Expression of GM-CSF receptors in male germ cells and their role in signaling for increased glucose and vitamin C transport

Abstract

We studied the expression and function of the granulocyte-macrophage colony stimulating factor (GM-CSF) receptor in male germ cells. RT-PCR showed expression of mRNAs encoding the alpha- and beta-subunits of the GM-CSF receptor in human testis, and the presence of the alpha- and beta-proteins was confirmed by immunoblotting with anti-alpha and anti-beta-antibodies. Immunolocalization studies showed the level of expression of GM-CSF alpha- and beta-subunits in the germ line in the testis and in ejaculated spermatozoa. Receptor binding studies using radiolabeled GM-CSF revealed that bull spermatozoa have about 105 high-affinity sites with a K(d) of 222 pM and approximately 1100 low-affinity sites with a K(d) of 10 nM. GM-CSF signaled, in a time- and dose-dependent manner, for an increased uptake of glucose and vitamin C.