Vascular endothelial cells express isoforms of protein kinase A inhibitor.

First published September 5, 2001; 10.1152/ ajpcell.00256.2001.—The expression and function of the endogenous inhibitor of cAMP-dependent protein kinase (PKI) in endothelial cells are unknown. In this study, overexpression of rabbit muscle PKI gene into endothelial cells inhibited the cAMP-mediated increase and exacerbated thrombin-induced decrease in endothelial barrier function. We investigated PKI expression in human pulmonary artery (HPAECs), foreskin microvessel (HMECs), and brain microvessel endothelial cells (HBMECs). RT-PCR using specific primers for human PKIα, human PKIγ, and mouse PKIβ sequences detected PKIα and PKIγ mRNA in all three cell types. Sequencing and BLAST analysis indicated that forward and reverse DNA strands for PKIα and PKIγ were of >96% identity with database sequences. RNase protection assays showed protection of the 542 nucleotides in HBMEC and HPAEC PKIα mRNA and 240 nucleotides in HBMEC, HPAEC, and HMEC PKIγ mRNA. Western blot analysis indicated that PKIγ protein was detected in all three cell types, whereas PKIα was found in HBMECs. In summary, endothelial cells from three different vascular beds express PKIα and PKIγ, which may be physiologically important in endothelial barrier function.