Perlecan Domain V Induces VEGf Secretion in Brain Endothelial Cells through Integrin α5β1 and ERK-Dependent Signaling Pathways

Abstract

Perlecan Domain V (DV) promotes brain angiogenesis by inducing VEGF release from brain endothelial cells (BECs) following stroke. In this study, we define the specific mechanism of DV interaction with the α5β1 integrin, identify the downstream signal transduction pathway, and further investigate the functional significance of resultant VEGF release. Interestingly, we found that the LG3 portion of DV, which has been suggested to possess most of DV’s angio-modulatory activity outside of the brain, binds poorly to α5β1 and induces less BEC proliferation compared to full length DV. Additionally, we implicate DV’s DGR sequence as an important element for the interaction of DV with α5β1. Furthermore, we investigated the importance of AKT and ERK signaling in DV-induced VEGF expression and secretion. We show that DV increases the phosphorylation of ERK, which leads to subsequent activation and stabilization of eIF4E and HIF-1α. Inhibition of ERK activity by U0126 suppressed DV-induced expression and secretion of VEGR in BECs. While DV was capable of phosphorylating AKT we show that AKT phosphorylation does not play a role in DV’s induction of VEGF expression or secretion using two separate inhibitors, LY294002 and Akt IV. Lastly, we demonstrate that VEGF activity is critical for DV increases in BEC proliferation, as well as angiogenesis in a BEC-neuronal co-culture system. Collectively, our findings expand our understanding of DV’s mechanism of action on BECs, and further support its potential as a novel stroke therapy.

Juvenile Traumatic Brain Injury Induces Long-Term Perivascular Matrix Changes Alongside Amyloid-Beta Accumulation

“…No changes in perlecan DV were revealed suggesting that despite an increase in total perlecan staining, there is no concomitant increase in perlecan proteolysis to generate perlecan-cleaved DV. As DV is proangiogenic in the brain, 14,16 this lack of a change in DV levels is consistent with the lack of increased angiogenesis that we also observed 2 and 6 months after jTBI (discussed further below). Unchanged DV levels in the presence of increased total perlecan staining after jTBI also suggest that the activity of DV-generating proteases are unaltered or perhaps diminished.…”

“…They are not merely components of an inert mat supporting brain cells, and growing evidence suggests that those proteins and their proteolytic fragments can be neuroprotective and affect angiogenesis. [14][15][16]18,19 As described previously, the vasoactive DV fragment of perlecan can induce neuroprotection and angiogenesis by increasing the production and release of VEGF by endothelial cells in different rodent stroke models. 14,16 It can compete with Ab for the binding to a2 integrin and thus inhibit neurotoxic pathways, 17 and it can reduce glial scar by inhibiting astrocyte proliferation.…”

“…[14][15][16]18,19 As described previously, the vasoactive DV fragment of perlecan can induce neuroprotection and angiogenesis by increasing the production and release of VEGF by endothelial cells in different rodent stroke models. 14,16 It can compete with Ab for the binding to a2 integrin and thus inhibit neurotoxic pathways, 17 and it can reduce glial scar by inhibiting astrocyte proliferation. 13 Interestingly, DV has also been shown to interact with a5b1 integrin receptor in endothelial cells, inducing Ab internalization, degradation and clearance, thereby reducing its toxicity.…”

Tumor-Derived GM-CSF Promotes Inflammatory Colon Carcinogenesis via Stimulating Epithelial Release of VEGF

“…The dissection of signaling pathways involved in this process revealed that the ERK-mediated pathway was required for GM-CSF-elicited VEGF expression. Indeed, ERK signaling is one of the major pathways that is responsible for VEGF expression induced by various stimuli in transformed or nontransformed cells (29,30). Of note, activation of ERK signaling seems to increase translocation of hypoxia-inducible factor 1a (HIF-1a) from cytoplasm to nuclei, consequently it binds to the VEGF promoter and initiates the transcription of the growth factor (31).…”

YKL‐40: The Search for New Biomarkers in Rheumatoid Arthritis

“…Kjaergaard et al [17] suggested that another heparan sulfate proteoglycan, perlecan, might be a possible ligand for YKL-40. It was revealed that perlecan comprised distinct efects on angiogenesis dependent on integrin coupling [17,18].…”