Syntenin promotes VEGF-induced VEGFR2 endocytosis and angiogenesis by increasing ephrin-B2 function in endothelial cells

Abstract

Syntenin, a tandem PDZ-domain-containing scaffold protein, is involved in the regulation of diverse biological functions, including protein trafficking, exosome biogenesis, and cancer metastasis. Here, we present the first study to explore the significance of syntenin in endothelial cells. Syntenin knockdown in human umbilical vein endothelial cells (HUVECs) impaired vascular endothelial growth factor (VEGF)-mediated proliferation, migration, invasion, vascular permeability, and nitric oxide (NO) production. Syntenin knockdown also suppressed expression of the VEGFR2 target genes VEGF, MMP2, and Nurr77 as well as VEGF-induced angiogenesis in vitro and in vivo. And it decreased cell-surface levels of ephrin-B2. Biochemical analyses revealed that syntenin exists in complex with VEGFR2 and ephrin-B2. Syntenin knockdown abolished the association between VEGFR2 and ephrin-B2, suggesting syntenin functions as a scaffold protein facilitating their association in HUVECs. Consistent with these observations, knocking down syntenin or ephrin-B2 abolished VEGF-induced endocytosis and VEGFR2 phosphorylation and activation of its downstream signaling molecules. Treatment with MG132, a proteasome inhibitor, rescued the downregulation of ephrin-B2 and VEGFR2 signaling induced by syntenin knockdown. These findings demonstrate that syntenin promotes VEGF signaling and, through its PDZ-dependent interaction with ephrin-B2, enhances VEGF-mediated VEGFR2 endocytosis and subsequent downstream signaling and angiogenesis in endothelial cells.

Multifaceted Roles of Caveolin-1 in Lung Cancer: A New Investigation Focused on Tumor Occurrence, Development and Therapy

“…Cav-1 can also combine with TβR-1 to induce its internalization and further cause its degradation mediated by ubiquitin-proteosome, thus blocking TGF-β signaling pathway. In contrast, syntenin, a scaffold protein that can interact with multiple membrane receptors, is able to prevent TβR-1 internalization and degradation by disassociating the TβR-1/Cav-1 complex, finally to facilitate lung cancer progression [86,87]. A metastasis-associated protein called EF-hand domain-containing protein D2 (EFHD2) is found to inhibit Cav-1 mRNA and protein expressions, and subsequently upregulate Snail and Vimentin as well as downregulate E-cadherin in A549 cells to enhance EMT.…”

Gαi1 and Gαi3mediate VEGF-induced VEGFR2 endocytosis, signaling and angiogenesis

“…Recent studies show that VEGFR2 endocytosis is indispensable for VEGFR2 signal transduction 8 , 9 . VEGFR2 internalization is reported to be regulated by Ephrin-B2, and its interacting protein, Dab2 (clathrin-associated protein disabled 2) as well as the cell polarity protein PAR-3 8 , 9 .…”

Syntenin overexpression in human lung cancer tissue and serum is associated with poor prognosis

“…Therefore, the increase of HIF-1 α reflects the occurrence and progress of cancer [33]. HIF-1 α and VEGF overexpressed in lung cancer are secreted into the blood and can be used to diagnose the cancer [34], Syntenin is shown to inhibit apoptosis [35] and inhibition of syntenin will reduce the activity of VEGF [19]. In melanoma, syntenin induces angiogenesis by activating Akt, leading to the expression of HIF-1α and the transcription of IGF-binding protein-2 (IGFBP-2), which induces the production of VEGF in endothelial cells and angiogenesis [36].…”

“…It is shown that the up-regulation of syntenin promotes the migration of non-metastatic cancer cells [16], and knockdown of syntenin inhibits the migration and invasion of cells [17,18]. In addition, syntenin has been shown to promote the formation of blood vessels [19]. VEGF has been demonstrated to be an important physiological and pathological factor for angiogenesis and play an important role in the occurrence and development of tumor [20].…”