Thyroid hormone induction of mitochondrial activity is coupled to mitophagy via ROS-AMPK-ULK1 signaling

Area of Science:

• Cell Biology
• Endocrinology
• Mitochondrial Biology

Background:

• Mitochondrial turnover is crucial for cellular health.
• Thyroid hormone (T3) enhances oxidative phosphorylation (OXPHOS), increasing reactive oxygen species (ROS) and potential mitochondrial damage.
• The mechanisms by which T3 maintains mitochondrial quality control remain unclear.

Purpose of the Study:

• To elucidate the hormonal regulation of mitochondrial turnover.
• To investigate the role of T3 in mitophagy and mitochondrial quality control.
• To identify the molecular pathway linking T3-induced ROS to mitophagy.

Main Methods:

• In vitro and in vivo hepatic cell models were utilized.
• Investigated the effects of T3 on oxidative phosphorylation, ROS production, and mitophagy.
• Utilized molecular techniques to examine the roles of CAMKK2, AMPK, and ULK1 in the T3 response.

Main Results:

• T3-induced ROS activates the CAMKK2-AMPK pathway, leading to ULK1 phosphorylation and mitochondrial recruitment.
• This pathway initiates mitophagy, a selective form of autophagy targeting damaged mitochondria.
• ULK1 deficiency in T3-treated cells impaired mitophagy and OXPHOS, but not general autophagy or lipophagy.

Conclusions:

• A novel ROS-AMPK-ULK1 signaling axis couples T3-induced mitochondrial activity with mitophagy.
• Mitophagy is essential for removing damaged mitochondria and sustaining efficient OXPHOS under T3 stimulation.
• This pathway highlights a critical mechanism for maintaining mitochondrial homeostasis regulated by thyroid hormone.