Biphasic activation of β-arrestin 1 upon interaction with a GPCR revealed by methyl-TROSY NMR

Abstractβ-arrestins (βarrs) play multifaceted roles in the function of G protein-coupled receptors (GPCRs). βarrs typically interact with phosphorylated C-terminal tail (C tail) and transmembrane core (TM core) of GPCRs. However, the effects of the C tail- and TM core-mediated interactions on the conformational activation of βarrs have remained elusive. Here, we show the conformational changes for βarr activation upon the C tail- and TM core-mediated interactions with a prototypical GPCR by nuclear magnetic resonance (NMR) spectroscopy. Our NMR analyses demonstrated that while the C tail-mediated interaction alone induces partial activation, in which βarr exists in equilibrium between basal and activated conformations, the TM core- and the C tail-mediated interactions together completely shift the equilibrium toward the activated conformation. The conformation-selective antibody, Fab30, promotes partially activated βarr into the activated-like conformation. This plasticity of βarr conformation in complex with GPCRs engaged in different binding modes may explain the multifunctionality of βarrs.

Role of Toll-Like Receptors in Neuroimmune Diseases: Therapeutic Targets and Problems

Toll-like receptors (TLRs) are a class of proteins playing a key role in innate and adaptive immune responses. TLRs are involved in the development and progression of neuroimmune diseases via initiating inflammatory responses. Thus, targeting TLRs signaling pathway may be considered as a potential therapy for neuroimmune diseases. However, the role of TLRs is elusive and complex in neuroimmune diseases. In addition to the inadequate immune response of TLRs inhibitors in the experiments, the recent studies also demonstrated that partial activation of TLRs is conducive to the production of anti-inflammatory factors and nervous system repair. Exploring the mechanism of TLRs in neuroimmune diseases and combining with developing the emerging drug may conquer neuroimmune diseases in the future. Herein, we provide an overview of the role of TLRs in several neuroimmune diseases, including multiple sclerosis, neuromyelitis optica spectrum disorder, Guillain-Barré syndrome and myasthenia gravis. Emerging difficulties and potential solutions in clinical application of TLRs inhibitors will also be discussed.

Transient Central Precocious Puberty: a new entity among the spectrum of Precocious Puberty?

Objective The aim of this study is to evaluate clinical, hormonal and ultrasound features in girls with precocious puberty (PP). Methods 96 girls referred to our center for PP between 1st January 2007 and 31th December 2017 fulfilled inclusion criteria and were recruited for the study. 3 groups of patients were considered. Group 1: 56 subjects with Central PP (CPP) requiring treatment with GnRH analogue; Group 2: 22 subjects characterized by some criteria of CPP without indication to treatment, “Transient CPP”(T-CPP); Group 3: 18 subjects with Isolated Thelarche (IT). A questionnaire about anamnestic and environmental data was provided to patients which were followed through normal clinical care. Results an increase in Groups 2 and 3 diagnosis was observed over the years. LH peak (UI/ml) at diagnosis was higher in Group 1 vs Group 2 (11.7 ± 7.8 vs 4.58 ± 1.60)(p < 0.001) and 3 (11.7 ± 7.9 vs 2.18 ± 1.15)(p < 0.001) and also in Group 2 vs Group 3 (4.58 ± 1.6 vs 2.18 ± 1.1)(p < 0.05). At 6–12 months, LH peak of Group 2 was lower (2.35 ± 1.3) compared with diagnosis data (4.58 ± 1.60)(p < 0.05). Uterine Longitudinal Diameter (ULD) (mm) was longer in Group 1 (42.53 ± 6.26) vs Group 2 (36.54 ± 4.86)(p < 0.001) and 3 (30.70 ± 4.74)(p < 0.001), and this difference is also found between Group 2 and 3 (p < 0.005). Potential exposure to herbicides and pesticides was reported in 17.5% in Group 2 vs 12.5% in Group 1 (p < 0.001). Conclusions This study seemed to indicate an increase in diagnosis of T-CPP and IT cases. To our knowledge, this is the first report of a form defined as T-CPP, characterized by a partial activation in the HPG axis normalizing over time. As for environmental factors, we indirectly evaluated the role of some endocrine disruptors (EDCs) affecting pubertal axis activation, without leading to a complete maturation.

