Compartmentalizing VEGF-Induced ERK2/1 Signaling in Placental Artery Endothelial Cell Caveolae: A Paradoxical Role of Caveolin-1 in Placental Angiogenesis in Vitro

Abstract

On vascular endothelial growth factor (VEGF) stimulation, both VEGF R1 and R2 receptors were phosphorylated in ovine fetoplacental artery endothelial (oFPAE) cells. Treatment with VEGF stimulated both time- and dose-dependent activation of ERK2/1 in oFPAE cells. VEGF-induced ERK2/1 activation was mediated by VEGFR2, but not VEGFR1, and was linked to intracellular calcium, protein kinase C, and Raf-1. VEGF stimulated oFPAE cell proliferation, migration, and tube formation in vitro. Blockade of ERK2/1 pathway attenuated VEGF-induced cell proliferation and tube formation but failed to inhibit migration in oFPAE cells. Disruption of caveolae by cholesterol depletion with methyl-beta-cyclodextrin or by down-regulation of its structural protein caveolin-1 blunted VEGF-induced ERK2/1 activation, proliferation, and tube formation in oFPAE cells, indicating an essential role of integral caveolae in these VEGF-induced responses. Adenoviral overexpression of caveolin-1 and addition of a caveolin scaffolding domain peptide also inhibited VEGF-stimulated ERK2/1 activation, cell proliferation, and tube formation in oFPAE cells. Furthermore, molecules comprising the ERK2/1 signaling module, including VEGFR2, protein kinase Calpha, Raf-1, MAPK kinase 1/2, and ERK2/1, resided with caveolin-1 in caveolae. VEGF transiently stimulated ERK2/1 activation in the caveolae similarly as in intact cells. Caveolae disruption greatly diminished ERK2/1 activation by VEGF in oFPAE cell caveolae. We conclude that caveolae function as a platform for compartmentalizing the VEGF-induced ERK2/1 signaling module. Caveolin-1 and caveolae play a paradoxical role in regulating VEGF-induced ERK2/1 activation and in vitro angiogenesis as evidenced by the similar inhibitory effects of down-regulation and overexpression of caveolin-1 and disruption of caveolae in oFPAE cells.

Small GTPase ARF6 controls VEGFR2 trafficking and signaling in diabetic retinopathy

“…It has been suggested that ARF6 mediates VEGF-induced phosphorylation of caveolin-1, which is important for cell migration and proliferation in HUVECs (19). However, the role of caveolin-1 in regulating endothelial VEGF signaling is not clear and may differ among endothelial cells originating from different vascular beds (20)(21)(22). In HRMECs, VEGF stimulation did not lead to the phosphorylation of caveolin-1 (Supplemental Figure 3A), suggesting that ARF6 may affect VEGF signaling via an alternative mechanism.…”

Blocking VEGF/Caveolin-1 signaling contributes to renal protection of fasudil in streptozotocin-induced diabetic rats

“…Caveolae are specialized plasma membrane microdomains morphologically defined as 50-to 100-nm omega-shaped invaginations according to electron microscopy observations [38,39] . Caveolin-1 functions as a scaffolding protein by directly interacting with various signaling molecules and integrates specific transmembrane signaling pathways in the caveolae, including VEGF signaling [40,41] . Our previous studies demonstrated that the VEGFR2/caveolin-1 association plays an important role in ECM accumulation in mesangial cells [23] .…”

Liver X Receptor Activation Reduces Angiogenesis by Impairing Lipid Raft Localization and Signaling of Vascular Endothelial Growth Factor Receptor-2

“…In line with this view, impairment of cholesterol homeostasis with itraconazole or cyclodextrin has been previously shown to affect vascular endothelial growth factor receptor-2 (VEGFR2) signaling in endothelial cells. 20,21 Taken together, these findings imply that the tissue actions of LXR agonists may also involve so far unappreciated antiangiogenic effects.…”