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Nature Communications Jun 2023The neurotensin receptor 1 (NTS) is a G protein-coupled receptor (GPCR) with promise as a drug target for the treatment of pain, schizophrenia, obesity, addiction, and...
The neurotensin receptor 1 (NTS) is a G protein-coupled receptor (GPCR) with promise as a drug target for the treatment of pain, schizophrenia, obesity, addiction, and various cancers. A detailed picture of the NTS structural landscape has been established by X-ray crystallography and cryo-EM and yet, the molecular determinants for why a receptor couples to G protein versus arrestin transducers remain poorly defined. We used CH-methionine NMR spectroscopy to show that binding of phosphatidylinositol-4,5-bisphosphate (PIP2) to the receptor's intracellular surface allosterically tunes the timescale of motions at the orthosteric pocket and conserved activation motifs - without dramatically altering the structural ensemble. β-arrestin-1 further remodels the receptor ensemble by reducing conformational exchange kinetics for a subset of resonances, whereas G protein coupling has little to no effect on exchange rates. A β-arrestin biased allosteric modulator transforms the NTS:G protein complex into a concatenation of substates, without triggering transducer dissociation, suggesting that it may function by stabilizing signaling incompetent G protein conformations such as the non-canonical state. Together, our work demonstrates the importance of kinetic information to a complete picture of the GPCR activation landscape.
Topics: Receptors, Neurotensin; beta-Arrestin 1; Receptors, G-Protein-Coupled; beta-Arrestins; GTP-Binding Proteins; Arrestin
PubMed: 37286565
DOI: 10.1038/s41467-023-38894-8 -
Frontiers in Immunology 2021Plasma membrane provides a biophysical and biochemical platform for immune cells to trigger signaling cascades and immune responses against attacks from foreign... (Review)
Review
Plasma membrane provides a biophysical and biochemical platform for immune cells to trigger signaling cascades and immune responses against attacks from foreign pathogens or tumor cells. Mounting evidence suggests that the biophysical-chemical properties of this platform, including complex compositions of lipids and cholesterols, membrane tension, and electrical potential, could cooperatively regulate the immune receptor functions. However, the molecular mechanism is still unclear because of the tremendous compositional complexity and spatio-temporal dynamics of the plasma membrane. Here, we review the recent significant progress of dynamical regulation of plasma membrane on immune receptors, including T cell receptor, B cell receptor, Fc receptor, and other important immune receptors, to proceed mechano-chemical sensing and transmembrane signal transduction. We also discuss how biophysical-chemical cues couple together to dynamically tune the receptor's structural conformation or orientation, distribution, and organization, thereby possibly impacting their ligand binding and related signal transduction. Moreover, we propose that electrical potential could potentially induce the biophysical-chemical coupling change, such as lipid distribution and membrane tension, to inevitably regulate immune receptor activation.
Topics: Animals; Binding Sites; Cell Membrane; Chemical Phenomena; Electrophysiological Phenomena; Humans; Mechanical Phenomena; Membrane Lipids; Protein Binding; Receptors, Immunologic; Signal Transduction
PubMed: 33679752
DOI: 10.3389/fimmu.2021.613185 -
Trends in Immunology Jul 2020How innate immunity gave rise to adaptive immunity in vertebrates remains unknown. We propose an evolutionary scenario beginning with pathogen-associated molecular... (Review)
Review
How innate immunity gave rise to adaptive immunity in vertebrates remains unknown. We propose an evolutionary scenario beginning with pathogen-associated molecular pattern(s) (PAMPs) being presented by molecule(s) on one cell to specific receptor(s) on other cells, much like MHC molecules and T cell receptors (TCRs). In this model, mutations in MHC-like molecule(s) that bound new PAMP(s) would not be recognized by original TCR-like molecule(s), and new MHC-like gene(s) would be lost by neutral drift. Integrating recombination activating gene (RAG) transposon(s) in a TCR-like gene would result in greater recognition diversity, with new MHC-like variants recognized and selected, along with a new RAG/TCR-like system. MHC genes would be selected to present many peptides, through multigene families, allelic polymorphism, and peptide-binding promiscuity.
