alphaB-crystallin regulation of angiogenesis by modulation of VEGF.
alphaB-crystallin is a chaperone belonging to the small heat shock protein family. Herein we show attenuation of intraocular angiogenesis in alphaB-crystallin knockout (alphaB-crystallin(-/-)) mice in 2 models of intraocular disease: oxygen-induced retinopathy and laser-induced choroidal neovascularization. Vascular endothelial growth factor A (VEGF-A) mRNA and hypoxia inducible factor-1alpha protein expression were induced during retinal angiogenesis, but VEGF-A protein expression remained low in alphaB-crystallin(-/-) retina versus wild-type mice, whereas VEGF-R2 expression was not affected. Both alphaB-crystallin and its phosphorylated serine59 formwere expressed, and immunoprecipitation revealed alphaB-crystallin binding to VEGF-A but not transforming growth factor-beta in cultured retinal pigment epithelial (RPE) cells. alphaB-crystallin and VEGF-A are colocalized in the endoplasmic reticulum in RPE cells under chemical hypoxia. alphaB-crystallin(-/-) RPE showed low VEGF-A secretion under serum-starved conditions compared with wild-type cells. VEGF-A is polyubiquitinated in control and alphaB-crystallin siRNA treated RPE; however, mono-tetra ubiquitinated VEGF-A increases with alphaB-crystallin knockdown. Endothelial cell apoptosis in newly formed vessels was greater in alphaB-crystallin(-/-) than wild-type mice. Proteasomal inhibition in alphaB-crystallin(-/-) mice partially restores VEGF-A secretion and angiogenic phenotype in choroidal neovascularization. Our studies indicate an important role for alphaB-crystallin as a chaperone for VEGF-A in angiogenesis and its potential as a therapeutic target.
Kase
Satoru
S
Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
He
Shikun
S
Sonoda
Shozo
S
Kitamura
Mizuki
M
Spee
Christine
C
Wawrousek
Eric
E
Ryan
Stephen J
SJ
Kannan
Ram
R
Hinton
David R
DR
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D015153:Blotting, Western; D020256:Choroidal Neovascularization / Q000235:genetics / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D020287:In Situ Nick-End Labeling; D051379:Mice; D018345:Mice, Knockout; D055213:Retinal Pigment Epithelium / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*; D038203:alpha-Crystallin B Chain / Q000235:genetics / Q000378:metabolism*
C525420:Cryab protein, mouse; D042461:Vascular Endothelial Growth Factor A; D038203:alpha-Crystallin B Chain