Copper is an essential regulator of the autophagic kinases ULK1/2 to drive lung adenocarcinoma

Abstract

Targeting aberrant kinase activity in cancer relies on unmasking cellular inputs such as growth factors, nutrients, and metabolites that contribute to cancer initiation and progression 1 . While the transition metal copper (Cu) is an essential nutrient that is traditionally viewed as a static cofactor within enzyme active sites 2 , a newfound role for Cu as a modulator of kinase signaling is emerging 3,4 . We discovered that Cu is required for the activity of the autophagic kinases ULK1/2 through a direct Cu-ULK1/2 interaction. Genetic loss of the Cu transporter Ctr1 or mutations in ULK1 that disrupt Cu-binding reduced ULK1/2-dependent signaling and autophagosome complex formation. Elevated intracellular Cu levels are associated with starvation induced autophagy and sufficient to enhance ULK1 kinase activity and in turn autophagic flux. Targeting autophagy machinery is a promising therapeutic strategy in cancers 5 , but is limited by the absence of potent inhibitors and the emergence of resistance. The growth and survival of lung tumors driven by KRAS G12D is diminished in the absence of Ctr1, depends on ULK1 Cu-binding, and is associated with reduced autophagy levels and signaling. These findings suggest a new molecular basis for exploiting Cu-chelation therapy to forestall autophagy signaling to limit proliferation and survival in cancer.By default, the dynamic and adaptive nature of signaling networks allows them to respond and, in some cases, sense extracellular and intracellular inputs 6 . While growth factors, nutrients, and metabolites are well-appreciated regulators of cell proliferation, the contribution of transition metals to cellular processes that support proliferation and contribute to malignant transformation are understudied. The transition metal copper (Cu) is essential for a diverse array of biological processes from cellular proliferation, neuropeptide processing, free radical detoxification, and

Sestrin2 Phosphorylation by ULK1 Induces Autophagic Degradation of Mitochondria Damaged by Copper-Induced Oxidative Stress

“…In addition, previous studies established that ULK1 can phosphorylate Sestrin2 and phosphorylated Sestrin2 activates ULK1 activity toward p62 phosphorylation as an autophagy induction signal [ 29 ]. Consistent with our work, Cu has been suggested to modulate autophagy signaling through direct interaction with ULK kinases in lung adenocarcinoma [ 42 ]. Moreover, Sestrins were reported to colocalize with mitochondria and regulate mitochondrial functions in C. elegans and human lung adenocarcinoma A549 cells [ 65 ].…”

“…Moreover, we have also observed previously that Sestrin2 can be phosphorylated by ULK1 [ 29 ]. In recent studies on lung carcinoma, ULK kinases were reported to induce autophagy by directly sensing the level of Cu [ 42 ]. We therefore interrogated the nature of these modifications and examined their role in the autophagic clearance of damaged mitochondria in our model.…”

“…Facile redox cycling of Cu between two oxidation states, Cu + [Cu (I)] and Cu 2+ [Cu (II)], can associate with generation of deleterious ROS [ 32 , 33 , 34 , 35 ]. When Cu is in excess, oxidative stress caused by Cu-catalyzed ROS is a well-established mechanism of mitochondrial damage [ 36 , 37 , 38 ], metabolic dysfunction [ 39 , 40 ], and autophagy induction [ 41 , 42 ] in the cells and tissues. Indeed, Cu has been shown to form bioactive complexes with various compounds and signaling molecules—thiosemicarbazone (Dp44mT) [ 43 ], HYF127c [ 44 ], BNMPH [ 45 ], Casiopeina III-ia [ 46 ], ETDPA [ 47 ], and ULK kinases [ 42 ]—to induce autophagy.…”

Structural and molecular determinants of CCS-mediated copper activation of MEK1/2

“…The cellular contexts in which a labile Cu pools is liberated are under active investigation. Two recent reports provide evidence of this phenomena in which depletion of the intracellular glutathione pools (Chung et al, 2019) or amino acid deprivation (Tsang et al, 2020) were sufficient to elevate Cu(I) levels. Further, both basal and growth factor stimulated MAPK signaling were diminished when point mutants of the Cu coordinating ligands were introduced, which suggests that Cu is a hardwired component of the pathway that is necessary for the other inputs.…”

Current Biomedical Use of Copper Chelation Therapy

“…Different lines of evidence suggest that increased copper content activates a series of autophagy-related genes [154]. Accordingly, copper chelation using TM has been shown to inhibit the Unc-51-like autophagy activating kinase 1 and 2 (Ulk1/2) in lung adenocarcinoma cells [155]. Recently, the combination of copper chelation with TM and autophagy inhibition by chloroquine has been evaluated to promote pancreatic cancer cells death [156].…”