A major lipid raft protein raftlin modulates T cell receptor signaling and enhances th17-mediated autoimmune responses

Elevated serum IL-17 A and CCL20 levels as potential biomarkers in major psychotic disorders: a case-control study

BACKGROUND

Major psychotic disorders (MPD), including schizophrenia (SCZ) and schizoaffective disorder (SAD), are severe neuropsychiatric conditions with unclear causes. Understanding their pathophysiology is essential for better diagnosis, treatment, and prognosis. Recent research highlights the role of inflammation and the immune system, particularly the Interleukin 17 (IL-17) family, in these disorders. Elevated IL-17 levels have been found in MPD, and human IL-17 A antibodies are available. Changes in chemokine levels, such as CCL20, are also noted in SCZ. This study investigates the relationship between serum levels of IL-17 A and CCL20 in MPD patients and their clinical characteristics.

METHOD

We conducted a case-control study at the Ibn Sina Psychiatric Hospital (Mashhad, Iran) in 2023. The study involved 101 participants, of which 71 were MPD patients and 30 were healthy controls (HC). The Positive and Negative Symptom Scale (PANSS) was utilized to assess the symptoms of MPD patients. Serum levels of CCL20 and IL-17 A were measured using Enzyme-Linked Immunosorbent Assay (ELISA) kits. We also gathered data on lipid profiles and Fasting Blood Glucose (FBS).

RESULTS

The mean age of patients was 41.04 ± 9.93 years. The median serum levels of CCL20 and IL-17 A were significantly elevated in MPD patients compared to HC (5.8 (4.1-15.3) pg/mL and 4.2 (3-5) pg/mL, respectively; p < 0.001). Furthermore, CCL20 and IL-17 A levels showed a positive correlation with the severity of MPD. MPD patients also had significantly higher FBS, cholesterol, and Low-Density Lipoprotein (LDL) levels, and lower High-Density Lipoprotein (HDL) levels compared to HC. No significant relationship was found between PANSS components and blood levels of IL17 and CCL20.

CONCLUSION

The current study revealed that the serum levels of IL-17 A and CCL20 in schizophrenia patients are higher than those in the control group. Metabolic factors such as FBS, cholesterol, HDL, and LDL also showed significant differences between MPD and HC. In conclusion, the findings suggest that these two inflammatory factors could serve as potential therapeutic targets and prognostic biomarkers for schizophrenia.

Raftlin - a potential biomarker for axial spondyloarthritis and psoriatic arthritis: An observational study

Our aim is to evaluate serum Raftlin levels as a biomarker for diagnosing and monitoring disease activity in patients with axial spondyloarthritis (axSpA) and Psoriatic arthritis (PsA). This trial included 40 axSpA patients, 40 PsA patients, and 40 healthy participants as the control group. Disease activity was assessed with Ankylosing Spondylitis Disease Activity Score for axSpA patients and The Disease Activity Index for Psoriatic Arthritis for PsA patients. The Spondyloarthritis Research Consortium of Canada index, health assessment questionnaire-disability index, and numeric rating scale were used to evaluate the enthesitis severity, disability, and pain status of all patients. Serum Raftlin levels were determined using the ELISA method. The 3 groups had no statistical differences regarding gender, age, weight, height, BMI, educational status, and exercise habits. The axSpA group had higher Raftlin levels than the PsA and control groups, and Raftlin levels were statistically significant in predicting the likelihood of axSpA. We found no statistically significant differences between the PsA and control groups. We found no statistically significant difference in Raftlin levels in HLA-B27 positive versus HLA-B27 negative patients in both axSpA and PsA groups. Our results also did not detect any correlation of Raftlin levels with Ankylosing Spondylitis Disease Activity Score, C-reactive protein, erythrocyte sedimentation rate, health assessment questionnaire-disability index, numeric rating scale, and Spondyloarthritis Research Consortium of Canada index in axSpA patients. Receiver operating characteristic analysis determined that Raftlin level ≥ 6.31 ng/mL discriminates axSpA from normal individuals with 92.5% sensitivity, 59% specificity, and an area under the curve of 0.738. Our results demonstrate that although serum Raftlin levels are elevated in axSpA patients, Raftlin cannot be used as an alone diagnostic marker for axSpA. Furthermore, it was not found to be related to the monitoring of disease activity, the level of pain, disability, or severity of enthesitis. This study is prospectively registered at www.clinicaltrials.gov (ID: NCT05771389).

A permutation-based approach using a rank-based statistic to identify sex differences in epigenetics

Epigenetic sex differences and their resulting implications for human health have been studied for about a decade. The objective of this paper is to use permutation-based inference and a new ranked-based test statistic to identify sex-based epigenetic differences in the human DNA methylome. In particular, we examine whether we could identify separations between the female and male distributions of DNA methylation across hundred of thousands CpG sites in two independent cohorts, the Swedish Adoption Twin study and the Lamarck study. Based on Fisherian p-values, we set a threshold for methylation differences "worth further scrutiny". At this threshold, we were able to confirm previously-found CpG sites that stratify with respect to sex. These CpG sites with sex differences in DNA methylation should be further investigated for their possible contribution to various physiological and pathological functions in the human body. We followed-up our statistical analyses with a literature review in order to inform the proposed disease implications for the loci we uncovered.

Tryptophan metabolite norharman secreted by cultivated Lactobacillus attenuates acute pancreatitis as an antagonist of histone deacetylases

BACKGROUND

Patients with acute pancreatitis (AP) exhibit specific phenotypes of gut microbiota associated with severity. Gut microbiota and host interact primarily through metabolites; regrettably, little is known about their roles in AP biological networks. This study examines how enterobacterial metabolites modulate the innate immune system in AP aggravation.

METHODS

In AP, alterations in gut microbiota were detected via microbiomics, and the Lactobacillus metabolites of tryptophan were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). By culturing Lactobacillus with tryptophan, differential metabolites were detected by LC-MS/MS. Lipopolysaccharide (LPS)-stimulated RAW264.7 cells and mice with cerulein plus LPS-induced AP were used to evaluate the biological effect of norharman on M1 macrophages activation in AP development. Further, RNA sequencing and lipid metabolomics were used for screening the therapeutic targets and pathways of norharman. Confocal microscopy assay was used to detect the structure of lipid rafts. Molecular docking was applied to predict the interaction between norharman and HDACs. Luciferase reporter assays and chromatin immunoprecipitation (ChIP) were used to explore the direct mechanism of norharman promoting Rftn1 expression. In addition, myeloid-specific Rftn1 knockout mice were used to verify the role of Rftn1 and the reversed effect of norharman.

