Abstract 631: Big Angiotensin-25 (Bang-25): A Novel Glycosylated Angiotensin-related Peptide Isolated From Human Urine

Abstract

The renin-angiotensin system (RAS) plays key roles in the regulation of blood pressure and body fluid dynamics. It is now recognized that a wide variety of tissues and organs, including the heart, vasculature, kidney and nervous system, among others, contain a local tissue RAS, which exerts autocrine/paracrine effects and acts independently of the systemic RAS. In 2006, we isolated and characterized proangiotensin-12, a component of the tissue RAS in rat small intestine. Similar angiotensin-related peptides had never been reported in humans. When we screened human urine gel filtration fractions for bioactive peptides using an antibody raised against the N-terminal portion of Angiotensin II (Ang II), we found a highly immunoreactive peptide with an apparent molecular weight of about 5,000. Therefore, we purified this peptide from 5.5 L of human urine using ion-exchange, gel-filtration, and affinity chromatography, and finally reverse-phase high-performance liquid chromatography (RP-HPLC) steps. We isolated and identified a novel Aogen-derived peptide, Big angiotensin-25 (Bang-25), which is composed of 25 amino acids and is N-glycosylated on its 14th amino acid (Asn) and has a cysteine linked to its 18th amino acid (Cys). We then assessed the distribution of Bang-25 in tissues by immunostaining with an antiserum raised against the C-terminal portion of the peptide. We found that Bang-25 was abundantly expressed in a number of human tissues, including kidney, heart, adrenal gland, pancreas and placenta. In the kidney, Bang-25 is localized predominantly to podocytes. Then, compared with angiotensinogen, Bang-25 is rapidly cleaved by chymase to Ang II, but is resistant to cleavage by renin. In the present study, we have isolated and identified a novel Angiotensin-derived peptide, Bang-25, which is composed of 25 amino acids and is N-glycosylated on its 14th amino acid (Asn) and has a cysteine linked to its 18th amino acid (Cys). The identification of Bang-25 suggests the existence of a RAS processing cascade different from the renin-catalyzed cleavage of Angiotensin to Ang I, and provides a potential target for assessing tissue RAS status and for the development of new therapeutic approaches to related diseases.