Carnosine synthase deficiency is compatible with normal skeletal muscle and olfactory function but causes reduced olfactory sensitivity in aging mice [Developmental Biology]
In this study, we generated a mouse line deficient in carnosine synthase (Carns1). HCDs were undetectable in the primary olfactory system and skeletal muscle of Carns1-deficient mice. Skeletal muscle contraction in these mice, however, was unaltered, and there was no evidence for reduced pH-buffering capacity in the skeletal muscle. Olfactory tests did not reveal any deterioration in 8-month-old mice lacking carnosine. In contrast, aging (18–24-month-old) Carns1-deficient mice exhibited olfactory sensitivity impairments that correlated with an age-dependent reduction in the number of olfactory receptor neurons. Whereas w...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Lihua Wang-Eckhardt, Asisa Bastian, Tobias Bruegmann, Philipp Sasse, Matthias Eckhardt Tags: Neurobiology Source Type: research
A novel stress-inducible CmtR-ESX3-Zn2+ regulatory pathway essential for survival of Mycobacterium bovis under oxidative stress [Microbiology]
Reactive oxygen species (ROS) are an unavoidable host environmental cue for intracellular pathogens such as Mycobacterium tuberculosis and Mycobacterium bovis; however, the signaling pathway in mycobacteria for sensing and responding to environmental stress remains largely unclear. Here, we characterize a novel CmtR-Zur-ESX3-Zn2+ regulatory pathway in M. bovis that aids mycobacterial survival under oxidative stress. We demonstrate that CmtR functions as a novel redox sensor and that its expression can be significantly induced under H2O2 stress. CmtR can physically interact with the negative regulator Zur and de-represses t...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Xiaohui Li, Liu Chen, Jingjing Liao, Jiechen Hui, Weihui Li, Zheng-Guo He Tags: Gene Regulation Source Type: research
Fluctuation in O-GlcNAcylation inactivates STIM1 to reduce store-operated calcium ion entry via down-regulation of Ser621 phosphorylation [Molecular Bases of Disease]
Stromal interaction molecule 1 (STIM1) plays a pivotal role in store-operated Ca2+ entry (SOCE), an essential mechanism in cellular calcium signaling and in maintaining cellular calcium balance. Because O-GlcNAcylation plays pivotal roles in various cellular function, we examined the effect of fluctuation in STIM1 O-GlcNAcylation on SOCE activity. We found that both increase and decrease in STIM1 O-GlcNAcylation impaired SOCE activity. To determine the molecular basis, we established STIM1-knockout HEK293 (STIM1-KO-HEK) cells using the CRISPR/Cas9 system and transfected STIM1 WT (STIM1-KO-WT-HEK), S621A (STIM1-KO-S621A-HEK...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Atsuo Nomura, Shunichi Yokoe, Kiichiro Tomoda, Takatoshi Nakagawa, Francisco Javier Martin-Romero, Michio Asahi Tags: Glycobiology and Extracellular Matrices Source Type: research
Genetic evidence for partial redundancy between the arginine methyltransferases CARM1 and PRMT6 [Signal Transduction]
CARM1 is a protein arginine methyltransferase (PRMT) that acts as a coactivator in a number of transcriptional programs. CARM1 orchestrates this coactivator activity in part by depositing the H3R17me2a histone mark in the vicinity of gene promoters that it regulates. However, the gross levels of H3R17me2a in CARM1 KO mice did not significantly decrease, indicating that other PRMT(s) may compensate for this loss. We thus performed a screen of type I PRMTs, which revealed that PRMT6 can also deposit the H3R17me2a mark in vitro. CARM1 knockout mice are perinatally lethal and display a reduced fetal size, whereas PRMT6 null mi...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Donghang Cheng, Guozhen Gao, Alessandra Di Lorenzo, Sandrine Jayne, Michael O. Hottiger, Stephane Richard, Mark T. Bedford Tags: Gene Regulation Source Type: research
Building better polymerases: Engineering the replication of expanded genetic alphabets [Molecular Biophysics]
We describe comparative structural, enzymatic, and molecular dynamics studies of WT and Klentaq variants, complexed with natural or noncanonical substrates. Combining these methods provides insight into how specific amino acid substitutions distant from the active site in a Klentaq DNA polymerase variant (ZP Klentaq) contribute to its ability to replicate UBPs with improved efficiency compared with Klentaq. This approach can therefore serve to guide any future rational engineering of replicative DNA polymerases. (Source: Journal of Biological Chemistry)
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Zahra Ouaray, Steven A. Benner, Millie M. Georgiadis, Nigel G. J. Richards Tags: JBC Reviews Source Type: research
