CD8CD25 T cells reduce atherosclerosis in apoE(−/−) mice

Background

It is increasingly evident that CD8⁺ T cells are involved in atherosclerosis but the specific subtypes have yet to be defined. CD8⁺CD25⁺ T cells exert suppressive effects on immune signaling and modulate experimental autoimmune disorders but their role in atherosclerosis remains to be determined. The phenotype and functional role of CD8⁺CD25⁺ T cells in experimental atherosclerosis were investigated in this study.

Methods and results

CD8⁺CD25⁺ T cells were observed in atherosclerotic plaques of apoE(−/−) mice fed hypercholesterolemic diet. Characterization by flow cytometric analysis and functional evaluation using a CFSE-based proliferation assays revealed a suppressive phenotype and function of splenic CD8⁺CD25⁺ T cells from apoE(−/−) mice. Depletion of CD8⁺CD25⁺ from total CD8⁺ T cells rendered higher cytolytic activity of the remaining CD8⁺CD25⁻ T cells. Adoptive transfer of CD8⁺CD25⁺ T cells into apoE(−/−) mice suppressed the proliferation of splenic CD4⁺ T cells and significantly reduced atherosclerosis in recipient mice.

Conclusions

Our study has identified an athero-protective role for CD8⁺CD25⁺ T cells in experimental atherosclerosis.     

The right response at the right time: Exploring helminth immune modulation in sticklebacks by experimental coinfection

Parasites are one of the strongest selective agents in nature. They select for hosts that evolve counter‐adaptive strategies to cope with infection. Helminth parasites are special because they can modulate their hosts’ immune responses. This phenomenon is important in epidemiological contexts, where coinfections may be affected. How different types of hosts and helminths interact with each other is insufficiently investigated. We used the three‐spined stickleback (Gasterosteus aculeatus) – Schistocephalus solidus model to study mechanisms and temporal components of helminth immune modulation. Sticklebacks from two contrasting populations with either high resistance (HR) or low resistance (LR) against S. solidus, were individually exposed to S. solidus strains with characteristically high growth (HG) or low growth (LG) in G. aculeatus. We determined the susceptibility to another parasite, the eye fluke Diplostomum pseudospathaceum, and the expression of 23 key immune genes at three time points after S. solidus infection. D. pseudospathaceum infection rates and the gene expression responses depended on host and S. solidus type and changed over time. Whereas the effect of S. solidus type was not significant after three weeks, T regulatory responses and complement components were upregulated at later time points if hosts were infected with HG S. solidus. HR hosts showed a well orchestrated immune response, which was absent in LR hosts. Our results emphasize the role of regulatory T cells and the timing of specific immune responses during helminth infections. This study elucidates the importance to consider different coevolutionary trajectories and ecologies when studying host‐parasite interactions.     

Anisotropy decay of fluorescence as an experimental approach to protein dynamics

This minireview makes an initial assessment of the progress made using anisotropy decay measurements for investigating the conformational changes and molecular dynamics in soluble systems. A critical analysis of available data is presented. The anisotropy decays of the tryptophan fluorescence of staphylococcal nuclease, adrenocorticotropin, melittin and of labeled transfer RNA were studied for investigating the functional conformational changes of these systems. The emissions of variously labeled immunoglobulins have been used to elucidate the conformations of these proteins before and after the binding of specific antibodies. Labeled myosin and its fragments have given information on the functional motions of the protein domains. The anisotropy decays of labeled and natural hemoglobin systems have been utilized for exploring the allosteric behavior of these molecules. The data suggest a wide applicability of this technique to the study of protein dynamics and conformational changes of macromolecules.     

Alpha7 Helix Plays an Important Role in the Conformational Stability of PTP1B

Abstract

The C-terminus of Protein Tyrosine Phosphatase 1B (PTP1B) includes an α-helix (α7), which forms an allosteric binding site 20 Å away from the active site. This helix is specific to PTP1B and its truncation decreases the catalytic activity significantly. Here, molecular dynamics (MD) simulations in the presence and absence of α7 were performed to investigate the role played by α7. The highly mobile α7 was found to maintain its contacts with loop 11 (L11)- α3 helix throughout the simulations. The interactions of Tyr152 on L11, Tyr176, Thr177 on the catalytically important WPD loop and Ser190 on α3 are important for the conformational stability and the concerted motions of the regions surrounding the WPD loop. In the absence of α7, L11 and WPD loop move away from their crystal structure conformations, resulting in the loss of the interactions in this region, and a decrease in the residue displacement correlations in the vicinity of WPD loop. Therefore, we suggest that one of the functionally important roles of α7 may be to limit the L11 and α3 motions, and, facilitate the WPD loop motions. Truncation of α7 in PTP1B is found to affect distant regions as well, such as the substrate recognition site and the phosphate binding-loop (P-loop), changing the conformations of these regions significantly. Our results show that the PTP1B specific α7 is important for the conformation and dynamics of the WPD loop, and also may play a role in ligand binding.     

