Luconi M, Muratori M, Maggi M, Pecchioli P, Peri A, Mancini M, Filimberti E, Forti G, Baldi E
Dipartimento di Fisiopatologia Clinica, Università di Firenze, Italy.
J Androl. 2000 Sep-Oct;21(5):676-88.
During the process of capacitation, spermatozoa undergo significant changes in membrane composition, including removal of decapacitating factors (DFs), which are present in seminal plasma, that lead to increased sensitivity to physiological stimuli of the acrosome reaction. In the present study we investigated the presence, localization, and effects on human spermatozoa of 2 proteins of seminal plasma origin, uteroglobin (UG) and transglutaminase (TG). These 2 proteins interact with one another because TG promotes covalent links of UG to sperm surface proteins. We found that UG is localized around the entire surface of ejaculated human sperm, whereas TG is predominantly localized in the neck. FACScan analysis confirmed the surface localization of both antigens and demonstrated that swim-up selection of spermatozoa was associated with a significant reduction in the contents of the 2 substances when compared with unselected samples. Western blot analysis of UG in total sperm lysates confirmed the lower content of the protein in swim-up-selected sperm. Swim-up-selected sperm were characterized by their ability to undergo a spontaneous, time-dependent increase of capacitation-characteristic chlortetracycline pattern of fluorescence and increase in responsiveness to progesterone. Such changes were not observed in unselected sperm. Exogenous addition of TG, together with recombinant rabbit UG, prevented the spontaneous increase in responsiveness to progesterone (acrosome reaction and intracellular calcium) at 24 hours in swim-up-selected sperm, suggesting the occurrence of a capacitation-inhibiting activity of the 2 substances. In addition, we found that endogenous UG and TG contents, as determined by FACScan analysis, were negatively correlated (P < .0001) with sperm motility and that exogenous addition of the 2 substances resulted in a substantial reduction of progressive motility (P < .01). Collectively, these data indicate that TG and UG represent 2 DFs, and contribute to understanding the biochemical mechanisms that characterize the process of capacitation.
在获能过程中，精子的膜成分会发生显著变化，包括去除存在于精浆中的去能因子（DFs），这会导致对顶体反应生理刺激的敏感性增加。在本研究中，我们调查了两种精浆来源的蛋白质——子宫珠蛋白（UG）和转谷氨酰胺酶（TG）在人类精子中的存在、定位及其对精子的影响。这两种蛋白质相互作用，因为TG促进UG与精子表面蛋白的共价连接。我们发现UG定位于射出的人类精子的整个表面，而TG主要定位于颈部。流式细胞仪分析证实了两种抗原的表面定位，并表明与未筛选的样本相比，精子的上浮筛选与这两种物质含量的显著降低有关。对总精子裂解物中UG的蛋白质印迹分析证实了上浮筛选的精子中该蛋白质含量较低。上浮筛选的精子的特征在于其能够经历获能特征性的金霉素荧光模式的自发、时间依赖性增加以及对孕酮反应性的增加。在未筛选的精子中未观察到此类变化。外源性添加TG以及重组兔UG可防止上浮筛选的精子在24小时时对孕酮反应性（顶体反应和细胞内钙）的自发增加，表明这两种物质具有获能抑制活性。此外，我们发现通过流式细胞仪分析确定的内源性UG和TG含量与精子活力呈负相关（P <.0001），并且外源性添加这两种物质会导致进行性运动能力大幅降低（P <.01）。总体而言，这些数据表明TG和UG代表两种去能因子，并有助于理解获能过程的生化机制。
