Gruber A D, Pauli B U
Department of Molecular Medicine, Cancer Biology Laboratories, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Biochim Biophys Acta. 1999 Mar 19;1444(3):418-23. doi: 10.1016/s0167-4781(99)00008-1.
A novel family of chloride channel proteins has recently been discovered including two bovine (Lu-ECAM-1, bCLCA1), one murine (mCLCA1), and two human (hCLCA1 and hCLCA2) members. Here, we describe the cloning, expression, and molecular characterization of a truncated human homolog, tentatively named hCLCA3. It was cloned from a human spleen cDNA library and is expressed in numerous tissues including lung, trachea, spleen, thymus, and mammary gland as determined by reverse transcriptase-polymerase chain reaction. Unlike all previously known CLCA family members which consistently encode an approximately 125-kDa transmembrane protein that is cleaved to form a heterodimer of two proteins of approximately 90 and 35 kDa, the 3.6-kb hCLCA3 mRNA encodes a 37-kDa glycoprotein that corresponds to the N-terminal extracellular domain of its homologs. Moreover, when expressed in human embryonic kidney 293 or Chinese hamster ovary cells, this 37-kDa glycoprotein is secreted into the culture supernatant. These observations suggest that hCLCA3 is a structurally divergent member of the CLCA family of proteins and that it does not act as a channel protein but has distinct, yet unidentified functions.
最近发现了一个新的氯离子通道蛋白家族，包括两个牛源成员（Lu-ECAM-1、bCLCA1）、一个鼠源成员（mCLCA1）和两个人源成员（hCLCA1和hCLCA2）。在此，我们描述了一种截短的人源同源物的克隆、表达及分子特征，暂命名为hCLCA3。它是从人脾脏cDNA文库中克隆得到的，通过逆转录-聚合酶链反应确定其在包括肺、气管、脾脏、胸腺和乳腺在内的多种组织中表达。与所有先前已知的CLCA家族成员不同，它们一致编码一种约125 kDa的跨膜蛋白，该蛋白被切割形成约90 kDa和35 kDa两种蛋白的异二聚体，而3.6 kb的hCLCA3 mRNA编码一种37 kDa的糖蛋白，对应于其同源物的N端细胞外结构域。此外，当在人胚肾293细胞或中国仓鼠卵巢细胞中表达时，这种37 kDa的糖蛋白会分泌到培养上清液中。这些观察结果表明，hCLCA3是CLCA蛋白家族中结构不同的成员，它不作为通道蛋白发挥作用，而是具有独特但尚未明确的功能。
