MMP activation-associated aminopeptidase N reveals a bivalent 14-3-3 binding motif [Protein Structure and Folding]
Aminopeptidase N (APN, CD13) is a transmembrane ectopeptidase involved in many crucial cellular functions. Besides its role as a peptidase, APN also mediates signal transduction and is involved in the activation of matrix metalloproteinases (MMPs). MMPs function in tissue remodeling within the extracellular space and are therefore involved in many human diseases, such as fibrosis, rheumatoid arthritis, tumor angiogenesis, and metastasis, as well as viral infections. However, the exact mechanism that leads to APN-driven MMP activation is unclear. It was previously shown that extracellular 14-3-3 adapter proteins bind to APN...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Sebastian Kiehstaller, Christian Ottmann, Sven Hennig Tags: Signal Transduction Source Type: research
The bacterial cell division protein fragment EFtsN binds to and activates the major peptidoglycan synthase PBP1b [Metabolism]
Peptidoglycan (PG) is an essential constituent of the bacterial cell wall. During cell division, the machinery responsible for PG synthesis localizes mid-cell, at the septum, under the control of a multiprotein complex called the divisome. In Escherichia coli, septal PG synthesis and cell constriction rely on the accumulation of FtsN at the division site. Interestingly, a short sequence of FtsN (Leu75–Gln93, known as EFtsN) was shown to be essential and sufficient for its functioning in vivo, but what exactly this sequence is doing remained unknown. Here, we show that EFtsN binds specifically to the major PG synthase PBP...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Adrien Boes, Frederic Kerff, Raphael Herman, Thierry Touze, Eefjan Breukink, Mohammed Terrak Tags: Microbiology Source Type: research
A drug-resistant {beta}-lactamase variant changes the conformation of its active-site proton shuttle to alter substrate specificity and inhibitor potency [Microbiology]
Lys234 is one of the residues present in class A β-lactamases that is under selective pressure due to antibiotic use. Located adjacent to proton shuttle residue Ser130, it is suggested to play a role in proton transfer during catalysis of the antibiotics. The mechanism underpinning how substitutions in this position modulate inhibitor efficiency and substrate specificity leading to drug resistance is unclear. The K234R substitution identified in several inhibitor-resistant β-lactamase variants is associated with decreased potency of the inhibitor clavulanic acid, which is used in combination with amoxicillin to overcome ...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Victoria Soeung, Shuo Lu, Liya Hu, Allison Judge, Banumathi Sankaran, B. V. Venkataram Prasad, Timothy Palzkill Tags: Enzymology Source Type: research
Humanin selectively prevents the activation of pro-apoptotic protein BID by sequestering it into fibers [Protein Structure and Folding]
Members of the B-cell lymphoma (BCL-2) protein family regulate mitochondrial outer membrane permeabilization (MOMP), a phenomenon in which mitochondria become porous and release death-propagating complexes during the early stages of apoptosis. Pro-apoptotic BCL-2 proteins oligomerize at the mitochondrial outer membrane during MOMP, inducing pore formation. Of current interest are endogenous factors that can inhibit pro-apoptotic BCL-2 mitochondrial outer membrane translocation and oligomerization. A mitochondrial-derived peptide, Humanin (HN), was reported being expressed from an alternate ORF in the mitochondrial genome a...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Daniel L. Morris, Sabrina Johnson, Christopher K. E. Bleck, Duck-Yeon Lee, Nico Tjandra Tags: Molecular Biophysics Source Type: research
A combinatorial native MS and LC-MS/MS approach reveals high intrinsic phosphorylation of human Tau but minimal levels of other key modifications [Neurobiology]
Abnormal changes of neuronal Tau protein, such as phosphorylation and aggregation, are considered hallmarks of cognitive deficits in Alzheimer's disease. Abnormal phosphorylation is thought to precede aggregation and therefore to promote aggregation, but the nature and extent of phosphorylation remain ill-defined. Tau contains ∼85 potential phosphorylation sites, which can be phosphorylated by various kinases because the unfolded structure of Tau makes them accessible. However, methodological limitations (e.g. in MS of phosphopeptides, or antibodies against phosphoepitopes) led to conflicting results regarding the extent...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Friedel Drepper, Jacek Biernat, Senthilvelrajan Kaniyappan, Helmut E. Meyer, Eva Maria Mandelkow, Bettina Warscheid, Eckhard Mandelkow Tags: Protein Structure and Folding Source Type: research