RESULTS

AP induced the dysfunction of gut microbiota and their metabolites, resulting in the suppression of Lactobacillus-mediated tryptophan metabolism pathway. The Lactobacillus metabolites of tryptophan, norharman, inhibited the release of inflammatory factor in vitro and in vivo, as a result of its optimal inhibitory action on M1 macrophages. Moreover, norharman blocked multiple inflammatory responses in AP exacerbation due to its ability to maintain the integrity of lipid rafts and restore the dysfunction of lipid metabolism. The mechanism of norharman's activity involved inhibiting the enzyme activity of histone deacetylase (HDACs) to increase histone H3 at lysine 9/14 (H3K9/14) acetylation, which increased the transcription level of Rftn1 (Raftlin 1) to inhibit M1 macrophages' activation.

CONCLUSIONS

The enterobacterial metabolite norharman can decrease HDACs activity to increase H3K9/14 acetylation of Rftn1, which inhibits M1 macrophage activation and restores the balance of lipid metabolism to relieve multiple inflammatory responses. Therefore, norharman may be a promising prodrug to block AP aggravation.

RORγt-Raftlin1 complex regulates the pathogenicity of Th17 cells and colonic inflammation

Th17 cells that produce Interleukin IL-17 are pathogenic in many human diseases, including inflammatory bowel disease, but are, paradoxically, essential for maintaining the integrity of the intestinal barrier in a non-inflammatory state. However, the intracellular mechanisms that regulate distinct transcriptional profiles and functional diversity of Th17 cells remain unclear. Here we show Raftlin1, a lipid raft protein, specifically upregulates and forms a complex with RORγt in pathogenic Th17 cells. Disruption of the RORγt-Raftlin1 complex results in the reduction of pathogenic Th17 cells in response to Citrobacter rodentium; however, there is no effect on nonpathogenic Th17 cells in response to commensal segmented filamentous bacteria. Mechanistically, we show that Raftlin1 recruits distinct phospholipids to RORγt and promotes the pathogenicity of Th17 cells. Thus, we have identified a mechanism that drives the pathogenic function of Th17 cells, which could provide a platform for advanced therapeutic strategies to dampen Th17-mediated inflammatory diseases.

Inflammatory Cytokines That Enhance Antigen Responsiveness of Naïve CD8+ T Lymphocytes Modulate Chromatin Accessibility of Genes Impacted by Antigen Stimulation

Naïve CD8⁺ T lymphocytes exposed to certain inflammatory cytokines undergo proliferation and display increased sensitivity to antigens. Such 'cytokine priming' can promote the activation of potentially autoreactive and antitumor CD8⁺ T cells by weak tissue antigens and tumor antigens. To elucidate the molecular mechanisms of cytokine priming, naïve PMEL-1 TCR transgenic CD8⁺ T lymphocytes were stimulated with IL-15 and IL-21, and chromatin accessibility was assessed using the assay for transposase-accessible chromatin (ATAC) sequencing. PMEL-1 cells stimulated by the cognate antigenic peptide mgp100_25-33 served as controls. Cytokine-primed cells showed a limited number of opening and closing chromatin accessibility peaks compared to antigen-stimulated cells. However, the ATACseq peaks in cytokine-primed cells substantially overlapped with those of antigen-stimulated cells and mapped to several genes implicated in T cell signaling, activation, effector differentiation, negative regulation and exhaustion. Nonetheless, the expression of most of these genes was remarkably different between cytokine-primed and antigen-stimulated cells. In addition, cytokine priming impacted the expression of several genes following antigen stimulation in a synergistic or antagonistic manner. Our findings indicate that chromatin accessibility changes in cytokine-primed naïve CD8⁺ T cells not only underlie their increased antigen responsiveness but may also enhance their functional fitness by reducing exhaustion without compromising regulatory controls.

Serum NOX1 and Raftlin as New Potential Biomarkers of Interest in Schizophrenia: A Preliminary Study

Introduction

There is increasing evidence that oxidative stress (OS) and neuroinflammation play a role in the neuroprogression of schizophrenia (SCZ). Promising novel candidates which have been proposed in the search for biomarkers of psychotic illness include NADPH oxidase 1,2 (NOX1,2) and raftlin. NOX1 from the NOX family is the main source of physiological reactive oxygen species (ROS) and raftlin, the main lipid raft protein, is associated with inflammatory processes. The aim of the present study was to evaluate serum NOX1 and raftlin levels in chronic stable patients with SCZ.

Methods

We measured serum NOX1 and raftlin levels from 45 clinically stable patients with SCZ and 45 healthy controls (HCs) matched for age, sex, and body-mass index. The Positive and Negative Syndrome Scale was applied to the patient group to evaluate the severity of psychotic symptoms.

Results

NOX1 and raftlin levels in the patients were statistically significantly higher than the HCs (NOX1 p<0.001, raftlin p<0.001). Both parameters showed very good diagnostic performance (NOX1 AUC = 0.931, raftlin AUC = 0.915). We obtained positive and significant correlations between serum levels of both biomarkers and symptom severity.

Discussion

This preliminary study indicating elevations in serum NOX1 and raftlin levels in patients with SCZ supports the importance of OS and inflammatory processes in the etiopathogenesis of the illness.

Expression of Major Lipid Raft Protein Raftlin in Chronic Rhinosinusitis with Nasal Polyps in Smoking and Non-Smoking Patients Correlated with Interleukin-17 and Tumor Necrosis Factor-α Levels

Raftlin, as an inflammatory biomarker, has been previously reported in chronic inflammatory diseases. This study investigates the expression of Raftlin in cigarette smokers and in chronic rhinosinusitis with nasal polyps (CRSwNP), as well as evaluating its correlation with interleukin-17 (IL-17) and tumor necrosis factor-α (TNF-α) levels. A total of 30 CRSwNP non-smoking and 16 CRSwNP + SK (smoking) patients undergoing endoscopic sinus surgery were enrolled, while 20 middle turbinate tissue pieces were examined and performed as the control group. In nasal mucosa epithelial staining, Raftlin levels were elevated in the columnar cells and were stained much more intensely in the CRSwNP and CRSwNP + SK groups. Raftlin was located more closely to the apical region of the epithelium in the CRSwNP + SK group; however, the Raftlin levels from whole nasal tissue pieces, according to ELISA data, showed that there was no significant difference between the three different study groups. A positive relationship by Pearson correlation was found between IL-17 or TNF-α levels and Raftlin levels. Taken together, these data indicate that increasing Raftlin expression in columnar cells might involve nasal epithelial remodeling in smokers with CRSwNP.

The role of raftlin in the pathogenesis of chronic rhinosinusitis with nasal polyps

PURPOSE

The aim of this study was to investigate the possible role of raftlin (RFTN) in chronic rhinosinusitis with nasal polyps (CRSwNP). There is no study in the literature investigating the role of RFTN in the pathogenesis of CRSwNP.

