Alcohol-induced microtubule acetylation leads to the accumulation of large, immobile lipid droplets

• Published in: American journal of physiology: Gastrointestinal and liver physiology 2019-10, Vol.317 (4), p.G373-G386
• Main Authors: Groebner, Jennifer L, Girón-Bravo, Marlene T, Rothberg, Mia L, Adhikari, Raghabendra, Tuma, Dean J, Tuma, Pamela L
• Format: Article
• Language: English
• Subjects: Acetylation; Acetyltransferase; Acetyltransferases - metabolism; Adipogenesis; Alcohol dehydrogenase; Alcohol Dehydrogenase - metabolism; Cell Line; Central Nervous System Depressants - pharmacology; Dynactin; Dynactin Complex - metabolism; Dynein; Dyneins - metabolism; Ethanol; Ethanol - pharmacology; Fatty liver; Hepatotoxicity; Humans; Kinesin; Life cycles; Lipid Droplets - drug effects; Lipid Droplets - metabolism; Lipid Metabolism - drug effects; Lipids; Liver diseases; Lymphocytes B; Microtubule Proteins - metabolism; Microtubules; Microtubules - drug effects; Microtubules - metabolism; Motility; Oleic acid; Oleic Acids - pharmacology; Protein transport; Steatosis; Tubulin
• ISSN: 0193-1857; 1522-1547
• DOI: 10.1152/ajpgi.00026.2019

Although steatosis (fatty liver) is a clinically well-described early stage of alcoholic liver disease, surprisingly little is known about how it promotes hepatotoxicity. We have shown that ethanol consumption leads to microtubule hyperacetylation that can explain ethanol-induced defects in protein trafficking. Because almost all steps of the lipid droplet life cycle are microtubule dependent and because microtubule acetylation promotes adipogenesis, we examined droplet dynamics in ethanol-treated cells. In WIF-B cells treated with ethanol and/or oleic acid (a fatty acid associated with the "Western" diet), we found that ethanol dramatically increased lipid droplet numbers and led to the formation of large, peripherally located droplets. Enhanced droplet formation required alcohol dehydrogenase-mediated ethanol metabolism, and peripheral droplet distributions required intact microtubules. We also determined that ethanol-induced microtubule acetylation led to impaired droplet degradation. Live-cell imaging revealed that droplet motility was microtubule dependent and that droplets were virtually stationary in ethanol-treated cells. To determine more directly whether microtubule hyperacetylation could explain impaired droplet motility, we overexpressed the tubulin-specific acetyltransferase αTAT1 to promote microtubule acetylation in the absence of alcohol. Droplet motility was impaired in αTAT1-expressing cells but to a lesser extent than in ethanol-treated cells. However, in both cases, the large immotile droplets (but not small motile ones) colocalized with dynein and dynactin (but not kinesin), implying that altered droplet-motor microtubule interactions may explain altered dynamics. These studies further suggest that modulating cellular acetylation is a potential strategy for treating alcoholic liver disease. Chronic alcohol consumption with the "Western diet" enhances the development of fatty liver and leads to impaired droplet motility, which may have serious deletrious effects on hepatocyte function.