Hyaluronan-Binding Protein 1 (HBAP-1) in Male Reproduction

Hyaluronan-binding protein 1 (HABP1), alternatively designated as p32, C1QBP, gC1qR, or HIV TAP (Tat-associated protein), is a highly conserved eukaryotic protein expressed across taxa from yeast to mammals, and is localized on the cell surface of diverse cell types. This protein exists in two distinct functional forms: firstly, a pro-protein exclusively found in male germ cells, suggesting its crucial role in spermatogenic differentiation; and secondly, a mature, post-translationally cleaved form localized on the sperm surface. Due to its specific affinity for hyaluronan (HA) a key constituent of reproductive fluids the mature form is actively involved in sperm penetration, sperm-oocyte interaction, and subsequent fertilization by mature human spermatozoa. This review aims to comprehensively elucidate the key functions of HABP1, with a specific focus on its implications in reproductive science.