Characterizing human {alpha}-1,6-fucosyltransferase (FUT8) substrate specificity and structural similarities with related fucosyltransferases [Protein Structure and Folding]
Mammalian Asn-linked glycans are extensively processed as they transit the secretory pathway to generate diverse glycans on cell surface and secreted glycoproteins. Additional modification of the glycan core by α-1,6-fucose addition to the innermost GlcNAc residue (core fucosylation) is catalyzed by an α-1,6-fucosyltransferase (FUT8). The importance of core fucosylation can be seen in the complex pathological phenotypes of FUT8 null mice, which display defects in cellular signaling, development, and subsequent neonatal lethality. Elevated core fucosylation has also been identified in several human cancers. However, the s...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Bhargavi M. Boruah, Renuka Kadirvelraj, Lin Liu, Annapoorani Ramiah, Chao Li, Guanghui Zong, Gerlof P. Bosman, Jeong-Yeh Yang, Lai-Xi Wang, Geert-Jan Boons, Zachary A. Wood, Kelley W. Moremen Tags: Glycobiology and Extracellular Matrices Source Type: research
Stop codon read-through of mammalian MTCH2 leading to an unstable isoform regulates mitochondrial membrane potential [Gene Regulation]
Stop codon read-through (SCR) is a process of continuation of translation beyond a stop codon. This phenomenon, which occurs only in certain mRNAs under specific conditions, leads to a longer isoform with properties different from that of the canonical isoform. MTCH2, which encodes a mitochondrial protein that regulates mitochondrial metabolism, was selected as a potential read-through candidate based on evolutionary conservation observed in the proximal region of its 3′ UTR. Here, we demonstrate translational read-through across two evolutionarily conserved, in-frame stop codons of MTCH2 using luminescence- and fluoresc...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Lekha E. Manjunath, Anumeha Singh, Sarthak Sahoo, Ashutosh Mishra, Jinsha Padmarajan, Chaithanya G. Basavaraju, Sandeep M. Eswarappa Tags: Protein Synthesis and Degradation Source Type: research
pH-dependent pyridoxine transport by SLC19A2 and SLC19A3: Implications for absorption in acidic microclimates [Metabolism]
SLC19A2 and SLC19A3, also known as thiamine transporters (THTR) 1 and 2, respectively, transport the positively charged thiamine (vitamin B1) into cells to enable its efficient utilization. SLC19A2 and SLC19A3 are also known to transport structurally unrelated cationic drugs, such as metformin, but whether this charge selectivity extends to other molecules, such as pyridoxine (vitamin B6), is unknown. We tested this possibility using Madin-Darby canine kidney II (MDCKII) cells and human embryonic kidney 293 (HEK293) cells for transfection experiments, and also using Caco-2 cells as human intestinal epithelial model cells. ...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Takahiro Yamashiro, Tomoya Yasujima, Hamid M. Said, Hiroaki Yuasa Tags: Membrane Biology Source Type: research
Mutation of an atypical oxirane oxyanion hole improves regioselectivity of the {alpha}/{beta}-fold epoxide hydrolase Alp1U [Enzymology]
Epoxide hydrolases (EHs) have been characterized and engineered as biocatalysts that convert epoxides to valuable chiral vicinal diol precursors of drugs and bioactive compounds. Nonetheless, the regioselectivity control of the epoxide ring opening by EHs remains challenging. Alp1U is an α/β-fold EH that exhibits poor regioselectivity in the epoxide hydrolysis of fluostatin C (compound 1) and produces a pair of stereoisomers. Herein, we established the absolute configuration of the two stereoisomeric products and determined the crystal structure of Alp1U. A Trp-186/Trp-187/Tyr-247 oxirane oxygen hole was identified in Al...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Liping Zhang, Bidhan Chandra De, Wenȷun Zhang, Attila Mandi, Zhuangȷie Fang, Chunfang Yang, Yiguang Zhu, Tibor Kurtan, Changsheng Zhang Tags: Enzymology Source Type: research
Enhanced enzyme kinetics of reverse transcriptase variants cloned from animals infected with SIVmac239 lacking viral protein X [Microbiology]
HIV Type 1 (HIV-1) and simian immunodeficiency virus (SIV) display differential replication kinetics in macrophages. This is because high expression levels of the active host deoxynucleotide triphosphohydrolase sterile α motif domain and histidine-aspartate domain–containing protein 1 (SAMHD1) deplete intracellular dNTPs, which restrict HIV-1 reverse transcription, and result in a restrictive infection in this myeloid cell type. Some SIVs overcome SAMHD1 restriction using viral protein X (Vpx), a viral accessory protein that induces proteasomal degradation of SAMHD1, increasing cellular dNTP concentrations and enabling ...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Si'Ana A. Coggins, Dong-Hyun Kim, Raymond F. Schinazi, Ronald C. Desrosier, Baek Kim Tags: Enzymology Source Type: research
