APOL1 risk variants enhance podocyte necrosis through compromising lysosomal membrane permeability

Am J Physiol Renal Physiol. 2014 Aug 1;307(3):F326-36. doi: 10.1152/ajprenal.00647.2013. Epub 2014 Jun 4.

Abstract

Development of higher rates of nondiabetic glomerulosclerosis (GS) in African Americans has been attributed to two coding sequence variants (G1 and G2) in the APOL1 gene. To date, the cellular function and the role of APOL1 variants (Vs) in GS are still unknown. In this study, we examined the effects of overexpressing wild-type (G0) and kidney disease risk variants (G1 and G2) of APOL1 in human podocytes using a lentivirus expression system. Interestingly, G0 inflicted podocyte injury only at a higher concentration; however, G1 and G2 promoted moderate podocyte injury at lower and higher concentrations. APOL1Vs expressing podocytes displayed diffuse distribution of both Lucifer yellow dye and cathepsin L as manifestations of enhanced lysosomal membrane permeability (LMP). Chloroquine attenuated the APOL1Vs-induced increase in podocyte injury, consistent with targeting lysosomes. The chloride channel blocker DIDS prevented APOL1Vs- induced injury, indicating a role for chloride influx in osmotic swelling of lysosomes. Direct exposure of noninfected podocytes with conditioned media from G1- and G2-expressing podocytes also induced injury, suggesting a contributory role of the secreted component of G1 and G2 as well. Adverse host factors (AHFs) such as hydrogen peroxide, hypoxia, TNF-α, and puromycin aminonucleoside augmented APOL1- and APOL1Vs-induced podocyte injury, while the effect of human immunodeficiency virus (HIV) on podocyte injury was overwhelming under conditions of APOLVs expression. We conclude that G0 and G1 and G2 APOL1 variants have the potential to induce podocyte injury in a manner which is further augmented by AHFs, with HIV infection being especially prominent.

Keywords: APOL1 risk variants; kidney disease; lysosomal membrane permeability; necrosis; podocyte.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / pharmacology
  • Actins / metabolism
  • African Americans / ethnology
  • African Americans / genetics
  • Apolipoprotein L1
  • Apolipoproteins / genetics*
  • Apolipoproteins / metabolism*
  • Cells, Cultured
  • Chloride Channels / antagonists & inhibitors
  • Chloride Channels / drug effects
  • Chloroquine / pharmacology
  • Genetic Predisposition to Disease / ethnology
  • Genetic Predisposition to Disease / genetics
  • Genetic Variation / genetics*
  • Glomerulosclerosis, Focal Segmental / ethnology
  • Glomerulosclerosis, Focal Segmental / genetics
  • Humans
  • Lipoproteins, HDL / genetics*
  • Lipoproteins, HDL / metabolism*
  • Lysosomes / physiology*
  • Necrosis / physiopathology
  • Permeability
  • Podocytes / drug effects
  • Podocytes / metabolism*
  • Podocytes / pathology*

Substances

  • APOL1 protein, human
  • Actins
  • Apolipoprotein L1
  • Apolipoproteins
  • Chloride Channels
  • Lipoproteins, HDL
  • Chloroquine
  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid