1 tyrosine phosphorylation modulate its ability to recruit and associate with ankyrin. The purpose of the present study was to test our hypothesis that tyrosine-phosphorylated beta1 (pYbeta1) and nonphosphorylated beta1 subunits may be differentially localized in heart and thus interact with different cytoskeletal and signaling proteins. We developed an antibody that specifically recognizes pYbeta1 and investigated the differential subcellular localization of beta1 and pYbeta1 in mouse ventricular myocytes. We found that pYbeta1 colocalized with connexin-43, N-cadherin, and Nav1.5 at intercalated disks but was not detected at the t-tubules. Anti-pYbeta1 immunoprecipitates N-cadherin from heart membranes and from cells transfected with beta1 and N-cadherin in the absence of other sodium channel subunits. pYbeta1 does not associate with ankyrinB in heart membranes. N-cadherin and connexin-43 associate with Nav1.5 in heart membranes as assessed by co-immunoprecipitation assays. We propose that sodium channel complexes at intercalated disks of ventricular myocytes are composed of Nav1.5 and pYbeta1 and that these complexes are in close association with both N-cadherin and connexin-43. beta1 phosphorylation appears to regulate its localization to differential subcellular domains.
Malhotra et al. (Sat,) reported a other. Tyrosine-phosphorylated beta1 (pYbeta1) subunit localization vs. Nonphosphorylated beta1 subunits was evaluated on Subcellular localization and protein associations of pYbeta1 and beta1 in cardiac myocytes. Tyrosine-phosphorylated sodium channel beta1 subunits colocalize with connexin-43, N-cadherin, and Nav1.5 at intercalated disks in mouse ventricular myocytes, but not at t-tubules.