scholarly journals On the TRAIL of Better Therapies: Understanding TNFRSF Structure-Function

Cells ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 764 ◽  
Author(s):  
Éva S. Vanamee ◽  
Denise L. Faustman
Keyword(s):  
Cell Surface ◽  
Ligand Binding ◽  
Structure Function ◽  
Apoptotic Cell ◽  
Hexagonal Lattice ◽  
Receptor Activation ◽  
Tnf Receptor ◽  
Downstream Signaling ◽  
Site Cluster ◽  
The Right

Tumor necrosis factor (TNF) superfamily ligands show diverse biological functions, such as the induction of apoptotic cell death or cell survival and proliferation, making them excellent therapeutic targets for cancer and autoimmunity. We review the latest literature on TNF receptor superfamily signaling with a focus on structure-function. Using combinatorics, we argue that receptors that cluster on the cell surface and are activated by membrane-bound ligands need to arrange in a highly ordered manner, as the probability of random ligand and receptor arrangements matching up for receptor activation is very low. A growing body of evidence indicates that antiparallel receptor dimers that sequester the ligand binding site cluster on the cell surface, forming a hexagonal lattice. Upon ligand binding, this arrangement puts the activated receptors at the right distance to accommodate the downstream signaling partners. The data also suggest that the same geometry is utilized regardless of receptor type. The unified model provides important clues about TNF receptor signaling and should aid the design of better therapies for cancer and various immune mediated diseases.

scholarly journals Vav Family Proteins Couple to Diverse Cell Surface Receptors

2000 ◽  
Vol 20 (17) ◽  
pp. 6364-6373 ◽  
Author(s):  
Sheri L. Moores ◽  
Laura M. Selfors ◽  
Jessica Fredericks ◽  
Timo Breit ◽  
Keiko Fujikawa ◽  
...  
Keyword(s):  
Growth Factor ◽  
Cell Surface ◽  
Tyrosine Phosphorylation ◽  
Tyrosine Kinases ◽  
Protein Tyrosine Kinase ◽  
Receptor Activation ◽  
Cell Surface Receptors ◽  
Nucleotide Exchange ◽  
Surface Receptors ◽  
Downstream Signaling

ABSTRACT Vav proteins are guanine nucleotide exchange factors for Rho family GTPases which activate pathways leading to actin cytoskeletal rearrangements and transcriptional alterations. Vav proteins contain several protein binding domains which can link cell surface receptors to downstream signaling proteins. Vav1 is expressed exclusively in hematopoietic cells and tyrosine phosphorylated in response to activation of multiple cell surface receptors. However, it is not known whether the recently identified isoforms Vav2 and Vav3, which are broadly expressed, can couple with similar classes of receptors, nor is it known whether all Vav isoforms possess identical functional activities. We expressed Vav1, Vav2, and Vav3 at equivalent levels to directly compare the responses of the Vav proteins to receptor activation. Although each Vav isoform was tyrosine phosphorylated upon activation of representative receptor tyrosine kinases, integrin, and lymphocyte antigen receptors, we found unique aspects of Vav protein coupling in each receptor pathway. Each Vav protein coprecipitated with activated epidermal growth factor and platelet-derived growth factor (PDGF) receptors, and multiple phosphorylated tyrosine residues on the PDGF receptor were able to mediate Vav2 tyrosine phosphorylation. Integrin-induced tyrosine phosphorylation of Vav proteins was not detected in nonhematopoietic cells unless the protein tyrosine kinase Syk was also expressed, suggesting that integrin activation of Vav proteins may be restricted to cell types that express particular tyrosine kinases. In addition, we found that Vav1, but not Vav2 or Vav3, can efficiently cooperate with T-cell receptor signaling to enhance NFAT-dependent transcription, while Vav1 and Vav3, but not Vav2, can enhance NFκB-dependent transcription. Thus, although each Vav isoform can respond to similar cell surface receptors, there are isoform-specific differences in their activation of downstream signaling pathways.

scholarly journals Loss-of-Function Mutations in the Human Luteinizing Hormone Receptor Predominantly Cause Intracellular Retention

Endocrinology ◽  
2016 ◽  
Vol 157 (11) ◽  
pp. 4364-4377 ◽  
Author(s):  
Claire Louise Newton ◽  
Ross Calley Anderson ◽  
Arieh Anthony Katz ◽  
Robert Peter Millar
Keyword(s):  
Luteinizing Hormone ◽  
Cell Surface ◽  
Ligand Binding ◽  
Hormone Receptors ◽  
Receptor Activation ◽  
Luteinizing Hormone Receptor ◽  
Cell Surface Expression ◽  
Receptor Function ◽  
Loss Of Function ◽  
Pharmacological Chaperone

