Atrial natriuretic peptide degradation by CPA47 cells - Evidence for a divalent cation-independent cell-surface proteolytic activity

Abstract Atrial natriuretic peptide (ANP) is rapidly cleared and degraded in vivo. Nonguanylate-cyclase receptors (C-ANPR) and a metalloproteinase, neutral endopeptidase (EC 3.4.24.11) (NEP 24.11), are thought to be responsible for its metabolism. We investigated the mechanisms of ANP degradation by an endothelial-derived cell line, CPA47. CPA47 cells degraded 88% of 125 I-ANP after 1 h at 37°C as determined by HPLC. Medium preconditioned by these cells degraded 41% of the 125 I-ANP, and this activity was inhibited by a divalent cation chelator, EDTA. Furthermore, a cell-surface proteolytic activity degraded 125 I-ANP in the presence of EDTA when receptor-mediated endocytosis was inhibited either by low temperature (4°C) or by hyperosmolarity at 37°C. The metalloproteinase NEP 24.11, is unlikely to be the cell-surface peptidase because 125 I-ANP is degraded by CPA47 cells at 4°C in the presence of 5 mM EDTA. These data indicate that CPA47 cells can degrade ANP by a novel divalent cation-independent cell-surface proteolytic activity.