Induction of lysosomal and mitochondrial biogenesis by AMPK phosphorylation of FNIP1

Cells respond to mitochondrial poisons with rapid activation of the adenosine monophosphate-activated protein kinase (AMPK), causing acute metabolic changes through phosphorylation and prolonged adaptation of metabolism through transcriptional effects. Transcription factor EB (TFEB) is a major effector of AMPK that increases expression of lysosome genes in response to energetic stress, but how AMPK activates TFEB remains unresolved. We demonstrate that AMPK directly phosphorylates five conserved serine residues in folliculin-interacting protein 1 (FNIP1), suppressing the function of the folliculin (FLCN)-FNIP1 complex. FNIP1 phosphorylation is required for AMPK to induce nuclear translocation of TFEB and TFEB-dependent increases of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) and estrogen-related receptor alpha (ERRα) messenger RNAs. Thus, mitochondrial damage triggers AMPK-FNIP1-dependent nuclear translocation of TFEB, inducing sequential waves of lysosomal and mitochondrial biogenesis.

HDAC3 is critical in tumor development and therapeutic resistance in Kras-mutant non-small cell lung cancer

HDAC3 is one of the main targets of histone deacetylase (HDAC) inhibitors in clinical development as cancer therapies, yet the in vivo role of HDAC3 in solid tumors is unknown. We identified a critical role for HDAC3 in Kras-mutant lung cancer. Using genetically engineered mouse models (GEMMs), we found that HDAC3 is required for lung tumor growth in vivo. HDAC3 was found to direct and enhance the transcription effects of the lung cancer lineage transcription factor NKX2-1 to mediate expression of a common set of target genes. We identified FGFR1 as a critical previously unidentified target of HDAC3. Leveraging this, we identified that an HDAC3-dependent transcriptional cassette becomes hyperactivated as Kras/LKB1-mutant cells develop resistance to the MEK inhibitor trametinib, and this can be reversed by treatment with the HDAC1/HDAC3 inhibitor entinostat. We found that the combination of entinostat plus trametinib treatment elicits therapeutic benefit in the Kras/LKB1 GEMM.

Genetic Analysis Reveals AMPK Is Required to Support Tumor Growth in Murine Kras-Dependent Lung Cancer Models

AMPK, a conserved sensor of low cellular energy, can either repress or promote tumor growth depending on the context. However, no studies have examined AMPK function in autochthonous genetic mouse models of epithelial cancer. Here, we examine the role of AMPK in murine Kras^G12D-mediated non-small-cell lung cancer (NSCLC), a cancer type in humans that harbors frequent inactivating mutations in the LKB1 tumor suppressor-the predominant upstream activating kinase of AMPK and 12 related kinases. Unlike LKB1 deletion, AMPK deletion in Kras^G12D lung tumors did not accelerate lung tumor growth. Moreover, deletion of AMPK in Kras^G12D p53^f/f tumors reduced lung tumor burden. We identified a critical role for AMPK in regulating lysosomal gene expression through the Tfe3 transcription factor, which was required to support NSCLC growth. Thus, AMPK supports the growth of Kras^G12D-dependent lung cancer through the induction of lysosomes, highlighting an unrecognized liability of NSCLC.

Reciprocal zones of excitation and inhibition in the neostriatum

Single-unit activity was recorded in the rat neostriatum at different distances from the point of an infusion of either glutamate or serotonin. In each case, firing rate at the distant site (0.8-1.5 mm) was the mirror image of that at the near site (0.1-0.3 mm). These reciprocal changes were blocked by a subsequent injection of haloperidol, a dopamine antagonist. It appears that a lateral inhibitory network, intrinsic to the neostriatum and possibly modulated by dopamine, plays an important role in the operation of the neostriatum.

Reciprocal changes in the firing rate of neostriatal and dorsal raphe neurons following local infusions or systemic injections of D-amphetamine: evidence for neostriatal heterogeneity

A local infusion of d-amphetamine (d-AMPH) into the dorsal raphe nucleus (DRN) inhibited neuronal activity in this site and produced a mirror-image excitation in the ventrolateral, but not dorsomedial, neostriatum. This effect, which was mimicked by 5-methoxy-N,N-dimethyltryptamine, a serotonin autoreceptor agonist, was not altered by pretreatment with alpha-methyl-p-tyrosine. Similar regional differences in neostriatal activity were obtained following an electrolytic lesion of the DRN or an intraperitoneal injection of d-AMPH. In fact, whereas 1.0 mg/kg of d-AMPH accelerated ventrolateral activity and inhibited dorsomedial neurons, 7.5 mg/kg produced the opposite effect. At both doses, however, DRN activity was inversely related to firing rate in the ventrolateral, but not dorsomedial, neostriatum. These results indicate that only certain regions of the neostriatum are responsive to changes in DRN activity and that these regions respond differently to systemic injections of d-AMPH than other neostriatal sites.

Dorsal raphe neurons: self-inhibition by an amphetamine-induced release of endogenous serotonin

A direct infusion of amphetamine into the dorsal raphe nucleus of the rat inhibited the activity of serotonergic neurons in this site. An intravenous injection of 5-methoxy-N,N-dimethyltryptamine, a serotonin autoreceptor agonist, mimicked this effect. The amphetamine-induced depression of firing rate was blocked by a subsequent injection of methiothepin, a putative serotonin autoreceptor antagonist, but not by pretreatment with a-methyl-p-tyrosine which depletes brain catecholamines. Amphetamine infusions into the surrounding periaqueductal gray or brainstem reticular formation failed to change dorsal raphe activity. The results of these studies indicate that endogenous serotonin, which can be released by a direct infusion of amphetamine, suppresses neuronal activity in the dorsal raphe nucleus by a process of self-inhibition.

Apparent serotonergic modulation of the dose-dependent biphasic response of neostriatal neurons produced by D-amphetamine

Previous reports indicate that amphetamine produces a dose-dependent shift to the firing rate of neurons in the anterior neostriatum that parallels the shift in behavior from locomotion to focused stereotypy. To determine if para-chlorophenylalanine (PCPA), which alters the pattern of the behavioral response to amphetamine, also changes the pattern of the neuronal response to the drug, a dose-response analysis was performed on amphetamine-induced changes in unit activity in the anterior neostriatum of rats pretreated 48 h previously with 300 mg/kg PCPA or vehicle. An intraperitoneal injection of 1.0 mg/kg D-amphetamine, which inhibited neostriatal activity in vehicle controls, produced in PCPA-pretreated animals a prolonged excitation. In contrast, the pronounced increase in firing rate produced by 7.5 mg/kg D-amphetamine in control rats was significantly reduced following PCPA pretreatment. Liquid chromatography with electrochemical detection revealed that compared to controls, PCPA produced a significant reduction of serotonin, but not dopamine or norepinephrine, in the telencephalon. The differential effects of PCPA on the action of low and high doses of D-amphetamine in the anterior neostriatum may explain the differential influence of serotonergic systems on amphetamine-induced locomotion add stereotypy.