Proteasome inhibitors induce AMPK activation via CaMKKβ in human breast cancer cells

Abstract

The purpose of present study is to examine the mechanism of the 5'-AMP-activated protein kinase (AMPK) activation induced by proteasome inhibitors. AMPK activation and ubiquitin proteasome system (UPS) inhibition have gained great attention as therapeutic strategies for the treatment of certain types of cancers. While AMPK serves as a master regulator of cellular metabolism, UPS regulates protein homeostasis. However, the relationship between these two important pathways is not very clear. We observe that proteasome inhibition leads to AMPK activation in human breast cancer cells. siRNA transfection, western blotting, qPCR, and proteasomal inhibition assays were used to study the mechanism of proteasome inhibitor-induced AMPK activation using human triple-negative breast cancer, lung, and cervical cancer cell lines. We report that a variety of proteasome inhibitors activate AMPK in all the tested different cancer cell lines. Our data using liver kinase B1-deficient cancer cells suggest that proteasome inhibitor-induced AMPK activation is primarily mediated by Calcium/Calmodulin-dependent kinase kinase β (CaMKKβ). This hypothesis is supported by that pharmacological or genetic inhibition of CaMKKβ leads to a decrease in proteasome inhibitor-induced AMPK activation. Additionally, the AMPK-activating function of the FDA-approved proteasome inhibitor bortezomib depends on an increase in intracellular calcium levels as calcium chelation abrogates its induced AMPK activation. Finally, bortezomib-mediated upregulation in CaMKKβ levels is due to its enhanced protein synthesis. These data suggest that proteasome inhibitors indirectly activate AMPK in human cancer cells primarily via Ca(2+)-CaMKKβ-dependent pathway.

Lopinavir-Ritonavir Combination Induces Endoplasmic Reticulum Stress and Kills Urological Cancer Cells

“…Previous studies demonstrated that ER stress induced AMPK expression in malignancies (11,12). Furthermore, AMPK is known to act against cancer by suppressing the mTOR pathway (13).…”

“…ER stress induction can also trigger AMPK activation by decreasing cellular ATP levels (27,28). Another important mechanism of AMPK activation is regulation of the AMPK-activating calcium/calmodulin-dependent kinase kinase (CaMKK)-beta by ER stress (12,29,30). Furthermore, our previous studies revealed that ER stress induction is closely associated with AMPK activation (31,32).…”

The Ca 2+ /Calmodulin/CaMKK2 Axis: Nature's Metabolic CaMshaft

“…Perhaps even more significant is the potential for targeting the CaMKK2/CaMKIV signaling axis by using STO-609 as a therapeutic recourse. Several studies have focused on Ca 2+ signaling components, and CaMKK2 in particular, to explore new therapeutic avenues for combatting fatty liver disease and cancer [39,40]. Baicalin, a polyphenolic compound, decreased fat, liver, and whole body weights in HFD-fed mice by inhibiting the CaMKK2-AMPK pathway [39], while bortezomib, a proteasome inhibitor and multiple myeloma therapeutic agent, activated CaMKK2 protein synthesis in human breast cancer cell lines [40].…”

Hypothalamic AMPK as a Regulator of Energy Homeostasis

“…Recent studies identified the ubiquitin proteasome system as a factor regulating AMPK activity directly and indirectly [ 54 , 55 ]. AMPK-related kinases, such as AMPK-related kinase 5 (NUAK1) and microtubule-affinity-regulating kinase 4 (MARK4), are polyubiquitinated in vivo and interact with the deubiquitinating enzyme ubiquitin specific protease-9 (USP9X).…”