Volume 22, Issue S1 p. 964.32-964.32
Physiology
Free Access

The Immunosuppressive drugs rapamycin and FK506 decrease vasodilation by increasing PKCbetai-mediated phosphorylation of eNOS Thr495

Valorie L. Chiasson

Valorie L. Chiasson

Dept. of Internal Medicine, Texas A&M Health Science Center, Temple, TX

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Brett M. Mitchell

Brett M. Mitchell

Dept. of Internal Medicine, Texas A&M Health Science Center, Temple, TX

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Abstract

PKC is known to phosphorylate eNOS at Thr495, which decreases NO production and endothelial function. We have shown previously that the conventional PKC family (isoforms alpha, betaI, betaII, gamma) mediates the increased eNOS Thr495 phosphorylation and endothelial dysfunction caused by rapamycin and FK506. Here we sought to determine which of these PKC isoforms was responsible for phosphorylating eNOS at this inhibitory site. Endothelium-intact mouse aortas were treated acutely with rapamycin or FK506 (1 uM, 30 min) with or without the PKCalpha inhibitor Ro-32-0432 (0.01 uM), the PKCbetaII inhibitor CG53353 (1 uM), or a PKCbeta inhibitor (0.1 uM) and NO-mediated relaxation responses and eNOS Thr495 phosphorylation were measured. Inhibition of PKCalpha and PKCbetaII had little effect on NO-mediated relaxation whereas PKCbeta inhibition completely restored relaxation responses to or beyond control levels in rapamycin- and FK506-treated aortas. Similar effects were seen on eNOS Thr495 phosphorylation in rapamycin-treated aortas. These preliminary data suggest that PKCbetaI is the isozyme that phosphorylates eNOS Thr495 in response to rapamycin and FK506. We are currently measuring PKC isoform-specific activation and performing PKC isoform-specific knockdown studies in rapamycin- and FK506-treated endothelial cells to confirm these findings. (Supported by HL084299 to BMM)