FEBS Journal最新文献

Cancer immunotherapy represents a very encouraging mode of treatment for cancer where one's immune system is utilized to eliminate tumor cells. Wayne et al. explore inhibition of DNA damage response (DDR) pathways with small molecule inhibitors as a means to prime cells with immune response. These findings suggest that a one-size-fits-all approach cannot be used when harnessing immune response via DDR inhibitors and genotoxic agents, which are required ultimately for the success of immunotherapy. Comment on: https://doi.org/10.1111/febs.15747.

Circular RNAs (circRNAs) are a recently discovered class of noncoding RNAs found in many species across the eukaryotic kingdom. These intriguing RNA species are formed through a unique mechanism that is known as back splicing in which the 5' and 3' termini are covalently joined. Recent research has revealed that viruses also encode a repertoire of circRNAs. Some of these viral circRNAs are abundantly expressed and are reported to play a role in disease pathogenesis. A growing number of studies also indicate that host circRNAs are involved in immune responses against virus infections with either an antiviral or proviral role. In this review, we briefly introduce circRNA, its biogenesis, and mechanism of action. We go on to summarize the latest research on the expression, regulation, and functions of viral and host-encoded circRNAs during the host-virus interaction, with the aim of highlighting the potential of viral and host circRNAs as a suitable target for diagnostic biomarker development and therapeutic treatment of viral-associated diseases. We conclude by discussing the current limitations in knowledge and significance of elucidating the roles of circRNAs in host-virus interactions, as well as future directions for this emerging field.

Activating stimulator of interferon genes to turn immunologically refractive cold tumor hot is an exciting therapeutic approach to increase the clinical responsiveness of some human cancers to immune checkpoint inhibitors. DNA damaging drugs and PARP inhibitors are two types of agents that have demonstrated this potential. Inhibitors of Chk1 or Wee1 induce DNA damage in cancer cells in predominantly the S-phase population. Increased cytoplasmic single-stranded and double-stranded DNA (dsDNA) from this DNA damage resulted in increased tank-binding kinase 1 (TBK1) phosphorylation in a range of cancer cell lines. However, despite robust increases in pTBK1, no downstream consequences of TBK1 phosphorylation were observed (namely no increase in pIRF3/7, interferon regulatory factor (IRF)-dependent gene expression or a type I IFN response). In combination with cytotoxic chemotherapy such as gemcitabine or camptothecin (CPT), Chk1 inhibition increased cytoplasmic dsDNA compared with the cytotoxic alone but attenuated the cytotoxic chemotherapy-induced increase in IRF1 protein and STAT1 phosphorylation through inhibition of nuclear RelB translocation. Despite increased cytoplasmic DNA and TBK1 activation, inhibition of Chk1, ataxia telangiectasia and Rad3-related protein, or Wee1 failed to activate a type I IFN response. We discuss the potential underlying mechanisms for this lack of IRF-dependent gene response and how this might influence the clinical strategies of combining Chk1 or Wee1 inhibitors with immune checkpoint inhibitors.

We investigated the mechanisms associated with E22K mutation in myosin regulatory light chain (RLC), found to cause hypertrophic cardiomyopathy (HCM) in humans and mice. Specifically, we characterized the mechanical profiles of papillary muscle fibers from transgenic mice expressing human ventricular RLC wild-type (Tg-WT) or E22K mutation (Tg-E22K). Because the two mouse models expressed different amounts of transgene, the B6SJL mouse line (NTg) was used as an additional control. Mechanical experiments were carried out on Ca²⁺ - and ATP-activated fibers and in rigor. Sinusoidal analysis was performed to elucidate the effect of E22K on tension and stiffness during activation/rigor, tension-pCa, and myosin cross-bridge (CB) kinetics. We found significant reductions in active tension (by 54%) and stiffness (active by 40% and rigor by 54%). A decrease in the Ca²⁺ sensitivity of tension (by ∆pCa ~ 0.1) was observed in Tg-E22K compared with Tg-WT fibers. The apparent (=measured) rate constant of exponential process B (2πb: force generation step) was not affected by E22K, but the apparent rate constant of exponential process C (2πc: CB detachment step) was faster in Tg-E22K compared with Tg-WT fibers. Both 2πb and 2πc were smaller in NTg than in Tg-WT fibers, suggesting a kinetic difference between the human and mouse RLC. Our results of E22K-induced reduction in myofilament stiffness and tension suggest that the main effect of this mutation was to disturb the interaction of RLC with the myosin heavy chain and impose structural abnormalities in the lever arm of myosin CB. When placed in vivo, the E22K mutation is expected to result in reduced contractility and decreased cardiac output whereby leading to HCM.

Sub-discipline: Bioenergetics.

Database: The data that support the findings of this study are available from the corresponding authors upon reasonable request.

Animal protocol: BK20150353 (Soochow University).

Research governance: School of Nursing: Hua-Gang Hu: seuboyh@163.com; Soochow University: Chen Ge chge@suda.edu.cn.

