Pigment epithelium‐derived factor binds to cell‐surface F1‐ATP synthase
Authors: Notari Luigi , Arakaki Naokatu , Mueller David , Meier Scott , Amaral Juan , Becerra S. P. 
Published: April 2010

Pigment epithelium‐derived factor (PEDF), a potent blocker of angiogenesis in vivo, and of endothelial cell migration and tubule formation, binds with high affinity to an as yet unknown protein on the surfaces of endothelial cells. Given that protein fingerprinting suggested a match of a ∼ 60 kDa PEDF‐binding protein in bovine retina with Bos taurus F1‐ATP synthase β‐subunit, and that F1Fo‐ATP synthase components have been identified recently as cell‐surface receptors, we examined the direct binding of PEDF to F1. Size‐exclusion ultrafiltration assays showed that recombinant human PEDF formed a complex with recombinant yeast F1. Real‐time binding as determined by surface plasmon resonance demonstrated that yeast F1 interacted specifically and reversibly with human PEDF. Kinetic evaluations revealed high binding affinity for PEDF, in agreement with PEDF affinities for endothelial cell surfaces. PEDF blocked interactions between F1 and angiostatin, another antiangiogenic factor, suggesting overlapping PEDF‐binding and angiostatin‐binding sites on F1. Surfaces of endothelial cells exhibited affinity for PEDF‐binding proteins of ∼ 60 kDa. Antibodies to F1β‐subunit specifically captured PEDF‐binding components in endothelial plasma membranes. The extracellular ATP synthesis activity of endothelial cells was examined in the presence of PEDF. PEDF significantly reduced the amount of extracellular ATP produced by endothelial cells, in agreement with direct interactions between cell‐surface ATP synthase and PEDF. In addition to demonstrating that PEDF binds to cell‐surface F1, these results show that PEDF is a ligand for endothelial cell‐surface F1Fo‐ATP synthase. They suggest that PEDF‐mediated inhibition of ATP synthase may form part of the biochemical mechanisms by which PEDF exerts its antiangiogenic activity.

Structured digital abstract

MINT‐7711286: angiostatin (uniprotkb:P00747) physically interacts (MI:0915) with F‐ATPase alpha subunit (uniprotkb:P07251), F‐ATPase beta subunit (uniprotkb:P00830), F‐ATPase gamma subunit (uniprotkb:P38077), F‐ATPase delta subunit (uniprotkb:Q12165) and F‐ATPase epsilon subunit (uniprotkb:P21306) by competition binding (MI:0405)

MINT‐7711113: angiostatin (uniprotkb:P00747) physically interacts (MI:0915) with F‐ATPase epsilon subunit (uniprotkb:P21306), F‐ATPase delta subunit (uniprotkb:Q12165), F‐ATPase gamma subunit (uniprotkb:P38077), F‐ATPase beta subunit(uniprotkb:P00830) and F‐ATPase alpha subunit (uniprotkb:P07251) by surface plasmon resonance (MI:0107)

MINT‐7711060: F‐ATPase gamma subunit (uniprotkb:P38077), F‐ATPase beta subunit (uniprotkb:P00830), F‐ATPase alpha subunit (uniprotkb:P07251) and PEDF (uniprotkb:P36955) physically interact (MI:0915) by molecular sieving (MI:0071)

MINT‐7711313: F‐ATPase epsilon subunit (uniprotkb:P21306), F‐ATPase delta subunit (uniprotkb:Q12165), PEDF (uniprotkb:P36955), F‐ATPase alpha subunit (uniprotkb:P07251), F‐ATPase beta subunit (uniprotkb:P00830) and F‐ATPase gamma subunit(uniprotkb:P38077) physically interact (MI:0915) by molecular sieving (MI:0071)

MINT‐7711083: PEDF (uniprotkb:P36955) physically interacts (MI:0915) with F‐ATPase epsilon subunit (uniprotkb:P21306), F‐ATPase delta subunit (uniprotkb:Q12165), F‐ATPase gamma subunit (uniprotkb:P38077), F‐ATPase beta subunit (uniprotkb:P00830) and F‐ATPase alpha subunit (uniprotkb:P07251) by surface plasmon resonance (MI:0107)