Full activation of an α7-α3β4 nicotinic receptor complex avoids receptor desensitization in human chromaffin cells

Abstractα7 nicotinic receptors have been involved in numerous pathologies. A hallmark of these receptors is their extremely fast desensitization, a process not fully understood yet. Here we show that human native α7 and α3β4 nicotinic receptors physically interact in human chromaffin cells of adrenal glands. The full activation of this α7-α3β4 receptor complex avoids subtypes receptor desensitization, leading to gradual increase of currents with successive acetylcholine pulses. Instead, full and partial activation with choline of α7 and α3β4 subtypes, respectively, of this linked receptor leads to α7 receptor desensitization. Therefore choline, a product of the acetylcholine hydrolysis, acts as a brake by limiting the increase of currents by acetylcholine. Very importantly, the efficiency of the α7-α3β4 interaction diminishes in subjets older than 50 years, accordingly increasing receptor desensitization and decreasing nicotinic currents. These results open a new line of research to achieve improved therapeutic treatments for nicotinic receptors related diseases.

To Probe Full and Partial Activation of Human Peroxisome Proliferator-Activated Receptors by Pan-Agonist Chiglitazar Using Molecular Dynamics Simulations

Chiglitazar is a promising new-generation insulin sensitizer with low reverse effects for the treatment of type II diabetes mellitus (T2DM) and has shown activity as a nonselective pan-agonist to the human peroxisome proliferator-activated receptors (PPARs) (i.e., full activation of PPARγ and a partial activation of PPARα and PPARβ/δ). Yet, it has no high-resolution complex structure with PPARs and its detailed interactions and activation mechanism remain unclear. In this study, we docked chiglitazar into three experimentally resolved crystal structures of hPPAR subtypes, PPARα, PPARβ/δ, and PPARγ, followed by 3 μs molecular dynamics simulations for each system. Our MM-GBSA binding energy calculation revealed that chiglitazar most favorably bound to hPPARγ (-144.6 kcal/mol), followed by hPPARα (-138.0 kcal/mol) and hPPARβ (-135.9 kcal/mol), and the order is consistent with the experimental data. Through the decomposition of the MM-GBSA binding energy by residue and the use of two-dimensional interaction diagrams, key residues involved in the binding of chiglitazar were identified and characterized for each complex system. Additionally, our detailed dynamics analyses support that the conformation and dynamics of helix 12 play a critical role in determining the activities of the different types of ligands (e.g., full agonist vs. partial agonist). Rather than being bent fully in the direction of the agonist versus antagonist conformation, a partial agonist can adopt a more linear conformation and have a lower degree of flexibility. Our finding may aid in further development of this new generation of medication.

Agonism of CD11b reprograms innate immunity to sensitize pancreatic cancer to immunotherapies

Although checkpoint immunotherapies have revolutionized the treatment of cancer, not all tumor types have seen substantial benefit. Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy in which very limited responses to immunotherapy have been observed. Extensive immunosuppressive myeloid cell infiltration in PDAC tissues has been postulated as a major mechanism of resistance to immunotherapy. Strategies concomitantly targeting monocyte or granulocyte trafficking or macrophage survival, in combination with checkpoint immunotherapies, have shown promise in preclinical studies, and these studies have transitioned into ongoing clinical trials for the treatment of pancreatic and other cancer types. However, compensatory actions by untargeted monocytes, granulocytes, and/or tissue resident macrophages may limit the therapeutic efficacy of such strategies. CD11b/CD18 is an integrin molecule that is highly expressed on the cell surface of these myeloid cell subsets and plays an important role in their trafficking and cellular functions in inflamed tissues. Here, we demonstrate that the partial activation of CD11b by a small-molecule agonist (ADH-503) leads to the repolarization of tumor-associated macrophages, reduction in the number of tumor-infiltrating immunosuppressive myeloid cells, and enhanced dendritic cell responses. These actions, in turn, improve antitumor T cell immunity and render checkpoint inhibitors effective in previously unresponsive PDAC models. These data demonstrate that molecular agonism of CD11b reprograms immunosuppressive myeloid cell responses and potentially bypasses the limitations of current clinical strategies to overcome resistance to immunotherapy.