Lipid-Dependent Activation of the Orphan G Protein-Coupled Receptor, GPR3.

The class A orphan G protein-coupled receptor (GPCR), GPR3, has been implicated in a variety of conditions, including Alzheimer's and premature ovarian failure. GPR3 constitutively couples with Gαs, resulting in the production of cAMP in cells. While tool compounds and several putative endogenous ligands have emerged for the receptor, its endogenous ligand, if it exists, remains a mystery.

A STAT3 protein complex required for mitochondrial mRNA stability and cancer.

Signal transducer and activator of transcription 3 (STAT3) is a potent transcription factor necessary for life whose activity is corrupted in diverse diseases, including cancer. STAT3 biology was presumed to be entirely dependent on its activity as a transcription factor until the discovery of a mitochondrial pool of STAT3, which is necessary for normal tissue function and tumorigenesis. However, the mechanism of this mitochondrial activity remained elusive.

A structural basis for amylin receptor phenotype.

Amylin receptors (AMYRs) are heterodimers of the calcitonin (CT) receptor (CTR) and one of three receptor activity-modifying proteins (RAMPs), AMYR, AMYR, and AMYR. Selective AMYR agonists and dual AMYR/CTR agonists are being developed as obesity treatments; however, the molecular basis for peptide binding and selectivity is unknown. We determined the structure and dynamics of active AMYRs with amylin, AMYR with salmon CT (sCT), AMYR with sCT or human CT (hCT), and CTR with amylin, sCT, or hCT.

Personalised medicines for familial hypercalcemia and hyperparathyroidism.

Loss-of-function calcium-sensing receptor (CASR) mutations cause mineral metabolism disorders, familial hypocalciuric hypercalcemia, or neonatal severe hyperparathyroidism and increase the risk of femoral fracture, chronic kidney disease, coronary heart disease, and other diseases. In severe cases, CaSR mutations are lethal. Off-label use of the CaSR-positive allosteric modulator (PAM), cinacalcet, corrects hypercalcemia in some patients with CaSR mutations.

Epitope length variants balance protective immune responses and viral escape in HIV-1 infection.

Cytotoxic T lymphocyte (CTL) and natural killer (NK) cell responses to a single optimal 10-mer epitope (KK10) in the human immunodeficiency virus type-1 (HIV-1) protein p24Gag are associated with enhanced immune control in patients expressing human leukocyte antigen (HLA)-B27:05. We find that proteasomal activity generates multiple length variants of KK10 (4-14 amino acids), which bind TAP and HLA-B27:05. However, only epitope forms ≥8 amino acids evoke peptide length-specific and cross-reactive CTL responses.

Development of AC265347-Inspired Calcium-Sensing Receptor Ago-Positive Allosteric Modulators.

The calcium-sensing receptor (CaSR) is a clinical target in the treatment of hyperparathyroidism and related diseases. However, clinical use of approved CaSR-targeting drugs such as cinacalcet is limited due to adverse side effects including hypocalcaemia, nausea and vomiting, and in some instances, a lack of efficacy. The CaSR agonist and positive allosteric modulator (ago-PAM), AC265347, is chemically distinct from clinically-approved CaSR PAMs.

Therapeutic Opportunities of Targeting Allosteric Binding Sites on the Calcium-Sensing Receptor.

The CaSR is a class C G protein-coupled receptor (GPCR) that acts as a multimodal chemosensor to maintain diverse homeostatic functions. The CaSR is a clinical therapeutic target in hyperparathyroidism and has emerged as a putative target in several other diseases. These include hyper- and hypocalcaemia caused either by mutations in the gene or in genes that regulate CaSR signaling and expression, and more recently in asthma.

Structure and dynamics of the CGRP receptor in apo and peptide-bound forms.

G protein-coupled receptors (GPCRs) are key regulators of information transmission between cells and organs. Despite this, we have only a limited understanding of the behavior of GPCRs in the apo state and the conformational changes upon agonist binding that lead to G protein recruitment and activation. We expressed and purified unmodified apo and peptide-bound calcitonin gene-related peptide (CGRP) receptors from insect cells to determine their cryo-electron microscopy (cryo-EM) structures, and we complemented these with analysis of protein conformational dynamics using hydrogen-deuterium exchange mass spectrometry and three-dimensional variance analysis of the cryo-EM data.

International Union of Basic and Clinical Pharmacology. CVIII. Calcium-Sensing Receptor Nomenclature, Pharmacology, and Function.

The calcium-sensing receptor (CaSR) is a class C G protein-coupled receptor that responds to multiple endogenous agonists and allosteric modulators, including divalent and trivalent cations, L-amino acids, -glutamyl peptides, polyamines, polycationic peptides, and protons. The CaSR plays a critical role in extracellular calcium (Ca ) homeostasis, as demonstrated by the many naturally occurring mutations in the CaSR or its signaling partners that cause Ca homeostasis disorders. However, CaSR tissue expression in mammals is broad and includes tissues unrelated to Ca homeostasis, in which it, for example, regulates the secretion of digestive hormones, airway constriction, cardiovascular effects, cellular differentiation, and proliferation.

Negative allosteric modulators of the human calcium-sensing receptor bind to overlapping and distinct sites within the 7-transmembrane domain.

Background And Purpose: Negative allosteric modulators (NAMs) that target the calcium-sensing receptor (CaS receptor) were originally developed for the treatment of osteoporosis by stimulating the release of endogenous parathyroid hormone, but failed in human clinical trials. Several chemically and structurally distinct NAM scaffolds have been described, but it is not known how these different scaffolds interact with the CaS receptor to inhibit receptor signalling in response to agonists.

Experimental Approach: In the present study, we used a mutagenesis approach combined with analytical pharmacology and computational modelling to probe the binding sites of four distinct NAM scaffolds.

