Pharmacological targeting of native CatSper channels reveals a required role in maintenance of sperm hyperactivation.
The four sperm-specific CatSper ion channel proteins are required for hyperactivated motility and male fertility, and for Ca(2+) entry evoked by alkaline depolarization. In the absence of external Ca(2+), Na(+) carries current through CatSper channels in voltage-clamped sperm. Here we show that CatSper channel activity can be monitored optically with the [Na(+)](i)-reporting probe SBFI in populations of intact sperm. Removal of external Ca(2+) increases SBFI signals in wild-type but not CatSper2-null sperm. The rate of the indicated rise of [Na(+)](i) is greater for sperm alkalinized with NH(4)Cl than for sperm acidified with propionic acid, reflecting the alkaline-promoted signature property of CatSper currents. In contrast, the [Na(+)](i) rise is slowed by candidate CatSper blocker HC-056456 (IC(50) approximately 3 microM). HC-056456 similarly slows the rise of [Ca(2+)](i) that is evoked by alkaline depolarization and reported by fura-2. HC-056456 also selectively and reversibly decreased CatSper currents recorded from patch-clamped sperm. HC-056456 does not prevent activation of motility by HCO(3) (-) but does prevent the development of hyperactivated motility by capacitating incubations, thus producing a phenocopy of the CatSper-null sperm. When applied to hyperactivated sperm, HC-056456 causes a rapid, reversible loss of flagellar waveform asymmetry, similar to the loss that occurs when Ca(2+) entry through the CatSper channel is terminated by removal of external Ca(2+). Thus, open CatSper channels and entry of external Ca(2+) through them sustains hyperactivated motility. These results indicate that pharmacological targeting of the CatSper channel may impose a selective late-stage block to fertility, and that high-throughput screening with an optical reporter of CatSper channel activity may identify additional selective blockers with potential for male-directed contraception.
Carlson
Anne E
AE
Department of Physiology and Biophysics, University of Washington, Seattle, Washington, United States of America.
Burnett
Lindsey A
LA
del Camino
Donato
D
Quill
Timothy A
TA
Hille
Bertil
B
Chong
Jayhong A
JA
Moran
Magdalene M
MM
Babcock
Donner F
DF
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects*; D017136:Ion Transport; D008297:Male; D051379:Mice; D012964:Sodium / Q000378:metabolism; D013094:Spermatozoa / Q000187:drug effects*
D015220:Calcium Channels; C488642:Catsper1 protein, mouse; D012964:Sodium; D002118:Calcium