Maier Bernhard, Medrano Silvia, Sleight Susan B, Visconti Pablo E, Scrable Heidi
Department of Neuroscience Center for Research in Contraceptive and Reproductive Health, University of Virginia, Charlottesville, Virginia 22903, USA.
Biol Reprod. 2003 Jan;68(1):67-76. doi: 10.1095/biolreprod.102.004143.
In neurons, arc (activity regulated, cytoskeleton associated) is an immediate early gene (IEG) that is rapidly and transiently induced by excitatory stimulation. It is believed to mediate rapid strengthening of signaling structures at activated synaptic sites. Unlike most IEGs, arc does not encode nuclear transcription factor, but an effector molecule that associates with the actin cytoskeleton. Cytoskeletal rearrangements of microtubule- and actin-based networks that occur at activated synapses also take place in similar fashion during the formation of the acrosome, the site of regulated exocytosis at fertilization. In this paper, arc is reported to be highly expressed both at the RNA and protein levels in postmeiotic germ cells in the testis of adult mice. Immunofluorescence studies reveal that arc is first present in the perinuclear region of round, elongating, and elongate spermatids, where it colocalizes with the developing acrosome. In isolated mature sperm, arc is present in the acrosomal region of the sperm head, the centriole region of the neck, and the principal piece of the tail. Arc is lost to varying degrees during sperm capacitation and in acrosome-reacted sperm. Phalloidin staining of mature sperm cells reveals an overlapping pattern of filamentous-actin and arc expression. These results support a role for arc and the actin cytoskeleton in the acrosome formation, the sperm acrosome reaction, and in sperm cell motility.
在神经元中，arc（活性调节的细胞骨架相关蛋白）是一种即刻早期基因（IEG），可被兴奋性刺激快速且短暂地诱导表达。据信它能介导激活的突触部位信号结构的快速增强。与大多数即刻早期基因不同，arc不编码核转录因子，而是一种与肌动蛋白细胞骨架相关的效应分子。在激活的突触处发生的基于微管和肌动蛋白网络的细胞骨架重排，在顶体形成过程中也以类似方式发生，顶体是受精时调节性胞吐作用的部位。在本文中，据报道arc在成年小鼠睾丸减数分裂后的生殖细胞中，在RNA和蛋白质水平均高表达。免疫荧光研究表明，arc最初出现在圆形、伸长和成熟精子细胞的核周区域，在那里它与发育中的顶体共定位。在分离的成熟精子中，arc存在于精子头部的顶体区域、颈部的中心粒区域和尾部的主段。在精子获能过程中和顶体反应后的精子中，arc会不同程度地丢失。成熟精子细胞的鬼笔环肽染色显示丝状肌动蛋白和arc表达有重叠模式。这些结果支持arc和肌动蛋白细胞骨架在顶体形成、精子顶体反应以及精子细胞运动中的作用。
