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J Am Soc Nephrol. 2015 Feb;26(2):339-48. doi: 10.1681/ASN.2013091017. Epub 2014 Jul 10.

Localization of APOL1 protein and mRNA in the human kidney: nondiseased tissue, primary cells, and immortalized cell lines.

Author information

1
Internal Medicine-Nephrology, lima@wakehealth.edu bfreedma@wakehealth.edu.
2
Pathology-Lipid Sciences, and.
3
Internal Medicine-Nephrology.
4
Biochemistry, Wake Forest School of Medicine, Winston-Salem, North Carolina;
5
Children's Renal Unit, Bristol Royal Hospital for Children, University of Bristol, Bristol, United Kingdom;
6
Learning and Research Southmead Hospital Bristol, University of Bristol, Bristol, United Kingdom;
7
Internal Medicine II-Nephrology/Transplantation, University Medical Center, Regensburg, Germany;
8
Department of Internal Medicine-Nephrology, University of Michigan at Ann Arbor Medical School, Ann Arbor, Michigan;
9
Departments of Surgical Sciences-Urology and.
10
Internal Medicine-Nephrology, Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina;
11
Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts; and.
12
Renal Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
13
Pathology-Lipid Sciences, and Biochemistry, Wake Forest School of Medicine, Winston-Salem, North Carolina;

Abstract

Although APOL1 gene variants are associated with nephropathy in African Americans, little is known about APOL1 protein synthesis, uptake, and localization in kidney cells. To address these questions, we examined APOL1 protein and mRNA localization in human kidney and human kidney-derived cell lines. Indirect immunofluorescence microscopy performed on nondiseased nephrectomy cryosections from persons with normal kidney function revealed that APOL1 protein was markedly enriched in podocytes (colocalized with synaptopodin and Wilms' tumor suppressor) and present in lower abundance in renal tubule cells. Fluorescence in situ hybridization detected APOL1 mRNA in glomeruli (podocytes and endothelial cells) and tubules, consistent with endogenous synthesis in these cell types. When these analyses were extended to renal-derived cell lines, quantitative RT-PCR did not detect APOL1 mRNA in human mesangial cells; however, abundant levels of APOL1 mRNA were observed in proximal tubule cells and glomerular endothelial cells, with lower expression in podocytes. Western blot analysis revealed corresponding levels of APOL1 protein in these cell lines. To explain the apparent discrepancy between the marked abundance of APOL1 protein in kidney podocytes observed in cryosections versus the lesser abundance in podocyte cell lines, we explored APOL1 cellular uptake. APOL1 protein was taken up readily by human podocytes in vitro but was not taken up efficiently by mesangial cells, glomerular endothelial cells, or proximal tubule cells. We hypothesize that the higher levels of APOL1 protein in human cryosectioned podocytes may reflect both endogenous protein synthesis and APOL1 uptake from the circulation or glomerular filtrate.

KEYWORDS:

chronic kidney disease; gene expression; gene transcription; lipids; pathology

PMID:
25012173
PMCID:
PMC4310650
DOI:
10.1681/ASN.2013091017
[Indexed for MEDLINE]
Free PMC Article
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