METHODS

The present study was designed as a case-control study and conducted between 25.09.2020 and 01.01.2022. CRSwNP and control groups were formed in the study. Serum and tissue samples were taken from each patient in the study and their RFTN levels were measured. While nasal polyps were used for tissue samples in the CRSwNP group, middle meatus mucosa obtained during concha bullosa surgery was used in the control group.

RESULTS

The control group included 31 patients (8 female, 23 male) and the CRSwNP group included 49 patients (14 female, 35 male). The mean age of the control group was 40.42 ± 9.99 years, while the mean age of the CRSwNP group was 43.47 ± 10.19 years. When the groups are compared in terms of gender and age, there were no statistically significant differences (p = 0.78, p = 0.19, respectively). The serum RFTN levels in the control and CRSwNP groups were 7.85 ± 10.87 ng/ml, and 7.02 ± 8.59 ng/ml, respectively (p = 0.45). The tissue RFTN levels in the control group and CRSwNP group were 87.15 ± 69.91 ng/ml, and 66.50 ± 17.10 ng/ml, respectively (p = 0.04, statistically significant).

CONCLUSION

RFTN deficiency in nasal polyp tissue may be one of the reasons for the development of CRSwNP. Further studies are needed to elucidate the role of RFTN in CRSwNP.

Roles of Oxidative Stress and Raftlin in Wound Healing Under Negative-Pressure Wound Therapy

Background

Negative-pressure wound therapy (NPWT) is an effective way to promote wound healing. However, its mechanisms have not been investigated thoroughly. Growing evidence suggests that oxidative stress and Raftlin levels play important roles in wound healing. However, whether NPWT promotes wound healing through this mechanism remains unclear.

Purpose

Our study focuses on the different levels of oxidative stress and antioxidant response between wounds treated by NPWT and routine dressing change. The objective of this study was to measure the differences in Raftlin levels between the two groups, which is a new biomarker related to wound healing.

Methods

We divided 48 male Sprague-Dawley rats with identical full-thickness skin defects into two groups. At specific times (0, 3, 5, 7, 9, 11, and 13 days after surgery), wound tissue samples were obtained for immunohistochemistry and biochemical analysis. The expression of Raftlin and levels of oxidative stress, including malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) levels were measured by biochemical analysis. Wound-healing times were also compared.

Results

In the NPWT group, MDA levels were significantly decreased on days 3, 5, and 7. Furthermore, the expressions of SOD and CAT were significantly reduced on days 3 and 5. Our data also revealed that Raftlin was significantly upregulated across the whole period of wound healing. Moreover, wound healing in the NPWT group was significantly more rapid (16 days on average) than in the control group (24 days on average). On day 13 post surgery, the wound-healing percentage in the NPWT group was 91%, while that in the control group was 48%.

Conclusion

NPWT may promote wound healing by upregulating Raftlin and inhibiting oxidative stress levels.

Evaluation of preoperative and postoperative serum interleukin-6, interleukin-8, tumor necrosis factor α and raftlin levels in patients with obstructive sleep apnea

BACKGROUND

Raftlin is a large, major lipid raft protein of cell membranes. Raftlin levels have not been previously examined in patients with obstructive sleep apnea (OSA). Our study aimed to evaluate the changes in raftlin, interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor alpha (TNFα) values from the preoperative state to the third month postoperatively in patients undergoing expansion sphincter pharyngoplasty for OSA.

METHODS

Of 60 patients, 10 patients had mild OSA (AHI 5-14), 10 moderate (AHI 15-29), 10 severe (AHI ≥ 30), and 30 with AHI < 5 formed a control group. Preoperatively and at 3 months post-operatively, IL-6, IL-8, TNFα, and raftlin values were measured.

RESULTS

Preoperatively, mean raftlin levels were 914.4 ± 62.7 pg/mL for controls, 910.0 ± 42.5 pg/mL in mild, 1000.5 ± 63.3 pg/mL in moderate, and 1386.3 ± 101.4 pg/mL in severe groups, with moderate and severe groups significantly elevated compared to controls (p < 0.001). Preoperatively to 3 months post-operatively, raftlin levels decreased significantly in each OSA group (p < 0.05). Levels of IL-6, IL-8 and TNFα followed similar patterns at baseline and after surgical intervention.

CONCLUSIONS

Raftlin levels at the third postoperative month decreased significantly compared with preoperative levels in parallel with other markers of inflammation.

Raftlin is recruited by neuropilin-1 to the activated VEGFR2 complex to control proangiogenic signaling

Background

VEGFR2 (vascular endothelial growth factor receptor 2) is the major pro-angiogenic receptor in endothelial cells. Compared to other members of the receptor tyrosine kinase family, we know relatively few VEGFR2 signaling partners. Our objective was to use mass spectrometry-based proteomics to identify novel binding partners of activated VEGFR2.

Methods

We created an endothelial cell line stably expressing GFP-tagged VEGFR2 and isolated activated receptor complexes. Analysis by mass spectrometry identified raftlin as a novel binding partner of VEGFR2.

Results

We found that raftlin is recruited to the activated VEGFR2 complex via the co-receptor Nrp1 (neuropilin-1). We show that raftlin regulates the surface levels of Nrp1 in endothelial cells, controlling the availability of Nrp1 for VEGFR2 interaction. Raftlin stabilizes active VEGFR2 at the cell surface by inhibiting endocytosis of the activated receptor. Raftlin also promotes recycling of internalized VEGFR2 to the cell surface. Raftlin alters the signaling outcomes of VEGFR2 activation, inhibiting the activation of p38 and FAK (focal adhesion kinases) specifically. Both pathways are linked to cell migration in endothelial cells, and raftlin inhibits endothelial cell migration in response to VEGF.

Conclusion

Nrp1 is an important co-receptor for VEGFR2; however, its functions are still only partially understood. We show that raftlin works with Nrp1 in endothelial cells to control intracellular trafficking of the activated VEGFR2. This modulates the response to VEGF and controls endothelial cell migration.

Electronic supplementary material

The online version of this article (10.1007/s10456-020-09715-z) contains supplementary material, which is available to authorized users.

