SLC9A1 blocking peptide

Non-alcoholic fatty liver disease NAFLD is closely associated with the dysregulation of lipid homeostasis. Diet-induced hepatic steatosis, which can initiate NAFLD progression, has been shown to be dramatically reduced in mice lacking the electroneutral Na+/H+ exchanger NHE1 (Slc9a1). In this study, we investigated if NHE1 deficiency had effects in liver that could contribute to the apparent protection against aberrant lipid accumulation. RT-PCR and immunoblot analyses of wild-type and NHE1-null livers revealed an expression profile that strongly suggested attenuation of both de nova lipogenesis and hepatic stellate cell activation, which is implicated in liver fibrosis. This included upregulation of the farnesoid X receptor FXR, peroxisome proliferator-activated receptor PPAR gamma, its co-activator PGC1 alpha, and sestrin 2, an antioxidant protein involved in hepatic metabolic homeostasis. Furthermore, expression levels of the pro-lipogenic liver X receptor LXR alpha, and acetyl CoA carboxylases 1 and 2 were downregulated. These changes were associated with evidence of reduced cellular stress, which persisted even upon exposure to a high-fat diet, and the better preservation of insulin signaling, as evidenced by protein kinase B/Akt phosphorylation (Ser473). These results indicate that NHE1 deficiency may protect against NAFLD pathogenesis, which is significant given the availability of highly specific NHE1 inhibitors. (C) 2014 Elsevier Inc. All rights reserved.

Hypoxia and extracellular acidosis are pathophysiological hallmarks of aggressive solid tumors. Regulation of intracellular pH (pH(i)) is essential for the maintenance of tumor cell metabolism and proliferation in this microenvironment and key proteins involved in pH(i) regulation are of interest for therapeutic development. Carbonic anhydrase 9 (CA9) is one of the most robustly regulated proteins by the hypoxia inducible factor (HIF) and contributes to pH(i) regulation. Here, we have investigated for the first time, the role of CA9 via complete genomic knockout (ko) and compared its impact on tumor cell physiology with the essential pHi regulator Na+/H+ exchanger 1 (NHE1). Initially, we established NHE1-ko LS174 cells with inducible CA9 knockdown. While increased sensitivity to acidosis for cell survival in 2-dimensions was not observed, clonogenic proliferation and 3-dimensional spheroid growth in particular were greatly reduced. To avoid potential confounding variables with use of tetracycline-inducible CA9 knockdown, we established CA9-ko and NHE1/CA9-dko cells. NHE1-ko abolished recovery from NH4Cl pre-pulse cellular acid loading while both NHE1 and CA9 knockout reduced resting pH(i). NHE1-ko significantly reduced tumor cell proliferation both in normoxia and hypoxia while CA9-ko dramatically reduced growth in hypoxic conditions. Tumor xenografts revealed substantial reductions in tumor growth for both NHE1-ko and CA9-ko. A notable induction of CA12 occurred in NHE1/CA9-dko tumors indicating a potential means to compensate for loss of pH regulating proteins to maintain growth. Overall, these genomic knockout results strengthen the pursuit of targeting tumor cell pH regulation as an effective anticancer strategy.