Olfactory Receptors in Semen and in the Male Tract: From Proteome to Proteins

Abstract

The estimated number of testicular olfactory receptors (ORs) in mammals range between 20 and 66. Previous data reported the role of hOR17-4 and mOR23 in sperm–oocyte chemiotaxis. Proteomic analysis was performed to understand which are the ORs expressed in seminal plasma. Seminal samples by four fertile men were analyzed by an Ultimate 3000Nano/Micro-HPLC apparatus coupled with an LTQ-Orbitrap XL hybrid mass spectrometer. Western blot analysis confirmed the expression of three identified ORs. The expression of ORs in sperm cells, testis, and epididymis was evaluated by confocal microscopy analysis. In seminal plasma eight different ORs were identified by proteomics and three ORs have been confirmed by western blot. Confocal microscopy analysis revealed that OR4S1, OR4C13, and OR1I1 are expressed on the surface of sperm cells. In testicular tissue, OR4S1 and OR1I1 are expressed in spermatocytes and spermatids and OR4C13 is expressed throughout all the tubules. In patients with spermatocyte maturation arrest OR4S1 and OR1I1 expression was reduced and a weak positivity for OR4C13 was detected in the spermatogonia. OR4S1, OR4C13, and OR1I1 had intense and diffuse staining in the epididymis. This study initiated a new methodology for screening OR repertoire in sperms, testis and epididymis. Our results open new insights into OR involvement in sperm maturation and migration.

Advances in Cryopreservation of Bull Sperm

“…Confocal microscopy is used to evaluate sperm characteristics such as the acrosome, chromatin, and membrane. More specifically, cytoskeletal proteins, such as, spectrin, tubulin and actin in the head of sperm can be examined by laser confocal fluorescence microscopy (105–107), likewise, expression of surface proteins in sperm cells can be evaluated (108). This microscopy allows observation of sperm movement (109), but lack of qualification and quantification of various characteristics, and provides accurate visualization of mitochondria; can be used to analyze mitochondria functionality at the single-cell level (110), while also can be adjusted for tracking of motion of sperms with active mitochondria (111).…”

Ovarian odorant-like biomolecules in promoting chemotaxis behavior of spermatozoa olfactory receptors during migration, maturation, and fertilization

“…They can also be expressed in other tissues such as the cardiac cells, autonomic nervous system, spleen, prostate, and testis with wide distribution on the sperm cell [79,80]. More than 20 members of the olfactory receptors (ORs) family have been identified in sperm cells playing different roles at various stages in the movement (e.g., speed, strength, and direction) of spermatozoa towards the egg while genomics analysis revealed that approximately 50 receptors could be expressed in the testis [81,82]. These ORs are structurally similar to those receptors found in the olfactory epithelium mediating the sense of smell.…”

“…Although the exact expression status and physiological significance of the different testicular ORs are yet to be fully explained, works of literature have reported that hOR17-4 and mOR23 can influence the chemotactic movement of sperm cells towards the egg by identifying different stimuli and activating cellular transduction signals which interpret these stimuli into a coordinated movement pattern [2,85]. The ORs, hOR17-4, and mOR23 can influence the spermatogenic process, promote epididymal growth, influence acrosome reaction, and initiate flagella movement in the mature spermatozoa to enhance sperm-oocyte interaction in addition to their significant role in chemotaxis [81]. On the other hand, ORs can facilitate cell-to-cell communication as well as identifying internal and external ligands [86].…”

Is It Possible to Predict the Odor of a Molecule on the Basis of its Structure?

“…In humans, the vomeronasal organ is vestigial and nonfunctional [81], and the existence of functional accessory olfactory systems is still unclear [41]. Furthermore, olfactory receptors have been described in nontypical olfactory tissues such as myocardial and erythroid cells, ganglia, spleen, colon, prostate, and testis [82]. Olfactory receptors were found in mature sperm, revealing a potential role in sperm–oocyte chemiotaxis [82].…”

“…Furthermore, olfactory receptors have been described in nontypical olfactory tissues such as myocardial and erythroid cells, ganglia, spleen, colon, prostate, and testis [82]. Olfactory receptors were found in mature sperm, revealing a potential role in sperm–oocyte chemiotaxis [82].…”