Mutations in G protein–coupled receptors (GPCRs) have been identified for many endocrine hormone signaling deficiencies. Inactivating mutations can impair ligand binding, receptor activation/coupling to signaling pathways, or can cause receptor misfolding and consequent impaired expression at the cell membrane. Here we examine the cell surface expression, ligand binding, and signaling of a range of mutant human luteinizing hormone receptors (LHRs) identified as causing reproductive dysfunction in human patients. The data obtained reveal how mutations in GPCRs can have diverse and severely deleterious effects on receptor function. Furthermore, it was found that impaired functionality of the majority of the mutant LHRs was due to reduced expression at the cell surface (14/20) while only two mutations caused impaired binding affinity and two impaired in signaling. An additional two mutations were found to cause no impairment of receptor function. These data demonstrate that the majority of LHR mutations lead to intracellular retention and highlight the potential for novel pharmacological chaperone therapeutics that can “rescue” expression/function of retained mutant GPCRs.

scholarly journals Functional Characterization of Naturally Occurring Pathogenic Mutations in the Human Leptin Receptor

Endocrinology ◽  
2008 ◽  
Vol 149 (12) ◽  
pp. 6043-6052 ◽  
Author(s):  
Wendy Kimber ◽  
Frank Peelman ◽  
Xavier Prieur ◽  
Teresia Wangensteen ◽  
Stephen O'Rahilly ◽  
...  
Keyword(s):  
Cell Surface ◽  
Ligand Binding ◽  
Binding Site ◽  
Molecular Mechanisms ◽  
Leptin Receptor ◽  
Receptor Activation ◽  
Cell Surface Expression ◽  
Missense Mutations ◽  
Naturally Occurring

We have recently reported the first naturally occurring missense mutations in the leptin receptor (LR) in patients with severe obesity. We have examined the molecular mechanisms by which these extracellular domain mutations disrupt LR signaling. The Ala409Glu mutant receptor is expressed at the cell surface, binds leptin normally but fails to signal to downstream pathways. A409 is present on the surface-exposed region of the Ig-like domain that forms the binding site III for interaction with leptin. This binding site does not appear to contribute to the binding affinity of leptin to its receptor but is critical for receptor activation in response to ligand binding. The Trp664Arg and His684Pro mutations are predicted to impair receptor folding. Both mutants result in a complete inability to signal to downstream pathways despite evidence for some residual cell surface expression and ligand binding. The Arg612His mutant falls in the second subdomain of the high-affinity binding site for leptin, and results in a receptor that shows evidence for intracellular retention but retains some residual signaling. These studies, which represent the first detailed characterization of the functional properties of naturally occurring missense mutations in the human LR, indicate that most such mutations affect receptor folding and expression at the cell surface rather than primarily impairing ligand binding. The exception is Ala409Glu, which interferes with the coupling of ligand binding to receptor activation. Naturally occurring mutations associated with human obesity are valuable tools with which to explore structure/function relationships within the LR.

scholarly journals Insertion of a Synthetic Switch Into Insulin Provides Metabolite-Dependent Regulation of Hormone-Receptor Activation

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A440-A440
Author(s):  
Yen-Shan Chen ◽  
Jeremy Gleaton ◽  
Yanwu Yang ◽  
Balamurugan Dhayalan ◽  
Nelson B Phillips ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Insulin Signaling ◽  
Large Scale ◽  
Glucose Sensor ◽  
Phenylboronic Acid ◽  
Receptor Activation ◽  
Insulin Analog ◽  
Structural Reorganization ◽  
Nmr Studies ◽  
Downstream Signaling

Abstract Insulin signaling requires conformational change: whereas the free hormone and its receptor each adopt autoinhibited conformations, their binding leads to large-scale structural reorganization. To test the coupling between insulin’s “opening” and receptor activation, we inserted an artificial ligand-dependent switch into insulin. Ligand binding disrupts an internal tether designed to stabilize the hormone’s native closed and inactive conformation, thereby enabling productive receptor engagement. This scheme exploited a diol sensor (meta-fluoro-phenylboronic acid at GlyA1) and internal diol (3,4-dihydroxybenzoate at LysB28). The sensor recognizes monosaccharides (fructose > glucose). Studies of insulin signaling in human hepatoma-derived cells (HepG2) demonstrated fructose-dependent receptor autophosphorylation leading to appropriate downstream signaling events, including a specific kinase cascade and metabolic gene regulation (gluconeogenesis and lipogenesis). Addition of glucose (an isomeric ligand with negligible sensor affinity) did not activate the receptor. Similarly, metabolite-regulated signaling was not observed in control studies of (i) an unmodified insulin analog or (ii) an analog containing a diol sensor in the absence of internal tethering. Although as expected CD-detected secondary structure was unaffected by ligand binding, heteronuclear NMR studies revealed subtle local and nonlocal monosaccharide-dependent changes in structure. Insertion of a synthetic switch into insulin has thus demonstrated coupling between hinge-opening and holoreceptor signaling. In addition to this basic finding, our results provide proof of principle for a mechanism-based metabolite-responsive insulin. In particular, replacement of the present fructose sensor by an analogous glucose sensor may enable translational development of a “smart” insulin analog designed to mitigate risk of hypoglycemia in the treatment of diabetes mellitus.

