Seminal plasma choline phospholipid-binding proteins stimulate cellular cholesterol and phospholipid efflux.
Bovine seminal plasma (BSP) contains a family of phospholipid-binding proteins (BSP-A1/-A2, BSP-A3 and BSP-30-kDa, collectively called BSP proteins) that potentiate sperm capacitation induced by high-density lipoproteins. We showed recently that BSP proteins stimulate cholesterol efflux from epididymal spermatozoa and play a role in capacitation. Here, we investigated whether or not BSP proteins could stimulate cholesterol and phospholipid efflux from fibroblasts. Cells were radiolabeled ([3H]cholesterol or [3H]choline) and the appearance of radioactivity in the medium was determined in the presence of BSP proteins. Alcohol precipitates of bovine seminal plasma (designated crude BSP, cBSP), purified BSP-A1/-A2, BSP-A3 and BSP-30-kDa proteins stimulated cellular cholesterol and choline phospholipid efflux from fibroblasts. Efflux mechanistic differences were observed between BSP proteins and other cholesterol acceptors. Preincubation of BSP-A1/-A2 proteins with choline prevented cholesterol efflux, an effect not observed with apolipoprotein A-I. Also, the rate of BSP-induced efflux was rapid during the first 20 min, but leveled off thereafter in contrast to a relatively slow, but constant, rate of cholesterol efflux mediated by apolipoprotein A-I, apolipoprotein A-I-containing reconstituted lipoproteins (LpA-I) and high-density lipoproteins. These results indicate that fibroblasts are a good cell model to study the mechanism of lipid efflux mediated by BSP proteins.
Moreau
R
R
Department of Medicine, University of Montreal and Guy Bernier Research Centre, Maisonneuve-Rosemont Hospital, 5415 L'Assomption, Montreal, Que. H1T 2M4, Canada.
Frank
P G
PG
Perreault
C
C
Marcel
Y L
YL
Manjunath
P
P
D001054:Apolipoproteins A / Q000494:pharmacology; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D005347:Fibroblasts; D006801:Humans; D017270:Lipoprotein(a) / Q000494:pharmacology; D008075:Lipoproteins, HDL / Q000494:pharmacology; D010743:Phospholipids / Q000378:metabolism*; D029584:Prostatic Secretory Proteins; D011506:Proteins / Q000494:pharmacology*; D012661:Semen / Q000737:chemistry*; D029589:Seminal Plasma Proteins
D001054:Apolipoproteins A; D017270:Lipoprotein(a); D008075:Lipoproteins, HDL; D010743:Phospholipids; D029584:Prostatic Secretory Proteins; D011506:Proteins; D029589:Seminal Plasma Proteins; C043076:beta-microseminoprotein; D002784:Cholesterol