The heptameric structure of the flagellar regulatory protein FlrC is indispensable for ATPase activity and disassembled by cyclic-di-GMP [Protein Structure and Folding]
The bacterial enhancer-binding protein (bEBP) FlrC, controls motility and colonization of Vibrio cholerae by regulating the transcription of class-III flagellar genes in σ54-dependent manner. However, the mechanism by which FlrC regulates transcription is not fully elucidated. Although, most bEBPs require nucleotides to stimulate the oligomerization necessary for function, our previous study showed that the central domain of FlrC (FlrCC) forms heptamer in a nucleotide-independent manner. Furthermore, heptameric FlrCC binds ATP in “cis-mediated” style without any contribution from sensor I motif 285REDXXYR291 of the tr...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Shrestha Chakraborty, Maitree Biswas, Sanjay Dey, Shubhangi Agarwal, Tulika Chakrabortty, Biplab Ghosh, Jhimli Dasgupta Tags: Signal Transduction Source Type: research
A human cancer cell line initiates DNA replication normally in the absence of ORC5 and ORC2 proteins [DNA and Chromosomes]
The origin recognition complex (ORC), composed of six subunits, ORC1–6, binds to origins of replication as a ring-shaped heterohexameric ATPase that is believed to be essential to recruit and load MCM2–7, the minichromosome maintenance protein complex, around DNA and initiate DNA replication. We previously reported the creation of viable cancer cell lines that lacked detectable ORC1 or ORC2 protein without a reduction in the number of origins firing. Here, using CRISPR-Cas9–mediated mutations, we report that human HCT116 colon cancer cells also survive when ORC5 protein expression is abolished via a mutation in the i...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Etsuko Shibata, Anindya Dutta Tags: DNA and Chromosomes Source Type: research
Cholesterol sensing by CD81 is important for hepatitis C virus entry [Protein Structure and Folding]
In this study we investigate CD81 cholesterol sensing in the context of its activity as a receptor for hepatitis C virus (HCV). Structure-led mutagenesis of the cholesterol-binding pocket reduced CD81–cholesterol association but had disparate effects on HCV entry, both reducing and enhancing CD81 receptor activity. We reasoned that this could be explained by alterations in the consequences of cholesterol binding. To investigate this further we performed molecular dynamic simulations of CD81 with and without cholesterol; this identified a potential allosteric mechanism by which cholesterol binding regulates the conformati...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Machaela Palor, Lenka Steȷskal, Piya Mandal, Annasara Lenman, Maria Pia Alberione, Jared Kirui, Rebecca Moeller, Stefan Ebner, Felix Meissner, Gisa Gerold, Adrian J. Shepherd, Joe Grove Tags: Microbiology Source Type: research
A Gs-RhoGEF interaction: An old G protein finds a new job [Cell Biology]
The heterotrimeric G proteins are known to have a variety of downstream effectors, but Gs was long thought to be specifically coupled to adenylyl cyclases. A new study indicates that activated Gs can also directly interact with a guanine nucleotide exchange factor for Rho family small GTPases, PDZ-RhoGEF. This novel interaction mediates activation of the small G protein Cdc42 by Gs-coupled GPCRs, inducing cytoskeletal rearrangements and formation of filopodia-like structures. Furthermore, overexpression of a minimal PDZ-RhoGEF fragment can down-regulate cAMP signaling, suggesting that this effector competes with canonical ...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Vladlen Z. Slepak, Alexey Pronin Tags: Editors ' Picks Highlights Source Type: research
G{alpha}s directly drives PDZ-RhoGEF signaling to Cdc42 [Cell Biology]
Gα proteins promote dynamic adjustments of cell shape directed by actin-cytoskeleton reorganization via their respective RhoGEF effectors. For example, Gα13 binding to the RGS-homology (RH) domains of several RH-RhoGEFs allosterically activates these proteins, causing them to expose their catalytic Dbl-homology (DH)/pleckstrin-homology (PH) regions, which triggers downstream signals. However, whether additional Gα proteins might directly regulate the RH-RhoGEFs was not known. To explore this question, we first examined the morphological effects of expressing shortened RH-RhoGEF DH/PH constructs of p115RhoGEF/ARHGEF1, PD...
Source: Journal of Biological Chemistry - December 11, 2020 Category: Chemistry Authors: Aleȷandro Castillo–Kauil, Irving Garcia–Jimenez, Rodolfo Daniel Cervantes–Villagrana, Sendi Rafael Adame–Garcia, Yarely Mabell Beltran–Navarro, J. Silvio Gutkind, Guadalupe Reyes–Cruz, Jose Vazquez–Prado Tags: Editors ' Picks Source Type: research
