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Internalization of Angiotensinogen in Renal Proximal Tubules: Evidence for Mitochondrial Trafficking
Author(s) -
Wilson Bryan,
CruzDiaz Nildris,
Su Yixin,
Rose James C.,
Chappell Mark C.
Publication year - 2016
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.30.1_supplement.967.5
Subject(s) - internalization , percoll , endoplasmic reticulum , renal cortex , cytosol , intracellular , kidney , cell fractionation , mitochondrion , renin–angiotensin system , biology , angiotensin ii , microbiology and biotechnology , medicine , endocrinology , enzyme , chemistry , biochemistry , cell , receptor , centrifugation , blood pressure
Evidence for an intrarenal renin‐angiotensin system (RAS) is well established. The renal proximal tubules, which constitute a key functional component of the kidney, express the RAS precursor angiotensinogen (Aogen); however, it is unclear the extent that tubular Aogen reflects local synthesis or internalization. Therefore, the current study determined whether Aogen is internalized by proximal tubules and the intracellular pattern of distribution. Proximal tubules were isolated from the kidney cortex of male sheep by enzymatic digestion and a discontinuous Percoll gradient. Tubules were incubated with 125I‐Aogen for 2 hrs at 37°C in DMEM/F12 media. Approximately 10% of exogenous 125I‐Aogen was internalized by sheep tubules. Subcellular fractionation revealed that 21 ± 4% of the internalized 125I‐Aogen associated with the mitochondrial fraction, with additional labeling in the nucleus [60 ± 7%], endoplasmic reticulum [4 ± 0.5%] and cytosol [15 ± 4%; n=4]. Subsequent studies determined whether Mito directly internalize 125I‐Aogen using isolated Mito from renal cortex and human HK‐2 cells. Sheep cortical Mito and the HK‐2 Mito internalized 125I‐Aogen at a comparable rate of [33 ± 9 vs. 21 ± 10 fmol/min/mg protein; n=3]. Lastly, unlabeled Aogen (100 nM) competed for 125I‐Aogen uptake to a greater extent than human albumin in HK‐2 Mito [60 ± 2% vs. 16 ± 13%; n=3]. Collectively, our data demonstrate Aogen internalization and subsequent trafficking to the Mito in proximal tubules. We conclude that this pathway may provide a precursor source for the intracellular expression of angiotensin peptides in the tubules. Support or Funding Information Grant Funding Source: Supported by AHA grant 15PRE25120007 and NIH grants HL56973, HL52972, HL112237, and HD047584.