scholarly journals Residue 6.43 defines receptor function in class F GPCRs

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ainoleena Turku ◽  
Hannes Schihada ◽  
Pawel Kozielewicz ◽  
Carl-Fredrik Bowin ◽  
Gunnar Schulte
Keyword(s):  
Ligand Binding ◽  
G Protein ◽  
Conformational Changes ◽  
Mutational Analysis ◽  
Receptor Activation ◽  
Receptor Function ◽  
Protein Activation ◽  
Downstream Signaling ◽  
Activation Mechanisms ◽  
Class F

AbstractThe class Frizzled of G protein-coupled receptors (GPCRs), consisting of ten Frizzled (FZD1-10) subtypes and Smoothened (SMO), remains one of the most enigmatic GPCR families. While SMO relies on cholesterol binding to the 7TM core of the receptor to activate downstream signaling, underlying details of receptor activation remain obscure for FZDs. Here, we aimed to investigate the activation mechanisms of class F receptors utilizing a computational biology approach and mutational analysis of receptor function in combination with ligand binding and downstream signaling assays in living cells. Our results indicate that FZDs differ substantially from SMO in receptor activation-associated conformational changes. SMO manifests a preference for a straight TM6 in both ligand binding and functional readouts. Similar to the majority of GPCRs, FZDs present with a kinked TM6 upon activation owing to the presence of residue P6.43. Functional comparison of FZD and FZD P6.43F mutants in different assay formats monitoring ligand binding, G protein activation, DVL2 recruitment and TOPflash activity, however, underlines further the functional diversity among FZDs and not only between FZDs and SMO.

scholarly journals Insertion of a synthetic switch into insulin provides metabolite-dependent regulation of hormone–receptor activation

2021 ◽  
Vol 118 (30) ◽  
pp. e2103518118
Author(s):  
Yen-Shan Chen ◽  
Jeremy Gleaton ◽  
Yanwu Yang ◽  
Balamurugan Dhayalan ◽  
Nelson B. Phillips ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Insulin Signaling ◽  
Glucose Sensor ◽  
Phenylboronic Acid ◽  
Receptor Activation ◽  
Insulin Analog ◽  
Functional Coupling ◽  
Structural Reorganization ◽  
Nmr Studies ◽  
Downstream Signaling

Insulin-signaling requires conformational change: whereas the free hormone and its receptor each adopt autoinhibited conformations, their binding leads to structural reorganization. To test the functional coupling between insulin’s “hinge opening” and receptor activation, we inserted an artificial ligand-dependent switch into the insulin molecule. Ligand-binding disrupts an internal tether designed to stabilize the hormone’s native closed and inactive conformation, thereby enabling productive receptor engagement. This scheme exploited a diol sensor (meta-fluoro-phenylboronic acid at GlyA1) and internal diol (3,4-dihydroxybenzoate at LysB28). The sensor recognizes monosaccharides (fructose > glucose). Studies of insulin-signaling in human hepatoma-derived cells (HepG2) demonstrated fructose-dependent receptor autophosphorylation leading to appropriate downstream signaling events, including a specific kinase cascade and metabolic gene regulation (gluconeogenesis and lipogenesis). Addition of glucose (an isomeric ligand with negligible sensor affinity) did not activate the hormone. Similarly, metabolite-regulated signaling was not observed in control studies of 1) an unmodified insulin analog or 2) an analog containing a diol sensor without internal tethering. Although secondary structure (as probed by circular dichroism) was unaffected by ligand-binding, heteronuclear NMR studies revealed subtle local and nonlocal monosaccharide-dependent changes in structure. Insertion of a synthetic switch into insulin has thus demonstrated coupling between hinge-opening and allosteric holoreceptor signaling. In addition to this foundational finding, our results provide proof of principle for design of a mechanism-based metabolite-responsive insulin. In particular, replacement of the present fructose sensor by an analogous glucose sensor may enable translational development of a “smart” insulin analog to mitigate hypoglycemic risk in diabetes therapy.

