Localization of AMP kinase is regulated by stress, cell density, and signaling through the MEK→ERK1/2 pathway

Abstract

5'-AMP-activated protein kinase (AMPK) serves as an energy sensor and is at the center of control for a large number of metabolic reactions, thereby playing a crucial role in Type 2 diabetes and other human diseases. AMPK is present in the nucleus and cytoplasm; however, the mechanisms that regulate the intracellular localization of AMPK are poorly understood. We have now identified several factors that control the distribution of AMPK. Environmental stress regulates the intracellular localization of AMPK, and upon recovery from heat shock or oxidant exposure AMPK accumulates in the nuclei. We show that under normal growth conditions AMPK shuttles between the nucleus and the cytoplasm, a process that depends on the nuclear exporter Crm1. However, nucleocytoplasmic shuttling does not take place in high-density cell cultures, for which AMPK is confined to the cytoplasm. Furthermore, we demonstrate that signaling through the mitogen-activated protein kinase kinase (MEK)-->extracellular signal-regulated kinase 1/2 (ERK1/2) cascade plays a crucial role in controlling the proper localization of AMPK. As such, pharmacological inhibitors that interfere with this pathway alter AMPK distribution under nonstress conditions. Taken together, our studies identify novel links between the physiological state of the cell, the activation of MEK-->ERK1/2 signaling, and the nucleocytoplasmic distribution of AMPK. This sets the stage to develop new strategies to regulate the intracellular localization of AMPK and thereby the modification of targets that are relevant to human disease.

The active form of the metabolic sensor AMP-activated protein kinase α (AMPKα) directly binds the mitotic apparatus and travels from centrosomes to the spindle midzone during mitosis and cytokinesis

“…These findings expand earlier studies revealing that there is no direct link between the phosphorylation of Thr172 of AMPKα and the subcellular localization of total AMPKα. 32 Co-staining analyses of P-AMPKα Thr172 and α-tubulin in early and late stages of mitosis. At prophase, as chromosomes condense and the replicated centrosomes begin to separate, P-AMPKα Thr172 appeared to associate closely with the two asters of α-tubulin stained microtubules that begin to nucleate from mature centrosomes (Fig.…”

Metabolic Stress Modulates Motor Patterning via AMP-Activated Protein Kinase

“…Since NaN 3 is known to increase AMPK activity in other cell types (Jing and Ismail-Beigi, 2007;Guan et al, 2008;Kréneisz et al, 2009) we suggest that AMPK could be activated in the locust ventilatory neuropile in response to NaN 3 . AMPK activation can occur via different mechanisms (Hardie and Hawley, 2001;Lindsley and Rutter, 2004;Kodiha et al, 2007), and it is likely that AMPK was activated through different pathways in response to NaN 3 and AICAR. Given that AICAR induced rhythm changes without inducing SD, we conclude that AMPK is sufficient for the motor pattern changes induced by chemical anoxia.…”

Targeting AMPK for Therapeutic Intervention in Type 2 Diabetes

“…Our current model of AMPK trafficking proposes that the kinase shuttles between the nucleus and the cytoplasm. Data from our group and others support this idea, as they demonstrated that the nuclear carrier Crm1 is essential for AMPK export from the nucleus to the cytoplasm (Kazgan et al, 2010;Kodiha et al, 2007). How the subunit impacts the proper targeting of the holoenzyme is at present not entirely clear.…”

“…The list of AMPK substrates was compiled from PhosphoSitePlus (phosphosite.org). AMPK is found in the nucleus and cytoplasm which reflects functions for the enzyme in both locations (Kodiha et al, 2007;Witczak et al, 2008). Although the kinase is associated with multiple compartments, 1 and 2 subunits differ in their nucleocytoplasmic distribution.…”

“…It was proposed that AMPK concentrates in the cytoplasm when the heterotrimeric enzyme contains the 1 subunit (Suzuki et al, 2007). However, this model is difficult to reconcile with the fact that both 1 and 2 subunits can be detected in the nucleus (Kodiha et al, 2007). Furthermore, recent studies suggest that the myristoylation of 1 and 2 subunit is particularly important for AMPK activation, as AMPdependent myristoylation provides a switch that triggers Thr172 phosphorylation (Oakhill et al, 2010).…”