Nagdas Subir K, Baccas Marissa, Dejean Christina, Richardson Leea'
Department of Chemistry and Physics, Fayetteville State University, North Carolina, USA.
J Cell Biol Mol Sci. 2016;1(1). Epub 2016 Aug 2.
Syntaxins are membrane integrated Q-SNARE proteins known to participate in exocytosis. Vesicle docking involves the binding of two plasma membrane proteins, syntaxin and SNAP-25, to the vesicle membrane protein VAMP to form a stable trimeric core complex; synaptophysin is thought to regulate the formation of this complex. Although the members of Q-SNARE proteins are characterized in somatic cells, it is not known whether related proteins function in the sperm acrosome reaction. The objective of the present study is to identify and localize syntaxin in bovine epididymal spermatozoa and to determine the fate of syntaxin 2 during the acrosome reaction. Western blots of caput and cauda sperm lysates and plasma membrane fractions, stained with anti-syntaxin 2, revealed the presence of a 31kDa band in both sperm lysates and plasma membrane fractions, respectively. Indirect immunofluorescence localized syntaxin 2 to the anterior but not the equatorial regions of the acrosomal segment. Several biochemical analyses demonstrated that syntaxin 2 is an integral component of bovine cauda sperm plasma membranes. Our immunoblot data reveals that syntaxin 2 of bovine cauda sperm is released after lysophosphatidylcholine (LPC)-induced acrosomal exocytosis. It is assumed that syntaxin 2 may be involved in triggering the acrosome reaction through a ligand-receptor mediated signal transduction pathway.
Syntaxins是膜整合的Q-SNARE蛋白，已知参与胞吐作用。囊泡对接涉及两种质膜蛋白Syntaxin和SNAP-25与囊泡膜蛋白VAMP结合，形成稳定的三聚体核心复合物；突触素被认为可调节该复合物的形成。尽管Q-SNARE蛋白成员在体细胞中有特征描述，但尚不清楚相关蛋白在精子顶体反应中是否发挥作用。本研究的目的是鉴定和定位牛附睾精子中的Syntaxin，并确定顶体反应过程中Syntaxin 2的命运。用抗Syntaxin 2对附睾头和附睾尾精子裂解物及质膜部分进行蛋白质免疫印迹分析，结果显示在精子裂解物和质膜部分均出现一条31kDa的条带。间接免疫荧光将Syntaxin 2定位在顶体节段的前部而非赤道区域。多项生化分析表明Syntaxin 2是牛附睾尾精子质膜的一个组成成分。我们的免疫印迹数据显示，溶血磷脂酰胆碱（LPC）诱导顶体胞吐作用后，牛附睾尾精子的Syntaxin 2会释放出来。推测Syntaxin 2可能通过配体-受体介导的信号转导途径参与触发顶体反应。
