[Frontiers in Bioscience 1, d146-160, August 1, 1996]
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CAVEAT LECTOR



INTERACTION OF HUMAN SPERMATOZOA WITH THE ZONA PELLUCIDA OF OOCYTE: DEVELOPMENT OF THE ACROSOME REACTION

Patricio Morales1 and Miguel Llanos2

1 P. Catholic University of Chile, Faculty of Biological Sciences. P. O. Box 114-D. Santiago, Chile.

2INTA, University of Chile, P. O. Box 138-11. Santiago, Chile.

5. SPERM BINDING PROTEINS / RECEPTORS FOR THE ZONA PELLUCIDA WITH A ROLE IN THE ACROSOME REACTION

As was discussed above, work from several laboratories has revealed presence of multiple ZP3 binding proteins/receptors on the sperm cell. Therefore, it is quite possible that multiple sperm binding proteins/receptors could all be involved in mediating the biological actions of ZP3, the primary sperm binding, and induction of the AR. This multiple interactive capacity could be due to different specialized domains in ZP3, which all face the sperm head surface. Each of these domains could be structurally adequate (or specialized) to interact and/or activate a particular sperm binding protein/receptor, to permit binding of spermatozoa to the ZP3, and to subsequently induce production of intracellular second messengers that lead to AR. It is also possible that ZP3 interacts and activates one type of sperm receptor with the subsequent activation of other receptor (s) (33). Interaction of ZP3 with the sperm surface may occur in a multivalent fashion. Thus, different sperm binding proteins/receptors could, together, constitute a functional ZP3 receptor signal-transduction complex that is capable of transducing intracellular signals to modulate the AR (33).

In human, the candidate receptors for the ZP with a role in the AR are: a 95-kDa protein with characteristics of a protein tyrosine kinase termed zona receptor kinase (ZRK) (28) and a 51 Kd protein, that is also a tyrosine kinase and which subsequently was recognized as the human FA-1 antigen (34, 35). A role for a sperm glycine receptor/Cl- channel in the ZP initiated AR has also recently been suggested (36).

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