Localization of Guanylate Cyclase Receptor, Inositol Trisphosphate Receptor, and Calmodulin in Boar Spermatozoa

Abstract

Several proteins present on the sperm membranes serve as signal transducers facilitating sperm maturation, capacitation, acrosome reaction and fertilization. Among them, guanylate cyclase (GC), the inositol trisphosphate receptor (IP 3 R) and calmodulin have been reported rather extensively. Although biochemical data clearly suggest their roles in the fertilization process, the precise location of these proteins in the sperm membranes have not been adequately investigated and need clarification. Using immunolocalization procedures we report that guanylate cyclase receptors (GCR) are localized on the apical region of the acrosome and on the postacrosomal plasmalemma, while IP 3 Rs are present in the neck region of the sperm and at lower density along the axonemal membrane. In contrast, calmodulin is restricted to the postacrosomal, basal nuclear membrane and the neck region that corresponds to the redundant nuclear envelope and ER vesicles, with some reaction along the middle piece and tail membranes. Colocalization of these proteins on the sperm membrane together with biochemical data as reported previously provide further insight into their role in the spermatozoan motility and possibly the fertilization process.

IP3R Channels in Male Reproduction

“…In early spermatogenic cells, IP3R1 and IP3R3 had higher expression levels than IP3R2 ( Figure 3). The expression of IP3R was also detected in the mature sperm of boars and humans [39], and cattle [40]. IP3R was reported to be localized in the acrosome and the principal piece of the flagellum in mature sperm of mice, but the precise location of IP3Rs in sperm remains controversial because of inconsistent results in different studies [7], and the precise subcellular location of IP3R in sperm remains to be determined.…”

“…As mentioned above, 2-APB is an inhibitor of IP3R channels [68]. Xestospongin C is a reversible and nonspecific IP3R antagonist inhibiting the IP3-induced Ca 2+ increase [39]. These inhibitors or agonists can be applied as a tool to determine the roles of the IP3R channel in calcium signaling.…”

Efeito da Adição de Cálcio sobre a Hiperativação Espermática: Avaliação Computadorizada

“…Os canais de liberação de Ca 2+ com receptores inositol 1,4,5-trifosfato (IP 3 R 1 ) regulam a liberação de cálcio dos estoques em resposta à ligação de IP3 e Ca 2 + (TAYLOR; TOVEY, 2010). Nos espermatozoides suínos, o IP 3 R 1 está presente na peça intermediária e no acrossoma (HARAYAMA et al, 2005) e o IP3R1 está localizado na região do colo dos espermatozoides e em menor densidade ao longo da membrana axonemal (GUGSSA et al, 2010).…”