Plasmalemmal vacuolar H⁺‐ATPase is decreased in microvascular endothelial cells from a diabetic model

Abstract

Angiogenesis requires invasion of extracellular matrix (ECM) proteins by endothelial cells and occurs in hypoxic and acidic environments that are not conducive for cell growth and survival. We hypothesize that angiogenic cells must exhibit a unique system to regulate their cytosolic pH in order to cope with these harsh conditions. The plasmalemmal vacuolar type H(+)-ATPase (pmV-ATPase) is used by cells exhibiting an invasive phenotype. Because angiogenesis is impaired in diabetes, we hypothesized that pmV-ATPase is decreased in microvascular endothelial cells from diabetic rats. The in vitro angiogenesis assays demonstrated that endothelial cells were unable to form capillary-like structures in diabetes. The proton fluxes were slower in cells from diabetic than normal model, regardless of the presence or absence of Na(+) and HCO(3) (-) and were suppressed by V-H(+)-ATPase inhibitors. Immunocytochemical data revealed that pmV-ATPases were inconspicuous at the plasma membrane of cells from diabetic whereas in normal cells were prominent. The pmV-ATPase activity was lower in cells from diabetic than normal models. Inhibition of V-H(+)-ATPase suppresses invasion/migration of normal cells, but have minor effects in cells from diabetic models. These novel observations suggest that the angiogenic abnormalities in diabetes involve a decrease in pmV-ATPase in microvascular endothelial cells.

The a3 Isoform Vacuolar Type H+-ATPase Promotes Distant Metastasis in the Mouse B16 Melanoma Cells

“…In addition to increased protease expression and activity, our data show that knockdown of VATPase a3 caused the decrease in cellular motility. Several reports indicated that V-ATPase in plasma membranes also colocalizes with actin at the leading edge of migrating cells, suggesting that V-ATPase is involved in dynamic actin remodeling (37,38). These data collectively indicate that V-ATPase a3 in plasma membranes possesses dual roles and thus contributes to the increase in cancer invasiveness.…”

The vacuolar-ATPase modulates matrix metalloproteinase isoforms in human pancreatic cancer

“…Endothelial cells adjacent to an induced wound display inducible and prominent plasma membrane v-ATPase localization and activity 10. Endothelial cells obtained from diabetic rat models, however, display significantly reduced cell surface v-ATPase activity and show a functional impairment in migratory behavior 40. These findings indicate that physiological and wound-repair processes likely require plasma membrane v-ATPase activity, possibly due to the effects on MMPs.…”

V-ATPase functions in normal and disease processes

“…Normal microvascular endothelial cells have been shown to express plasma membrane V-ATPase, particularly at the leading edge of migrating cells [31,32]. Moreover, inhibition of V-ATPases with the specific inhibitor bafilomycin greatly reduced the invasiveness of these cells, suggesting that V-ATPases play a key role in angiogenesis.…”

“…It has recently been shown that microvascular endothelial cells from a diabetic rat model are deficient in plasma membrane V-ATPase [31,32]. Because angiogenesis is defective in diabetes and because V-ATPases have been implicated in an invasive phenotype, it has been suggested that the absence of plasma membrane V-ATPase activity in microvascular endothelial cells may contribute to defective angiogenesis in diabetes.…”