Custom distinctions in the interaction of G-protein beta subunits with N-type (CaV2.2) versus P/Q-type (CaV2.1) calcium channels

Inhibition of N- (Cav2.2) and P/Q-type (Cav2.1) calcium channels by G-proteins contribute importantly to presynaptic inhibition as well as to the effects of opiates and cannabinoids. Accordingly, elucidating the molecular mechanisms underlying G-protein inhibition of voltage-gated calcium channels has been a major research focus. So far, inhibition is thought to result from the interaction of multiple proposed sites with the Gbetagamma complex (Gbetagamma). Far less is known about the important interaction sites on Gbetagamma itself. Here, we developed a novel electrophysiological paradigm, "compound-state willing-reluctant analysis," to describe Gbetagamma interaction with N- and P/Q-type channels, and to provide a sensitive and efficient screen for changes in modulatory behavior over a broad range of potentials. The analysis confirmed that the apparent (un)binding kinetics of Gbetagamma with N-type are twofold slower than with P/Q-type at the voltage extremes, and emphasized that the kinetic discrepancy increases up to ten-fold in the mid-voltage range. To further investigate apparent differences in modulatory behavior, we screened both channels for the effects of single point alanine mutations within four regions of Gbeta1, at residues known to interact with Galpha. These residues might thereby be expected to interact with channel effectors. Of eight mutations studied, six affected G-protein modulation of both N- and P/Q-type channels to varying degrees, and one had no appreciable effect on either channel. The remaining mutation was remarkable for selective attenuation of effects on P/Q-, but not N-type channels. Surprisingly, this mutation decreased the (un)binding rates without affecting its overall affinity. The latter mutation suggests that the binding surface on Gbetagamma for N- and P/Q-type channels are different. Also, the manner in which this last mutation affected P/Q-type channels suggests that some residues may be important for "steering" or guiding the protein into the binding pocket, whereas others are important for simply binding to the channel.     

Overview of Voltage-Dependent Calcium Channels

Voltage-dependent calcium channels couple electrical signals to cellular responses in excitable cells. Calcium channels are crucial for excitation–secretion coupling in neurons and endocrine cells, and excitation–contraction coupling in muscle. Several pharmacologically and kinetically distinct calcium channel types have been identified at the electrophysiological and molecular levels. This review summarizes the basic properties of voltage-dependent calcium channels, including mechanisms of ion permeation and block, gating kinetics, and modulation by G proteins and second messengers.     

Structural link between γ-aminobutyric acid type A (GABAA) receptor agonist binding site and inner β-sheet governs channel activation and allosteric drug modulation

Rapid opening and closing of pentameric ligand-gated ion channels (pLGICs) regulate information flow throughout the brain. For pLGICs, it is postulated that neurotransmitter-induced movements in the extracellular inner β-sheet trigger channel activation. Homology modeling reveals that the β4-β5 linker physically connects the neurotransmitter binding site to the inner β-sheet. Inserting 1, 2, 4, and 8 glycines in this region of the GABA(A) receptor β-subunit progressively decreases GABA activation and converts the competitive antagonist SR-95531 into a partial agonist, demonstrating that this linker is a key element whose length and flexibility are optimized for efficient signal propagation. Insertions in the α- and γ-subunits have little effect on GABA or SR-95531 actions, suggesting that asymmetric motions in the extracellular domain power pLGIC gating. The effects of insertions on allosteric modulator actions, pentobarbital, and benzodiazepines, have different subunit dependences, indicating that modulator-induced signaling is distinct from agonist gating.     

WJSC 6th Anniversary Special Issues（2）:Mesenchymal stem cells Mesenchymal stem cells help pancreatic islet transplantation to control type 1 diabetes

Islet cell transplantation has therapeutic potential to treat type 1 diabetes,which is characterized by autoimmune destruction of insulin-producing pancreatic isletβcells.It represents a minimal invasive approach forβcell replacement,but long-term blood control is still largely unachievable.This phenomenon can be attributed to the lack of islet vasculature and hypoxic environment in the immediate post-transplantation period that contributes to the acute loss of islets by ischemia.Moreover,graft failures continue to occur because of immunological rejection,despite the use of potent immunosuppressive agents.Mesenchymal stem cells(MSCs)have the potential to enhance islet transplantation by suppressing inflammatory damage and immune mediated rejection.In this review we discuss the impact of MSCs on islet transplantation and focus on the potential role of MSCs in protecting islet grafts from early graft failure and from autoimmune attack.     

Regulation of the promoter region of the human adiponutrin/PNPLA3 gene by glucose and insulin

Previous biochemical, cardiovascular and behavioral work has given evidence for the existence of antagonistic galanin receptor-5-HT1A receptor interactions in the brain. In this study we investigated the existence of GalR1-5-HT1A receptor heteromers and their functional characteristics. In mammalian cells transfected with GFP2-tagged 5-HT1A receptor and YFP-tagged GalR1 receptor, a proximity-based fluorescence resonance energy transfer technique was used and it has been demonstrated that GalR1-5-HT1A receptors heteromerize. Furthermore, signaling by either the mitogen-activated protein kinase (MAPK) or adenylyl cyclase (AC) pathways by these heteromers indicates a trans-inhibition phenomenon through their interacting interface via allosteric mechanisms that block the development of an excessive activation of G_i/o and an exaggerated inhibition of AC or stimulation of MAPK activity. The presence of these heteromers in the discrete brain regions is postulated based on the existence of GalR-5-HT1A receptor-receptor interactions previously described in the brain and gives rise to explore possible novel therapeutic strategies for treatment of depression by targeting the GalR1-5-HT1A heteromers.