Broad CD8 T cell cross-recognition of distinct influenza A strains in humans.

Newly-emerged and vaccine-mismatched influenza A viruses (IAVs) result in a rapid global spread of the virus due to minimal antibody-mediated immunity. In that case, established CD8 T-cells can reduce disease severity. However, as mutations occur sporadically within immunogenic IAV-derived T-cell peptides, understanding of T-cell receptor (TCRαβ) cross-reactivity towards IAV variants is needed for a vaccine design.

Identification of Global and Ligand-Specific Calcium Sensing Receptor Activation Mechanisms.

Calcium sensing receptor (CaSR) positive allosteric modulators (PAMs) are therapeutically important. However, few are approved for clinical use, in part due to complexities in assessing allostery at a receptor where the endogenous agonist (extracellular calcium) is present in all biologic fluids. Such complexity impedes efforts to quantify and optimize allosteric drug parameters (affinity, cooperativity, and efficacy) that dictate PAM structure-activity relationships (SARs).

A T Cell Receptor Locus Harbors a Malaria-Specific Immune Response Gene.

Immune response (Ir) genes, originally proposed by Baruj Benacerraf to explain differential antigen-specific responses in animal models, have become synonymous with the major histocompatibility complex (MHC). We discovered a non-MHC-linked Ir gene in a T cell receptor (TCR) locus that was required for CD8 T cell responses to the Plasmodium berghei GAP50 epitope in mice expressing the MHC class I allele H-2D. GAP50-specific CD8 T cell responses emerged from a very large pool of naive Vβ8.

Molecular challenges imposed by MHC-I restricted long epitopes on T cell immunity.

It has widely been accepted that major histocompatibility complex class I molecules (MHC-I) are limited to binding small peptides of 8-10 residues in length. However, this consensus has recently been challenged with the identification of longer peptides (≥11 residues) that can also elicit cytotoxic CD8+ T cell responses. Indeed, a growing number of studies demonstrate that these non-canonical epitopes are important targets for the immune system.

Reversed T Cell Receptor Docking on a Major Histocompatibility Class I Complex Limits Involvement in the Immune Response.

The anti-viral T cell response is drawn from the naive T cell repertoire. During influenza infection, the CD8 T cell response to an H-2D-restricted nucleoprotein epitope (NP) is characterized by preferential expansion of T cells bearing TRBV13 T cell receptors (TCRs) and avoidance of TRBV17 T cells, despite the latter dominating the naive precursor repertoire. We found two TRBV17 TCRs that bound H-2D-NP with a 180° reversed polarity compared to the canonical TCR-pMHC-I docking.

Lack of Heterologous Cross-reactivity toward HLA-A*02:01 Restricted Viral Epitopes Is Underpinned by Distinct αβT Cell Receptor Signatures.

αβT cell receptor (TCR) genetic diversity is outnumbered by the quantity of pathogenic epitopes to be recognized. To provide efficient protective anti-viral immunity, a single TCR ideally needs to cross-react with a multitude of pathogenic epitopes. However, the frequency, extent, and mechanisms of TCR cross-reactivity remain unclear, with conflicting results on anti-viral T cell cross-reactivity observed in humans.

Molecular basis for universal HLA-A*0201-restricted CD8+ T-cell immunity against influenza viruses.

Memory CD8(+)T lymphocytes (CTLs) specific for antigenic peptides derived from internal viral proteins confer broad protection against distinct strains of influenza A virus (IAV). However, immune efficacy can be undermined by the emergence of escape mutants. To determine how T-cell receptor (TCR) composition relates to IAV epitope variability, we used ex vivo peptide-HLA tetramer enrichment and single-cell multiplex analysis to compare TCRs targeted to the largely conserved HLA-A*0201-M158and the hypervariable HLA-B*3501-NP418antigens.

HIV-1-Specific CD8 T Cells Exhibit Limited Cross-Reactivity during Acute Infection.

Prior work has demonstrated that HIV-1-specific CD8 T cells can cross-recognize variant epitopes. However, most of these studies were performed in the context of chronic infection, where the presence of viral quasispecies makes it difficult to ascertain the true nature of the original antigenic stimulus. To overcome this limitation, we evaluated the extent of CD8 T cell cross-reactivity in patients with acute HIV-1 clade B infection.

Interspecies Variation in the Functional Consequences of Mutation of Cytochrome c.

The naturally occurring human cytochrome c variant (G41S) is associated with a mild autosomal dominant thrombocytopenia (Thrombocytopenia Cargeeg) caused by dysregulation of platelet production. The molecular basis of the platelet production defect is unknown. Despite high conservation of cytochrome c between human and mouse (91.

Enhancing the peroxidase activity of cytochrome c by mutation of residue 41: implications for the peroxidase mechanism and cytochrome c release.

The peroxidase activity of cytochrome c may play a key role in the release of cytochrome c from the mitochondrial intermembrane space in the intrinsic apoptosis pathway. Induction of the peroxidase activity of cytochrome c is ascribed to partial unfolding and loss of axial co-ordination between the haem Fe and Met80, and is thought to be triggered by interaction of cytochrome c with cardiolipin (diphosphatidylglycerol) in vivo. However, the reaction mechanism for the peroxidase activity of either native or cardiolipin-bound cytochrome c is uncertain.

Conformational change and human cytochrome c function: mutation of residue 41 modulates caspase activation and destabilizes Met-80 coordination.

Cytochrome c is a highly conserved protein, with 20 residues identical in all eukaryotic cytochromes c. Gly-41 is one of these invariant residues, and is the position of the only reported naturally occurring mutation in cytochrome c (human G41S). The basis, if any, for the conservation of Gly-41 is unknown.