The effect of oxidative stress and Raftlin levels on wound healing

Reactive oxygen species (ROS) are crucial in all wound-healing processes. Raftlin also plays an important role in the induction of the autoimmune response and the vascular inflammatory response. Inflammatory mediators induce continuous synthesis and secretion. To the best of our knowledge, although there are studies in the literature on antioxidant enzyme levels (superoxide dismutase [SOD], catalase [CAT]) and oxidative stress markers, there are no studies on the comparison of these levels in wound patients with the activities of Raftlin, which is known to play a role in the vascular endothelial response. The aim of this study was to compare the levels of oxidative stress and antioxidant response between wound patients and a control group and to compare the levels of Raftlin between the two groups, which is a new biomarker in inflammatory diseases. Between January 2018 and September 2018, 30 healthy control patients and 30 patients with wounds were enrolled in the study as volunteers. Tissue samples were collected and were sent to the biochemistry laboratory to determine the levels of oxidative stress, antioxidant enzymes, and Raftlin, which play an important role in wound healing. The following were evaluated: SOD and CAT levels (as a measure of antioxidant enzymes); malondialdehyde (MDA) levels (as a measure of free oxygen radicals); and Raftlin, which is a lipid raft protein used in determining the level of inflammatory and autoimmune response. The analyses determined a statistically significant correlation between MDA, SOD, CAT, and Raftlin values in wound patients (p<0.05). Raftlin was a considerable parameter in determining the prognostic process of wound healing. The levels of tissue Raftlin were significantly higher in wounded patients. A significant increase in MDA, SOD, and CAT activities of the wounded patients also suggested that the oxidant and antioxidant effect was balanced and that external antioxidant supplementation was not required.

Smoking alters hydroxyprostaglandin dehydrogenase expression in fetal membranes

INTRODUCTION

The way in which tobacco smoking increases the risk of preterm labor remains uncertain. Altered prostaglandin metabolism is one potential mechanism.

METHODS

Proteins in fetal membrane samples (amniochoriodecidua) from 20 women were relatively quantified using Tandem Mass Tagging nano-liquid chromatography mass spectrometry.

RESULTS

Prostaglandin synthases and two enzymes involved in prostaglandin degradation, hydroxyprostaglandin dehydrogenase (HPGD) and CBR1, were detected by the mass spectrometer. The expression of HPGD was significantly lower in smokers relative to non-smokers (0.43 fold, p = 0.016). There was no effect of labor, inflammatory status or gestational age on the HPGD levels.

DISCUSSION

We describe for the first time an association between maternal smoking and HPGD expression. We propose that reduced expression of HPGD is one mechanism through which smoking may contribute to preterm labor. Lower levels of this enzyme, key to metabolising prostaglandins, may result in higher levels of prostaglandins and therefore precipitate labor prematurely.

Reciprocal modulation of helper Th1 and Th17 cells by the β2-adrenergic receptor agonist drug terbutaline

Catecholamine hormones are powerful regulators of the immune system produced by the sympathetic nervous system (SNS). They regulate the adaptive immune system by altering T-cell differentiation into T helper (Th) 1 and Th2 cell subsets, but the effect on Th17 cells is not known. Th17 cells, defined, in part, by chemokine receptor CCR6 and cytokine interleukin (IL)-17A, are crucial for mediating certain pathogen-specific responses and are linked with several autoimmune diseases. We demonstrated that a proportion of human Th17 cells express beta 2-adrenergic receptor (β2AR), a G protein-coupled receptor that responds to catecholamines. Activation of peripheral blood mononuclear cells, which were obtained from venous blood drawn from healthy volunteers, with anti-cluster of differentiation 3 (CD3) and anti-CD28 and with a β2-agonist drug, terbutaline (TERB), augmented IL-17A levels (P < 0.01) in the majority of samples. TERB reduced interferon gamma (IFNγ) indicating that IL-17A and IFNγ are reciprocally regulated. Similar reciprocal regulation was observed with dbcAMP. Proliferation of Th cells was monitored by carboxyfluorescein diacetate N-succinimidyl ester labeling and flow cytometry with antibody staining for CD3 and CD4. TERB increased proliferation by a small but significant margin (P < 0.001). Next, Th17 cells (CD4⁺ CXCR3^- CCR6⁺ ) were purified using an immunomagnetic positive selection kit, which removes all other mononuclear cells. TERB increased IL-17A from purified Th17 cells, which argues that TERB acts directly on Th17 cells. Thus, hormone signals from the SNS maintain a balance of Th cells subtypes through the β2AR.

The Adaptor Protein Rai/ShcC Promotes Astrocyte-Dependent Inflammation during Experimental Autoimmune Encephalomyelitis

Th17 cells have been casually associated to the pathogenesis of autoimmune disease. We have previously demonstrated that Rai/ShcC, a member of the Shc family of adaptor proteins, negatively regulates Th17 cell differentiation and lupus autoimmunity. In this study, we have investigated the pathogenic outcome of the Th17 bias associated with Rai deficiency on multiple sclerosis development, using the experimental autoimmune encephalomyelitis (EAE) mouse model. We found that, unexpectedly, EAE was less severe in Rai(-/-) mice compared with their wild-type counterparts despite an enhanced generation of myelin-specific Th17 cells that infiltrated into the CNS. Nevertheless, when adoptively transferred into immunodeficient Rai(+/+) mice, these cells promoted a more severe disease compared with wild-type encephalitogenic Th17 cells. This paradoxical phenotype was caused by a dampened inflammatory response of astrocytes, which were found to express Rai, to IL-17. The results provide evidence that Rai plays opposite roles in Th17 cell differentiation and astrocyte activation, with the latter dominant over the former in EAE, highlighting this adaptor as a potential novel target for the therapy of multiple sclerosis.

Raftlin Controls Lipopolysaccharide-Induced TLR4 Internalization and TICAM-1 Signaling in a Cell Type-Specific Manner

The clathrin-dependent endocytic pathway is crucial for endosomal TLR3- and TLR4-mediated Toll-IL-1R domain-containing adaptor molecule-1 (TICAM-1) signaling. TLR4 uses a different signaling platform, plasma membrane and endosomes, for activation of TIRAP-MyD88 and TICAM-2-TICAM-1, respectively. LPS-induced endocytosis of TLR4 is mandatory for TICAM-1-mediated signaling including IFN-β production. Several molecules/mechanisms such as CD14, clathrin, and phosphatidylinositol metabolism have been reported to act as inducers of TLR4 translocation. However, the molecular mechanism of spatiotemporal regulation of TLR4 signaling remains unresolved. We have previously shown that Raftlin is essential for clathrin-dependent endocytosis of TLR3 ligand in human epithelial cells and myeloid dendritic cells (DCs). In this article, we demonstrate that Raftlin also mediated LPS-induced TLR4 internalization and TICAM-1 signaling in human monocyte-derived DCs and macrophages (Mo-Mϕs). When Raftlin was knocked down, LPS-induced TLR4-mediated IFN-β promoter activation, but not NF-κB activation, was decreased in HEK293 cells overexpressing TLR4/MD-2 or TLR4/MD-2/CD14. LPS-induced IFN-β production by monocyte-derived DCs and Mo-Mϕs was significantly decreased by knockdown of Raftlin. Upon LPS stimulation, Raftlin moved from the cytoplasm to the plasma membrane in Mo-Mϕs, where it colocalized with TLR4. Raftlin associated with clathrin-associated adaptor protein-2 in resting cells and transiently bound to TLR4 and clathrin at the cell surface in response to LPS. Thus, Raftlin appears to modulate cargo selection as an accessary protein of clathrin-associated adaptor protein-2 in clathrin-mediated endocytosis of TLR3/4 ligands.

Abnormal lipid rafts related ganglioside expression and signaling in T lymphocytes in immune thrombocytopenia patients

Aberrant T lymphocytes signaling is considered to play a crucial role in the abnormal immune state of primary immune thrombocytopenia (ITP). Lipid raft has been verified to engage in the T cell receptor (TCR)-mediated T lymphocytes signal transduction. Whether lipid raft-associated T cells signal transduction has impact on the pathogenesis of ITP is still unconfirmed. In this study, we aimed to reveal the abnormality in structure and function of lipid rafts (LRs) in CD4(+) and CD8(+) T lymphocytes of patients with ITP. Our results showed that there was an increased lipid raft aggregation in ITP patients, while this kind of increase would not be influenced by platelet counts or therapeutic regimes. Stimulation by anti-CD3/CD28 monoclonal antibodies promoted enhanced lipid raft clustering in T lymphocytes of ITP patients compared with negative controls. Methyl-β-cyclodextrin (MβCD) could block the abnormal lipid raft aggregation and disrupt the TCR-mediated T cells proliferation and cytokines secretion, including both proinflammatory cytokines and anti-inflammatory cytokines. The spontaneous activation of T lymphocytes from ITP patients might be due to the elevated co-localization of protein tyrosine phosphatase (PTP) CD45 and lipid rafts in patients' CD4(+) and CD8(+) T lymphocytes. These findings suggest that the autoactivation of T lymphocytes from ITP patients may lead to the abnormality in lipid raft structure and raft-anchored proteins, and the changes conversely promote the TCR-mediated T cells activation of ITP patients.

Differences in CD44 Surface Expression Levels and Function Discriminates IL-17 and IFN-γ Producing Helper T Cells

CD44 is a prominent activation marker which distinguishes memory and effector T cells from their naïve counterparts. It also plays a role in early T cell signaling events as it is bound to the lymphocyte-specific protein kinase and thereby enhances T cell receptor signalling. Here, we investigated whether IFN-γ and IL-17 producing T helper cells differ in their CD44 expression and their dependence of CD44 for differentiation. Stimulation of CD4+ T cells with allogeneic dendritic cells resulted in the formation of three distinguishable populations: CD44+, CD44++ and CD44+++. In vitro and in vivo generated allo-reactive IL-17 producing T helper cells were mainly CD44+++ as compared to IFN-γ+ T helper cells, which were CD44++. This effect was enhanced under polarizing conditions. T helper 17 polarization led to a shift towards the CD44+++ population, whereas T helper 1 polarization diminished this population. Furthermore, blocking CD44 decreased IL-17 secretion, while IFN-γ was barely affected. Titration experiments revealed that low T cell receptor and CD28 stimulation supported T helper 17 rather than T helper 1 development. Under these conditions CD44 could act as a co-stimulatory molecule and replace CD28. Indeed, rested CD44+++CD4+ T cells contained already more total and especially phosphorylated zeta-chain-associated protein kinase 70 as compared to CD44++ cells. Our results support the notion, that CD44 enhances T cell receptor signaling strength by delivering lymphocyte-specific protein kinase, which is required for induction of IL-17 producing T helper cells.

The dual role of scavenger receptor class A in development of diabetes in autoimmune NOD mice

Human type 1 diabetes is an autoimmune disease that results from the autoreactive destruction of pancreatic β cells by T cells. Antigen presenting cells including dendritic cells and macrophages are required to activate and suppress antigen-specific T cells. It has been suggested that antigen uptake from live cells by dendritic cells via scavenger receptor class A (SR-A) may be important. However, the role of SR-A in autoimmune disease is unknown. In this study, SR-A-/- nonobese diabetic (NOD) mice showed significant attenuation of insulitis, lower levels of insulin autoantibodies, and suppression of diabetes development compared with NOD mice. We also found that diabetes progression in SR-A-/- NOD mice treated with low-dose polyinosinic-polycytidylic acid (poly(I:C)) was significantly accelerated compared with that in disease-resistant NOD mice treated with low-dose poly(I:C). In addition, injection of high-dose poly(I: C) to mimic an acute RNA virus infection significantly accelerated diabetes development in young SR-A-/- NOD mice compared with untreated SR-A-/- NOD mice. Pathogenic cells including CD4+CD25+ activated T cells were increased more in SR-A-/- NOD mice treated with poly(I:C) than in untreated SR-A-/- NOD mice. These results suggested that viral infection might accelerate diabetes development even in diabetes-resistant subjects. In conclusion, our studies demonstrated that diabetes progression was suppressed in SR-A-/- NOD mice and that acceleration of diabetes development could be induced in young mice by poly(I:C) treatment even in SR-A-/- NOD mice. These results suggest that SR-A on antigen presenting cells such as dendritic cells may play an unfavorable role in the steady state and a protective role in a mild infection. Our findings imply that SR-A may be an important target for improving therapeutic strategies for type 1 diabetes.

Loss of Sprouty4 in T cells ameliorates experimental autoimmune encephalomyelitis in mice by negatively regulating IL-1β receptor expression

Th17 cells, which have been implicated in autoimmune diseases, require IL-6 and TGF-β for early differentiation. To gain pathogenicity, however, Th17 cells require IL-1β and IL-23. The underlying mechanism by which these confer pathogenicity is not well understood. Here we show that Sprouty4, an inhibitor of the PLCγ-ERK pathway, critically regulates inflammatory Th17 (iTh17) cell differentiation. Sprouty4-deficient mice, as well as mice adoptively transferred with Sprouty4-deficient T cells, were resistant to experimental autoimmune encephalitis (EAE) and showed decreased Th17 cell generation in vivo. In vitro, Sprouty4 deficiency did not severely affect TGF-β/IL-6-induced Th17 cell generation but strongly impaired Th17 differentiation induced by IL-1/IL-6/IL-23. Analysis of Th17-related gene expression revealed that Sprouty4-deficient Th17 cells expressed lower levels of IL-1R1 and IL-23R, while RORγt levels were similar. Consistently, overexpression of Sprouty4 or pharmacological inhibition of ERK upregulated IL-1R1 expression in primary T cells. Thus, Sprouty4 and ERK play a critical role in developing iTh17 cells in Th17 cell-driven autoimmune diseases.