Distant coupling between RNA editing and alternative splicing of the osmosensitive cation channel Tmem63b [Cell Biology]
In this study, we identified a brain-specific A-to-I RNA editing that changed glutamine to arginine (Q/R) at exon 20 and an alternative splicing of exon 4 in Tmem63b, which encodes a ubiquitously expressed osmosensitive cation channel. The channel isoforms lacking exon 4 occurred in ∼80% of Tmem63b mRNAs in the brain but were not detected in other tissues, suggesting a brain-specific splicing. We found that the Q/R editing was catalyzed by Adar2 (Adarb1) and required an editing site complementary sequence located in the proximal 5′ end of intron 20. Moreover, the Q/R editing was almost exclusively identified in the spl...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Dan Wu, Yan-Yu Zang, Yong-Yun Shi, Chang Ye, Wen-Min Cai, Xiao-Hui Tang, Liyun Zhao, Yong Liu, Zhenji Gan, Gui-quan Chen, Yun Xu, Jian-Jun Yang, Yun Stone Shi Tags: RNA Source Type: research
Inhibition of oxidative metabolism by nitric oxide restricts EMCV replication selectively in pancreatic beta-cells [Enzymology]
Environmental factors, such as viral infection, are proposed to play a role in the initiation of autoimmune diabetes. In response to encephalomyocarditis virus (EMCV) infection, resident islet macrophages release the pro-inflammatory cytokine IL-1β, to levels that are sufficient to stimulate inducible nitric oxide synthase (iNOS) expression and production of micromolar levels of the free radical nitric oxide in neighboring β-cells. We have recently shown that nitric oxide inhibits EMCV replication and EMCV-mediated β-cell lysis and that this protection is associated with an inhibition of mitochondrial oxidative metaboli...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Joshua D. Stafford, Chay Teng Yeo, John A. Corbett Tags: Metabolism Source Type: research
BMP-9 and LDL crosstalk regulates ALK-1 endocytosis and LDL transcytosis in endothelial cells [Signal Transduction]
Bone morphogenetic protein-9 (BMP-9) is a circulating cytokine that is known to play an essential role in the endothelial homeostasis and the binding of BMP-9 to the receptor activin-like kinase 1 (ALK-1) promotes endothelial cell quiescence. Previously, using an unbiased screen, we identified ALK-1 as a high-capacity receptor for low-density lipoprotein (LDL) in endothelial cells that mediates its transcytosis in a nondegradative manner. Here we examine the crosstalk between BMP-9 and LDL and how it influences their interactions with ALK-1. Treatment of endothelial cells with BMP-9 triggers the extensive endocytosis of AL...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Bo Tao, Jan R. Kraehling, Siavash Ghaffari, Cristina M. Ramirez, Sungwoon Lee, Joseph W. Fowler, Warren L. Lee, Carlos Fernandez-Hernando, Anne Eichmann, William C. Sessa Tags: Cell Biology Source Type: research
Disease-associated mutations in inositol 1,4,5-trisphosphate receptor subunits impair channel function [Molecular Bases of Disease]
In this report, we investigated representative disease-associated missense mutations to determine their effects on IP3R channel activity. Additionally, we designed concatenated IP3R constructs to create tetrameric channels with a predefined subunit composition to explore the functionality of heteromeric channels. Using calcium imaging techniques to assess IP3R channel function, we observed that all the mutations studied resulted in severely attenuated Ca2+ release when expressed as homotetramers. However, some heterotetramers retained varied degrees of function dependent on the composition of the tetramer. Our findings sug...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Lara E. Terry, Kamil J. Alzayady, Amanda M. Wahl, Sundeep Malik, David I. Yule Tags: Signal Transduction Source Type: research
The endosomal trafficking regulator LITAF controls the cardiac Nav1.5 channel via the ubiquitin ligase NEDD4-2 [Computational Biology]
The QT interval is a recording of cardiac electrical activity. Previous genome-wide association studies identified genetic variants that modify the QT interval upstream of LITAF (lipopolysaccharide-induced tumor necrosis factor-α factor), a protein encoding a regulator of endosomal trafficking. However, it was not clear how LITAF might impact cardiac excitation. We investigated the effect of LITAF on the voltage-gated sodium channel Nav1.5, which is critical for cardiac depolarization. We show that overexpressed LITAF resulted in a significant increase in the density of Nav1.5-generated voltage-gated sodium current INa an...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Nilufer N. Turan, Karni S. Moshal, Karim Roder, Brett C. Baggett, Anatoli Y. Kabakov, Saroȷ Dhakal, Ryota Teramoto, David Yi–Eng Chiang, Mingwang Zhong, An Xie, Yichun Lu, Samuel C. Dudley Jr., Calum A. MacRae, Alain Karma, Gideon Koren Tags: Protein Synthesis and Degradation Source Type: research
