title: FK506 binding protein 12/12.6 depletion increases endothelial nitric oxide synthase threonine 495 phosphorylation and blood pressure.
abstract: Chronic treatment with the immunosuppressive drug rapamycin leads to hypertension; however, the mechanisms are unknown. Rapamycin binds FK506 binding protein 12 and its related isoform 12.6 (FKBP12/12.6) and displaces them from intracellular Ca2+ release channels (ryanodine receptors) eliciting a Ca2+ leak from the endoplasmic/sarcoplasmic reticulum. We tested whether this Ca2+ leak promotes conventional protein kinase C-mediated endothelial NO synthase phosphorylation at Thr495, which reduces production of the vasodilator NO. Rapamycin treatment of control mice for 7 days, as well as genetic deletion of FKBP12.6, increased systolic arterial pressure significantly compared with controls. Untreated aortas from FKBP12.6-/- mice and in vitro rapamycin-treated control aortas had similarly decreased endothelium-dependent relaxation responses and NO production and increased endothelial NO synthase Thr495 phosphorylation and protein kinase C activity. Inhibition of either conventional protein kinase C or ryanodine receptor restored endothelial NO synthase Thr495 phosphorylation and endothelial function to control levels. Rapamycin induced a small increase in basal intracellular Ca2+ levels in isolated endothelial cells, and rapamycin or FKBP12.6 gene deletion decreased acetylcholine-induced intracellular Ca2+ release, all of which were reversed by ryanodine. These data demonstrate that displacement of FKBP12/12.6 from ryanodine receptors induces an endothelial intracellular Ca2+ leak and increases conventional protein kinase C-mediated endothelial NO synthase Thr495 phosphorylation leading to decreased NO production and endothelial dysfunction. This molecular mechanism may, in part, explain rapamycin-induced hypertension.
authors.affiliation: Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Tex 77030, USA.
authors.forename: Cheng
authors.initials: C
authors.lastname: Long
authors.forename: Leslie G
authors.initials: LG
authors.lastname: Cook
authors.forename: Susan L
authors.initials: SL
authors.lastname: Hamilton
authors.forename: Gang-Yi
authors.initials: GY
authors.lastname: Wu
authors.forename: Brett M
authors.initials: BM
authors.lastname: Mitchell
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects; D006973:Hypertension / Q000139:chemically induced / Q000503:physiopathology; D007166:Immunosuppressive Agents / Q000009:adverse effects*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D010766:Phosphorylation; D020033:Protein Isoforms / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D020123:Sirolimus / Q000009:adverse effects*; D022021:Tacrolimus Binding Proteins / Q000172:deficiency / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism
chemical_list: D007166:Immunosuppressive Agents; D020033:Protein Isoforms; D019837:Ryanodine Receptor Calcium Release Channel; D013912:Threonine; D052250:Nitric Oxide Synthase Type III; D022021:Tacrolimus Binding Proteins; D002118:Calcium; D020123:Sirolimus