Caveolae protect endothelial cells from membrane rupture during increased cardiac output

Abstract

Caveolae are strikingly abundant in endothelial cells, yet the physiological functions of caveolae in endothelium and other tissues remain incompletely understood. Previous studies suggest a mechanoprotective role, but whether this is relevant under the mechanical forces experienced by endothelial cells in vivo is unclear. In this study we have sought to determine whether endothelial caveolae disassemble under increased hemodynamic forces, and whether caveolae help prevent acute rupture of the plasma membrane under these conditions. Experiments in cultured cells established biochemical assays for disassembly of caveolar protein complexes, and assays for acute loss of plasma membrane integrity. In vivo, we demonstrate that caveolae in endothelial cells of the lung and cardiac muscle disassemble in response to acute increases in cardiac output. Electron microscopy and two-photon imaging reveal that the plasma membrane of microvascular endothelial cells in caveolin 1−/− mice is much more susceptible to acute rupture when cardiac output is increased. These data imply that mechanoprotection through disassembly of caveolae is important for endothelial function in vivo.

Caveolin-1 modulates intraocular pressure: implications for caveolae mechanoprotection in glaucoma

“…As conventional outflow pathway cells are normally subjected and responsive to fluctuating mechanical loads3, we determined whether caveolae, putative mechanosensors/protectors212223242526272830, respond to mechanical stimulation in human TM cells subjected to a model of cyclic mechanical stretch that mimics ocular pulse fluctuation. Association of PTRF/cavin-1, which is essential for caveolae formation and dissociates from Cav-1 during caveolae disassembly2130, was assessed by co-immunoprecipitation.…”

“…Association of PTRF/cavin-1, which is essential for caveolae formation and dissociates from Cav-1 during caveolae disassembly2130, was assessed by co-immunoprecipitation. As shown in Fig.…”

“…We have previously found retinal functional deficits and vascular pathologies in mice deficient in Cav-11920 but the associations of these with glaucomatous injury are unknown. Caveolae are implicated in mechanoprotection2122232425 and mechanotransduction2627 and transduce flow-mediated vasodilation by endothelial nitric oxide synthase (eNOS)28, an important mediator of IOP529. As the conventional outflow pathway tissues that maintain IOP homeostasis are subject to large mechanical loads, we hypothesized that caveolae serve a critical function as membrane mechanosensors/protectors in the pressure-dependent aqueous humor drainage.…”

Membrane Supply and Demand Regulates F-Actin in a Cell Surface Reservoir

“…For example, as apparent cell surface area gets smaller during apical cell constriction in gastrulating embryos, or during oscillatory contractions in cultured cells, membrane reservoirs of blebs, folds, and filopodia form (Kapustina et al, 2013; Martin et al, 2010; Nowotarski et al, 2014; Sweeton et al, 1991). Conversely, to prevent plasma membrane rupture during mechanical stretching in human myotubes and endothelial cells, reservoirs of surface invaginations flatten out (Cheng et al, 2015; Sinha et al, 2011). Membrane is transferred to and from reservoirs as cells change their shape in cytokinesis, cell spreading, phagocytosis, and tissue morphogenesis (Figard et al, 2013; Gauthier et al, 2011; Masters et al, 2013; Sedzinski et al, 2011; Tan and Zaidel-Bar, 2015).…”

“…For example, caveolae constitute a small membrane reservoir, storing <1% of cell surface area in invaginations supported by caveolar protein complexes (Sinha et al, 2011). Inactivation of caveolar complex formation blocks reservoir formation, and disassembly of the caveolar complexes upon cell stretching correlates with reservoir depletion (Cheng et al, 2015; Sinha et al, 2011). Thus, mechanical and/or molecular signals acting on the caveolar scaffold control reservoir formation and utilization.…”