Proteomics of seminal fluid

Abstract

Seminal fluid or semen is a complex mixture consisting of spermatozoa suspended within the secretions of male accessory sex glands. Although most studies of seminal fluid have emphasized the importance of spermatozoa morphology, concentration, and motility, and of biochemical constituents such as fructose and zinc, the significance of the protein composition of this biological fluid is receiving increasing attention. As detailed in this chapter, numerous studies have been conducted to investigate the protein composition of spermatozoa, seminal plasma (i.e., the acellular component of seminal fluid), and prostasomes (i.e., membrane-bound vesicles of prostatic origin present in seminal fluid). Most of these investigations were based on 2D gel electrophoresis, but most of the resolved proteins were not identified. Several proteins in seminal fluid have, however, already found potential use as markers for the assessment of reproductive function (e.g., neutral α-glucosidase and semenogelin 1) and as forensic tools for semen detection (e.g., semenogelin 1 and prostate-specific antigen [PSA]). Studies of spermatozoa are providing insights into immune infertility and identifying potential targets for contraceptive vaccines. In addition, because 20 to 30% of the volume of seminal fluid is derived from secretions of the prostate gland, this proximate biological fluid serves as a rich resource for biomarkers of prostatic disease, including cancer. Recent advances in technology for comparative proteomic studies will facilitate future biomarker discovery studies of this important biological fluid.