Regulation of the p85/p110 Phosphatidylinositol 3′-Kinase: Stabilization and Inhibition of the p110α Catalytic Subunit by the p85 Regulatory Subunit

We propose a novel model for the regulation of the p85/p110α phosphatidylinositol 3′-kinase. In insect cells, the p110α catalytic subunit is active as a monomer but its activity is decreased by coexpression with the p85 regulatory subunit. Similarly, the lipid kinase activity of recombinant glutathione S-transferase (GST)-p110α is reduced by 65 to 85% upon in vitro reconstitution with p85. Incubation of p110α/p85 dimers with phosphotyrosyl peptides restored activity, but only to the level of monomeric p110α. These data show that the binding of phosphoproteins to the SH2 domains of p85 activates the p85/p110α dimers by inducing a transition from an inhibited to a disinhibited state. In contrast, monomeric p110 had little activity in HEK 293T cells, and its activity was increased 15- to 20-fold by coexpression with p85. However, this apparent requirement for p85 was eliminated by the addition of a bulky tag to the N terminus of p110α or by the growth of the HEK 293T cells at 30°C. These nonspecific interventions mimicked the effects of p85 on p110α, suggesting that the regulatory subunit acts by stabilizing the overall conformation of the catalytic subunit rather than by inducing a specific activated conformation. This stabilization was directly demonstrated in metabolically labeled HEK 293T cells, in which p85 increased the half-life of p110. Furthermore, p85 protected p110 from thermal inactivation in vitro. Importantly, when we examined the effect of p85 on GST-p110α in mammalian cells at 30°C, culture conditions that stabilize the catalytic subunit and that are similar to the conditions used for insect cells, we found that p85 inhibited p110α. Thus, we have experimentally distinguished two effects of p85 on p110α: conformational stabilization of the catalytic subunit and inhibition of its lipid kinase activity. Our data reconcile the apparent conflict between previous studies of insect versus mammalian cells and show that p110α is both stabilized and inhibited by dimerization with p85.     

Abrogation of CD40-CD154 Signaling Impedes the Homeostasis of Thymic Resident Regulatory T Cells by Altering the Levels of IL-2, but Does Not Affect Regulatory T Cell Development

A greater understanding of the function of the human immune system at the single-cell level in healthy individuals is critical for discerning aberrant cellular behavior that occurs in settings such as autoimmunity, immunosenescence, and cancer. To achieve this goal, a systems-level approach capable of capturing the response of the interdependent immune cell types to external stimuli is required. In this study, an extensive characterization of signaling responses in multiple immune cell subpopulations within PBMCs from a cohort of 60 healthy donors was performed using single-cell network profiling (SCNP). SCNP is a multiparametric flow cytometry-based approach that enables the simultaneous measurement of basal and evoked signaling in multiple cell subsets within heterogeneous populations. In addition to establishing the interindividual degree of variation within a broad panel of immune signaling responses, the possible association of any observed variation with demographic variables including age and race was investigated. Using half of the donors as a training set, multiple age- and race-associated variations in signaling responses in discrete cell subsets were identified, and several were subsequently confirmed in the remaining samples (test set). Such associations may provide insight into age-related immune alterations associated with high infection rates and diminished protection following vaccination and into the basis for ethnic differences in autoimmune disease incidence and treatment response. SCNP allowed for the generation of a functional map of healthy immune cell signaling responses that can provide clinically relevant information regarding both the mechanisms underlying immune pathological conditions and the selection and effect of therapeutics.     

Preserved Proinsulin Production in Homozygous Protein Tyrosine Phosphatase Nonreceptor Type 22 C1858T Variant Type 1 Diabetes: A Possible Explanation for Absence of Overt Ketoacidosis Despite Omission of Exogenous Insulin

ObjectiveTo report a postulated mechanism for resistance to overt ketoacidosis due to prolonged insulin omission in a severely hyperglycemic woman with a 14-year history of autoimmune type 1 diabetes (T1D).MethodsHistory, physical examination, laboratory testing, and genotyping were performed. We also review the medical literature pertinent to this patient’s phenotype and genotype.ResultsProinsulin levels remained within the normal range (suppressed with hypoglycemia) despite simultaneous almost unmeasurable C-peptide levels during hyperglycemia. We confirmed a homozygous (TT) variant of protein tyrosine phosphatase nonreceptor type 22 (PTPN22) 1858T, a T1D susceptibility gene associated with higher proinsulin levels.ConclusionThe extraordinarily preserved proinsulin biological activity may explain the unusual resistance to overt ketoacidosis despite omission of exogenous insulin administration for extended periods of time. The role of the associated PTPN22 1858TT variant remains speculative. (Endocr Pract. 2013;19:426-430)     

