Acrosomal alkalization triggers Ca2+ release and acrosome reaction in mammalian spermatozoa. Issue 6 (4th January 2018)

• Record Type: Journal Article
• Authors: Chávez, Julio C.; De la Vega‐Beltrán, José L.; José, Omar; Torres, Paulina; Nishigaki, Takuya; Treviño, Claudia L.; Darszon, Alberto
• Is Part Of: Journal of cellular physiology. Volume 233:Issue 6(2018:Jun.)
• Page Start: 4735
• Page End: 4747
• Publication Date: 2018-01-04
• Subjects: acrosome alkalization -- acrosome reaction -- calcium -- sperm; Physiology -- Periodicals; Cell physiology -- Periodicals; 571.6
• DOI: 10.1002/jcp.26262
• Languages: English
• ISSNs: 0021-9541

Abstract

Abstract : The sperm acrosome reaction (AR), an essential event for mammalian fertilization, involves Ca 2+ permeability changes leading to exocytosis of the acrosomal vesicle. The acrosome, an intracellular Ca 2+ store whose luminal pH is acidic, contains hydrolytic enzymes. It is known that acrosomal pH (pHacr ) increases during capacitation and this correlates with spontaneous AR. Some AR inducers increase intracellular Ca 2+ concentration ([Ca 2+ ]i ) through Ca 2+ release from internal stores, mainly the acrosome. Catsper, a sperm specific Ca 2+ channel, has been suggested to participate in the AR. Curiously, Mibefradil and NNC55‐0396, two CatSper blockers, themselves elevate [Ca 2+ ]i by unknown mechanisms. Here we show that these compounds, as other weak bases, can elevate pHacr, trigger Ca 2+ release from the acrosome, and induce the AR in both mouse and human sperm. To our surprise, μM concentrations of NNC55‐0396 induced AR even in nominally Ca 2+ free media. Our findings suggest that alkalization of the acrosome is critical step for Ca 2+ release from the acrosome that leads to the acrosome reaction. Abstract : We show evidence that an elevation of acrosomal pH triggers Ca 2+ release from the acrosome and induce the acrosomal reaction in both, mouse and human spermatozoa.