The α1-Antitrypsin Gene Is Expressed in a Human Intestinal Epithelial Cell Line

• Published in: The Journal of biological chemistry 1989-06, Vol.264 (16), p.9485-9490
• Main Authors: Perlmutter, D H, Daniels, J D, Auerbach, H S, De Schryver-Kecskemeti, K, Winter, H S, Alpers, D H
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Gene expression; Molecular and cellular biology; Molecular genetics
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)60557-5

α1-Antitrypsin (α1-AT) is considered a typical plasma protein and a prototype of the serine proteinase inhibitor (serpin) family. It is synthesized in hepatocytes and, to a lesser extent, in macrophages. In this study we show that the α1-AT gene is also expressed in human intestine and in a human colonic epithelial tumor cell line, Caco2. A single 1.6-kilobase α1-AT-specific mRNA is present in jejunum and in Caco2 cells. It is identical in apparent size to that present in human hepatoma HepG2 cells but slightly smaller than that present in human macrophages, cells in which an alternative upstream transcriptional start site is used. Synthesis and secretion of α1-AT in Caco2 cells is similar to that in HepG2 cells. It is synthesized as an ∼ 52-kDa precursor polypeptide, converted to its mature, fully glycosylated 55-kDa form intracellularly, and the native protein is secreted with a half-time of 37 min. Functionally active α1-AT is secreted into the basolateral and apical (luminal) fluid in pulse-chase labeling experiments of Caco2 cells cultured in polarized orientation on collagen-coated nitrocellulose membranes. Expression of α1-AT in Caco2 enterocytes is not affected by soluble factors that regulate expression of α1-AT in macrophages and hepatocytes. However, expression of α1-AT increases markedly in Caco2 cells as they differentiate into enteric villous-type cells.