Thrombospondin-1 modulates VEGF signaling via CD36 by recruiting SHP-1 to VEGFR2 complex in microvascular endothelial cells

Abstract

• TSP-1 binding to CD36 recruits SHP-1 to CD36-VEGFR2 complex in microvascular endothelial cells.• SHP-1 recruitment to CD36-VEGFR2 complex dephosphorylates VEGFR2 and inhibits angiogenesis.Thrombospondin-1 (TSP-1) inhibits growth factor signaling at the receptor level in microvascular endothelial cells (MVEC), and CD36 has been suggested to be involved in this inhibition, but the mechanisms are not known. We hypothesized that CD36-TSP-1 interaction recruits Src homology 2 domain-containing protein tyrosine phosphatase (SHP)-1 to the vascular endothelial growth factor receptor 2 (VEGFR2) signaling complex and attenuates vascular endothelial growth factor (VEGF) signaling. Western blots of anti-CD36 and anti-VEGFR2 immunoprecipitates from VEGF-treated MVEC showed that exposure of the cells to a recombinant protein containing the CD36 binding domain of thrombospondin-1 (known as the TSR domain) induced association of SHP-1 with the VEGFR2/CD36 signaling complex and thereby suppressed VEGFR2 phosphorylation. SHP-1 phosphatase activity was increased in immunoprecipitated VEGFR2 complexes from TSR-treated cells. Silencing CD36 expression in MVEC by small interfering RNA (siRNA) or genetic deletion of cd36 in mice showed that TSR-induced SHP-1/VEGFR2 complex formation required CD36 in vitro and in vivo. Silencing SHP-1 expression in MVEC by siRNA abrogated TSR-mediated inhibition of VEGFR2 phosphorylation as well as TSRmediated inhibition of VEGF-induced endothelial cell migration and tube formation. These studies reveal a SHP-1-mediated antiangiogenic pathway induced by CD36-TSP-1 interaction that inhibits VEGFR2 signaling and they provide a novel target to modulate angiogenesis therapeutically. (Blood. 2013;122(10):1822-1832 Introduction CD36 is a multiligand scavenger receptor expressed on the surface of platelets, MVEC, mononuclear phagocytes, adipocytes, hepatocytes, myocytes, and some epithelia.1 It was first identified as glycoprotein IV on platelets.2 On MVEC, CD36 is a receptor for TSP-1 and related proteins containing the so-called "thrombospondin type I structural homology domain (TSR)." It functions as a negative regulator of angiogenesis 1,[3][4][5] and therefore plays a role in tumor growth, inflammation, wound healing, and other pathological processes requiring neovascularization. 6,7 Binding of TSP-1 or TSR proteins to CD36 inhibits growth factor-induced proangiogenic signals that mediate endothelial cell proliferation, migration, and tube formation, and instead generates antiangiogenic signals that lead to apoptosis. 4,8 In vivo, CD36 null mice exhibit an increase in vessel density in the brain, an organ in which early angiogenesis is modulated by high levels of TSP-1, increased tumor angiogenesis in subcutaneously injected TSP-expressing tumor cells, and a lack of response to antiangiogenic effect of TSP-1 in in vivo angiogenesis assays. 8,9 It was recently shown that TSP-1 also inhibits growth factor signaling at the vascular endothelial growth factor (VEGF) receptor 2 (VEGFR2) receptor level in end...

Contribution of Human Fibroblasts and Endothelial Cells to the Hallmarks of Inflammation as Determined by Proteome Profiling

“…Finally, regulatory mechanisms control undesired escalation of angiogenesis. Activation of antiangiogenic factors such as thrombospondin-1 (TSP1) and TSP2, or downregulation of proangiogenic factors such as angiotensin-converting enzyme or c-type lectin domain family 14 member A are involved here (51)(52)(53)(54). ECM reorganization is strongly interlinked with angiogenesis and related proteins were found regulated in both cell types as well.…”

Supporting Roles of Platelet Thrombospondin-1 and CD36 in Thrombus Formation on Collagen

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Shear stress‐induced angiogenesis in mouse muscle is independent of the vasodilator mechanism and quickly reversible

“…2006), and, when complexed with its receptor, CD36, inhibits VEGFR2 (Chu et al . 2013). This reduces angiogenesis readouts in vitro (Klenotic et al .…”