1.Targeted proteomics identify metabolism-dependent interactors of yeast cytochrome c peroxidase: implications in stress response and heme trafficking.
Kathiresan M1, English AM1. Metallomics. 2016 Mar 16. [Epub ahead of print]
Recently we discovered that cytochrome c peroxidase (Ccp1) functions primarily as a mitochondrial H2O2 sensor and heme donor in yeast cells. When cells switch their metabolism from fermentation to respiration mitochondrial H2O2 levels spike, and overoxidation of its polypeptide labilizes Ccp1's heme. A large pool of heme-free Ccp1 exits the mitochondria and enters the nucleus and vacuole. To gain greater insight into the mechanisms of Ccp1's H2O2-sensing and heme-donor functions during the cell's different metabolic states, here we use glutathione-S-transferase (GST) pulldown assays, combined with 1D gel electrophoresis and mass spectrometry to probe for interactors of apo- and holoCcp1 in extracts from 1 d fermenting and 7 d stationary-phase respiring yeast. We identified Ccp1's peroxidase cosubstrate Cyc1 and 28 novel interactors of GST-apoCcp1 and GST-holoCcp1 including mitochondrial superoxide dismutase 2 (Sod2) and cytosolic Sod1, the mitochondrial transporter Pet9, the three yeast isoforms of glyceraldehyde-3-phosphate dehydrogenase (Tdh3/2/1), heat shock proteins including Hsp90 and Hsp70, and the main peroxiredoxin in yeast (Tsa1) as well as its cosubstrate, thioreoxin (Trx1).
2.Antidepressant action of ketamine via mTOR is mediated by inhibition of nitrergic Rheb degradation.
Harraz MM1, Tyagi R1, Cortés P1, Snyder SH1,2,3. Mol Psychiatry. 2016 Mar;21(3):313-9. doi: 10.1038/mp.2015.211. Epub 2016 Jan 19.
As traditional antidepressants act only after weeks/months, the discovery that ketamine, an antagonist of glutamate/N-methyl-d-aspartate (NMDA) receptors, elicits antidepressant actions in hours has been transformative. Its mechanism of action has been elusive, though enhanced mammalian target of rapamycin (mTOR) signaling is a major feature. We report a novel signaling pathway wherein NMDA receptor activation stimulates generation of nitric oxide (NO), which S-nitrosylates glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Nitrosylated GAPDH complexes with the ubiquitin-E3-ligase Siah1 and Rheb, a small G protein that activates mTOR. Siah1 degrades Rheb leading to reduced mTOR signaling, while ketamine, conversely, stabilizes Rheb that enhances mTOR signaling. Drugs selectively targeting components of this pathway may offer novel approaches to the treatment of depression.
3.Diacylglycerol pyrophosphate binds and inhibits the glyceraldehyde-3-phosphate dehydrogenase in barley aleurone.
Astorquiza PL1, Usorach J1, Racagni G1, Villasuso AL2. Plant Physiol Biochem. 2016 Apr;101:88-95. doi: 10.1016/j.plaphy.2016.01.012. Epub 2016 Jan 27.
The aleurona cell is a model that allows the study of the antagonistic effect of gibberellic acid (GA) and abscisic acid (ABA). Previous results of our laboratory demonstrated the involvement of phospholipids during the response to ABA and GA. ABA modulates the levels of diacylglycerol, phosphatidic acid and diacylglycerol pyrophosphate (DAG, PA, DGPP) through the activities of phosphatidate phosphatases, phospholipase D, diacylglycerol kinase and phosphatidate kinase (PAP, PLD, DGK and PAK). PA and DGPP are key phospholipids in the response to ABA, since both are capable of modifying the hydrolitic activity of the aleurona. Nevertheless, little is known about the mechanism of action of these phospholipids during the ABA signal. DGPP is an anionic phospholipid with a pyrophosphate group attached to diacylglycerol. The ionization of the pyrophosphate group may be important to allow electrostatic interactions between DGPP and proteins. To understand how DGPP mediates cell functions in barley aleurone, we used a DGPP affinity membrane assay to isolate DGPP-binding proteins from Hordeum vulgare, followed by mass spectrometric sequencing.
4.Engineering and systems-level analysis of Saccharomyces cerevisiae for production of 3-hydroxypropionic acid via malonyl-CoA reductase-dependent pathway.
Kildegaard KR1, Jensen NB1,2, Schneider K1, Czarnotta E3, Özdemir E1, Klein T1, Maury J1, Ebert BE3, Christensen HB1, Chen Y4,5, Kim IK4,5,6, Herrgård MJ1, Blank LM3, Forster J1, Nielsen J1,4, Borodina I7. Microb Cell Fact. 2016 Mar 15;15(1):53. doi: 10.1186/s12934-016-0451-5.
BACKGROUND: In the future, oil- and gas-derived polymers may be replaced with bio-based polymers, produced from renewable feedstocks using engineered cell factories. Acrylic acid and acrylic esters with an estimated world annual production of approximately 6 million tons by 2017 can be derived from 3-hydroxypropionic acid (3HP), which can be produced by microbial fermentation. For an economically viable process 3HP must be produced at high titer, rate and yield and preferably at low pH to minimize downstream processing costs.