Topics: Adaptive Immunity; Animals; DNA Transposable Elements; Evolution, Molecular; Genes, RAG-1; Immunity, Innate; Major Histocompatibility Complex; Receptors, Antigen, T-Cell
PubMed: 32467030
DOI: 10.1016/j.it.2020.05.002 -
Cytokine Mar 2022Interleukin (IL)-38 is the least well-understood cytokine of the IL-1 family. Since its discovery twenty years ago, numerous studies have linked IL-38 to diverse... (Review)
Review
Interleukin (IL)-38 is the least well-understood cytokine of the IL-1 family. Since its discovery twenty years ago, numerous studies have linked IL-38 to diverse pathologies, especially in the context of autoimmune and inflammatory processes, while its role in cancer has been less explored. Broad anti-inflammatory effects have been reported for IL-38 in both in vitro and in vivo models, and, together with its homology to the IL-1 and IL-36 receptor antagonists, have raised expectations about its potential therapeutic utility. Data in human and mouse experimental systems support a negative regulatory role of IL-38 on the Th17 axis through effects on T cells and myeloid cells. Additional studies point to tolerogenic functions of IL-38, acting on dendritic cells and regulatory T cells, as well as to inhibition of pro-inflammatory macrophage activity. IL-38 further exhibits anti-inflammatory and tissue protective properties in epithelial and mesenchymal cells. However, published data also reveal variability and inconsistent dose-dependencies of these anti-inflammatory effects, as well as context-dependent pro-inflammatory properties of IL-38, and are difficult to interpret due to the high heterogeneity in the materials and experimental designs used across studies. In addition, it is still not clear which receptor(s) is/are fundamental for IL-38 signalling, and the biological impact of N-terminal processing of the protein remains to be clarified. In this review, we provide an overview of our current knowledge of IL-38 biology, discuss persistent controversies surrounding this cytokine, and highlight some questions to be addressed to facilitate progress towards a better understanding of its mechanisms of action.
Topics: Animals; Cytokines; Inflammation; Mice; Neoplasms; T-Lymphocytes, Regulatory; Th17 Cells
PubMed: 35066449
DOI: 10.1016/j.cyto.2022.155808 -
Nature Communications Feb 2022AMPA-type glutamate receptors (AMPARs) mediate rapid signal transmission at excitatory synapses in the brain. Glutamate binding to the receptor's ligand-binding domains...
AMPA-type glutamate receptors (AMPARs) mediate rapid signal transmission at excitatory synapses in the brain. Glutamate binding to the receptor's ligand-binding domains (LBDs) leads to ion channel activation and desensitization. Gating kinetics shape synaptic transmission and are strongly modulated by transmembrane AMPAR regulatory proteins (TARPs) through currently incompletely resolved mechanisms. Here, electron cryo-microscopy structures of the GluA1/2 TARP-γ8 complex, in both open and desensitized states (at 3.5 Å), reveal state-selective engagement of the LBDs by the large TARP-γ8 loop ('β1'), elucidating how this TARP stabilizes specific gating states. We further show how TARPs alter channel rectification, by interacting with the pore helix of the selectivity filter. Lastly, we reveal that the Q/R-editing site couples the channel constriction at the filter entrance to the gate, and forms the major cation binding site in the conduction path. Our results provide a mechanistic framework of how TARPs modulate AMPAR gating and conductance.