scholarly journals Functional Characterization and Structural Modeling of Obesity Associated Mutations in the Melanocortin 4 Receptor

Endocrinology ◽  
2008 ◽  
Vol 150 (1) ◽  
pp. 114-125 ◽  
Author(s):  
Karen Tan ◽  
Irina D. Pogozheva ◽  
Giles S. H. Yeo ◽  
Dirk Hadaschik ◽  
Julia M. Keogh ◽  
...  
Keyword(s):  
Cell Surface ◽  
Ligand Binding ◽  
Functional Characterization ◽  
Structural Modeling ◽  
Receptor Activation ◽  
Cell Surface Expression ◽  
Structural Basis ◽  
Conformational Rearrangement ◽  
Mc4r Gene ◽  
Melanocortin 4 Receptor

Mutations in the melanocortin 4 receptor (MC4R) gene are the most common known cause of monogenic human obesity. The MC4R gene was sequenced in 2000 subjects with severe early-onset obesity. We detected seven different nonsense and 19 nonsynonymous mutations in a total of 94 probands, some of which have been reported previously by others. We functionally characterized the 11 novel obesity associated missense mutations. Seven of these mutants (L54P, E61K, I69T, S136P, M161T, T162I, and I269N) showed impaired cell surface trafficking, reduced level of maximal binding of the radioligand [125I]NDP-MSH, and reduced ability to generate cAMP in response to ligand. Four mutant MC4Rs (G55V, G55D, S136F, and A303T) displayed cell surface expression and agonist binding similar to the wild-type receptor but showed impaired cAMP production, suggesting that these residues are likely to be critical for conformational rearrangement essential for receptor activation. Homology modeling of these mutants using a model of MC4R based on the crystal structure of the β2-adrenoreceptor was used to provide insights into the possible structural basis for receptor dysfunction. Transmembrane (TM) domains 1, 3, 6, 7, and peripheral helix 8 appear to participate in the agonist-induced conformational rearrangement necessary for coupling of ligand binding to signaling. We conclude that G55V, G55D, S136F, and A303T mutations are likely to strengthen helix-helix interactions between TM1 and TM2, TM3 and TM6, and TM7 and helix 8, respectively, preventing relative movement of these helices during receptor activation. The combination of functional studies and structural modeling of naturally occurring pathogenic mutations in MC4R can provide valuable information regarding the molecular mechanism of MC4R activation and its dysfunction in human disease. Among obesity-associated melanocortin-4 receptor mutations, four transmembrane domains and peripheral helix 8 are necessary for coupling of ligand binding to signaling.

scholarly journals Biosensors Monitor Ligand-Selective Effects at Kappa Opioid Receptors

2021 ◽  
Author(s):  
Lucie Oberhauser ◽  
Miriam Stoeber
Keyword(s):  
Subcellular Location ◽  
Receptor Activation ◽  
Cellular Level ◽  
Two Dimensions ◽  
Kappa Opioid Receptor ◽  
Kappa Opioid ◽  
Downstream Signaling ◽  
Regulator Protein ◽  
Cellular Context ◽  
Selective Effects

AbstractThe kappa opioid receptor (KOR) has emerged as a promising therapeutic target for pain and itch treatment. There is growing interest in biased agonists that preferentially activate select signaling pathways downstream of KOR activation on the cellular level due to their therapeutic promise in retaining the analgesic and antipruritic effects and eliminating the sedative and dysphoric effects of KOR signaling on the physiological level. The concept of ligand-selective signaling includes that biased ligands promote KOR to selectively recruit one transducer or regulator protein over another, introducing bias into the signaling cascade at the very receptor-proximal level. Measuring agonist effects directly at the receptor has remained challenging and previous studies have focused on inferring agonist-selective KOR engagement with G protein relative to β-arrestin based on downstream signaling readouts. Here we discuss novel strategies to directly assess ligand-selective effects on receptor activation using KOR-interacting biosensors. The conformation-specific cytoplasmic biosensors are disconnected from the endogenous signaling machinery and provide a direct receptor-proxy readout of ligand effects in living cells. Receptor–biosensor interaction is ligand concentration dependent and can be used to determine relative ligand potency and efficacy. In addition, the biosensors reveal the existence of two dimensions of agonist bias in the cellular context: Firstly, agonists can selectively produce discrete protein-engaged KOR states and secondly, agonists can differ in the precise subcellular location at which they activate KOR. We discuss the value and the limitations of using orthogonal receptor-interacting biosensors in the quest to understand functional selectivity amongst KOR agonists in the cellular context.

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