Loss of hepatic chaperone-mediated autophagy accelerates proteostasis failure in aging

Area of Science:

• Cellular Biology
• Aging Research
• Proteostasis

Background:

• Chaperone-mediated autophagy (CMA) is crucial for protein quality control by degrading cytosolic proteins via lysosomes.
• CMA function declines with age, impacting cellular health and proteostasis.
• Understanding CMA's role in aging liver is vital for addressing age-related diseases.

Purpose of the Study:

• To investigate the impact of impaired CMA on liver proteostasis in aging mice.
• To identify compensatory mechanisms and their limitations in response to CMA deficiency.
• To elucidate the contribution of CMA malfunction to age-associated hepatic dysfunction.

Main Methods:

• Utilized a mouse model with liver-specific defective chaperone-mediated autophagy (CMA).
• Analyzed proteostasis, stress resistance, and drug metabolism in young and old mice with impaired CMA.
• Compared CMA-deficient livers to controls to assess compensatory proteolytic systems.

Main Results:

• In young mice, other proteolytic systems partially compensated for CMA loss, maintaining proteostasis.
• Compensatory mechanisms were insufficient against proteotoxicity from stress or aging.
• Old mice with CMA blockage showed altered protein homeostasis, increased oxidative stress susceptibility, impaired drug metabolism, and worsened metabolic dysregulation.

Conclusions:

• CMA's regulatory role is essential and cannot be fully compensated for, even in young organisms.
• While other systems can handle CMA's protein degradation role initially, their age-related decline limits compensatory capacity.
• CMA malfunction significantly contributes to age-associated decline in proteostasis and stress resistance, leading to severe hepatic dysfunction in older individuals.