Carrasquel Martínez Gabriela, Aldana Andrés, Carneiro Jorge, Treviño Claudia Lydia, Darszon Alberto
Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México.
Centro de Ciencias de la Complejidad, Universidad Nacional Autónoma de México, Ciudad de México, México.
Mol Hum Reprod. 2022 Mar 8;28(3). doi: 10.1093/molehr/gaac005.
Mammalian sperm capacitation is a prerequisite for successful fertilization. Capacitation involves biochemical and physiological modifications of sperm as they travel through the female reproductive tract. These modifications prepare the sperm to undergo the acrosome reaction (AR), an acrosome vesicle exocytosis that is necessary for gamete fusion. Capacitation requires an increase in both intracellular calcium ([Ca2+]i) and pH (pHi). Mouse sperm capacitation is accompanied by acrosomal alkalinization and artificial elevation of the acrosome pH (pHa) is sufficient to trigger the AR in mouse and human sperm, but it is unknown if pHa increases naturally during human sperm capacitation. We used single-cell imaging and image-based flow cytometry to evaluate pHa during capacitation and its regulation. We found that pHa progressively increases during capacitation. The V-ATPase, which immunolocalized to the acrosome and equatorial segment, is mainly responsible for the acidity of the acrosome. It is likely that the regulation of V-ATPase is at least in part responsible for the progressive increase in pHa during capacitation. Acrosome alkalinization was dependent on extracellular HCO3- and Ca2+. Inhibition of the HCO3--dependent adenylyl cyclase and protein kinase A induced significant pHa changes. Overall, alkalinization of the acrosome may be a key step in the path toward the AR.
哺乳动物精子获能是成功受精的先决条件。获能涉及精子在雌性生殖道中运行时发生的生化和生理变化。这些变化使精子为顶体反应（AR）做好准备，顶体反应是一种顶体小泡胞吐作用，是配子融合所必需的。获能需要细胞内钙（[Ca2+]i）和pH值（pHi）都升高。小鼠精子获能伴随着顶体碱化，人工升高顶体pH值（pHa）足以触发小鼠和人类精子的顶体反应，但尚不清楚在人类精子获能过程中pHa是否自然升高。我们使用单细胞成像和基于图像的流式细胞术来评估获能过程中的pHa及其调节。我们发现，在获能过程中pHa逐渐升高。免疫定位在顶体和赤道段的V-ATP酶主要负责顶体的酸性。V-ATP酶的调节很可能至少部分地导致了获能过程中pHa的逐渐升高。顶体碱化依赖于细胞外HCO3-和Ca2+。抑制依赖HCO3-的腺苷酸环化酶和蛋白激酶A会引起显著的pHa变化。总体而言，顶体碱化可能是通向顶体反应途径中的关键一步。