Effect of cholesterol depletion on interleukin-8 production in human respiratory epithelial cells

PURPOSE

The lipid entities of cell membranes are components of the immune system and important mediators of inflammation. Despite increasing interest in the function of epithelial cells in inflammation, the role of cholesterol in this process has not been described. Here, we investigated the effect of cholesterol depletion on the inflammatory process in airway epithelial cells via the expression of interleukin (IL)-8 as a marker of inflammation.

METHODS

A 549 cells were treated with 0.5% methyl-β-cyclodextrin as a selective cholesterol extractor. The IL-8 level was assessed by enzyme-linked immunosorbent assay and reassessed after cholesterol repletion. Mitogen-activated protein kinase (MAPK) inhibitors were used to determine the upstream signaling pathway for IL-8 production in cholesterol-depleted cells.

RESULTS

We found a relationship between the amount of cholesterol in A 549 cells and inflammation of the airway. IL-8 production was increased in cholesterol-depleted A 549 cells and restored by cholesterol repletion. IL-8 production was decreased by pretreatment with the extracellular signal-regulated kinase (ERK) inhibitor U0126 but not with JNK inhibitor II or the p38 MAPK inhibitor SB202190.

CONCLUSIONS

Our findings suggest that inflammatory responses are increased in cholesterol-depleted epithelial cells via the MAPK signaling system, predominantly by the ERK pathway. We conclude that the lipid components of airwayepithelial cells may play a role in the inflammatory process.

Cannabinoids decrease the th17 inflammatory autoimmune phenotype

Cannabinoids, the Cannabis constituents, are known to possess anti-inflammatory properties but the mechanisms involved are not understood. Here we show that the main psychoactive cannabinoid, Δ-9-tetrahydrocannabinol (THC), and the main nonpsychoactive cannabinoid, cannabidiol (CBD), markedly reduce the Th17 phenotype which is known to be increased in inflammatory autoimmune pathologies such as Multiple Sclerosis. We found that reactivation by MOG35-55 of MOG35-55-specific encephalitogenic T cells (cells that induce Experimental Autoimmune Encephalitis when injected to mice) in the presence of spleen derived antigen presenting cells led to a large increase in IL-17 production and secretion. In addition, we found that the cannabinoids CBD and THC dose-dependently (at 0.1-5 μM) suppressed the production and secretion of this cytokine. Moreover, the mRNA and protein of IL-6, a key factor in Th17 induction, were also decreased. Pretreatment with CBD also resulted in increased levels of the anti-inflammatory cytokine IL-10. Interestingly, CBD and THC did not affect the levels of TNFα and IFNγ. The downregulation of IL-17 secretion by these cannabinoids does not seem to involve the CB1, CB2, PPARγ, 5-HT1A or TRPV1 receptors. In conclusion, the results show a unique cannabinoid modulation of the autoimmune cytokine milieu combining suppression of the pathogenic IL-17 and IL-6 cytokines along with boosting the expression of the anti-inflammatory cytokine IL-10.

CDK inhibitors suppress Th17 and promote iTreg differentiation, and ameliorate experimental autoimmune encephalomyelitis in mice

Th17 cells, which have been implicated in autoimmune diseases, require IL-6 and TGF-β for early differentiation. Several Smad-independent pathways including the JNK and the RhoA-ROCK pathways have been implicated in the induction of RORγt, the master regulator of Th17, however, molecular mechanisms underlying Smad-independent pathway remain largely unknown. To identify novel pathways involved in Th17 differentiation, we screened 285 chemical inhibitors for known signaling pathways. Among them, we found that Kenpaullone, a GSK3-β and CDK inhibitor, efficiently suppressed TGF-β-mediated RORγt induction and enhanced Foxp3 induction in primary T cells. Another CDK inhibitor, Roscovitine, but not other GSK3-β inhibitors, suppressed Th17 differentiation and enhanced iTreg development. Kenpaullone and Roscovitine suppressed experimental autoimmune encephalomyelitis (EAE), a typical Th17-mediated autoimmune disease model. These two compounds enhanced STAT5 phosphorylation and restored IL-2 production in the presence of TGF-β. These data suggest that CDK inhibitors modulate TGF-β-signaling pathways, which restore TGF-β-mediated suppression of IL-2 production, thereby modifying the Th17/iTreg balance.

Genome wide mapping reveals PDE4B as an IL-2 induced STAT5 target gene in activated human PBMCs and lymphoid cancer cells

IL-2 is the primary growth factor for promoting survival and proliferation of activated T cells that occurs following engagement of the Janus Kinase (JAK)1–3/and Signal Transducer and Activator of Transcription (STAT) 5 signaling pathway. STAT5 has two isoforms: STAT5A and STAT5B (commonly referred to as STAT5) which, in T cells, play redundant roles transcribing cell cycle and survival genes. As such, inhibition of STAT5 by a variety of mechanisms can rapidly induce apoptosis in certain lymphoid tumor cells, suggesting that it and its target genes represent therapeutic targets to control certain lymphoid diseases. To search for these molecules we aligned IL-2 regulated genes detected by Affymetrix gene expression microarrays with the STAT5 cistrome identified by chip-on-ChIP analysis in an IL-2-dependent human leukemia cell line, Kit225. Select overlapping genes were then validated using qRT²PCR medium-throughput arrays in human PHA-activated PBMCs. Of 19 putative genes, one key regulator of T cell receptor signaling, PDE4B, was identified as a novel target, which was readily up-regulated at the protein level (3 h) in IL-2 stimulated, activated human PBMCs. Surprisingly, only purified CD8+ primary T-cells expressed PDE4B, but not CD4+ cells. Moreover, PDE4B was found to be highly expressed in CD4+ lymphoid cancer cells, which suggests that it may represent a physiological role unique to the CD8+ and lymphoid cancer cells and thus might represent a target for pharmaceutical intervention for certain lymphoid diseases.

The Shc family protein adaptor, Rai, acts as a negative regulator of Th17 and Th1 cell development

Rai, a Shc adapter family member, acts as a negative regulator of antigen receptor signaling in T and B cells. Rai(-/-) mice develop lupus-like autoimmunity associated to the spontaneous activation of self-reactive lymphocytes. Here, we have addressed the potential role of Rai in the development of the proinflammatory Th1 and Th17 subsets, which are centrally implicated in the pathogenesis of a number of autoimmune diseases, including lupus. We show that Rai(-/-) mice display a spontaneous Th1/Th17 bias. In vitro polarization experiments on naive and effector/memory CD4(+) T cells demonstrate that Rai(-/-) favors the development and expansion of Th17 but not Th1 cells, indicating that Rai modulates TCR signaling to antagonize the pathways driving naive CD4(+) T cell differentiation to the Th17 lineage, while indirectly limiting Th1 cell development in vivo. Th1 and Th17 cell infiltrates were found in the kidneys of Rai(-/-) mice, providing evidence that Rai(-/-) contributes to the development of lupus nephritis, not only by enhancing lymphocyte activation but also by promoting the development and expansion of proinflammatory effector T cells. Interestingly, T cells from SLE patients were found to have a defect in Rai expression, suggesting a role for Rai in disease pathogenesis.

