Murine SPAM1 is secreted by the estrous uterus and oviduct in a form that can bind to sperm during capacitation: acquisition enhances hyaluronic acid-binding ability and cumulus dispersal efficiency

Abstract

Sperm uptake of epididymal sperm adhesion molecule 1 (SPAM1) in vitro has recently been shown to be a marker of sperm maturation, since acquisition of this surface hyaluronidase increases cumulus dispersal efficiency. Here, we demonstrate that this glycosyl phosphatidylinositol-linked sperm antigen, previously shown to be expressed during estrous in the female reproductive tract, is secreted in the uterine and oviductal fluids (ULF and OF respectively) in a 67 kDa form, which can bind to sperm. We show that it can be acquired by caudal sperm from Spam1 null, Spam1-deficient mutant, and wild-type (WT) mice in vitro during incubation in ULF or OF at 37 8C, as detected by immunocytochemistry and flow cytometry. SPAM1 binding after ULF incubation was localized predominantly to the acrosome and the mid-piece of the flagella of Spam1 null sperm in a pattern identical to that of WT sperm. After ULF incubation, WT sperm demonstrated a significantly (P!0.001) enhanced hyaluronic acid-binding ability, and the involvement of SPAM1 in this activity was shown by a significant (P!0.001) decrease in binding when sperm were exposed to SPAM1 antiserum-inhibited ULF. Importantly, when Spam1 null sperm were exposed to ULF with SPAM1 accessible (in the presence of pre-immune serum) or inaccessible (in the presence of SPAM1 antiserum) for uptake, there was a significant difference in cumulus dispersal efficiency. Taken together, these results suggest that in the sperm surface remodeling that occurs prior to and during capacitation, the fertilizing competence of sperm is increased via acquisition of SPAM1, and likely other hyaluronidases, from the female tract.

Network Analyses of Sperm–Egg Recognition and Binding: Ready to Rethink Fertility Mechanisms?

“…Clusterin, and other lipid carriers such as APOA1, serve as GPI-linked protein monomer stabilizers, donors to the sperm plasma membrane (PM), and as acceptors of cholesterol. This interesting datum was confirmed by the finding that when Spam1 -/-were exposed to accessible Spam1 there was a significant difference in cumulus dispersal efficiency (Griffiths et al, 2008), thus suggesting that the sperm surface remodeling occurring prior to and during capacitation could involve the functional expression of Spam1, in an integrated cross-talk between male and female structures. This specific peculiarity, could explain the fertility of Spam1 -/-mice.…”

Oviductal secretion and gamete interaction

“…It has been found to be secreted in the female reproductive tract (including the oviduct) and it can bind to sperm (Griffiths et al 2008). It was shown that hyaluronic acid interacts with the R4 S Ghersevich and others PH-20 protein anchored on the macaque and human sperm membrane increasing the basal levels of intracellular calcium and promoting the induced acrosome reaction (Sabeur et al 1998, Cherr et al 1999.…”

Clusterin Facilitates Exchange of Glycosyl Phosphatidylinositol-Linked SPAM1 Between Reproductive Luminal Fluids and Mouse and Human Sperm Membranes1

“…During post-testicular maturation of sperm, a variety of glycosyl phosphatidylinositol (GPI)-linked proteins are added to the surface of the sperm as they traverse the male and female tract [1][2][3]. These proteins include receptors and immunoprotection molecules, as well as enzymes that participate in both sperm maturation and the fertilization processes [2,3].…”