title: Localization of APOL1 protein and mRNA in the human kidney: nondiseased tissue, primary cells, and immortalized cell lines.
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.
authors.affiliation: Internal Medicine-Nephrology, lima@wakehealth.edu bfreedma@wakehealth.edu.
authors.forename: Lijun
authors.initials: L
authors.lastname: Ma
authors.affiliation: Pathology-Lipid Sciences, and.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Shelness
authors.affiliation: Internal Medicine-Nephrology.
authors.forename: James A
authors.initials: JA
authors.lastname: Snipes
authors.affiliation: Internal Medicine-Nephrology.
authors.forename: Mariana
authors.initials: M
authors.lastname: Murea
authors.affiliation: Biochemistry, Wake Forest School of Medicine, Winston-Salem, North Carolina;
authors.forename: Peter A
authors.initials: PA
authors.lastname: Antinozzi
authors.affiliation: Pathology-Lipid Sciences, and.
authors.forename: Dongmei
authors.initials: D
authors.lastname: Cheng
authors.affiliation: Children's Renal Unit, Bristol Royal Hospital for Children, University of Bristol, Bristol, United Kingdom;
authors.forename: Moin A
authors.initials: MA
authors.lastname: Saleem
authors.affiliation: Learning and Research Southmead Hospital Bristol, University of Bristol, Bristol, United Kingdom;
authors.forename: Simon C
authors.initials: SC
authors.lastname: Satchell
authors.affiliation: Internal Medicine II-Nephrology/Transplantation, University Medical Center, Regensburg, Germany;
authors.forename: Bernhard
authors.initials: B
authors.lastname: Banas
authors.affiliation: Children's Renal Unit, Bristol Royal Hospital for Children, University of Bristol, Bristol, United Kingdom;
authors.forename: Peter W
authors.initials: PW
authors.lastname: Mathieson
authors.affiliation: Department of Internal Medicine-Nephrology, University of Michigan at Ann Arbor Medical School, Ann Arbor, Michigan;
authors.forename: Matthias
authors.initials: M
authors.lastname: Kretzler
authors.affiliation: Departments of Surgical Sciences-Urology and.
authors.forename: Ashok K
authors.initials: AK
authors.lastname: Hemal
authors.affiliation: Pathology-Lipid Sciences, and.
authors.forename: Lawrence L
authors.initials: LL
authors.lastname: Rudel
authors.affiliation: Internal Medicine-Nephrology, Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina;
authors.forename: Snezana
authors.initials: S
authors.lastname: Petrovic
authors.affiliation: Pathology-Lipid Sciences, and.
authors.forename: Allison
authors.initials: A
authors.lastname: Weckerle
authors.affiliation: Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts; and.
authors.forename: Martin R
authors.initials: MR
authors.lastname: Pollak
authors.affiliation: Renal Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Ross
authors.affiliation: Pathology-Lipid Sciences, and Biochemistry, Wake Forest School of Medicine, Winston-Salem, North Carolina;
authors.forename: John S
authors.initials: JS
authors.lastname: Parks
authors.affiliation: Internal Medicine-Nephrology, lima@wakehealth.edu bfreedma@wakehealth.edu.
authors.forename: Barry I
authors.initials: BI
authors.lastname: Freedman
mesh_terms: D000075944:Apolipoprotein L1; D001053:Apolipoproteins / Q000378:metabolism*; D001706:Biopsy; D002460:Cell Line; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D006801:Humans; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D007678:Kidney Glomerulus / Q000378:metabolism* / Q000473:pathology; D007687:Kidney Tubules, Proximal / Q000378:metabolism* / Q000473:pathology; D008075:Lipoproteins, HDL / Q000378:metabolism*; D050527:Mesangial Cells / Q000378:metabolism* / Q000473:pathology; D008856:Microscopy, Fluorescence; D009392:Nephrectomy; D050199:Podocytes / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism*
chemical_list: C108666:APOL1 protein, human; D000075944:Apolipoprotein L1; D001053:Apolipoproteins; D008075:Lipoproteins, HDL; D012333:RNA, Messenger
keywords: chronic kidney disease; gene expression; gene transcription; lipids; pathology