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ApoL1 Overexpression Drives Variant-Independent Cytotoxicity.


ABSTRACT: Coding variants in the APOL1 gene are associated with kidney diseases in African ancestral populations; yet, the underlying biologic mechanisms remain uncertain. Variant-dependent autophagic and cytotoxic cell death have been proposed as pathogenic pathways mediating kidney injury. To examine this possibility, we conditionally expressed APOL1-G0 (reference), -G1, and -G2 (variants) using a tetracycline-regulated system in HEK293 cells. Autophagy was monitored biochemically and cell death was measured using multiple assays. We measured intracellular Na+ and K+ content with atomic absorption spectroscopy and APOL1-dependent currents with whole-cell patch clamping. Neither reference nor variant APOL1s induced autophagy. At high expression levels, APOL1-G0, -G1, and -G2 inserted into the plasma membrane and formed pH-sensitive cation channels, causing collapse of cellular Na+ and K+ gradients, phosphorylation of p38 mitogen-activated protein kinase, and cell death, without variant-dependent differences. APOL1-G0 and -G2 exhibited similar channel properties in whole-cell patch clamp experiments. At low expression levels, neither reference nor variant APOL1s localized on the plasma membrane, Na+ and K+ gradients were maintained, and cells remained viable. Our results indicate that APOL1-mediated pore formation is critical for the trypanolytic activity of APOL1 and drives APOL1-mediated cytotoxicity in overexpression systems. The absence of cytotoxicity at physiologic expression levels suggests variant-dependent intracellular K+ loss and cytotoxicity does not drive kidney disease progression.

SUBMITTER: O'Toole JF 

PROVIDER: S-EPMC5827587 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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ApoL1 Overexpression Drives Variant-Independent Cytotoxicity.

O'Toole John F JF   Schilling William W   Kunze Diana D   Madhavan Sethu M SM   Konieczkowski Martha M   Gu Yaping Y   Luo Liping L   Wu Zhenzhen Z   Bruggeman Leslie A LA   Sedor John R JR  

Journal of the American Society of Nephrology : JASN 20171127 3


Coding variants in the <i>APOL1</i> gene are associated with kidney diseases in African ancestral populations; yet, the underlying biologic mechanisms remain uncertain. Variant-dependent autophagic and cytotoxic cell death have been proposed as pathogenic pathways mediating kidney injury. To examine this possibility, we conditionally expressed APOL1-G0 (reference), -G1, and -G2 (variants) using a tetracycline-regulated system in HEK293 cells. Autophagy was monitored biochemically and cell death  ...[more]

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