Ischia R, Lovisetti-Scamihorn P, Hogue-Angeletti R, Wolkersdorfer M, Winkler H, Fischer-Colbrie R
Department of Pharmacology, University of Innsbruck, A-6020 Innsbruck, Austria.
J Biol Chem. 1997 Apr 25;272(17):11657-62. doi: 10.1074/jbc.272.17.11657.
The chromogranins comprise a class of acidic proteins that are secreted from large dense core vesicles and expressed in neuronal and endocrine tissues. We describe here the molecular characterization of NESP55 (neuroendocrine secretory protein of Mr 55,000), a novel member of the chromogranins. Several NESP55 cDNA clones were isolated from bovine chromaffin cell libraries. The cDNA sequence of NESP55 totals 1499 nucleotides. All of the clones that were isolated contained in their 3'-untranslated mRNA a sequence that was homologous to exon 2 of the G-protein Gsalpha. The open reading frame encodes for an acidic and hydrophilic protein of 241 amino acids with a predicted molecular mass of 27,494 Da. An antiserum directed against the C terminus of NESP55 labeled a band of Mr 55,000 with an acidic pI ranging from 4.4 to 5.2 in one- and two-dimensional immunoblots of secretory proteins from chromaffin granules. NESP55 is localized within the cell to the large dense secretory vesicles and is expressed, apart from the adrenal medulla, in the anterior and posterior pituitary and various regions of the brain. For the physiological function, one interesting factor has emerged. NESP55 is proteolytically processed within the chromaffin granule to smaller peptides that might be physiologically active. One tetrapeptide, Leu-Ser-Ala-Leu (LSAL), present in the NESP55 sequence and flanked by arginine residues suitable for cleavage by prohormone convertases, has been identified recently as an endogenous antagonist of the serotonergic 5-HT1B receptor subtype. Alterations in the serotonergic system are thought to play an important role in mental disorders, especially depression, and might be related to abnormal ethanol consumption. It is tempting to speculate that increased expression of NESP55 or its proteolytically derived peptide LSAL might contribute to the pathophysiology of the serotonergic transmission.
嗜铬粒蛋白是一类酸性蛋白，由大的致密核心囊泡分泌，在神经组织和内分泌组织中表达。我们在此描述嗜铬粒蛋白新成员NESP55（分子量为55,000的神经内分泌分泌蛋白）的分子特征。从牛嗜铬细胞文库中分离出几个NESP55 cDNA克隆。NESP55的cDNA序列全长1499个核苷酸。所有分离得到的克隆在其3'非翻译mRNA中都含有一段与G蛋白Gsα亚基外显子2同源的序列。开放阅读框编码一个由241个氨基酸组成的酸性亲水性蛋白，预测分子量为27,494 Da。一种针对NESP55 C末端的抗血清在嗜铬颗粒分泌蛋白的一维和二维免疫印迹中标记出一条分子量为55,000的条带，其酸性pI范围为4.4至5.2。NESP55在细胞内定位于大的致密分泌囊泡，除肾上腺髓质外，还在前脑垂体、后脑垂体和大脑的各个区域表达。关于其生理功能，出现了一个有趣的因素。NESP55在嗜铬粒体内被蛋白水解加工成可能具有生理活性的较小肽段。最近已鉴定出一种存在于NESP55序列中的四肽Leu-Ser-Ala-Leu（LSAL），其两侧为适合激素原转化酶切割的精氨酸残基，是5-羟色胺能5-HT1B受体亚型的内源性拮抗剂。5-羟色胺能系统的改变被认为在精神障碍尤其是抑郁症中起重要作用，并且可能与异常饮酒有关。很诱人推测NESP55或其蛋白水解衍生肽LSAL表达的增加可能导致5-羟色胺能传递的病理生理学变化。