Topics: Animals; Calcium Channels; Cryoelectron Microscopy; Glutamic Acid; HEK293 Cells; Humans; Mutation; Patch-Clamp Techniques; Protein Domains; Rats; Receptors, AMPA; Recombinant Proteins; Synaptic Transmission; Transfection
PubMed: 35136046
DOI: 10.1038/s41467-022-28404-7 -
Journal of Alzheimer's Disease : JAD 2021Alzheimer's disease (AD), the main cause of dementia worldwide, is characterized by a complex and multifactorial etiology. In large part, excitatory neurotransmission in... (Review)
Review
Alzheimer's disease (AD), the main cause of dementia worldwide, is characterized by a complex and multifactorial etiology. In large part, excitatory neurotransmission in the central nervous system is mediated by glutamate and its receptors are involved in synaptic plasticity. The N-methyl-D-aspartate (NMDA) receptors, which require the agonist glutamate and a coagonist such as glycine or the D-enantiomer of serine for activation, play a main role here. A second D-amino acid, D-aspartate, acts as agonist of NMDA receptors. D-amino acids, present in low amounts in nature and long considered to be of bacterial origin, have distinctive functions in mammals. In recent years, alterations in physiological levels of various D-amino acids have been linked to various pathological states, ranging from chronic kidney disease to neurological disorders. Actually, the level of NMDA receptor signaling must be balanced to promote neuronal survival and prevent neurodegeneration: this signaling in AD is affected mainly by glutamate availability and modulation of the receptor's functions. Here, we report the experimental findings linking D-serine and D-aspartate, through NMDA receptor modulation, to AD and cognitive functions. Interestingly, AD progression has been also associated with the enzymes related to D-amino acid metabolism as well as with glucose and serine metabolism. Furthermore, the D-serine and D-/total serine ratio in serum have been recently proposed as biomarkers of AD progression. A greater understanding of the role of D-amino acids in excitotoxicity related to the pathogenesis of AD will facilitate novel therapeutic treatments to cure the disease and improve life expectancy.
Topics: Alzheimer Disease; Amino Acids; Animals; Aspartic Acid; Humans; Receptors, N-Methyl-D-Aspartate; Serine
PubMed: 33554911
DOI: 10.3233/JAD-201217 -
The Journal of Neuroscience : the... Jul 2022NMDARs are ionotropic glutamate receptors widely expressed in the CNS, where they mediate phenomena as diverse as neurotransmission, information processing,...
NMDARs are ionotropic glutamate receptors widely expressed in the CNS, where they mediate phenomena as diverse as neurotransmission, information processing, synaptogenesis, and cellular toxicity. They function as glutamate-gated Ca-permeable channels, which require glycine as coagonist, and can be modulated by many diffusible ligands and cellular cues, including mechanical stimuli. Previously, we found that, in cultured astrocytes, shear stress initiates NMDAR-mediated Ca entry in the absence of added agonists, suggesting that more than being mechanosensitive, NMDARs may be mechanically activated. Here, we used controlled expression of rat recombinant receptors and noninvasive on-cell single-channel current recordings to show that mild membrane stretch can substitute for the neurotransmitter glutamate in gating NMDAR currents. Notably, stretch-activated currents maintained the hallmark features of the glutamate-gated currents, including glycine-requirement, large unitary conductance, high Ca permeability, and voltage-dependent Mg blockade. Further, we found that the stretch-gated current required the receptor's intracellular domain. Our results are consistent with the hypothesis that mechanical forces can gate endogenous NMDAR currents even in the absence of synaptic glutamate release, which has important implications for understanding mechanotransduction and the physiological and pathologic effects of mechanical forces on cells of the CNS. We show that, in addition to enhancing currents elicited with low agonist concentrations, membrane stretch can gate NMDARs in the absence of the neurotransmitter glutamate. Stretch-gated currents have the principal hallmarks of the glutamate-gated currents, including requirement for glycine, large Na conductance, high Ca permeability, and voltage-dependent Mg block. Therefore, results suggest that mechanical forces can initiate cellular processes presently attributed to glutamatergic neurotransmission, such as synaptic plasticity and cytotoxicity. Given the ubiquitous presence of mechanical forces in the CNS, this discovery identifies NMDARs as possibly important mechanotransducers during development and across the lifespan, and during pathologic processes, such as those associated with traumatic brain injuries, shaken infant syndrome, and chronic traumatic encephalopathy.
