Molecular cloning of putative members of the Na/H exchanger gene family. cDNA cloning, deduced amino acid sequence, and mRNA tissue expression of the rat Na/H exchanger NHE-1 and two structurally related proteins.
Molecular cloning of putative members of the Na/H exchanger gene family. cDNA cloning, deduced amino acid sequence, and mRNA tissue expression of the rat Na/H exchanger NHE-1 and two structurally related proteins.
复制标题
DOI：
10.1016/s0021-9258(19)50428-8
复制
发表时间：
1992-05
期刊：
影响因子：
--
通讯作者：
Julius Orlowski;R. Kandasamy;G. Shull
中科院分区：
文献类型：
--
作者：
Julius Orlowski;R. Kandasamy;G. Shull
生化和药理学数据支持多种形式的Na/H交换(NHE)的存在。最近从兔回肠绒毛上皮细胞(Tse，C.M.，Ma，A.I.，Yang，V.W.，Watson，A.J.M.，Levine，S.，Montrose，M.H.，Potter，J.，Sardet，C.，Pouysségur，J.和Donowitz，M.(1991)EMBO J.10,1957-1967；Tse，C.M.，Watson，A.J.M.，Ma，A.I.，Pouysségur，J.和Donowitz，M.(1991)胃肠病学100，A258)。为了鉴定该交换器的其他分子形式，在低严格杂交条件下使用NHE-1cDNA探针筛选了大鼠脑、心、肾、胃和脾的cDNA文库。编码大鼠NHE-1和两个结构相关蛋白NHE-3和NHE-4的cDNA已经被分离出来。根据推导的氨基酸序列，NHE-1、-3和-4大小相似，相对分子质量分别为91,506，92,997和81,427。总体而言，这两种蛋白质表现出大约40%的氨基酸同源性，并具有相似的亲水性特征，表明它们具有相同的跨膜组织。预测的三种蛋白质的N末端跨膜区，跨度在453到503个氨基酸之间，表现出最高的同源性(45%-49%)。相反，C末端的细胞质区域跨越247到378个氨基酸，表现出很低的氨基酸同源性(24%-31%)。组织分布研究表明，NHE-1mRNA在所研究的所有组织中都存在不同水平，而NHE-3和NHE-4mRNAs的分布较为有限。NHE-3mRNA在结肠和小肠中高水平表达，在肾脏和胃中也有显著表达。NHE-4在胃中含量最高，其次是小肠和结肠，肾脏、脑、子宫和骨骼肌中含量较少。这些数据表明，哺乳动物Na/H交换器功能多样性的分子基础至少部分是基于一个基因家族多个成员的表达。
Biochemical and pharmacological data support the existence of multiple forms of the Na/H exchanger (NHE). Two isoforms, termed NHE-1 and NHE-2, have recently been isolated from rabbit ileal villus epithelial cells (Tse, C. M., Ma, A. I., Yang, V. W., Watson, A. J. M., Levine, S., Montrose, M. H., Potter, J., Sardet, C., Pouysségur, J., and Donowitz, M. (1991) EMBO J. 10, 1957-1967; Tse, C. M., Watson, A. J. M., Ma, A. I., Pouysségur, J., and Donowitz, M. (1991) Gastroenterology 100, A258). To identify additional molecular forms of the exchanger, rat brain, heart, kidney, stomach, and spleen cDNA libraries were screened for their presence using an NHE-1 cDNA probe under low stringency hybridization conditions. cDNAs encoding rat NHE-1 and two structurally related proteins, designated NHE-3 and NHE-4, have been isolated. Based on the deduced amino acid sequences, NHE-1, -3, and -4 are similar in size, having relative molecular masses of 91,506, 92,997, and 81,427, respectively. Overall, the proteins exhibit approximately 40% amino acid identity to each other and have similar hydropathy profiles, suggesting that they have the same transmembrane organization. The predicted N-terminal transmembrane regions of the three proteins, which span between 453 and 503 amino acids, exhibit the highest degree of identity (45-49%). In contrast, the C-terminal cytoplasmic regions, which span between 247 and 378 amino acids, exhibit very low amino acid identity (24-31%). Tissue distribution studies reveal that the NHE-1 mRNA is present at varying levels in all tissues examined, whereas NHE-3 and NHE-4 mRNAs exhibit a more limited distribution. NHE-3 mRNA is expressed at high levels in colon and small intestine, with significant levels also present in kidney and stomach. NHE-4 mRNA is most abundant in stomach, followed by intermediate levels in small intestine and colon and lesser amounts in kidney, brain, uterus, and skeletal muscle. These data suggest that the molecular basis for the functional diversity of the Na/H exchanger in mammals is based, at least in part, on expression of multiple members of a gene family.