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Evidence for an angiotensin‐(1‐7) neuropeptidase in the brain medulla of sheep (1140.6)
Author(s) -
Marshall Allyson,
Pirro Nancy,
Rose James,
Diz Debra,
Chappell Mark
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.1140.6
Subject(s) - chemistry , neprilysin , angiotensin iii , renin–angiotensin system , angiotensin ii , medicine , bradykinin , endocrinology , neurotensin , enzyme , neuropeptide , biochemistry , angiotensin receptor , blood pressure , biology , receptor
Angiotensin‐(1‐7) [Ang 7] is an alternative product of the renin‐angiotensin system (RAS). In contrast to Ang II, Ang 7 exhibits central actions to lower blood pressure and improve baroreflex sensitivity. We identified a thiol‐sensitive peptidase that metabolized Ang 7 to Ang‐(1‐4) (Ang 4) in CSF of adult sheep. This activity was 2.5‐fold higher in sheep with antenatal glucocorticoid exposure while CSF Ang 7 levels were 50% lower compared to controls. To characterize this peptidase, we purified the protein 1400‐fold from the brain medulla by multiple chromatography steps monitored by 125I‐Ang 7 conversion to Ang 4. Chelating agents o‐phenanthroline and EDTA, as well as the mercury compounds APMA and PCMB, but not the cysteine protease inhibitor E64 blocked peptidase activity. Specific inhibitors to neprilysin, neurolysin, or thimet oligopeptidase were ineffective while the activity was abolished by the metallopeptidase inhibitor JMV 390 (Ki = 0.7 nM). HPLC analysis confirmed the processing of unlabeled Ang 7 to Ang 4 by the peptidase, but revealed <5% hydrolysis of Ang II or Ang I and no hydrolysis of neurotensin, bradykinin or apelin. Kinetic studies using 125I‐labeled Ang 7 and Ang I show similar Kms (2.6 and 4.3 μM), but a higher Vmax for Ang 7 (72 vs. 6 nmol/min/mg for Ang I, p<0.01, n=3). We conclude that evidence for an Ang 7 neuropeptidase may portend a novel pathway to influence actions of the peptide within the brain. Grant Funding Source : Supported by HD47584