Proteomic analysis of heparin-binding proteins from human seminal plasma: a step towards identifi cation of molecular markers of male fertility.

ABSTRACT

Glycosaminoglycans, especially heparin, are involved in various cell processes such as apoptosis, cell cycle control, platelet activation, capacitation, acrosome reaction and sperm decondensation. Heparin-binding proteins (HBPs) are essential constituents of human seminal fl uid, which bind to sperm lipids containing the phosphorylcholine group and mediate the fertilization process. We utilized a proteomic set-up consisting of affi nity chromatography, isoelectric focusing (IEF) coupled with matrix-assisted laser desorption/ionization time-of-fl ight tandem mass spectrometry (MALDI TOF/MS) for protein analysis of human HBPs. We resolved 70 different spots on two-dimensional (2-D) gel and subsequently identifi ed these proteins. Forty different types of proteins were identifi ed. Functional analysis revealed that 38% of the proteins belonged to the enzyme category, 20% were involved in RNA processing and transcription, 18% in structure and transport function, and 16% in cell recognition and signal transduction. We also identifi ed 8% of proteins with unknown functions, although their expression in seminal fl uid has been documented. Proteins of seminal fl uid that bind heparin may be directly involved in sperm capacitation and acrosome reaction (AR), which are the two critical steps for fertilization. This information on HBPs would be useful for identifying potential biomarkers of fertility in the near future.