Journal of Lipid Research
Volume 61, Issue 12, December 2020, Pages 1675-1686
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Research Articles
Depletion of essential isoprenoids and ER stress induction following acute liver-specific deletion of HMG-CoA reductase

https://doi.org/10.1194/jlr.RA120001006Get rights and content
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HMG-CoA reductase (Hmgcr) is the rate-limiting enzyme in the mevalonate pathway and is inhibited by statins. In addition to cholesterol, Hmgcr activity is also required for synthesizing nonsterol isoprenoids, such as dolichol, ubiquinone, and farnesylated and geranylgeranylated proteins. Here, we investigated the effects of Hmgcr inhibition on nonsterol isoprenoids in the liver. We have generated new genetic models to acutely delete genes in the mevalonate pathway in the liver using AAV-mediated delivery of Cre-recombinase (AAV-Cre) or CRISPR/Cas9 (AAV-CRISPR). The genetic deletion of Hmgcr by AAV-Cre resulted in extensive hepatocyte apoptosis and compensatory liver regeneration. At the biochemical level, we observed decreased levels of sterols and depletion of the nonsterol isoprenoids, dolichol and ubiquinone. At the cellular level, Hmgcr-null hepatocytes showed ER stress and impaired N-glycosylation. We further hypothesized that the depletion of dolichol, essential for N-glycosylation, could be responsible for ER stress. Using AAV-CRISPR, we somatically disrupted dehydrodolichyl diphosphate synthase subunit (Dhdds), encoding a branch point enzyme required for dolichol biosynthesis. Dhdds-null livers showed ER stress and impaired N-glycosylation, along with apoptosis and regeneration. Finally, the combined deletion of Hmgcr and Dhdds synergistically exacerbated hepatocyte ER stress. Our data show a critical role for mevalonate-derived dolichol in the liver and suggest that dolichol depletion is at least partially responsible for ER stress and apoptosis upon potent Hmgcr inhibition.

cholesterol synthesis and regulation
liver
endoplasmic reticulum
animal models
3-hydroxy-3-methylglutaryl-coenzyme A
adeno-associated virus
dolichol
dehydrodolichyl diphosphate synthase subunit
clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9

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This article contains supplemental data.

Author contributions—M.D.G. and W.R.L. conceptualization; M.D.G. and W.R.L. design; M.D.G. experiments; M.D.G. analysis; A.H. viral vector production; K.E.J., J.C.B., A.M.D., A.H., A.L., R.H.H., and M.F. technical and intellectual support; K.R.P. transmission electron microscopy data analysis; K.R.P. pathological scores; J.H. and C.H.B. lipidomics; M.D.G. and W.R.L. writing-original draft; M.D.G., K.E.J., J.C.B., A.M.D., A.H., A.L., R.H.H., M.F., K.R.P., J.H., C.H.B, and W.R.L. writing-editing and review.

Author ORCIDs—Christoph H. Borchers http://orcid.org/0000-0003-2394-6512; William R. Lagor http://orcid.org/0000-0002-1703-5125

Funding and additional information—This work was supported by the National Institutes of Health (HL132840 and DK124477 to W.R.L.; T32HL07676 and T32GM08321 to K.E.J.; T32HL07676 to A.M.D.; and R01-HL132840-02S1 to M.F.), the American Heart Association (19POST34430092 to M.D.G. and 19PRE34380467 to A.M.D.). This work was also supported by the Texas Digestive Diseases Morphology Core (P30DK56338) and the Integrated Microscopy Core (DK56338 and CA125123). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Conflict of interest—The authors declare that they have no conflicts of interest with the contents of this article.

Abbreviations

    Aat

    α-1 antitrypsin

    ALP

    alkaline phosphatase

    ALT

    alanine aminotransferase

    Dhdds

    dehydrodolichyl diphosphate synthase subunit

    DKO

    double KO

    GC

    genome copy

    gRNA

    guide RNA

    Hmgcr

    HMG-CoA reductase

    HLP

    hybrid liver-specific promoter

    Insig

    insulin-induced gene

    LSKO

    liver-specific KO

    PDSS

    prenyl diphosphate synthase

    SaCas9

    Staphylococcus aureus Cas9

.

Manuscript received June 26, 2020, and in revised form October 12, 2020. Published, JLR Papers in Press, October 27, 2020, DOI 10.1194/jlr.RA120001006.