Alteration of the Thymic T Cell Repertoire by Rotavirus Infection Is Associated with Delayed Type 1 Diabetes Development in Non-Obese Diabetic Mice

Rotaviruses are implicated as a viral trigger for the acceleration of type 1 diabetes in children. Infection of adult non-obese diabetic (NOD) mice with rotavirus strain RRV accelerates diabetes development, whereas RRV infection in infant NOD mice delays diabetes onset. In this study of infant mice, RRV titers and lymphocyte populations in the intestine, mesenteric lymph nodes (MLN) and thymus of NOD mice were compared with those in diabetes-resistant BALB/c and C57BL/6 mice. Enhanced intestinal RRV infection occurred in NOD mice compared with the other mouse strains. This was associated with increases in the frequency of CD8αβ TCRαβ intraepithelial lymphocytes, and their PD-L1 expression. Virus spread to the MLN and T cell numbers there also were greatest in NOD mice. Thymic RRV infection is shown here in all mouse strains, often in combination with alterations in T cell ontogeny. Infection lowered thymocyte numbers in infant NOD and C57BL/6 mice, whereas thymocyte production was unaltered overall in infant BALB/c mice. In the NOD mouse thymus, effector CD4⁺ T cell numbers were reduced by infection, whereas regulatory T cell numbers were maintained. It is proposed that maintenance of thymic regulatory T cell numbers may contribute to the increased suppression of inflammatory T cells in response to a strong stimulus observed in pancreatic lymph nodes of adult mice infected as infants. These findings show that rotavirus replication is enhanced in diabetes-prone mice, and provide evidence that thymic T cell alterations may contribute to the delayed diabetes onset following RRV infection.     

In Vitro Effects of Immunosuppressive Agents on Cytokine Production by HTLV-I-Infected T Cell Clones Derived from the Ocular Fluid of Patients with HTLV-I Uveitis

The present study was designed to investigate the in vitro effects of potential therapeutic agents on cytokine production by five HTVL-I-infected T cell clones (TCC) established from the ocular fluid of patients with HTLV-I uveitis. Each of the five HTLV-I-infected TCC was cultured at 1 × 10⁶ cells/ml with or without an immunosuppressive agent (hydrocortisone, FK506, rapamycin, indomethacin, or prostaglandin E₂) for 22 hr in humidified 5% CO₂ in air at 37 C. The production of various cytokines in the culture supernatant from each TCC was measured by ELISA. The HTLV-I-infected TCC produced high amounts of IL-1α, IL-3, IL-6, IL-8, TNF-α, IFN-γ, and GM-CSF, and low but significant levels of IL-2 and IL-10 without any stimuli. Hydrocortisone severely depressed the production by these TCC of all the cytokines except for IL-2, which was slightly increased. Prostaglandin E₂ depressed the production of IL-1α, while it up-regulated the production of IL-6, TNF-α, and IFN-γ. Rapamycin depressed the production of IL-6 and TNF-α, and FK506 depressed the production of TNF-α. Hydrocortisone also severely depressed the cytokine production by PHA-stimulated peripheral blood mononuclear cells obtained from healthy volunteers. Of the immunosuppressive agents tested, hydrocortisone exhibited the strongest suppression of cytokine production by HTLV-I-infected TCC. This result was in agreement with the in vivo effects of hydrocortisone in patients with HTLV-I uveitis. These TCC will be useful in investigating the effects of potential therapeutic agents for HTLV-I uveitis in vitro.     

Effects of Postnatal Stress on the Development of Type 1 Diabetes in Bank Voles (Clethrionomys glareolus)

Wild bank voles (Clethrionomys glareolus) kept in the laboratory under barren housing conditions develop high incidences of type 1 diabetes mellitus due to beta cell– specific lysis in association with the appearance of GAD65, IA-2, and insulin autoantibodies. Wild-caught and immediately analyzed voles show no histological signs of diabetes, and the disease may therefore be induced by circumstances related to the housing of the animals in captivity. We tested the possibility that postnatal stress by either maternal separation or water immersion at different intervals would induce diabetes in adult bank voles. We found that low-frequent stress during the first 21 days of life increases, whereas high-frequent stress markedly reduces, the incidence of type 1 diabetes in adulthood. These results differentiate the role of early-experienced stress on subsequent type 1 diabetes development and emphasize that the bank vole may serve as a useful new animal model for the disease.     

珍珠质自然涂层钛种植体表面对MC3T3E1成骨样细胞的作用

为了研究珍珠质自然涂层钛种植体表面的体外生物相容性,将珍珠质自然涂层的钛片与MC3T3E1成骨样细胞复合培养以观察细胞的生长、增殖和分化.分别以羟基磷灰石涂层钛片和没有涂层的纯钛片作为对照组,以MC3T3E1细胞单纯培养作为空白组,分别培养3天,5天和7天,通过倒置相差显微镜和扫描电镜观察细胞生长情况,流式细胞技术检测细胞增殖活性,金氏比色法检测碱性磷酸酶(ALP)活性以及蛋白质印迹(Western blotting)法测定转化生长因子-β1(TGF-β1)表达水平.结果发现,细胞在珍珠质周围能形成良好附着,在其表面生长丰满.细胞培养第3天,第5天和第7天时,珍珠质表面的细胞增殖指数分别为(35.9±2.5)%、(69.7±3.3)%和(58.2±2.6)%,ALP活性分别为(6.123±2.917)U/g、(17.486±1.986)U/g和(23.987±1.372)U/g.第5天和7天时,实验组的细胞增殖指数、ALP活性和TGF-β1表达水平显著高于对照组和空白组(P<0.05).珍珠质自然涂层钛表面有利于MC3T3E1细胞的生长、增殖和分化,表明了珍珠质涂层能提高种植体表面的生物相容性,有可能会促进种植后的骨整合.     

Effects of chromium picolinate on glucose uptake in insulin-resistant 3T3-L1 adipocytes involve activation of p38 MAPK

Chromium picolinate (CrPic) has been discovered as a supplemental or alternative medication for type 2 diabetes, but its mechanism of action is not well understood. The purpose of this study was to explore the possible anti-diabetic mechanisms of CrPic in insulin-resistant 3T3-L1 adipocytes; the insulin resistance was induced by treatment with high glucose and insulin for 24 h. The effects of CrPic on glucose metabolism and the glucose uptake-inducing activity of CrPic were investigated. Meanwhile, the effects of CrPic on glucose transporter 4 (GLUT4) translocation were visualized by immonofluorescence microscopy. In addition, its effects on insulin signaling pathways and mitogen-activated protein kinase (MAPK) signaling cascades were assessed by immunoblotting analysis and real-time PCR. The results showed that CrPic induced glucose metabolism and uptake, as well as GLUT4 translocation to plasma membrane (PM) in both control and insulin-resistant 3T3-L1 adipocytes without any changes in insulin receptor β (IR-β), protein kinase B (AKt), c-Cbl, extracellular signal-regulated kinase (ERK), c-Jun phosphorylation and c-Cbl-associated protein (CAP) mRNA levels. Interestingly, CrPic was able to increase the basal and insulin-stimulated levels of p38 MAPK activation in the control and insulin-resistant cells. Pretreatment with the specific p38 MAPK inhibitor SB203580 partially inhibited the CrPic-induced glucose transport, but CrPic-activated translocation of GLUT4 was not inhibited by SB203580. This study provides an experimental evidence of the effects of CrPic on glucose uptake through the activation of p38 MAPK and it is independent of the effect on GLUT4 translocation. The findings also suggest exciting new insights into the role of p38 MAPK in glucose uptake and GLUT4 translocation.     

Effects of Human Type 1α Metabotropic Glutamate Receptor Expression Level on Phosphoinositide and Ca2+ Signalling in an Inducible Cell Expression System

Abstract: Stable expression of the human type 1α metabotropic glutamate (mGlu1α) receptor was achieved in Chinese hamster ovary cells using an isopropyl-β- d -thiogalactoside (IPTG)-repressible expression system. Treatment of the cells with IPTG resulted in a time- and concentration-dependent induction of receptor expression. Maximal expression was obtained after treatment of the cells with 100 µ M IPTG for 20 h, leading to a marked increase in receptor immunoreactivity detected by western blot, >30-fold stimulation of ³H-labelled inositol phosphate (³H-InsP) production, and a robust increase in intracellular calcium concentration in single cells after stimulation with 20 µ M quisqualate. The basal level of ³H-InsP accumulation in cells induced with IPTG was increased by two- to threefold as compared with control cells; however, this basal activity was found to be dependent on glutamate released by the cells into the incubation medium. Following IPTG treatment, stable expression of the mGlu1α receptor was maintained for at least 1 week. Taken together, these results clearly indicate the advantages of working with an inducible expression system when studying the biochemical and pharmacological properties of the human mGlu1α receptor in transfected cells.     

