CatSper: Novel target for an oral contraceptive

DESCRIPTION (provided by applicant): Hydra Biosciences Inc. will develop a novel class of non-hormonal, oral contraceptives based on the discovery by our co-founder, David Clapham, M.D./ Ph.D., of a sperm specific ion channel, CatSper. Male mice lacking CatSper have poor sperm motility and are sterile. These and other studies carried out by Dr. Clapham suggest that pharmacological agents that block CatSper may serve as an ideal contraceptive: first, because CatSper expression is confined to sperm, its disruption may exhibit few side effects; second, a drug that specifically blocks CatSper may be effectively delivered to both males and females; third, a CatSper blocker may be fast acting and only need to be used just before or after intercourse. A stable cell line that functionally expresses CatSper is required for screening for CatSper blockers. Though native CatSper is expressed on the cell surface of sperm, CatSper fails to localize to the plasma membrane in heterologous systems. In this fast track application we propose two strategies for producing a cell line that functionally expresses CatSper. The first is to bypass the obstacle by making chimeric ion channels. The second is to overcome the obstacle by identifying, through a yeast two-hybrid screen, proteins that are required to traffic CatSper to the cell surface. In Phase I, the milestones are to generate the basic molecular biology reagents required for both strategies. First, we will clone chimeric CatSper channels. Second, we will clone four bait vectors needed for a yeast two-hybrid screen (Y-2-H) to identify accessory proteins that bind and guide CatSper to the cell surface. In Phase II, we will test whether the chimeric clones or the co-expression of binding proteins facilitate functional expression. First, we wilt determine whether CatSper mediated current can be measured in cell lines expressing chimeric CatSper channel. Second, we will identify proteins that bind CatSper and determine whether co-expression with CatSper produces a functional cell line. Third, we will optimize the cell line to maximize its use in high throughput screening. Once a functional cell line is established, Hydra Biosciences Inc. in collaboration with a pharmaceutical company will screen small molecule libraries for CatSper blockers and develop a novel non-hormonal, oral contraceptive.