Spreds Are Essential for Embryonic Lymphangiogenesis by Regulating Vascular Endothelial Growth Factor Receptor 3 Signaling

Abstract

Spred/Sprouty family proteins negatively regulate growth factor-induced ERK activation. Although the individual physiological roles of Spred-1 and Spred-2 have been investigated using gene-disrupted mice, the overlapping functions of Spred-1 and Spred-2 have not been clarified. Here, we demonstrate that the deletion of both Spred-1 and Spred-2 resulted in embryonic lethality at embryonic days 12.5 to 15.5 with marked subcutaneous hemorrhage, edema, and dilated lymphatic vessels filled with erythrocytes. This phenotype resembled that of Syk ؊/؊ and SLP-76 ؊/؊ mice with defects in the separation of lymphatic vessels from blood vessels. The number of LYVE-1-positive lymphatic vessels and lymphatic endothelial cells increased markedly in Spred-1/2-deficient embryos compared with WT embryos, while the number of blood vessels was not different. Ex vivo colony assay revealed that Spred-1/2 suppressed lymphatic endothelial cell proliferation and/or differentiation. In cultured cells, the overexpression of Spred-1 or Spred-2 strongly suppressed vascular endothelial growth factor-C (VEGF-C)/VEGF receptor (VEGFR)-3-mediated ERK activation, while Spred-1/2-deficient cells were extremely sensitive to VEGFR-3 signaling. These data suggest that Spreds play an important role in lymphatic vessel development by negatively regulating VEGF-C/VEGFR-3 signaling.

Spred-2 deficiency exacerbates acetaminophen‐induced hepatotoxicity in mice

“…Spred-2 KO mice backcrossed into the C57BL/6J background have been previously reported [11,12]. C57BL/6J mice were used as the wild-type (WT) mice.…”

Sprouty4 negatively regulates protein kinase C activation by inhibiting phosphatidylinositol 4,5-biphosphate hydrolysis

“…Similarly, Sprouty4 inhibits vascular endothelial growth factor (VEGF)-A-induced PKC-mediated ERK activation, whereas Sprouty4 does not inhibit EGF as well as VEGF-C-mediated ERK activation (Sasaki et al, 2001(Sasaki et al, , 2003Taniguchi et al, 2007). Molecular basis for the suppression of the PKC pathway remains to be solved.…”

Inside bloody lymphatics

“…6 A somewhat similar phenotype also occurs in mice deficient in 2 suppressors of phosphorylation of the mitogen-activated protein kinase-extracellular 10 receptor kinase downstream of VEGF-C/ VEGFR-3 signaling. 7 Podoplanin in lymphatic endothelial cells is critical for platelet activation where the podoplanin-positive lymphatic vessels are separated from the cardinal veins as shown in studies of podoplanin knockout embryos. 2 Podoplanin binds to and activates the C-type lectin receptor 2 (CLEC-2), specifically expressed in platelets, which in turn leads to activation of Syk and phosphorylation of SLP-76.…”