Schiller M R, Darlington D N
Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
J Histochem Cytochem. 1996 Dec;44(12):1489-96. doi: 10.1177/44.12.8985141.
RESP18 (regulated endocrine-specific protein of 18 KD) is an endoplasmic reticulum (ER) protein that was identified by coordinate dopaminergic regulation with pro-opiomelanocortin in the rat neurointermediate pituitary. Many attributes of RESP18 suggest an important function in neuroendocrine cells. Several neuropeptides, growth factors, and enzymes involved in biosynthesis of classical chemical neurotransmitters, have been identified in germ cells, Sertoli cells, and spermatozoa. In this study, screening of reproductive tissues revealed high levels of RESP18 protein and mRNA in the testes but not in ovaries or epididymis. The testes and sperm expressed 18-KD RESP18 and a unique 19-KD isoform. To better understand RESP18 expression in the testes, we have examined the stages of the cycle of the seminiferous epithelium by immunohistochemistry and Western blot analyses. Immunohistochemical analysis showed that RESP18 protein was expressed exclusively in spermatocytes and maturing spermatids. RESP18 protein was expressed at high levels in Step 1-8 round spermatids, in which the PC4 prohormone convertase, nerve growth factor, and proenkephalin are also expressed. Western blots, Northern blots, and indirect immunofluorescence staining demonstrated RESP18 expression in sperm.
RESP18（18千道尔顿调节性内分泌特异性蛋白）是一种内质网（ER）蛋白，它是通过与大鼠神经垂体中间叶中阿片促黑皮质素原的多巴胺能协同调节而被鉴定出来的。RESP18的许多特性表明其在神经内分泌细胞中具有重要功能。在生殖细胞、支持细胞和精子中已鉴定出几种参与经典化学神经递质生物合成的神经肽、生长因子和酶。在本研究中，对生殖组织的筛查显示，睾丸中RESP18蛋白和mRNA水平较高，而卵巢或附睾中则没有。睾丸和精子表达18千道尔顿的RESP18和一种独特的19千道尔顿异构体。为了更好地了解RESP18在睾丸中的表达，我们通过免疫组织化学和蛋白质印迹分析检查了生精上皮周期的各个阶段。免疫组织化学分析表明，RESP18蛋白仅在精母细胞和成熟精子细胞中表达。RESP18蛋白在第1-8步圆形精子细胞中高水平表达，其中PC4激素原转化酶、神经生长因子和脑啡肽原也有表达。蛋白质印迹、Northern印迹和间接免疫荧光染色证明精子中有RESP18表达。
