Bovine Seminal Plasma Phospholipid-Binding Proteins Stimulate Phospholipid Efflux from Epididymal Sperm1

Abstract

Several studies have shown that sperm capacitation was accompanied by a change in the lipid composition of the sperm membrane. In cattle, the major proteins of (bovine)seminal plasma (BSP proteins: BSP-A1/A2, BSP-A3, and BSP-30-kDa) potentiate sperm capacitation induced by high-density lipoprotein (HDL). Our recent studies indicate that these proteins and HDL stimulate sperm cholesterol efflux during capacitation. In order to gain more insight into the mechanisms of BSP-mediated sperm capacitation, we studied whether or not BSP proteins induce phospholipid efflux from epididymal sperm membrane. By direct determination of choline phospholipids on unlabeled epididymal sperm, the results show that sperm incubated in the presence of BSP-A1/A2 protein lost 34.4% of their choline phospholipids compared with the control (11.5%). Similar results were obtained using labeled epididymal sperm. Labeling was carried out by incubating washed epididymal sperm for 1 h with medium containing [(3)H]palmitic acid. The majority of the label was incorporated into sperm phosphatidylcholine. Studies of sperm phospholipid efflux were done by incubating the labeled sperm with purified BSP proteins, delipidated BSA, or bovine seminal ribonuclease (RNase, control protein). When labeled ([(3)H]phospholipid) epididymal sperm were incubated with BSP proteins (20-120 microg/ml) for 8 h, the sperm lost [(3)H]phospholipid in a dose-dependent manner (maximum efflux of approximately 30%). After the incubation with BSP proteins, the efflux particles were fractionated by size-exclusion chromatography. Analysis of the fractions obtained showed that the [(3)H]phospholipid was associated with BSP proteins. BSA (6 mg/ml) stimulated a specific phospholipid efflux of approximately 22%. In contrast, bovine RNase (120 microg/ml) did not stimulate phospholipid efflux. These results indicate that BSP proteins participate in the sperm cholesterol and phospholipid efflux that occurs during capacitation.

Horse Seminal Plasma proteins (HSP-1 and HSP-2) concentration: a possible marker for poor fertility?

“…This is consistent with previous findings of Novak et al (2010) in the breeding season. HSP-1/2 shares significant homology with PDC-109 (Calvete et al 1995) and this protein at higher concentrations induces membrane permeabilisation (Gasset et al 1997), stimulates cholesterol and phosphatidylcholine efflux (Therien et al 1999), and also acts in the perturbation of the membrane integrity (Calvete et al 2007). Perhaps the greater amount of HSP-1/2 in seminal plasma, as detected in samples from stallions with poor fertility, had the same negative effect as PDC-109 above mentioned.…”

Las proteínas del plasma seminal incrementan la viabilidad espermática post-descongelación del semen de toros Sanmartinero

“…La cantidad relativa de cada banda (entre 26 y 22%) y su aparición en todas las fracciones, demostrada en la electroforesis unidimensional, indicó que estas proteínas son las más abundantes dentro del PS. En este sentido se ha evidenciado que las proteínas BSP, son las más abundantes en el PS bovino (2,19,22,23). La concentración de estas proteínas en el PS está entre 20 y 40 mg/ml, lo que corresponde a una concentración de entre el 30 y el 60% de las proteínas totales del PS.…”

“…Por tanto, los presentes resultados podrían deberse al efecto de adsorción a la membrana espermática que presentan proteínas específicas del PS. Proteínas como las BSP (posiblemente contenidas en la fracción 21-25), poseen la capacidad de adsorción a la membrana plasmática por su interacción con los fosfolípidos de la misma (9,19,22,23), lo que permite explicar en parte, el efecto de recuperación de la viabilidad espermática evidenciada por la fracción. El efecto decapacitante de éstas proteínas se encuentra asociado a su cantidad.…”

Influence of the Prostatic Fluid from the First and Third Fractions of the Ejaculates on the Cryosurvival of Poodle Dog Sperm

“…These proteins also bind to the sperm surface at ejaculation via interactions with choline phospholipids present in the sperm membrane. These proteins appear to participate in the bovine sperm membrane lipid modifications that occur during Capacitation [39] . De Souza and coworkers [28] reported that the proteins resembling BSP were found in crossbred dog seminal plasma (58.6, 67 and 61.5 kDa).…”