An angiotensin-(l-7) peptidase in the kidney cortex, proximal tubules, andhuman HK-2 epithelial cells that is distinct from insulin-degrading enzyme

摘要

Angiotensin 1-7 [ANG-(1-7)] is expressed within the kidney and exhibits renoprotectiveactions that antagonize the inflammatory, fibrotic, and pro-oxidanteffects of ANG II. We previously identified an peptidase that prefer-entially metabolized ANG-(l-7) to ANG-(l-4) in the brain medullaand cerebrospinal fluid (CSF) of sheep (Marshall AC, Pirro NT, RoseJC, Diz DI, Chappell MC. JNeurochem 130; 313-323, 2014); thus thepresent study established the expression of the peptidase in the kidney.Utilizing a sensitive HPLC-based approach, we demonstrate a pepti-dase activity that hydrolyzed ANG-(l-7) to ANG-(l-4) in the sheepcortex, isolated tubules, and human HK-2 renal epithelial cells. Thepeptidase was markedly sensitive to the metallopeptidase inhibitorJMV-390; human HK-2 cells expressed subnanomolar sensitivity(IC50 = 0.5 nM) and the highest specific activity (123 ± 5fmolmin '-mg~’) compared with the tubules (96 ± 12 fmolmin-'-mg-1) and cortex (107 ± 9 fmol min-’ mg-1). Thepeptidase was purified 41-fold from HK-2 cells; the activity wassensitive to JMV-390, the chelator o-phenanthroline, and the mercury-containing compound /;-chloromercuribenzoic acid (PCMB), but notto selective inhibitors against neprilysin, neurolysin and thimet oligo-peptidase. Both ANG-(l-7) and its endogenous analog [Ala’]-ANG-(1-7) (alamandine) were preferentially hydrolyzed by the peptidasecompared with ANG II, [Asp1]-ANG II, ANG I, and ANG-(1-12).Although the ANG-(l-7) peptidase and insulin-degrading enzyme(IDE) share similar inhibitor characteristics of a metallothiolendopep-tidase, we demonstrate marked differences in substrate specificity,which suggest these peptidases are distinct. We conclude that anANG-(l-7) peptidase is expressed within the renal proximal tubuleand may play a potential role in the renal renin-angiotensin system toregulate ANG-(l-7) tone.