The high rate of unintended pregnancy can be attributed to inadequate access to or use of contraceptives, or both. It is important to provide alternative choices for effective contraception to meet the needs of people with different ethnic, cultural, and religious values. Since male-directed contraceptive options are extremely limited, development of male contraceptives with safety, efficiency and cost-performance is particularly desired. Adenine nucleotide translocase (Ant) facilitates ADP/ATP exchange across the mitochondrial inner membrane, thus making it essential for energy metabolism in eukaryotes. Among the four isoforms (Ant1-4) found in mammals, Ant4 is exclusively expressed in male germ cells. Ant4 expression is particularly high during male meiosis and is essential for progression of male meiosis. Targeted depletion of Ant4 in mice results in male meiotic arrest and subsequent male infertility. Since exogenous inhibition of male meiosis is considered one of the best approaches to develop male contraceptives, here we attempt to develop chemical compounds which specifically target Ant4. Based on a predicted structural pocket unique to Ant4 at the ADP/ATP binding site, we hypothesize that small molecules which selectively inhibit Ant4 over other Ants can be identified by a molecular docking approach, and that the identified small molecules will inhibit male meiosis and fertility in vivo. We will test these hypotheses through following step-by-step specific aims, and overall aim to develop novel male contraceptives. 1) Using a molecular docking approach, we will initially screen 300,000 small molecules in silico that potentially bind to and inhibit Ant4. 2) The 300 highest-scoring compounds will be screened for their ability to inhibit sperm motility in non-glycolytic conditions. 3) Biologically active compounds will then be tested for their ability to inhibit ADP/ATP exchange through Ant4. 4) The compounds will also be tested for the ability to inhibit male meiosis and fertility in vivo. 5) Further, the most promising lead compounds will be subjected to automated combinatorial optimization.
This study has the potential to identify lead compounds and to ultimately develop novel male contraceptives that selectively eliminate male meiotic spermatocytes without damaging other cell types in the body.
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