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APOL1 risk variants cause podocytes injury through enhancing endoplasmic reticulum stress.

ABSTRACT: Two coding sequence variants (G1 and G2) of Apolipoprotein L1 (APOL1) gene have been implicated as a higher risk factor for chronic kidney diseases (CKD) in African Americans when compared with European Americans. Previous studies have suggested that the APOL1 G1 and G2 variant proteins are more toxic to kidney cells than the wild-type APOL1 G0, but the underlying mechanisms are poorly understood. To determine whether endoplasmic reticulum (ER) stress contributes to podocyte toxicity, we generated human podocytes (HPs) that stably overexpressed APOL1 G0, G1, or G2 (Vec/HPs, G0/HPs, G1/HPs, and G2/HPs). Propidium iodide staining showed that HP overexpressing the APOL1 G1 or G2 variant exhibited a higher rate of necrosis when compared with those overexpressing the wild-type G0 counterpart. Consistently, the expression levels of nephrin and podocin proteins were significantly decreased in the G1- or G2-overexpressing cells despite the maintenance of their mRNA expressions levels. In contrast, the expression of the 78-kDa glucose-regulated protein ((GRP78), also known as the binding Ig protein, BiP) and the phosphorylation of the eukaryotic translation initiation factor 1 (eIF1) were significantly elevated in the G1/HPs and G2/HPs, suggesting a possible occurrence of ER stress in these cells. Furthermore, ER stress inhibitors not only restored nephrin protein expression, but also provided protection against necrosis in G1/HPs and G2/HPs, suggesting that APOL1 risk variants cause podocyte injury partly through enhancing ER stress.

SUBMITTER: Wen H

PROVIDER: S-EPMC6131197 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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APOL1 risk variants cause podocytes injury through enhancing endoplasmic reticulum stress.

Wen Hongxiu H Kumar Vinod V Lan Xiqian X Shoshtari Seyedeh Shadafarin Marashi SSM Eng Judith M JM Zhou Xiaogang X Wang Fang F Wang Haichao H Skorecki Karl K Xing Guolan G Wu Guisheng G Luo Huairong H Malhotra Ashwani A Singhal Pravin C PC

Bioscience reports 20180829 4

Two coding sequence variants (G1 and G2) of Apolipoprotein L1 (<i>APOL1</i>) gene have been implicated as a higher risk factor for chronic kidney diseases (CKD) in African Americans when compared with European Americans. Previous studies have suggested that the APOL1 G1 and G2 variant proteins are more toxic to kidney cells than the wild-type APOL1 G0, but the underlying mechanisms are poorly understood. To determine whether endoplasmic reticulum (ER) stress contributes to podocyte toxicity, we ...[more]

PMID: 29967295

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Project description:BackgroundMetabolic disorder is considered a well-established risk factor for endometrial carcinoma (EC). However, the mechanism remains unclear. Insulin resistance and excessive flux of free fatty acids serve as fundamental pathogenic factors in metabolic disorders, including obesity and type 2 diabetes. The aim of this study was to test the correlation between insulin resistance and dyslipidaemia in EC and to determine the effect of insulin and saturated fatty acids on EC cells.MethodsA retrospective study on the medical records of patients with EC and RNA-seq from the TCGA database analysed with edgR and Gene Ontology (GO) were used to assess the correlation of dyslipidaemia and diabetes as well as obesity. Crystal violet assays and CCK-8 assays were used to detect the proliferation of EC cells, and Annexin V-PI was used to examine apoptosis. Transient changes in mitochondrial Ca2+ and reactive oxygen species (ROS) were monitored via confocal microscopy. DNA damage was assessed by comet assays. Changes in signalling pathways were detected via phospho-kinase array. western blotting was used to assess the molecular changes in endoplasmic reticulum (ER) stress and DNA damage.ResultsWe found that glucose metabolism disorders accompanied dyslipidaemia in patients with EC. As a key regulator of glucose metabolism disorders, insulin promoted DNA damage, ROS and Ca2+ homoeostasis imbalance in a panel of established EC cell lines. Interestingly, excessive insulin boosted saturated fatty acid-induced pro-apoptotic effects in EC cells. Furthermore, our data showed that insulin synergised with saturated fatty acids to activate the mechanistic target of rapamycin kinase/70 kDa ribosomal protein S6 kinase (mTOR/p70S6K) pathway and ER stress, resulting in Ca2+ release from ER and unfolded protein response (UPR) activation, which contributed to combined insulin and saturated fatty acid treatment-induced apoptosis and tumour progression.ConclusionsOur data are the first to illustrate that impaired glucose metabolism accelerates dyslipidaemia-promoted EC progression, which is attributed to hyperinsulinaemia and saturated fatty acid-induced Ca2+ dyshomoeostasis and UPR activation in EC cells via ER stress.

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APOL1 risk variants cause podocytes injury through enhancing endoplasmic reticulum stress.

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APOL1 risk variants cause podocytes injury through enhancing endoplasmic reticulum stress.

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