The Genotype of the Donor for the (GT)n Polymorphism in the Promoter/Enhancer of FOXP3 Is Associated with the Development of Severe Acute GVHD but Does Not Affect the GVL Effect after Myeloablative HLA-Identical Allogeneic Stem Cell Transplantation

The FOXP3 gene encodes for a protein (Foxp3) involved in the development and functional activity of regulatory T cells (CD4+/CD25+/Foxp3+), which exert regulatory and suppressive roles over the immune system. After allogeneic stem cell transplantation, regulatory T cells are known to mitigate graft versus host disease while probably maintaining a graft versus leukemia effect. Short alleles (≤(GT)₁₅) for the (GT)_n polymorphism in the promoter/enhancer of FOXP3 are associated with a higher expression of FOXP3, and hypothetically with an increase of regulatory T cell activity. This polymorphism has been related to the development of auto- or alloimmune conditions including type 1 diabetes or graft rejection in renal transplant recipients. However, its impact in the allo-transplant setting has not been analyzed. In the present study, which includes 252 myeloablative HLA-identical allo-transplants, multivariate analysis revealed a lower incidence of grade III-IV acute graft versus host disease (GVHD) in patients transplanted from donors harboring short alleles (OR = 0.26, CI 0.08–0.82, p = 0.021); without affecting chronic GVHD or graft versus leukemia effect, since cumulative incidence of relapse, event free survival and overall survival rates are similar in both groups of patients.     

Anti‐Lipid Peroxidation, α‐Glucosidase and α‐Amylase Inhibitory Effects of the Extract of Capitula of Coreopsis tinctoria Nutt. and Protection Effects on High‐Fat/High‐Sugar and Streptozotocin‐Induced Type 2 Diabetes in Mice

Coreopsis tinctoria capitula (CTC) of the Compositae family has been used traditionally to treat various diseases in China, particularly type 2 diabetes mellitus (T2DM). This study evaluated the anti‐lipid peroxidation, α‐glucosidase and α‐amylase inhibitory effects of CTC extracts, and analyzed its chemical composition by HPLC. Moreover, the antioxidant activity and protection effects of CTC extracts were investigated on high‐fat/high‐sugar and streptozotocin‐induced T2DM mice. In vitro study, the ethyl acetate extract (EAE) and butanol extract (BE) of CTC exhibited anti‐lipid peroxidation (IC₅₀: BHA>BE or EAE>ascorbic acid, p<0.05) and α‐glucosidase inhibitory activity (IC₅₀: BE>EAE, p<0.05). In vivo, the BE at the dose of 600 mg/kg was intragastrically given to T2DM mice, which exhibited a certain extent of repair and improvement of the levels of CAT, GSH, GSH‐P_X, SOD, as well as plasma biomarkers, compared with those in the model group (p<0.05). These results demonstrated that CTC extracts have a positive effect to treat T2DM and it can be used for the treatment of T2DM in the future.     

Effects of sulfur amino acids, <Emphasis Type="SmallCaps">l</Emphasis>-methionine, <Emphasis Type="SmallCaps">l</Emphasis>-cystine and <Emphasis Type="SmallCaps">l</Emphasis>-cysteine on lipoprotein lipase and hormone-sensitive lipase in differentiated mouse 3T3-L1 adipocytes

Rats subcutaneously implanted with AH109A hepatoma cells show hyperlipidemia with high concentrations of serum triglyceride and nonesterified fatty acid, suppression of lipoprotein lipase (LPL), and elevation of hormone-sensitive lipase (HSL) activities during the growth of the hepatoma. Supplementation of the diet with sulfur amino acids such as l-methionine (Met) and l-cystine (Cys) improved hyperlipidemia by restoring LPL and HSL activities. In the present study, we have attempted to examine the effects of sulfur amino acids on the activity and mRNA level of LPL and the activity of HSL using 3T3-L1 cells, which are known to differentiate to adipocytes. The adipocytes were incubated with various concentrations of Met, Cys or l-cysteine (CysH) in the absence or presence of tumor necrosis factor-α (TNF-α). LPL activity was suppressed by TNF-α. In the absence of TNF-α, Met, Cys and CysH did not change the LPL activity. In the presence of TNF-α, Met and Cys significantly increased the LPL activity, and Met also enhanced the LPL mRNA level. HSL activity was also suppressed by TNF-α. In the absence of TNF-α, Met enhanced the HSL activity. In the presence of TNF-α, Met, Cys and CysH suppressed the HSL activity. Sulfur amino acids such as Met, Cys and CysH affected the LPL activity, mRNA level, and HSL activity in 3T3-L1 adipocytes. Some of these effects of sulfur amino acids were different between LPL and HSL, between the absence and the presence of TNF-α, and between 3T3-L1 adipocytes and the adipose tissue from rats.