title: Thrombospondin-1 modulates VEGF-A-mediated Akt signaling and capillary survival in the developing retina.
abstract: Microvascular development is often perceived to result from a balance of positive and negative factors that impact signaling for proliferation and survival. The survival signaling that results from hypoxia-induced VEGF-A has been well established, but the factors that antagonize this signaling have been poorly studied. As endogenous inhibitors of angiogenesis, thrombospondins (TSPs) are likely candidates to affect survival signaling. Here we report that TSP1 antagonized microvascular survival to retinal hyperoxia, and Akt signaling in both the retina and in cultured endothelial cells. TSP1 expression is correlated with the association of the CD36 receptor with Src versus Fyn. In the presence of TSP1, CD36 is coprecipitated with Fyn as previously shown by others. However, in the absence of TSP1, there is a preferential association with Src. We now demonstrate that these Src family kinases play an important role in modulating microvascular survival in response to TSP1 by crossing tsp1(-/-) mice to the src(-/-) and fyn(-/-) mice and testing the survival of retinal blood vessels in hyperoxia. We find that tsp1(-/-), fyn(-/-), and double-mutant tsp1(-/-)/fyn(-/-) mice have a similar enhancement of capillary survival in oxygen, whereas in a tsp(-/-) background, the loss of only one allele of src restores the balance in survival and apoptosis to that of wild-type mice. Taken together, we hypothesize that TSP1 antagonizes VEGF-driven Akt survival signaling in part through the recruitment of Fyn to membrane domains containing CD36, but when TSP1 is absent, an opposing Src recruitment contributes to VEGF-driven Akt phosphorylation and capillary survival.
authors.affiliation: Dept. of Pathology, Beth Israel Deaconess Medical Ctr. and Harvard Medical School, 330 Brookline Ave., Boston, MA 02215, USA.
authors.forename: Jingfang
authors.initials: J
authors.lastname: Sun
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Hopkins
authors.forename: Kaoru
authors.initials: K
authors.lastname: Tsujikawa
authors.forename: Carole
authors.initials: C
authors.lastname: Perruzzi
authors.forename: Irit
authors.initials: I
authors.lastname: Adini
authors.forename: Robert
authors.initials: R
authors.lastname: Swerlick
authors.forename: Paul
authors.initials: P
authors.lastname: Bornstein
authors.forename: Jack
authors.initials: J
authors.lastname: Lawler
authors.forename: Laura E
authors.initials: LE
authors.lastname: Benjamin
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D018955:CD36 Antigens / Q000378:metabolism; D002196:Capillaries / Q000201:enzymology / Q000503:physiopathology; D002470:Cell Survival; D002478:Cells, Cultured; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000201:enzymology; D006801:Humans; D018496:Hyperoxia / Q000201:enzymology* / Q000503:physiopathology; D051379:Mice; D018345:Mice, Knockout; D018919:Neovascularization, Physiologic; D010100:Oxygen / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051076:Proto-Oncogene Proteins c-fyn / Q000235:genetics / Q000378:metabolism; D012160:Retina / Q000201:enzymology* / Q000254:growth & development / Q000503:physiopathology; D012171:Retinal Vessels / Q000201:enzymology* / Q000254:growth & development / Q000503:physiopathology; D015398:Signal Transduction; D019700:Thrombospondin 1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D019699:Thrombospondins / Q000378:metabolism; D013997:Time Factors; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism; D000099262:Thrombospondin 2
chemical_list: D018955:CD36 Antigens; D010100:Oxygen; D051057:Proto-Oncogene Proteins c-akt; D051076:Proto-Oncogene Proteins c-fyn; D019700:Thrombospondin 1; D019699:Thrombospondins; D042461:Vascular Endothelial Growth Factor A; D019061:src-Family Kinases; D000099262:Thrombospondin 2; C467480:vascular endothelial growth factor A, mouse; C494960:Fyn protein, mouse