Diversity of IL-17-producing T lymphocytes

Interleukin (IL)-17 is a pro-inflammatory cytokine that plays critical roles in host defense against extracellular bacteria and fungi and also in the pathogenesis of autoimmune diseases. While CD4+ TCRαβ+ T helper (Th) 17 cells are the best-described cellular source of IL-17, many innate-like T cells are in fact potent producers of IL-17. Given the increasing interest in therapeutic modulation of the IL-17 axis, it is crucial to better understand the cellular origins of IL-17 in various infection and diseases settings. While the diverse population of IL-17-producing T cells share many common characteristics, notable differences also exist. In this review, we discuss the heterogeneity of IL-17-producing T cell types focusing on their development, regulation, and function.

A maximum likelihood QTL analysis reveals common genome regions controlling resistance to Salmonella colonization and carrier-state

BACKGROUND

The serovars Enteritidis and Typhimurium of the Gram-negative bacterium Salmonella enterica are significant causes of human food poisoning. Fowl carrying these bacteria often show no clinical disease, with detection only established post-mortem. Increased resistance to the carrier state in commercial poultry could be a way to improve food safety by reducing the spread of these bacteria in poultry flocks. Previous studies identified QTLs for both resistance to carrier state and resistance to Salmonella colonization in the same White Leghorn inbred lines. Until now, none of the QTLs identified was common to the two types of resistance. All these analyses were performed using the F2 inbred or backcross option of the QTLExpress software based on linear regression. In the present study, QTL analysis was achieved using Maximum Likelihood with QTLMap software, in order to test the effect of the QTL analysis method on QTL detection. We analyzed the same phenotypic and genotypic data as those used in previous studies, which were collected on 378 animals genotyped with 480 genome-wide SNP markers. To enrich these data, we added eleven SNP markers located within QTLs controlling resistance to colonization and we looked for potential candidate genes co-localizing with QTLs.

RESULTS

In our case the QTL analysis method had an important impact on QTL detection. We were able to identify new genomic regions controlling resistance to carrier-state, in particular by testing the existence of two segregating QTLs. But some of the previously identified QTLs were not confirmed. Interestingly, two QTLs were detected on chromosomes 2 and 3, close to the locations of the major QTLs controlling resistance to colonization and to candidate genes involved in the immune response identified in other, independent studies.

CONCLUSIONS

Due to the lack of stability of the QTLs detected, we suggest that interesting regions for further studies are those that were identified in several independent studies, which is the case of the QTL regions on chromosomes 2 and 3, involved in resistance to both Salmonella colonization and carrier state. These observations provide evidence of common genes controlling S. Typhimurium colonization and S. Enteritidis carrier-state in chickens.

T helper 17 cells and regulatory T-cell imbalance in paediatric patients with asthma

Asthma is a chronic inflammatory disorder of the lung, which is thought to be determined by the balance between the T helper (Th)2 and Th1 responses. This study evaluated whether the balance between Th17 cells and regulatory T cells (T(reg)) was impaired in asthma patients. The proportion of peripheral blood Th17 cells of the total CD4(+) cell population in asthma patients was significantly higher than in controls (mean ± SD 0.72 ± 0.5% versus 0.31 ± 0.4%, respectively). The proportion of peripheral T(reg) cells in asthma patients was significantly lower than in controls (mean ± SD 12.1 ± 4.6% versus 27.2 ± 7.5%, respectively). Analysis of mRNA generally confirmed the flow cytometry data, suggesting that the changes in cytokine levels were mediated at the transcription level. In paediatric asthma patients, the CD4(+) T-cell phenotype was skewed toward the Th17 phenotype, suggesting that a Th17/T(reg) functional imbalance plays a role in asthma.

Lipid rafts: signaling and sorting platforms of cells and their roles in cancer

Lipid rafts are defined as microdomains within the lipid bilayer of cellular membranes that assemble subsets of transmembrane or glycosylphosphatidylinisotol-anchored proteins and lipids (cholesterol and sphingolipids) and experimentally resist extraction in cold detergent (detergent-resistant membrane). These highly dynamic raft domains are essential in signaling processes and also form sorting platforms for targeted protein traffic. Lipid rafts are involved in protein endocytosis that occurs via caveolae or flotillin-dependent pathways. Non-constitutive protein components of rafts fluctuate dramatically in cancer with impacts on cell proliferation, signaling, protein trafficking, adhesion and apoptosis. This article focuses on the identification of candidate cancer-associated biomarkers in carcinoma cells using state-of-the-art proteomics.

Glycosphingolipid modification: structural diversity, functional and mechanistic integration of diabetes

Glycosphingolipids (GSLs) are present in all mammalian cell plasma membranes and intracellular membrane structures. They are especially concentrated in plasma membrane lipid domains that are specialized for cell signaling. Plasma membranes have typical structures called rafts and caveola domain structures, with large amounts of sphingolipids, cholesterol, and sphingomyelin. GSLs are usually observed in many organs ubiquitously. However, GSLs, including over 400 derivatives, participate in diverse cellular functions. Several studies indicate that GSLs might have an effect on signal transduction related to insulin receptors and epidermal growth factor receptors. GSLs may modulate immune responses by transmitting signals from the exterior to the interior of the cell. Guillain-Barré syndrome is one of the autoimmune disorders characterized by symmetrical weakness in the muscles of the legs. The targets of the immune response are thought to be gangliosides, which are one group of GSLs. Other GSLs may serve as second messengers in several signaling pathways that are important to cell survival or programmed cell death. In the search for clear evidence that GSLs may play critical roles in various biological functions, many researchers have made genetically engineered mice. Before the era of gene manipulation, spontaneous animal models or chemical-induced disease models were used.

Lowering glycosphingolipid levels in CD4+ T cells attenuates T cell receptor signaling, cytokine production, and differentiation to the Th17 lineage

Lipid rafts reportedly have a role in coalescing key signaling molecules into the immunological synapse during T cell activation, thereby modulating T cell receptor (TCR) signaling activity. Recent findings suggest that a correlation may exist between increased levels of glycosphingolipids (GSLs) in the lipid rafts of T cells and a heightened response of those T cells toward activation. Here, we show that lowering the levels of GSLs in CD4(+) T cells using a potent inhibitor of glucosylceramide synthase (Genz-122346) led to a moderation of the T cell response toward activation. TCR proximal signaling events, such as phosphorylation of Lck, Zap70 and LAT, as well as early Ca(2+) mobilization, were attenuated by treatment with Genz-122346. Concomitant with these events were significant reductions in IL-2 production and T cell proliferation. Similar findings were obtained with CD4(+) T cells isolated from transgenic mice genetically deficient in GM3 synthase activity. Interestingly, lowering the GSL levels in CD4(+) T cells by either pharmacological inhibition or disruption of the gene for GM3 synthase also specifically inhibited the differentiation of T cells to the Th(17) lineage but not to other Th subsets in vitro. Taken together with the recently reported effects of Raftlin deficiency on Th(17) differentiation, these results strongly suggest that altering the GSL composition of lipid rafts modulates TCR signaling activity and affects Th(17) differentiation.

