Proteasome Inhibition Activates Autophagy-Lysosome Pathway Associated With TFEB Dephosphorylation and Nuclear...

Area of Science:

• Cellular Biology
• Molecular Biology
• Proteostasis

Background:

• The ubiquitin-proteasome pathway (UPS) and autophagy-lysosome pathway (ALP) are key for protein degradation and proteostasis.
• Proteasome inhibition can trigger ALP activation as an adaptive mechanism.
• Transcription Factor EB (TFEB) is a known master regulator of the ALP.

Purpose of the Study:

• To investigate the characteristics of TFEB, including its half-life and degradation pathway.
• To elucidate the role of TFEB in the adaptive activation of the ALP following proteasome inhibition.
• To determine how proteasome impairment affects TFEB's stability, localization, and downstream gene expression.

Main Methods:

• Determined TFEB half-life in neuronal-like and non-neuronal cells.
• Investigated TFEB degradation via the proteasome pathway.
• Analyzed TFEB accumulation, dephosphorylation, and nuclear translocation upon proteasome impairment.
• Quantified the expression of TFEB downstream genes (e.g., LC3, cathepsin D, LAMP1).
• Assessed autophagosome biogenesis and autophagic flux.

Main Results:

• TFEB has a half-life of approximately 13.5 hours and is degraded by the proteasome.
• Proteasome impairment leads to TFEB accumulation, dephosphorylation, and nuclear translocation.
• This TFEB activation significantly upregulates ALP genes, including LC3-II, cathepsin D, and LAMP1.
• Proteasome inhibition enhances autophagosome biogenesis without disrupting autophagic flux.

Conclusions:

• TFEB exhibits specific degradation characteristics and is stabilized by proteasome impairment.
• TFEB acts as a crucial mediator linking proteasome dysfunction to ALP activation.
• This study enhances understanding of TFEB's role in cellular adaptive responses to proteotoxic stress.