Search results for "Bran"

The HMGB1 protein induces a metabolic type of tumour cell death by blocking aerobic respiration

2016

The high-mobility group box 1 (HMGB1) protein has a central role in immunological antitumour defense. Here we show that natural killer cell-derived HMGB1 directly eliminates cancer cells by triggering metabolic cell death. HMGB1 allosterically inhibits the tetrameric pyruvate kinase isoform M2, thus blocking glucose-driven aerobic respiration. This results in a rapid metabolic shift forcing cells to rely solely on glycolysis for the maintenance of energy production. Cancer cells can acquire resistance to HMGB1 by increasing glycolysis using the dimeric form of PKM2, and employing glutaminolysis. Consistently, we observe an increase in the expression of a key enzyme of glutaminolysis, malic …

Discovery and Biological Evaluation of Potent and Selective N-Methylene Saccharin-Derived Inhibitors for Rhomboid Intramembrane Proteases

2017

Rhomboids are intramembrane serine proteases and belong to the group of structurally and biochemically most comprehensively characterized membrane proteins. They are highly conserved and ubiquitously distributed in all kingdoms of life and function in a wide range of biological processes, including epidermal growth factor signaling, mitochondrial dynamics, and apoptosis. Importantly, rhomboids have been associated with multiple diseases, including Parkinson's disease, type 2 diabetes, and malaria. However, despite a thorough understanding of many structural and functional aspects of rhomboids, potent and selective inhibitors of these intramembrane proteases are still not available. In this …

Discovery and validation of 2-styryl substituted benzoxazin-4-ones as a novel scaffold for rhomboid protease inhibitors

2017

Abstract Rhomboids are intramembrane serine proteases with diverse physiological functions in organisms ranging from archaea to humans. Crystal structure analysis has provided a detailed understanding of the catalytic mechanism, and rhomboids have been implicated in various disease contexts. Unfortunately, the design of specific rhomboid inhibitors has lagged behind, and previously described small molecule inhibitors displayed insufficient potency and/or selectivity. Using a computer-aided approach, we focused on the discovery of novel scaffolds with reduced liabilities and the possibility for broad structural variations. Docking studies with the E. coli rhomboid GlpG indicated that 2-styry…

In vivo selection of heterotypically interacting transmembrane helices: Complementary helix surfaces, rather than conserved interaction motifs, drive…

2017

Single pass transmembrane proteins make up almost half of the whole transmembrane proteome. Contacts between such bitopic transmembrane proteins are common, and oligomerization of their single transmembrane helix is involved in triggering and regulation of signal transduction across cell membranes. In several recent analyses the distribution of amino acids at helix-helix contact sides has been analyzed, and e.g. a preference of amino acids with small side chains has been identified. Here we select amino acids, amino acid pairings and amino acid motifs, which mediate strong interactions of single-span transmembrane α-helices. Our analysis illustrates an architecture of TM helix dimers that i…

Permeating disciplines: Overcoming barriers between molecular simulations and classical structure-function approaches in biological ion transport

2017

Ion translocation across biological barriers is a fundamental requirement for life. In many cases, controlling this process-for example with neuroactive drugs-demands an understanding of rapid and reversible structural changes in membrane-embedded proteins, including ion channels and transporters. Classical approaches to electrophysiology and structural biology have provided valuable insights into several such proteins over macroscopic, often discontinuous scales of space and time. Integrating these observations into meaningful mechanistic models now relies increasingly on computational methods, particularly molecular dynamics simulations, while surfacing important challenges in data manage…

Direct Visualization of the Conformational Dynamics of Single Influenza Hemagglutinin Trimers

2018

Influenza hemagglutinin (HA) is the canonical type I viral envelope glycoprotein and provides a template for the membrane-fusion mechanisms of numerous viruses. The current model of HA-mediated membrane fusion describes a static "spring-loaded" fusion domain (HA2) at neutral pH. Acidic pH triggers a singular irreversible conformational rearrangement in HA2 that fuses viral and cellular membranes. Here, using single-molecule Förster resonance energy transfer (smFRET)-imaging, we directly visualized pH-triggered conformational changes of HA trimers on the viral surface. Our analyses reveal reversible exchange between the pre-fusion and two intermediate conformations of HA2. Acidification of p…

Border controls: Lipids control proteins and proteins control lipids.

2016

Phosphorylation of meprin β controls its cell surface abundance and subsequently diminishes ectodomain shedding

2021

Meprin β is a zinc-dependent metalloprotease exhibiting a unique cleavage specificity with strong preference for acidic amino acids at the cleavage site. Proteomic studies revealed a diverse substrate pool of meprin β including the interleukin-6 receptor (IL-6R) and the amyloid precursor protein (APP). Dysregulation of meprin β is often associated with pathological conditions such as chronic inflammation, fibrosis, or Alzheimer's disease (AD). The extracellular regulation of meprin β including interactors, sheddases, and activators has been intensively investigated while intracellular regulation has been barely addressed in the literature. This study aimed to analyze C-terminal phosphorylat…

The C-terminal Domains of Apoptotic BH3-only Proteins Mediate Their Insertion into Distinct Biological Membranes

2016

Changes in the equilibrium of pro- and anti-apoptotic members of the B-cell lymphoma-2 (Bcl-2) protein family in the mitochondrial outer membrane (MOM) induce structural changes that commit cells to apoptosis. Bcl-2 homology-3 (BH3)-only proteins participate in this process by either activating pro-apoptotic effectors or inhibiting anti-apoptotic components and by promoting MOM permeabilization. The association of BH3-only proteins with MOMs is necessary for the activation and amplification of death signals; however, the nature of this association remains controversial, as these proteins lack a canonical transmembrane sequence. Here we used an in vitro expression system to study the inserti…

Mcl-1 and Bok transmembrane domains : Unexpected players in the modulation of apoptosis

2020

The Bcl-2 protein family comprises both proand antiapoptotic members that control the permeabilization of the mitochondrial outer membrane, a crucial step in the modulation of apoptosis. Recent research has demonstrated that the carboxyl-terminal transmembrane domain (TMD) of some Bcl-2 protein family mem-bers can modulate apoptosis; however, the transmembrane interactome of the antiapoptotic protein Mcl-1 remains largely unexplored. Here, we demonstrate that the Mcl-1 TMD forms homooligomers in the mitochondrial membrane, competes with full-length Mcl-1 protein with regards to its antiapoptotic function, and induces cell death in a Bok-dependent manner. While the Bok TMD oligomers locate p…