Su Yi-Hsien, Chen Sheng-Hong, Zhou Huilin, Vacquier Victor D
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California-San Diego, La Jolla, CA 92093-0202, USA.
Dev Biol. 2005 Sep 1;285(1):116-25. doi: 10.1016/j.ydbio.2005.06.007.
The exocytotic acrosome reaction (AR), which is required for fertilization, occurs when sea urchin sperm contact the egg jelly (EJ) layer. Among other physiological changes, increases in adenylyl cyclase activity, cAMP and cAMP-dependent protein kinase (PKA) activity occur coincident with the AR. By using inhibitors of PKA, a permeable analog of cAMP and the phosphodiesterase inhibitor IBMX, we show that PKA activity is required for AR induction by EJ. A minimum of six sperm proteins are phosphorylated by PKA upon exposure to EJ, as detected by a PKA substrate-specific antibody. The phosphorylation of these proteins and the percentage of acrosome reacted sperm can be regulated by PKA modulators. The fucose sulfate polymer (FSP), a major component of EJ, is the molecule that triggers sperm PKA activation. Extracellular Ca(2+) is required for PKA activation. Six sperm proteins phosphorylated by PKA were identified by tandem mass spectrometry (MS/MS) utilizing the emerging sea urchin genome. Based on their identities and localizations in sperm head and flagellum, the putative functions of these proteins in sperm physiology and AR induction are discussed.
胞吐顶体反应（AR）是受精所必需的，当海胆精子接触到卵胶膜（EJ）层时就会发生。在其他生理变化中，腺苷酸环化酶活性、环磷酸腺苷（cAMP）和cAMP依赖性蛋白激酶（PKA）活性的增加与顶体反应同时发生。通过使用PKA抑制剂、一种可渗透的cAMP类似物和磷酸二酯酶抑制剂异丁基甲基黄嘌呤（IBMX），我们发现PKA活性是EJ诱导顶体反应所必需的。暴露于EJ时，至少有六种精子蛋白会被PKA磷酸化，这可通过一种PKA底物特异性抗体检测到。这些蛋白的磷酸化以及顶体反应精子的百分比可由PKA调节剂调节。硫酸岩藻糖聚合物（FSP）是EJ的主要成分，是触发精子PKA激活的分子。细胞外钙离子（Ca(2+)）是PKA激活所必需的。利用新出现的海胆基因组，通过串联质谱（MS/MS）鉴定了六种被PKA磷酸化的精子蛋白。基于它们在精子头部和鞭毛中的身份和定位，讨论了这些蛋白在精子生理和顶体反应诱导中的假定功能。
