Disruption of the endothelial ISOC causes phenotypic changes in pulmonary artery endothelial cells

Abstract

Endothelial cells express the transient receptor potential canonical (TRPC) homologues 1 and 4 that contribute to the molecular basis of a calcium-selective SOC entry channel, ISOC. We have previously shown that activation of ISOC, by addition of thapsigargin, results in increased permeability and intercellular gap formation in pulmonary artery endothelial cells (PAECs). Activation of the ISOC channel requires protein 4.1 binding on the carboxy terminus of the TRPC4 subunit. The TRPC4-protein4.1 interaction is mediated by a proline rich region/protein 4.1 binding (prr/4.1) domain on TRPC4. A competitive peptide with a sequence corresponding to the prr/4.1 domain was generated and transfected into PAECs. In these cells, thapsigargin-induced ISOC was abolished and intercellular gap formation reduced. These data represent acute changes resulting from ISOC disruption. However, chronic effects of TRPC4-protein 4.1 disruption are unknown. Therefore, PAECs were infected with a retroviral construct stably expressing the peptide corresponding to the prr/4.1 domain. PAECs expressing the prr/4.1 peptide exhibited decreased cell size, increased resistance, and increased proliferation. Thus, constant disruption of the TRPC4-protein 4.1 interaction causes phenotypic change in PAECs. Supported by HL60024