Topics: Animals; Glutamic Acid; Glycine; Humans; Mechanotransduction, Cellular; Rats; Receptors, N-Methyl-D-Aspartate; Synaptic Transmission
PubMed: 35705487
DOI: 10.1523/JNEUROSCI.0350-22.2022 -
Biophysical Journal May 2021Signal transduction within crowded cellular compartments is essential for the physiological function of cells. Although the accuracy with which receptors can probe the...
Signal transduction within crowded cellular compartments is essential for the physiological function of cells. Although the accuracy with which receptors can probe the concentration of ligands has been thoroughly investigated in dilute systems, the effect of macromolecular crowding on the inference of concentration remains unclear. In this work, we develop an algorithm to simulate reversible reactions between reacting Brownian particles. Our algorithm facilitates the calculation of reaction rates and correlation times for ligand-receptor systems in the presence of macromolecular crowding. Using this method, we show that it is possible for crowding to increase the accuracy of estimated ligand concentration based on receptor occupancy. In particular, we find that crowding can enhance the effective association rates between small ligands and receptors to a degree sufficient to overcome the increased chance of rebinding due to caging by crowding molecules. For larger ligands, crowding decreases the accuracy of the receptor's estimate primarily by decreasing the microscopic association and dissociation rates.
Topics: Ligands; Macromolecular Substances; Signal Transduction
PubMed: 33675760
DOI: 10.1016/j.bpj.2021.02.035 -
Frontiers in Cell and Developmental... 2021G protein-coupled receptors (GPCRs) are the largest class of human membrane proteins that bind extracellular ligands at their orthosteric binding pocket to transmit...
G protein-coupled receptors (GPCRs) are the largest class of human membrane proteins that bind extracellular ligands at their orthosteric binding pocket to transmit signals to the cell interior. Ligand binding evokes conformational changes in GPCRs that trigger the binding of intracellular interaction partners (G proteins, G protein kinases, and arrestins), which initiate diverse cellular responses. It has become increasingly evident that the preference of a GPCR for a certain intracellular interaction partner is modulated by a diverse range of factors, e.g., ligands or lipids embedding the transmembrane receptor. Here, by means of molecular dynamics simulations of the β-adrenergic receptor and β-arrestin2, we study how membrane lipids and receptor phosphorylation regulate GPCR-arrestin complex conformation and dynamics. We find that phosphorylation drives the receptor's intracellular loop 3 (ICL3) away from a native negatively charged membrane surface to interact with arrestin. If the receptor is embedded in a neutral membrane, the phosphorylated ICL3 attaches to the membrane surface, which widely opens the receptor core. This opening, which is similar to the opening in the G protein-bound state, weakens the binding of arrestin. The loss of binding specificity is manifested by shallower arrestin insertion into the receptor core and higher dynamics of the receptor-arrestin complex. Our results show that receptor phosphorylation and the local membrane composition cooperatively fine-tune GPCR-mediated signal transduction. Moreover, the results suggest that deeper understanding of complex GPCR regulation mechanisms is necessary to discover novel pathways of pharmacological intervention.
PubMed: 35004696
DOI: 10.3389/fcell.2021.807913 -
Frontiers in Immunology 2020The use of T cells reactive with intracellular tumor-associated or tumor-specific antigens has been a promising strategy for cancer immunotherapies in the past three... (Review)
Review
The use of T cells reactive with intracellular tumor-associated or tumor-specific antigens has been a promising strategy for cancer immunotherapies in the past three decades, but the approach has been constrained by a limited understanding of the T cell receptor's (TCR) complex functions and specificities. Newer TCR and T cell-based approaches are in development, including engineered adoptive T cells with enhanced TCR affinities, TCR mimic antibodies, and T cell-redirecting bispecific agents. These new therapeutic modalities are exciting opportunities by which TCR recognition can be further exploited for therapeutic benefit. In this review we summarize the development of TCR-based therapeutic strategies and focus on balancing efficacy and potency versus specificity, and hence, possible toxicity, of these powerful therapeutic modalities.
Topics: Animals; Humans; Immunotherapy; Receptors, Antigen, T-Cell
PubMed: 33569049
DOI: 10.3389/fimmu.2020.585385