Hyaluronan mediates sperm motility by enhancing phosphorylation of proteins including hyaluronan binding protein

The present study was carried out to explore the mechanisms underlying hyaluronan-induced sperm motility. We demonstrate for the first time the enhanced cellular protein phosphorylation in hyaluronic acid stimulated cauda spermatozoa. Labeling of spermatozoa with [Pi] orthophosphoric acid yielded a wide range of labeled phosphoproteins in presence of hyaluronan. Under these experimental conditions, we further show tyrosine specific phosphorylation of proteins. In addition, this is also the first report showing enhanced phosphorylation of 34 kDa hyaluronan binding protein in response to hyaluronan. The role of 34 kDa hyaluronan binding protein in hyaluronan-induced spermatozoa is supported by elevated production of inositol triphosphate accompanied by increased phosphorylation in Triton X-100 insoluble cytoskeletal proteins. The evidence strongly suggests the biological importance of hyaluronan binding protein phosphorylation in the transduction of signals resulting from the interaction of hyaluronate with the sperm surface.