Misfolded proteins in the endoplasmic reticulum (ER) are degraded by ER-associated degradation (ERAD). In mammalian cells, the HRD1-SEL1L membrane ubiquitin ligase complex plays a central role in this process. However, SEL1L is inherently unstable, and excess SEL1L is also degraded by ERAD. Accordingly, when proteasome activity is inhibited, multiple degradation intermediates of SEL1L appear in the cytosol. In this study, we searched for factors that inhibit SEL1L degradation and identified OS-9 and XTP3-B, two ER lectins that regulate glycoprotein ERAD. SEL1L degradation was characterized by a ladder of degradation products, and the C-terminal Pro-rich region of SEL1L was responsible for generation of this pattern. In the cytosol, these degradation intermediates stimulated aggregation of polyglutamine-expanded Huntingtin protein (Htt-polyQ-GFP) by interacting with aggregation-prone proteins, including Htt-polyQ-GFP. Collectively, our findings indicate that peptide fragments of ER proteins generated during ERAD may affect protein aggregation in the cytosol, revealing the interconnection of protein homeostasis across subcellular compartments.

Halohydrin dehalogenases (HHDHs) are promising enzymes for application in biocatalysis due to their promiscuous epoxide ring-opening activity with various anionic nucleophiles. So far, seven different HHDH subtypes A to G have been reported with subtype D containing the by far largest number of enzymes. Moreover, several characterized members of subtype D have been reported to display outstanding characteristics such as high catalytic activity, broad substrate spectra or remarkable thermal stability. Yet, no structure of a D-type HHDH has been reported to date that could be used to investigate and understand those features on a molecular level. We therefore solved the crystal structure of HheD2 from gamma proteobacterium HTCC2207 at 1.6 Å resolution and used it as a starting point for targeted mutagenesis in combination with molecular dynamics (MD) simulation, in order to study the low thermal stability of HheD2 in comparison with other members of subtype D. This revealed a hydrogen bond between conserved residues Q160 and D198 to be connected with a high catalytic activity of this enzyme. Moreover, a flexible surface region containing two α-helices was identified to impact thermal stability of HheD2. Exchange of this surface region by residues of HheD3 yielded a variant with 10 °C higher melting temperature and reaction temperature optimum. Overall, our results provide important insights into the structure-function relationship of HheD2 and presumably for other D-type HHDHs. DATABASES: Structural data are available in PDB database under the accession number 7B73.

Protein misfolding is a major driver of ageing-associated frailty and disease pathology. Although all cells possess multiple, well-characterised protein quality control systems to mitigate the toxicity of misfolded proteins, how they are integrated to maintain protein homeostasis ('proteostasis') in health-and how their disintegration contributes to disease-is still an exciting and fast-paced area of research. Under physiological conditions, the predominant route for misfolded protein clearance involves ubiquitylation and proteasome-mediated degradation. When the capacity of this route is overwhelmed-as happens during conditions of acute environmental stress, or chronic ageing-related decline-alternative routes for protein quality control are activated. In this review, we summarise our current understanding of how proteasome-targeted misfolded proteins are retrafficked to alternative protein quality control routes such as juxta-nuclear sequestration and selective autophagy when the ubiquitin-proteasome system is compromised. We also discuss the molecular determinants of these alternative protein quality control systems, attempt to clarify distinctions between various cytoplasmic spatial quality control inclusion bodies (e.g., Q-bodies, p62 bodies, JUNQ, aggresomes, and aggresome-like induced structures 'ALIS'), and speculate on emerging concepts in the field that we hope will spur future research-with the potential to benefit the rational development of healthy ageing strategies.

Substrate (or solute)-binding proteins (SBPs) selectively bind the target ligands and deliver them to the ATP-binding cassette (ABC) transport system for their translocation. Irrespective of the different types of ligands, SBPs are structurally conserved. A wealth of structural details of SBPs bound to different types of ligands and the physiological basis of their import are available; however, the uptake mechanism of nucleotides is still deficient. In this study, we elucidated the structural details of an SBP endogenously bound to a novel ligand, a derivative of uridylyl-3'-5'-phospho-guanosine (U3G); thus, we named it a U3G-binding protein (U3GBP). To the best of our knowledge, this is the first report of U3G (and a dinucleotide) binding to the SBP of ABC transport system, and thus, U3GBP is classified as a first member of subcluster D-I SBPs. Thermodynamic data also suggest that U3GBP can bind phospholipid precursor sn-glycerophosphocholine (GPC) at a site other than the active site. Moreover, a combination of mutagenic and structural information reveals that the protein U3GBP follows the well-known 'Venus Fly-trap' mechanism for dinucleotide binding. DATABASES: Structural data are available in RCSB Protein Data Bank under the accession number(s) 7C0F, 7C0K, 7C0L, 7C0O, 7C0R, 7C0S, 7C0T, 7C0U, 7C0V, 7C0W, 7C0X, 7C0Y, 7C0Z, 7C14, 7C15, 7C16, 7C19, and 7C1B.