Immunolocalization of heat shock protein 70 (Hsp 70) in boar spermatozoa and its role during fertilization

Abstract

The presence and cellular distribution of heat protein 70 (Hsp70) in ejaculated, capacitated, and acrosome-reacted boar spermatozoa was evaluated by immunofluorescence and Western blot; the role of Hsp70 during fertilization was also studied. In freshly ejaculated spermatozoa, Hsp70 immunoreactivity is present in a well-defined triangular-shaped area in the equatorial segment that seems to correspond to the equatorial sub-segment. The distribution of the fluorescent signal changes in capacitated sperm, that exhibit different patterns probably in relation to the stage of capacitation of individual cells; after acrosome reaction Hsp70 immunoreactivity is localized on both a thick sub-equatorial band and a triangle in the equatorial segment. In reacted spermatozoa, Hsp70 seems to be not only relocalized but also translocated from the inner to the outer leaflet of the sperm plasma membrane, as a significant (P < 0.05) increase in the proportion of unfixed cells showing the fluorescent signal has been recorded. No differences in Hsp70 amount between fresh, capacitated, and reacted semen were observed by Western blot. The presence of anti-Hsp70 antibody in the fertilization medium significantly reduced, in a concentration-dependent manner, the fertilization rate of both zona-intact and zona-free oocytes. The overall data demonstrate that Hsp70 is present on boar sperm with a dynamic redistribution as the sperm undergoes capacitation and acrosome reaction and suggest an important role of this protein during porcine gamete interaction.

Characterization of the porcine seminal plasma proteome comparing ejaculate portions

“…Among them, the most abundant in boar SP are spermadhesins, including AWN-1, AWN-3, AQN, PSP-I and PSP-II, with proved implication in the fertilizing ability of boar spermatozoa [31]. Heat shock 70 kDa protein and Lysosomal type alpha-D-mannosidase are other two SP-proteins encoded in GO as binding activity that have proven impact on sperm functionality [32,33]. Boar SP includes a large number of glycoproteins, which also includes the aforementioned spermadhesins.…”

Boar sperm tyrosine phosphorylation patterns in the presence of oviductal epithelial cells: in vitro, ex vivo, and in vivo models

“…During epididymal maturation, dephosphorylation and/or redistribution of phosphorylation occurs and the cauda spermatozoa exhibit only an intense triangular labeling in the posterior part of the acrosome and the equatorial subsegment (Jones et al 2008, Fàbrega et al 2011. SPACA1 and HSPA1A proteins have been determined in this event (Spinaci et al 2005, Jones et al 2008. The equatorial subsegment might be an organizing center that initiates membrane fusion during the fertilization process.…”

Distinct Gene Expression Profiles in Egg and Synergid Cells of Rice as Revealed by Cell Type-Specific Microarrays

“…Two genes (Os11g0187600 and Os03g0276800) encode heat shock protein 70 (HSP70). HSP70 is highly expressed in the egg cells of mouse (Mus musculus; Curci et al, 1987), newt (Pleurodeles waltl; Billoud et al, 1993), maize (Zea mays; Yang et al, 2006), and Arabidopsis (Wuest et al, 2010), and HSP70 is essential for fertilization in bovine (Bos taurus; Matwee et al, 2001) and boar (Sus scrofa domesticus; Spinaci et al, 2005). These results suggest that HSP70 abundance is a common characteristic of animal and plant eggs and that it is required for the fertilization process in both animals and plants.…”