Metabolic disorders and cancer: Hepatocyte store-operated Ca2+ channels in nonalcoholic fatty liver disease

Eunüs S. Ali, Grigori Y. Rychkov, Greg J. Barritt

    Research output: Chapter in Book/Report/Conference proceedingChapter

    8 Citations (Scopus)

    Abstract

    In steatotic hepatocytes, intracellular Ca2+ homeostasis is substantially altered compared to normal. Decreased Ca2+ in the endoplasmic reticulum (ER) can lead to ER stress, an important mediator of the progression of liver steatosis to nonalcoholic steatohepatitis, type 2 diabetes, and hepatocellular carcinoma. Store-operated Ca2+ channels (SOCs) in hepatocytes are composed principally of Orai1 and STIM1 proteins. Their main role is the maintenance of adequate Ca2+ in the lumen of the ER. In steatotic hepatocytes, store-operated Ca2+ entry (SOCE) is substantially inhibited. This inhibition is associated with a decrease in Ca2+ in the ER. Lipid-induced inhibition of SOCE is mediated by protein kinase C (PKC) and may involve the phosphorylation and subsequent inhibition of Orai1. Experimental inhibition of SOCE enhances lipid accumulation in normal hepatocytes incubated in the presence of exogenous fatty acids. The antidiabetic drug exendin-4 reverses the lipid-induced inhibition of SOCE and decreases liver lipid with rapid onset. It is proposed that lipid-induced inhibition of SOCE in the plasma membrane and of SERCA2b in the ER membrane leads to a persistent decrease in ER Ca2+, ER stress, and the ER stress response, which in turn enhances (amplifies) lipid accumulation. A low level of persistent SOCE due to chronic ER Ca2+ depletion in steatotic hepatocytes may contribute to an elevated cytoplasmic-free Ca2+ concentration leading to the activation of calcium-calmodulin kinase II (CaMKII), decreased lipid removal by autophagy, and insulin resistance. It is concluded that lipid-induced inhibition of SOCE plays an important role in the progression of liver steatosis to insulin insensitivity and hepatocellular carcinoma.

    Original languageEnglish
    Title of host publicationStore-Operated Ca2+ Entry (SOCE) Pathways
    Subtitle of host publicationEmerging Signaling Concepts in Human (Patho)physiology
    EditorsKlaus Groschner, Wolfgang F Graier, Christoph Romanin
    Place of PublicationSwitzerland
    PublisherSpringer New York LLC
    Pages595-621
    Number of pages27
    Volume993
    Edition2nd
    ISBN (Electronic)9783319577326
    ISBN (Print)9783319577319
    DOIs
    Publication statusPublished - 2017

    Publication series

    NameAdvances in Experimental Medicine and Biology
    Volume993
    ISSN (Print)0065-2598
    ISSN (Electronic)2214-8019

    Keywords

    • Cyclic AMP
    • Exendin-4
    • GLP-1
    • Intracellular Ca
    • Liver
    • Steatosis
    • Store-operated Ca entry

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  • Cite this

    Ali, E. S., Rychkov, G. Y., & Barritt, G. J. (2017). Metabolic disorders and cancer: Hepatocyte store-operated Ca2+ channels in nonalcoholic fatty liver disease. In K. Groschner, W. F. Graier, & C. Romanin (Eds.), Store-Operated Ca2+ Entry (SOCE) Pathways: Emerging Signaling Concepts in Human (Patho)physiology (2nd ed., Vol. 993, pp. 595-621). (Advances in Experimental Medicine and Biology; Vol. 993). Springer New York LLC. https://doi.org/10.1007/978-3-319-57732-6_30