Lipid Droplet Formation and Autophagy

Abstract

Objective: Lipid droplets (LDs) are cytoplasmic inclusions that have a neutral lipid core with a single phospholipid layer, while excess free fatty acids and glucose in plasma are converted to triacylglycerol (TAG) and stored as LDs. However, the mechanism for the generation and growth of LDs in cells is largely unknown. This review will explain the relationship between LD formation and autophagy.

Results: LD formation accompanied by accumulation of TAG induced by starvation was largely suppressed in the hepatocytes and cardiac myocytes that cannot execute autophagy. Under starvation conditions, LDs in addition to autophagosomes were abundantly formed in the cytoplasm of these tissue cells, although autophagosomes did not appear in wild-type and autophagy-unable cardiac myocytes. Moreover, LC3 was localized on the surface of LDs and LC3-II (lipidation form) was fractionated to a perilipin-positive lipid fraction from the starved liver.

Conclusion: Taken together, these results indicate that the LC3 conjugation system is critically involved in lipid metabolism via LD formation.