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Y. Zhang, J. Cai, A. Afzal, M.B. Grant, M.E. Boulton; VEGFR–1 Is Differentially Regulated by Pigment Epithelium–Derived Factor (PEDF) via Presenilin in RPE and Retinal Endothelial Cells . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5333.
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To compare the regulation of VEGFR–1 expression and cleavage in RPE and retinal endothelial cells (RECs) and to determine if this is linked with presenilin–1.
Human and bovine RPE and RECs were grown to confluence and exposed to a) VEGF (100ng/ml) or PEDF (100ng/ml) alone for 24 hr, or b) VEGF for 1hr followed by PEDF for 24 hr, or c) PEDF for 1hr followed by VEGF for 24 hr. The expression and localisation of VEGFR–1 and presenilin was assessed by immunocytochemistry and confocal microscopy. Western blot analysis was undertaken on extracted protein using antibodies against the C–terminus and the N–terminus of VEGFR–1 as well as presenilin–1.
Addition of PEDF to VEGF–stimulated RECs resulting in the appearance of a low molecular weight VEGFR–1 C–terminal fragment that was not present in cells treated with either VEGF or PEDF alone. By contrast, a number of different molecular weight C–terminal VEGFR–1 fragments were observed in untreated RPE cells. These were decreased after VEGF treatment and remained unchanged following addition of PEDF. We have previously shown that presenilin–1 is involved in the cleavage and translocation of the VEGFR–1 C–terminal domains. Presenilin–1 was expressed in both RPE cells and RECs and was translocated to the membrane following PEDF treatment. Presenilin–1 appeared as 3 different molecular weight bands which were differentially expressed in RPE cells and RECs. Expression patterns of presenilin–1 changed following VEGF and/or PEDF treatment.
Presenilin plays a pivotal role in the regulated intramembrane proteolysis of VEGFR–1 and its action is regulated by PEDF. Furthermore, PEDF regulation of VEGFR–1 differs between RPE cells and RECs.
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