Increased Susceptibility to Cisplatin‐Induced Acute Kidney Injury in the Kidneys of Na‐H Exchanger Regulatory Factor Isoform 1 (NHERF1) Deficient Mice

Abstract

NHERF1 is a PDZ binding protein that plays a critical role in defining both the renal proximal tubule brush border membrane (BBM) composition and regulating ion transport through modulation of trafficking and anchoring functions. In a NHERF1‐deficient opossum kidney (OK) cell line, we have observed slower cell growth, a decrease in total mRNA expression, diminished BBM protein glycosylation, and higher levels of phosphorylated PERK, a marker of ER stress. We hypothesized that kidneys from NHERF1 deficient mice were more susceptible to acute kidney injury as a result of increased ER stress. To test this hypothesis, we treated 2 month old WT and NHERF1 deficient mice with 20 mg/kg IP cisplatin for 72 hours. Hemotoxylin and eosin staining of the kidney cortex of NHERF1 deficient mice showed greater injury manifested by BBM sloughing, tubular cell detachment and vacuolization, and intratubular proteinaceous debris. NHERF1 KO mice treated with cisplatin also demonstrated decreased expression of GRP78, a prosurvival ER chaperone that is upregulated during ER stress. Using ID‐RP (C18) nanoflow ultra high performance liquid chromatography and nanoelectrospray‐mass spectrometry (MS), we examined the composition of the BBM of proximal tubule cells from 4 month old NHERF1 KO mice. Compared to WT mice, NHERF1 KO mice demonstrated decreased abundance of several proteins involved in cell survival including ACADS, CDK18, and PRKAR2A in the BBM, while the abundance of proteins specific to renal cell proliferation and survival such as FGFR2, GRN, and NOS3 were decreased 3 to 25 fold. Interestingly, proteins such as DAPK1, a positive mediator of gamma interferon‐induced programmed cell death, and GAK, a direct transcriptional target of p53 that is itself a stress‐induced protein involved in cell cycle arrest and apoptosis, were increased 2 and 19 fold in the NHERF1 KO BBM. We conclude that NHERF1 deficiency increases susceptibility to cisplatin‐induced AKI due to the presence of underlying ER stress and reduced expression of signaling pathways that promote cell survival.Support or Funding InformationUniversity of Louisville, NIH‐NIA Grant # 5R21 AG047474‐02