Michailov Yulia, Ickowicz Debbi, Breitbart Haim
The Mina & Everard Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel.
The Mina & Everard Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel.
Dev Biol. 2014 Dec 15;396(2):246-55. doi: 10.1016/j.ydbio.2014.10.009. Epub 2014 Oct 22.
Extracellular zinc regulates cell proliferation via the MAP1 kinase pathway in several cell types, and has been shown to act as a signaling molecule. The testis contains a relatively high concentration of Zn(2+), required in both the early and late stages of spermatogenesis. Despite the clinical significance of this ion, its role in mature sperm cells is poorly understood. In this study, we characterized the role of Zn(2+) in sperm capacitation and in the acrosome reaction. Western blot analysis revealed the presence of ZnR of the GPR39 type in sperm cells. We previously demonstrated the presence of active epidermal growth factor receptor (EGFR) in sperm, its possible transactivation by direct activation of G-protein coupled receptor (GPCR), and its involvement in sperm capacitation and in the acrosome reaction (AR). We show here that Zn(2+) activates the EGFR during sperm capacitation, which is mediated by activation of trans-membrane adenylyl cyclase (tmAC), protein kinase A (PKA), and the tyrosine kinase, Src. Moreover, the addition of Zn(2+) to capacitated sperm caused further stimulation of EGFR and phosphatydil-inositol-3-kinase (PI3K) phosphorylation, leading to the AR. The stimulation of the AR by Zn(2+) also occurred in the absence of Ca(2+) in the incubation medium, and required the tmAC, indicating that Zn(2+) activates a GPCR. The AR stimulated by Zn(2+) is mediated by GPR39 receptor, PKA, Src and the EGFR, as well as the EGFR down-stream effectors PI3K, phospholipase C (PLC) and protein kinase C (PKC). These data support a role for extracellular zinc, acting through the ZnR, in regulating multiple signaling pathways in sperm capacitation and the acrosome reaction.
细胞外锌通过丝裂原活化蛋白激酶1（MAP1激酶）途径在多种细胞类型中调节细胞增殖，并且已被证明可作为信号分子发挥作用。睾丸中含有相对较高浓度的锌离子（Zn(2+)），这在精子发生的早期和晚期阶段都是必需的。尽管这种离子具有临床意义，但其在成熟精子细胞中的作用仍知之甚少。在本研究中，我们对锌离子（Zn(2+)）在精子获能和顶体反应中的作用进行了表征。蛋白质印迹分析显示精子细胞中存在GPR39型锌受体（ZnR）。我们之前证明了精子中存在活性表皮生长因子受体（EGFR），其可能通过G蛋白偶联受体（GPCR）的直接激活而发生反式激活，并且其参与精子获能和顶体反应（AR）。我们在此表明，锌离子（Zn(2+)）在精子获能过程中激活EGFR，这是由跨膜腺苷酸环化酶（tmAC）、蛋白激酶A（PKA）和酪氨酸激酶Src的激活介导的。此外，向获能精子中添加锌离子（Zn(2+)）会进一步刺激EGFR和磷脂酰肌醇-3-激酶（PI3K）的磷酸化，从而导致顶体反应。在孵育培养基中不存在钙离子（Ca(2+)）的情况下，锌离子（Zn(2+)）对顶体反应的刺激也会发生，并且需要tmAC，这表明锌离子（Zn(2+)）激活了一种GPCR。锌离子（Zn(2+)）刺激的顶体反应由GPR39受体、PKA、Src和EGFR介导，以及EGFR下游效应器PI3K、磷脂酶C（PLC）和蛋白激酶C（PKC）介导。这些数据支持细胞外锌通过锌受体（ZnR）在调节精子获能和顶体反应中的多种信号通路中发挥作用。
