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2015 ; 27
(6
): 1186-97
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Participation of proteasome-ubiquitin protein degradation in autophagy and the
activation of AMP-activated protein kinase
#MMPMID25728513
Jiang S
; Park DW
; Gao Y
; Ravi S
; Darley-Usmar V
; Abraham E
; Zmijewski JW
Cell Signal
2015[Jun]; 27
(6
): 1186-97
PMID25728513
show ga
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
(??m). 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.