Odorant Receptor OR2C1 Is an Essential Modulator of Boar Sperm Capacitation by Binding with Heparin

Heparin, a class of glycosaminoglycans (GAGs), is widely used to induce sperm capacitation and fertilization. How heparin induces sperm capacitation remains unclear. Olfactory receptors (ORs) which are G protein-coupled receptors, have been proposed to be involved in sperm capacitation. However, the interaction between ORs and odor molecules and the molecular mechanism of ORs mediating sperm capacitation are still unclear. The present study aimed to explore the underlying interaction and mechanism between heparin and ORs in carrying out the boar sperm capacitation. The results showed that olfactory receptor 2C1 (OR2C1) is a compulsory unit which regulates the sperm capacitation by recognizing and binding with heparin, as determined by Dual-Glo Luciferase Assay and molecular docking. In addition, molecular dynamics (MD) simulation indicated that OR2C1 binds with heparin via a hydrophobic cavity comprises of Arg3, Ala6, Thr7, Asn171, Arg172, Arg173, and Pro287. Furthermore, we demonstrated that knocking down OR2C1 significantly inhibits sperm capacitation. In conclusion, we highlighted a novel olfactory receptor, OR2C1, in boar sperm and disclosed the potential binding of heparin to Pro287, a conserved residue in the transmembrane helices region 7 (TMH7). Our findings will benefit the further understanding of ORs involved in sperm capacitation and fertilization.