Role of Caveolar Compartmentation in Endothelium-Derived Hyperpolarizing Factor–Mediated Relaxation

Abstract

Background-In endothelial cells, caveolin-1, the structural protein of caveolae, acts as a scaffolding protein to cluster lipids and signaling molecules within caveolae and, in some instances, regulates the activity of proteins targeted to caveolae. Specifically, different putative mediators of the endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxation are located in caveolae and/or regulated by the structural protein caveolin-1, such as potassium channels, calcium regulatory proteins, and connexin 43, a molecular component of gap junctions. Methods and Results-Comparing relaxation in vessels from caveolin-1 knockout mice and their wild-type littermates, we observed a complete absence of EDHF-mediated vasodilation in isolated mesenteric arteries from caveolin-1 knockout mice. The absence of caveolin-1 is associated with an impairment of calcium homeostasis in endothelial cells, notably, a decreased activity of Ca 2ϩ -permeable TRPV4 cation channels that participate in nitric oxide-and EDHF-mediated relaxation. Moreover, morphological characterization of caveolin-1 knockout and wild-type arteries showed fewer gap junctions in vessels from knockout animals associated with a lower expression of connexins 37, 40, and 43 and altered myoendothelial communication. Finally, we showed that TRPV4 channels and connexins colocalize with caveolin-1 in the caveolar compartment of the plasma membrane. Conclusions-We demonstrated that expression of caveolin-1 is required for EDHF-related relaxation by modulating membrane location and activity of TRPV4 channels and connexins, which are both implicated at different steps in the EDHF-signaling pathway.

Low intravascular pressure activates endothelial cell TRPV4 channels, local Ca 2+ events, and IK Ca channels, reducing arteriolar tone

“…ECs contain a range of different TRP channels (21), and in resistance arteries, TRPV4 channels are intimately involved in vasodilation to EC-dependent agonists (22,23) and shear stress-induced dilation (24). Sustained activation to low pressure is a unique addition to this list.…”

Update on vascular endothelial Ca2+signalling: A tale of ion channels, pumps and transporters

“…TRPC3-and TRPC6-induced Ca 2+ inflow underpin the stimulatory effect of VEGF on endothelial proliferation, migration and permeability [18,231,236] , while ATP exploits TRPC3 to activate NF-κB and increase vascular cell adhesion molecule-1 expression [237] . TRPC3-driven NO synthesis and vasore- TRPV1 TRPV2 TRPV3 TRPV4 TRPV5 TRPV6 PCa/PNa and conductance (pS) [202] 10, 35-80 1-3, NM 12, 172 6, 90 > 100, 75 > 100, 40-70 Human coronary artery ECs [300] (+RT-PCR, WB, IHC) Human pulmonary artery ECs [415] +(RT-PCR) +(RT-PCR) +(RT-PCR) Human pulmonary microvascular ECs +(RT-PCR) Human cerebral microvascular ECs [272] +(RT-PCR, IC) Human cerebral arterioles ECs [305] +(RT-PCR, IHC) Human dermal microvascular ECs [319] +(RT-PCR, WB) Breast cancer derived microvascular ECs [319] +(RT-PCR, WB) Human umbilical vein ECs [227,277,296,301] +(RT-PCR) +(WB, IHC) Mouse aortic ECs [280,285,299,306] +(WB) +(RT-PCR, WB, NM, IHC) Mouse pulmonary artery ECs [313] +(WB, IHC) Mouse mesenteric artery ECs [27,280,302] +(RT-PCR, WB, IC) +(RT-PCR, IC) Mouse cerebral microvascular ECs +(RT-PCR) +(RT-PCR, WB) +(RT-PCR) Mouse dermal microvascular ECs [307] +(RT-PCR, WB) Mouse carotid artery ECs [290,296] +(IHC) Rat mesenteric artery ECs [226,275,302] +(WB) +(WB, IC, IHC) Rat femoral artery ECs [312] +(RT-PCR, IC) Rat pulmonary artery ECs [303] +(WB, IHC) Rat renal artery ECs [303] +(IHC) Rat cardiac microvascular ECs [303,…”

“…TRPV4-mediated Ca 2+ responses to heat and 4αPDD require an aromatic amino acid at the NH2-terminal of the third transmembrane domain [289] . Recent work proposed that Cav-1 governs TRPV4 activity and location to the plasma membrane in ECs [301] . NO, PGI2, and IKCa/SKCa/MaxiKmediated EDHF are vasodilatory pathways that are activated following by pharmacological activation of TRPV4 [27,291,[302][303][304] .…”

Pathogenesis of pulmonary hypertension: a case for caveolin-1 and cell membrane integrity

“…Interestingly, caveolae are the preferred site for Ca 2ϩ entry when the endoplasmic reticulum stores are depleted (55) (91,121). Caveolin-1 deletion-induced impaired Ca 2ϩ entry has been shown to affect the production of endothelium-derived hyperpolarizing factor adversely (113). In addition, increase in free cytosolic Ca 2ϩ concentration levels initiate prostacyclin synthesis (58).…”