Disruption of Plin5 degradation by CMA causes lipid homeostasis imbalance in NAFLD

BACKGROUND & AIMS: The pathological hallmark of nonalcoholic fatty liver disease (NAFLD) is an imbalance in hepatic lipid homeostasis, in which lipophagy has been found to play a vital role. However, the underlying molecular mechanisms remain unclear. We investigated the role of chaperone-mediated autophagy (CMA) in the pathogenesis of NAFLD. METHODS: CMA activity was evaluated in liver tissues from NAFLD patients and high-fat diet (HFD)-fed mice. Liver-specific LAMP2A-knockout mice and HepG2 cells lacking LAMP2A [L2A(-) cells] were used to investigate the influence of CMA on lipolysis in hepatocytes. The expression of Plin5, a lipid droplet (LD)-related protein, was also evaluated in human and mouse liver tissues and in [L2A(-)] cells. RESULTS: Here, we found disrupted CMA function in the livers of NAFLD patients and animal models, displaying obvious reduction of LAMP2A and concurrent with decreased levels of CMA-positive regulators. More LDs and higher serum triglycerides accumulated in liver-specific LAMP2A-knockout mice and L2A(-) cells under high-fat challenge. Meanwhile, deleting LAMP2A hindered LD breakdown but not increased LD formation. In addition, the LD-associated protein Plin5 is a CMA substrate, and its degradation through CMA is required for LD breakdown. CONCLUSIONS: We propose that the disruption of CMA-induced Plin5 degradation obstacles LD breakdown, explaining the lipid homeostasis imbalance in NAFLD.