Functional characterization and localization of GM-CSF receptor in bovine spermatozoa

Abstract

The granulocyte-macrophage colony stimulating factor (GM-CSF) is a pleiotropic cytokine with the main function of regulating the proliferation and differentiation of myeloid precursor cells as well as to stimulate the functioning of mature mononuclear granulocytes and phagocytes. Its receptor is a glycoprotein formed by two subunits, and ß, and it is expressed in precursor and mature myeloid cells, as well as in some nonhematopoietic cells. We have recently demonstrated that bull spermatozoa express functional GM-CSF receptors that signal an increased glucose and vitamin C uptake. The presence of GM-CSF receptor in epididymal and ejaculated spermatozoa was determined in this study and the a subunit was found in the acrosome and tail of the spermatozoa whilst the ß subunit was restricted to the tail. Computer assisted sperm analysis (CASA) demonstrated that the addition of GM-CSF to capacitated sperm in the presence of fructose increased the patterns of sperm motility in the majority of the variables analysed. Altogether, these findings suggest that GM-CSF is a key molecule to the better understanding of sperm physiology.