Participation of proteasome-ubiquitin protein degradation in autophagy and the activation of AMP-activated protein kinase.
Although activation of the AMP-activated protein kinase (AMPK) as well as of ubiquitin/proteasome degradative pathways play an essential role in the preservation of metabolic homeostasis, little is known concerning interactions between protein turnover and AMPK activity. In the present studies, we found that inhibition of the 26S proteasome resulted in rapid activation of AMPK in macrophages, epithelial and endothelial cells. This was associated with increased levels of non-degraded Ub-protein conjugates, in both cytosolic and mitochondrial fractions. Selective inhibitors of ubiquitination or siRNA-dependent knockdown of Ub-ligase E1 diminished AMPK activation in cells treated with MG132, a 26S proteasome inhibitor. In addition to inhibition of AMPK activation by Ub-ligase E1 inhibitors, deficiency in Park2 mitochondria-associated Ub-ligase E3 also reduced AMPK activation upon dissipation of mitochondrial membrane potential (Δψm). Accumulation of Ub-proteins was correlated with decreases in cellular bioenergetics, including mitochondria oxidative phosphorylation, and an increase in ROS formation. Antioxidants, such as N-acetyl-L-cysteine or mitochondria-targeted MitoTEMPO, effectively diminished MG132-induced AMPK activation. Glucose-dependent regulation of AMPK or AMPK-mediated autophagy was modulated by alterations in intracellular levels of Ub-protein conjugates. Our results indicate that accumulation of ubiquitinated proteins alter cellular bioenergetics and redox status, leading to AMPK activation.
Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294-0012, USA.
Shaoning
S
Jiang
Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294-0012, USA; Division of Infectious Diseases, Korea University Ansan Hospital, Ansan 425-707, Republic of Korea.
Dae Won
DW
Park
Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294-0012, USA.
Yong
Y
Gao
Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294-0012, USA; Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, AL 35294-0012, USA.
Saranya
S
Ravi
Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294-0012, USA; Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, AL 35294-0012, USA.
Victor
V
Darley-Usmar
Office of the Dean, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
Edward
E
Abraham
Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294-0012, USA; Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, AL 35294-0012, USA. Electronic address: zmijewsk@uab.edu.
Jaroslaw W
JW
Zmijewski
D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001343:Autophagy / Q000187:drug effects; D002460:Cell Line; D057809:HEK293 Cells; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism; D010085:Oxidative Phosphorylation / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D059748:Proteolysis / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination / Q000187:drug effects
D000975:Antioxidants; D007976:Leupeptins; D017382:Reactive Oxygen Species; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; C111567:parkin protein; D055372:AMP-Activated Protein Kinases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde
AMP kinase; Autophagy; Bioenergetics; PARK2; Proteasome; Ubiquitination