PAS kinase is an evolutionarily conserved serine/threonine protein kinase. Mammalian PAS kinase is activated under nutrient replete conditions and is important for controlling metabolic rate and energy homeostasis. In yeast, PAS kinase acts to increase the synthesis of structural carbohydrate at the expense of storage carbohydrates through phosphorylation of the enzyme UDP-glucose pyrophosphorylase. We have identified two pathways that activate yeast PAS kinase; one is responsive to nutrient conditions while the other is responsive to cell integrity stress. These pathways differentially activate the two PAS kinase proteins in Saccharomyces cerevisiae, Psk1 and Psk2, with Psk1 alone responding to activation by nonfermentative carbon sources. We demonstrate that, in addition to transcriptional effects, both of these pathways post-translationally activate PAS kinase via its regulatory N-terminus. As a whole, this system acts to coordinate glucose partitioning with alterations in demand due to changes in environmental and nutrient conditions.

PAS domain containing protein kinase (Pask) is an evolutionarily conserved protein kinase implicated in energy homeostasis and metabolic regulation across eukaryotic species. We now describe an unexpected role of Pask in promoting the differentiation of myogenic progenitor cells, embryonic stem cells and adipogenic progenitor cells. This function of Pask is dependent upon its ability to phosphorylate Wdr5, a member of several protein complexes including those that catalyze histone H3 Lysine 4 trimethylation (H3K4me3) during transcriptional activation. Our findings suggest that, during myoblast differentiation, Pask stimulates the conversion of repressive H3K4me1 to activating H3K4me3 marks on the promoter of the differentiation gene myogenin (Myog) via Wdr5 phosphorylation. This enhances accessibility of the MyoD transcription factor and enables transcriptional activation of the Myog promoter to initiate muscle differentiation. Thus, as an upstream kinase of Wdr5, Pask integrates signaling cues with the transcriptional network to regulate the differentiation of progenitor cells.DOI: http://dx.doi.org/10.7554/eLife.17985.001

Zinc is essential for function of mitochondria as a cofactor for several matrix zinc metalloproteins. We demonstrate that a labile cationic zinc component of low molecular mass exists in the yeast mitochondrial matrix. This zinc pool is homeostatically regulated in response to the cellular zinc status. This pool of zinc is functionally important because matrix targeting of a cytosolic zinc-binding protein reduces the level of labile zinc and interferes with mitochondrial respiratory function. We identified a series of proteins that modulate the matrix zinc pool, one of which is a novel conserved mitochondrial protein designated Mzm1. Mutant mzm1⌬ cells have reduced total and labile mitochondrial zinc, and these cells are hypersensitive to perturbations of the labile pool. In addition, mzm1⌬ cells have a destabilized cytochrome c reductase (Complex III) without any effects on Complexes IV or V. Thus, we have established that a link exists between Complex III integrity and the labile mitochondrial zinc pool.All known mitochondrial zinc-requiring metalloproteins are synthesized in the cytoplasm and must be imported as newly synthesized polypeptides into the organelle as with most resident proteins. Protein import into the mitochondria requires unfolded polypeptides, so folding and metallation occur upon import. Thus, a bioavailable pool of Zn(II) must be maintained within the mitochondria for efficient metallation reactions. The folding of metalloproteins is dependent on the availability and the selective insertion of the appropriate metal ion. Mis-metallation by a non-native metal ion may be deleterious yielding either an inactive protein or a misfolded state prone to aggregation.The zinc mitochondrial metalloproteome is large relative to other metals and distributed throughout the organelle (1). The zinc proteome is heavily populated by proteases and in yeast include the iAAA, mAAA, Oma1, Oct1, Icp55, Atp23, and the MPP protease complex. These proteases all share an essential HEXXH or HXXEH metal-binding motif and whereas many metalloproteinases can be activated in vitro by diverse divalent cations, Zn(II) is likely to be the physiological metal ion bound.Zn(II) is an abundant cofactor for a variety of additional metalloenzymes in mitochondria, including Adh3, Adh4, and

Summary Elevated hepatic synthesis of fatty acids and triglycerides, driven by hyperactivation of the SREBP-1c transcription factor, has been implicated as a causal feature of the metabolic syndrome. SREBP-1c activation requires the proteolytic maturation of the endoplasmic reticulum-bound precursor to the active, nuclear transcription factor, which is stimulated by feeding and insulin signaling. Here we show that feeding and insulin stimulate the hepatic expression of PASK. We also demonstrate, using genetic and pharmacologic approaches, that PASK is required for the proteolytic maturation of SREBP-1c in cultured cells and in mouse and rat liver. Inhibition of PASK improves lipid and glucose metabolism in dietary animal models of obesity and dyslipidemia. Administration of a PASK inhibitor decreases hepatic expression of lipogenic SREBP-1c target genes, decreases serum triglycerides and partially reverses insulin resistance. While the signaling network that controls SREBP-1c activation is complex, we propose that PASK is an important component with therapeutic potential.

Purpose Many women with major depressive disorder (MDD) respond inadequately to standard treatments. Augmentation of conventional antidepressants with creatine monohydrate and 5-hydroxytryptophan (5-HTP) could correct deficits in serotonin production and brain bioenergetics associated with depression in women, yielding synergistic benefit. We describe an open-label study of 5-HTP and creatine augmentation in women with MDD who had failed selective serotonin reuptake inhibitor (SSRI) or serotonin-norepinephrine reuptake inhibitor (SNRI) monotherapy. Methods 15 women who were adequately adherent to an SSRI or SNRI and currently suffering from MDD, with a 17-item Hamilton Depression Rating Scale (HAM-D) score ≥ 16, were treated with 5g of creatine monohydrate daily and 100mg of 5-HTP twice daily for 8 weeks, with 4 weeks of post-treatment follow-up. The primary outcome was change in mean HAM-D scores. Results Mean HAM-D scores declined from 18.9 ± 2.5 at pretreatment visits to 7.5 ±4.4 (p < 0.00001), a decrease of 60%. Participants did not experience any serious treatment-related adverse events. Conclusions Combination treatment with creatine and 5-HTP may represent an effective augmentation strategy for women with SSRI- or SNRI-resistant depression. Given the limitations of this small, open-label trial, future study in randomized, placebo-controlled trials is warranted.