A mixture of tetradecamer oligodeoxyribonucleotides complementary to the codons specifying the carboxyl-terminal sequence, Ile-His-Pro-Phe-His, of angiotensin was chemically synthesized as two pools and used for the isolation of a cDNA clone specific for angiotensinogen from a cDNA bank of rat liver mRNA sequences. The two pools (oligo 1 and oligo 2), each containing 24 oligodeoxyribonucleotides, were first used as primers to initiate reverse transcription of rat liver mRNA. One of the pools (oligo 1) was found to prime a specific 32P-labeled cDNA of approximately 160 nucleotides that contained the anticoding sequence corresponding exactly to the amino acid sequence of rat angiotensin. This cDNA, in turn, was used to rescreen cDNA clones that were isolated by initially selecting the rat liver cDNA bank by hybridization with the oligo 1 mixture. One clone thus obtained, designated pRag16, was subjected to nucleotide sequence analysis and verified to contain a nearly full-length cDNA sequence coding for rat angiotensinogen precursor. The deduced amino acid sequence indicates that the precursor molecular consists of angiotensinogen of 453 amino acid residues and a putative signal peptide of 24 amino acid residues. The predicted molecular weight and amino acid composition of angiotensinogen agree well with those determined by using the purified protein. An angiotensin moiety is located at the amino-terminal part of angiotensinogen, preceded directly by the signal peptide and followed by a large carboxyl-terminal sequence that contains two internally homologous sequences and three potential glycosylation sites.

https://www.pnas.org/content/pnas/80/8/2196.full.pdf

Cloning and sequence analysis of cDNA for rat angiotensinogen.

A ngiotensinogen is a moderately abundant / \ 55,000-60,000 Da serum glycoprotein that is -Z \ the precursor to the angiotensin peptides and is the only known naturally occurring renin substrate. It is synthesized by a variety of cells, most prominently hepatocytes, adipocytes, and astrocytes. Most angiotensinogen is extracellular (it is constitutively secreted); thus, there is apparently no way that an organism can orchestrate rapid changes in angiotensinogen concentration. The angiotensinogen gene is regulated by several hormones (e.g., glucocorticoid and estrogen), and angiotensinogen is an acute-phase protein. Angiotensinogen is a member of the serpin gene superfamily, but there is little reason to suppose that this protein is a serine protease inhibitor. The available evidence indicates that angiotensinogen functions solely as an extracellular reservoir of angiotensin peptides. In this article, we attempt a critical review of the literature on the biology of this protein, with an emphasis on recent molecular biological studies. We recommend other recent reviews, for example, those of Tewksbury or Campbell, for alternative views of this subject matter.

Molecular biology of angiotensinogen.

Hormonal control of angiotensinogen production

The renin substrate, angiotensinogen, was localized by immunocytochemistry in liver and kidney of normal rats by the use of an antiserum directed against pure rat angiotensinogen. This substrate was also examined in rats after bilateral nephrectomy, which is known to increase plasma angiotensinogen, and in rats treated with colchicine, which inhibits serum protein secretion. In normal rat liver, light microscopy showed the presence of immunoreactive material in a very few cells. The number of stained hepatocytes rose in rats treated with colchicine or after bilateral nephrectomy. Immuno-staining increased further when rats were both nephrectomized and colchicine treated. In the kidney, angiotensinogen was specifically located as granular formations in nephrocytes of the proximal tubule but never in the granular cells of the juxtaglomerular apparatus. The localization of these granular formations under the brush border suggests that angiotensinogen is reabsorbed from the glomerular ultrafiltrate rather than synthesized in the kidney.

C. Falge

Papers

Synthesis of angiotensinogen by isolated rat liver cells and its regulation in comparison to serum albumin

Proceedings: Synthesis and secretion of albumin and angiotensinogen by isolated rat liver cells.