AMPK is a highly conserved sensor of cellular energy status that is activated under conditions of low intracellular ATP. AMPK responds to energy stress by suppressing cell growth and biosynthetic processes, in part through its inhibition of the rapamycin-sensitive mTOR (mTORC1) pathway. AMPK phosphorylation of the TSC2 tumor suppressor contributes to suppression of mTORC1; however, TSC2-deficient cells remain responsive to energy stress. Using a proteomic and bioinformatics approach, we sought to identify additional substrates of AMPK that mediate its effects on growth control. We report here that AMPK directly phosphorylates the mTOR binding partner raptor on two well-conserved serine residues, and this phosphorylation induces 14-3-3 binding to raptor. The phosphorylation of raptor by AMPK is required for the inhibition of mTORC1 and cell-cycle arrest induced by energy stress. These findings uncover a conserved effector of AMPK that mediates its role as a metabolic checkpoint coordinating cell growth with energy status.

Adenosine monophosphate-activated protein kinase (AMPK) is a conserved sensor of intracellular energy activated in response to low nutrient availability and environmental stress. In a screen for conserved substrates of AMPK, we identified ULK1 and ULK2, mammalian orthologs of the yeast protein kinase Atg1, which is required for autophagy. Genetic analysis of AMPK or ULK1 in mammalian liver and C. elegans revealed a requirement for these kinases in autophagy. In mammals, loss of AMPK or ULK1 resulted in aberrant accumulation of the autophagy adaptor p62 and defective mitophagy. Reconstitution of ULK1-deficient cells with a mutant ULK1 that cannot be phosphorylated by AMPK revealed that such phosphorylation is required for mitochondrial homeostasis and cell survival following starvation. These findings uncover a conserved biochemical mechanism coupling nutrient status with autophagy and cell survival.

The Peutz-Jegher syndrome tumor-suppressor gene encodes a protein-threonine kinase, LKB1, which phosphorylates and activates AMPK [adenosine monophosphate (AMP)-activated protein kinase]. The deletion of LKB1 in the liver of adult mice resulted in a nearly complete loss of AMPK activity. Loss of LKB1 function resulted in hyperglycemia with increased gluconeogenic and lipogenic gene expression. In LKB1-deficient livers, TORC2, a transcriptional coactivator of CREB (cAMP response element-binding protein), was dephosphorylated and entered the nucleus, driving the expression of peroxisome proliferator-activated receptor-gamma coactivator 1alpha (PGC-1alpha), which in turn drives gluconeogenesis. Adenoviral small hairpin RNA (shRNA) for TORC2 reduced PGC-1alpha expression and normalized blood glucose levels in mice with deleted liver LKB1, indicating that TORC2 is a critical target of LKB1/AMPK signals in the regulation of gluconeogenesis. Finally, we show that metformin, one of the most widely prescribed type 2 diabetes therapeutics, requires LKB1 in the liver to lower blood glucose levels.

Circadian clocks coordinate behavioral and physiological processes with daily light-dark cycles by driving rhythmic transcription of thousands of genes. Whereas the master clock in the brain is set by light, pacemakers in peripheral organs, such as the liver, are reset by food availability, although the setting, or "entrainment," mechanisms remain mysterious. Studying mouse fibroblasts, we demonstrated that the nutrient-responsive adenosine monophosphate-activated protein kinase (AMPK) phosphorylates and destabilizes the clock component cryptochrome 1 (CRY1). In mouse livers, AMPK activity and nuclear localization were rhythmic and inversely correlated with CRY1 nuclear protein abundance. Stimulation of AMPK destabilized cryptochromes and altered circadian rhythms, and mice in which the AMPK pathway was genetically disrupted showed alterations in peripheral clocks. Thus, phosphorylation by AMPK enables cryptochrome to transduce nutrient signals to circadian clocks in mammalian peripheral organs.The mammalian hypothalamic suprachiasmatic nucleus (SCN) acts as a master pacemaker, aligning behavioral and physiological rhythms to light-dark cycles (1). Initially, the SCN was thought to be the only site of self-sustaining molecular pacemakers in mammals, but subsequent reports have shown such clocks to be ubiquitous (2,3). Unlike those in the SCN, clocks in non-light-sensitive organs are entrained by daily feeding (2,4,5), which

SUMMARY The LKB1 (also called STK11) tumor suppressor is mutationally inactivated in ~20% of non-small cell lung cancers (NSCLC). LKB1 is the major upstream kinase activating the energy-sensing kinase AMPK, making LKB1-deficient cells unable to appropriately sense metabolic stress. We tested the therapeutic potential of metabolic drugs in NSCLC and identified phenformin, a mitochondrial inhibitor and analog of the diabetes therapeutic metformin, as selectively inducing apoptosis in LKB1-deficient NSCLC cells. Therapeutic trials in Kras-dependent mouse models of NSCLC revealed that tumors with Kras and Lkb1 mutations, but not those with Kras and p53 mutations showed selective response to phenformin as a single agent, resulting in prolonged survival. This study suggests phenformin as a cancer metabolism-based therapeutic to selectively target LKB1-deficient tumors.

