title: BH3 domain-independent apolipoprotein L1 toxicity rescued by BCL2 prosurvival proteins.
abstract: The potent trypanolytic properties of human apolipoprotein L1 (APOL1) can be neutralized by the trypanosome variant surface antigen gene product known as serum resistance-associated protein. However, two common APOL1 haplotypes present uniquely in individuals of West African ancestry each encode APOL1 variants resistant to serum resistance-associated protein, and each confers substantial resistance to human African sleeping sickness. In contrast to the dominantly inherited anti-trypanosomal activity of APOL1, recessive inheritance of these two trypanoprotective APOL1 alleles predisposes to kidney disease. Proposed mechanisms of APOL1 toxicity have included BH3 domain-dependent autophagy and/or ion channel activity. We probed these potential mechanisms by expressing APOL1 in Xenopus laevis oocytes. APOL1 expression in oocytes increased ion permeability and caused profound morphological deterioration (toxicity). Coexpression of BCL2 family members rescued APOL1-associated oocyte toxicity in the order MCL1 ∼ BCLW > BCLXL ∼ BCL2A1 ≫ BCL2. Deletion of nine nominal core BH3 domain residues abolished APOL1-associated toxicity, but missense substitution of the same residues abolished neither oocyte toxicity nor its rescue by coexpressed MCL1. The APOL1 BH3 domain was similarly dispensable for the ability of APOL1 to rescue intact mice from lethal trypanosome challenge. Replacement of most extracellular Na(+) by K(+) also reduced APOL1-associated oocyte toxicity, allowing demonstration of APOL1-associated increases in Ca(2+) and Cl(-) fluxes and oocyte ion currents, which were similarly reduced by MCL1 coexpression. Thus APOL1 toxicity in Xenopus oocytes is BH3-independent, but can nonetheless be rescued by some BCL2 family proteins.
authors.affiliation: Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Medicine, Harvard Medical School, Boston, Massachusetts; and.
authors.forename: J F
authors.initials: JF
authors.lastname: Heneghan
authors.affiliation: Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Medicine, Harvard Medical School, Boston, Massachusetts; and.
authors.forename: D H
authors.initials: DH
authors.lastname: Vandorpe
authors.affiliation: Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Medicine, Harvard Medical School, Boston, Massachusetts; and.
authors.forename: B E
authors.initials: BE
authors.lastname: Shmukler
authors.forename: J A
authors.initials: JA
authors.lastname: Giovinazzo
authors.affiliation: The Graduate Center and Department of Biological Sciences, Hunter College of the City University of New York, New York, New York.
authors.forename: J A
authors.initials: JA
authors.lastname: Giovinnazo
authors.affiliation: The Graduate Center and Department of Biological Sciences, Hunter College of the City University of New York, New York, New York.
authors.forename: J
authors.initials: J
authors.lastname: Raper
authors.affiliation: Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Medicine, Harvard Medical School, Boston, Massachusetts; and.
authors.forename: D J
authors.initials: DJ
authors.lastname: Friedman
authors.affiliation: Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Medicine, Harvard Medical School, Boston, Massachusetts; and.
authors.forename: M R
authors.initials: MR
authors.lastname: Pollak
authors.affiliation: Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Medicine, Harvard Medical School, Boston, Massachusetts; and salper@bidmc.harvard.edu.
authors.forename: S L
authors.initials: SL
authors.lastname: Alper
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000075944:Apolipoprotein L1; D001053:Apolipoproteins / Q000096:biosynthesis* / Q000235:genetics / Q000633:toxicity*; D005260:Female; D006801:Humans; D008075:Lipoproteins, HDL / Q000096:biosynthesis* / Q000235:genetics / Q000633:toxicity*; D051379:Mice; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000235:genetics; D014982:Xenopus laevis
chemical_list: C108666:APOL1 protein, human; D000075944:Apolipoprotein L1; D001053:Apolipoproteins; C000595707:BCL2 protein, human; D008075:Lipoproteins, HDL; D019253:Proto-Oncogene Proteins c-bcl-2
keywords: Xenopus oocyte; apolipoprotein L1; hydrodynamic gene delivery; trypanosome; two-electrode voltage clamp