Mitophagy에서 리소좀 Ca2+ 에 의한 TFEB 활성화 및 ER -> 리소좀 Ca2+ refilling [Autophagy]
2022년 9월 6일 (화) 오전 10시 (한국시간)
세미나 개요 Although the role of pancreatic β-cell macroautophagy/autophagy is well known, that of β-cell mitophagy is unclear. We investigated the changes of lysosomal Ca2+ by mitochondrial or metabolic stress that can modulate TFEB activation and, additionally, the role of TFEB-induced mitophagy in β-cell function. Mitochondrial or metabolic stress induces mitophagy, which is mediated by lysosomal Ca2+ release, increased cytosolic [Ca2+] and subsequent TFEB activation. Lysosomal Ca2+ release is replenished by ER→lysosome Ca2+ refilling through ER Ca2+ exit channels, which is important for the increase of cytosolic [Ca2+] and mitophagy by mitochondrias tressors. High-fat diet (HFD) feeding imposing metabolic stress in vivo augments pancreatic β-cell mitophagy, probably as an adaptation to metabolic stress. HFD-induced increase of β-cell mitophagy is reduced by tfeb KO, leading to increased ROS and decreased mitochondrial complex activity or oxygen consumption in tfeb-KO islets. In tfeb△β-cell mice, HFD-induced glucose intolerance and β-cell dysfunction are aggravated. Expression of mitophagy receptor genes including Optn or Calcoco2 is increased by mitochondrial or metabolic stressors in a TFEB-dependent manner, likely contributing to increased mitophagy. These results suggest that lysosomal Ca2+ release in conjunction with ER→lysosome Ca2+ refilling is important for TFEB activation and mitophagy induction, which contributes to pancreatic β-cell adaptation to metabolic stress.