SUMMARY Class IIa histone deacetylases (HDACs) are signal-dependent modulators of transcription with established roles in muscle differentiation and neuronal survival. We show here that in liver, Class IIa HDACs (HDAC4, 5, and 7) are phosphorylated and excluded from the nucleus by AMPK family kinases. In response to the fasting hormone glucagon, Class IIa HDACs are rapidly dephosphorylated and translocated to the nucleus where they associate with the promoters of gluconeogenic enzymes such as G6Pase. In turn, HDAC4/5 recruit HDAC3, which results in the acute transcriptional induction of these genes via deacetylation and activation of Foxo family transcription factors. Loss of Class IIa HDACs in murine liver results in inhibition of FOXO target genes and lowers blood glucose, resulting in increased glycogen storage. Finally, suppression of Class IIa HDACs in mouse models of Type 2 Diabetes ameliorates hyperglycemia, suggesting that inhibitors of Class I/II HDACs may be potential therapeutics for metabolic syndrome.

Peutz-Jeghers syndrome (PJS) is a familial cancer disorder due to inherited loss of function mutations in the LKB1/ STK11 serine/ threonine kinase. PJS patients develop gastrointestinal hamartomas with 100% penetrance often in the second decade of life, and demonstrate an increased predisposition toward the development of a number of additional malignancies. Among mitogenic signaling pathways, the mammalian-target of rapamycin complex 1 (mTORC1) pathway is hyperactivated in tissues and tumors derived from LKB1-deficient mice. Consistent with a central role for mTORC1 in these tumors, rapamycin as a single agent results in a dramatic suppression of preexisting GI polyps in LKB1؉/؊ mice. However, the key targets of mTORC1 in LKB1-deficient tumors remain unknown. We demonstrate here that these polyps, and LKB1-and AMPK-deficient mouse embryonic fibroblasts, show dramatic up-regulation of the HIF-1␣ transcription factor and its downstream transcriptional targets in an rapamycin-suppressible manner. The HIF-1␣ targets hexokinase II and Glut1 are up-regulated in these polyps, and using FDG-PET, we demonstrate that LKB1؉/؊ mice show increased glucose utilization in focal regions of their GI tract corresponding to these gastrointestinal hamartomas. Importantly, we demonstrate that polyps from human PeutzJeghers patients similarly exhibit up-regulated mTORC1 signaling, HIF-1␣, and GLUT1 levels. Furthermore, like HIF-1␣ and its target genes, the FDG-PET signal in the GI tract of these mice is abolished by rapamycin treatment. These findings suggest a number of therapeutic modalities for the treatment and detection of hamartomas in PJS patients, and potential for the screening and treatment of the 30% of sporadic human lung cancers bearing LKB1 mutations.AMPK ͉ FDG-PET ͉ glycolysis ͉ hamartoma ͉ polyposis

The treatment of HIV-associated lymphoma has changed since the widespread use of highly active antiretroviral therapy. HIV-infected individuals can tolerate more intensive chemotherapy, as they have better hematologic reserves and fewer infections. This has led to higher response rates in patients with HIV-associated Hodgkin disease (HD) or non-Hodgkin lymphoma (NHL) treated with chemotherapy in conjunction with antiretroviral therapy. However, for patients with refractory or relapsed disease, salvage chemotherapy still offers little chance of long-term survival. In the non-HIV setting, patients with relapsed Hodgkin disease (HD) or non-Hodgkin lymphoma (NHL) have a better chance of long-term remission with high-dose chemotherapy with autologous stem cell rescue (ASCT) compared with conventional salvage chemotherapy. IntroductionThe incidence of Hodgkin disease (HD) and non-Hodgkin lymphoma (NHL) in HIV-infected individuals is much greater than in the HIV-negative population. 1,2 In earlier decades the treatment of lymphoma in the setting of immune deficiency was far less successful than in the HIV-negative patient. 3 This was in part due to the poor hematologic reserves of HIV-infected patients but was also due to higher rates of infection and higher rates of relapse of the lymphoma. The advent of highly active antiretroviral therapy (HAART) altered the natural history of HIV infection by reducing the incidence of opportunistic infections and improving the underlying immune deficiency. 4 In addition, combining HAART with chemotherapy or consolidating chemotherapy with HAART has increased remission rates in both HIV-associated Hodgkin and non-Hodgkin lymphoma. 5,6 Recent studies also have confirmed that the International Prognostic Index (IPI) is applicable to patients treated with HAART and chemotherapy. 7 For HIV-infected lymphoma patients with high-risk features as defined by the IPI, relapse rates are still high after conventional chemotherapy. Furthermore, for HIV-infected patients with either relapsed HD or NHL the current salvage chemotherapy regimens offer little chance of long-term survival.In the HIV-negative setting, studies have shown that high-dose therapy with autologous stem cell transplant (ASCT) is the optimal therapy for relapsed HD and NHL. [8][9][10] As the procedure-related mortality of ASCT has decreased, ongoing studies are exploring its use in high-risk first remission patients. 10 Now that HIV-infected individuals have markedly improved immune and hematologic function, the use of both solid organ and ASCT is being explored in patients with underlying immunodeficiency and concomitant malignancy or organ dysfunction. 11-15 Herein we report the City of Hope Comprehensive Cancer Center experience on the largest single institution series of patients with HIV-associated lymphomas undergoing ASCT. Our initial experience demonstrated the feasibility of this approach in terms of stem cell mobilization, engraftment, and low regimen-related toxicity. 16 Now with long-term follow-up in a larger ser...