NSun2 promotes cell migration through methylating autotaxin mRNA [Cell Biology]
NSun2 is an RNA methyltransferase introducing 5-methylcytosine into tRNAs, mRNAs, and noncoding RNAs, thereby influencing the levels or function of these RNAs. Autotaxin (ATX) is a secreted glycoprotein and is recognized as a key factor in converting lysophosphatidylcholine into lysophosphatidic acid (LPA). The ATX-LPA axis exerts multiple biological effects in cell survival, migration, proliferation, and differentiation. Here, we show that NSun2 is involved in the regulation of cell migration through methylating ATX mRNA. In the human glioma cell line U87, knockdown of NSun2 decreased ATX protein levels, whereas overexpre...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Xin Xu, Yihua Zhang, Junjie Zhang, Xiaotian Zhang Tags: Gene Regulation Source Type: research
Structural transitions in Orb2 prion-like domain relevant for functional aggregation in memory consolidation [Molecular Biophysics]
The recent structural elucidation of ex vivo Drosophila Orb2 fibrils revealed a novel amyloid formed by interdigitated Gln and His residue side chains belonging to the prion-like domain. However, atomic-level details on the conformational transitions associated with memory consolidation remain unknown. Here, we have characterized the nascent conformation and dynamics of the prion-like domain (PLD) of Orb2A using a nonconventional liquid-state NMR spectroscopy strategy based on 13C detection to afford an essentially complete set of 13Cα, 13Cβ, 1Hα, and backbone 13CO and 15N assignments. At pH 4, where His residues are pr...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Javier Oroz, Sara S. Felix, Eurico J. Cabrita, Douglas V. Laurents Tags: Protein Structure and Folding Source Type: research
Tyrosine phosphorylation of the scaffold protein IQGAP1 in the MET pathway alters function [Signal Transduction]
IQGAP1 is a key scaffold protein that regulates numerous cellular processes and signaling pathways. Analogous to many other cellular proteins, IQGAP1 undergoes post-translational modifications, including phosphorylation. Nevertheless, very little is known about the specific sites of phosphorylation or the effects on IQGAP1 function. Here, using several approaches, including MS, site-directed mutagenesis, siRNA-mediated gene silencing, and chemical inhibitors, we identified the specific tyrosine residues that are phosphorylated on IQGAP1 and evaluated the effect on function. Tyr-172, Tyr-654, Tyr-855, and Tyr-1510 were phos...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Andrew C. Hedman, Dean E. McNulty, Zhigang Li, Laetitia Gorisse, Roland S. Annan, David B. Sacks Tags: Signal Transduction Source Type: research
PDE5 inhibition rescues mitochondrial dysfunction and angiogenic responses induced by Akt3 inhibition by promotion of PRC expression [Bioenergetics]
Akt3 regulates mitochondrial content in endothelial cells through the inhibition of PGC-1α nuclear localization and is also required for angiogenesis. However, whether there is a direct link between mitochondrial function and angiogenesis is unknown. Here we show that Akt3 depletion in primary endothelial cells results in decreased uncoupled oxygen consumption, increased fission, decreased membrane potential, and increased expression of the mitochondria-specific protein chaperones, HSP60 and HSP10, suggesting that Akt3 is required for mitochondrial homeostasis. Direct inhibition of mitochondrial homeostasis by the model o...
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Daniel G. Corum, Dorea P. Jenkins, James A. Heslop, Lacey M. Tallent, Gyda C. Beeson, Jeremy L. Barth, Rick G. Schnellmann, Robin C. Muise-Helmericks Tags: Cell Biology Source Type: research
{alpha}-Synuclein facilitates endocytosis by elevating the steady-state levels of phosphatidylinositol 4,5-bisphosphate [Membrane Biology]
This study provides evidence for a critical involvement of PIPs in α-Syn–mediated membrane trafficking. (Source: Journal of Biological Chemistry)
Source: Journal of Biological Chemistry - December 25, 2020 Category: Chemistry Authors: Meir Schechter, Merav Atias, Suaad Abd Elhadi, Dana Davidi, Daniel Gitler, Ronit Sharon Tags: Neurobiology Source Type: research