Evidence for somatic gene conversion and deletion in bipolar disorder, Crohn's disease, coronary artery disease, hypertension, rheumatoid arthritis, type-1 diabetes, and type-2 diabetes

BACKGROUND

During gene conversion, genetic information is transferred unidirectionally between highly homologous but non-allelic regions of DNA. While germ-line gene conversion has been implicated in the pathogenesis of some diseases, somatic gene conversion has remained technically difficult to investigate on a large scale.

METHODS

A novel analysis technique is proposed for detecting the signature of somatic gene conversion from SNP microarray data. The Wellcome Trust Case Control Consortium has gathered SNP microarray data for two control populations and cohorts for bipolar disorder (BD), cardiovascular disease (CAD), Crohn's disease (CD), hypertension (HT), rheumatoid arthritis (RA), type-1 diabetes (T1D) and type-2 diabetes (T2D). Using the new analysis technique, the seven disease cohorts are analyzed to identify cohort-specific SNPs at which conversion is predicted. The quality of the predictions is assessed by identifying known disease associations for genes in the homologous duplicons, and comparing the frequency of such associations with background rates.

RESULTS

Of 28 disease/locus pairs meeting stringent conditions, 22 show various degrees of disease association, compared with only 8 of 70 in a mock study designed to measure the background association rate (P < 10-9). Additional candidate genes are identified using less stringent filtering conditions. In some cases, somatic deletions appear likely. RA has a distinctive pattern of events relative to other diseases. Similarities in patterns are apparent between BD and HT.

CONCLUSIONS

The associations derived represent the first evidence that somatic gene conversion could be a significant causative factor in each of the seven diseases. The specific genes provide potential insights about disease mechanisms, and are strong candidates for further study.

Raftlin is involved in the nucleocapture complex to induce poly(I:C)-mediated TLR3 activation

The double-stranded RNA analog, poly(I:C), extracellularly activates both the endosomal Toll-like receptor (TLR) 3 and the cytoplasmic RNA helicase, melanoma differentiation-associated gene 5, leading to the production of type I interferons (IFNs) and inflammatory cytokines. The mechanism by which extracellular poly(I:C) is delivered to TLR3-positive organelles and the cytoplasm remains to be elucidated. Here, we show that the cytoplasmic lipid raft protein, Raftlin, is essential for poly(I:C) cellular uptake in human myeloid dendritic cells and epithelial cells. When Raftlin was silenced, poly(I:C) failed to enter cells and induction of IFN-β production was inhibited. In addition, cellular uptake of B-type oligodeoxynucleotide that shares its uptake receptor with poly(I:C) was suppressed in Raftlin knockdown cells. Upon poly(I:C) stimulation, Raftlin was translocated from the cytoplasm to the plasma membrane where it colocalized with poly(I:C), and thereafter moved to TLR3-positive endosomes. Thus, Raftlin cooperates with the uptake receptor to mediate cell entry of poly(I:C), which is critical for activation of TLR3.

Signal transduction pathways and transcriptional regulation in Th17 cell differentiation

Over the last decade, our understanding of helper/effector T cell differentiation has changed dramatically. The discovery of interleukin (IL-)17-producing T cells (Th17) and other subsets has changed our view of T cell-mediated immunity. Characterization of the signaling pathways involved in the Th17 commitment has provided exciting new insights into the differentiation of CD4+ T cells. Importantly, the emerging data on conversion among polarized T helper cells have raised the question how we should view such concepts as T cell lineage commitment, terminal differentiation and plasticity. In this review, we will discuss the current understanding of the signaling pathways, molecular interactions, and transcriptional and epigenetic events that contribute to Th17 differentiation and acquisition of effector functions.

IRF4 and its regulators: evolving insights into the pathogenesis of inflammatory arthritis?

Accumulating evidence from murine and human studies supports a key role for interleukin-17 (IL-17) and IL-21 in the pathogenesis of inflammatory arthritis. The pathways and molecular mechanisms that underlie the production of IL-17 and IL-21 are being rapidly elucidated. This review focuses on interferon regulatory factor 4 (IRF4), a member of the IRF family of transcription factors, which has emerged as a crucial controller of both IL-17 and IL-21 production. We first outline the complex role of IRF4 in the function of CD4(+) T cells and then discuss recent studies from our laboratory that have revealed a surprising role for components of Rho GTPase-mediated pathways in controlling the activity of IRF4. A better understanding of these novel pathways will hopefully provide new insights into mechanisms responsible for the development of inflammatory arthritis and potentially guide the design of novel therapeutic approaches.

Receptor-mediated suppression of potassium currents requires colocalization within lipid rafts

Expression of KCNQ2/3 (Kv7.2 and -7.3) heteromers underlies the neuronal M current, a current that is suppressed by activation of a variety of receptors that couple to the hydrolysis of phosphatidylinositol 4,5-bisphosphate. Expression of Kv7.2/7.3 channels in human embryonic kidney (HEK) 293 cells produced a noninactivating potassium current characteristic of M current. Muscarinic receptors endogenous to HEK293 cells were identified as being M3 by pharmacology and Western blotting, producing a rise of intracellular calcium ([Ca2+](i)) upon activation. Activation of these endogenous muscarinic receptors however, failed to suppress expressed Kv7.2/7.3 current. Current suppression was reconstituted by coexpression of HA-tagged muscarinic m1 or m3 receptors. Examination of membrane fractions showed that both expressed receptors and Kv7.2 and -7.3 channel subunits resided within lipid rafts. Disruption of lipid rafts by pretreatment of cells expressing either m1 or m3 muscarinic receptors with methyl-beta-cyclodextrin produced a loss of localization of proteins within lipid raft membrane fractions. This pretreatment also abolished both the increase of [Ca2+](i) and suppression of expressed Kv7.2/7.3 current evoked by activation of expressed m1 or m3 muscarinic receptors. A similar loss of muscarinic receptor-mediated suppression of M current native to rat dorsal root ganglion neurons was observed after incubating dissociated cells with methyl-beta-cyclodextrin. These data suggested that lipid rafts colocalized both muscarinic receptors and channel subunits to enable receptor-mediated suppression of channel activity, a spatial colocalization that enables specificity of coupling between receptor and ion channel.