Discs large (Dlg1) complexes in lymphocyte activation

T cell antigen recognition involves the formation of a structured interface between antigen-presenting and T cells that facilitates the specific transmission of activating and desensitizing stimuli. The molecular machinery that organizes the signaling molecules and controls their disposition in response to activation remains poorly understood. We show here that in T cells Discs large (Dlg1), a PDZ domain-containing protein, is recruited upon activation to cortical actin and forms complexes with early participants in T cell activation. Transient overexpression of Dlg1 attenuates basal and Vav1-induced NFAT reporter activation. Reduction of Dlg1 expression by RNA interference enhances both CD3- and superantigen-mediated NFAT activation. Attenuation of antigen receptor signaling appears to be a complex, highly orchestrated event that involves the mutual segregation of important elements of the early signaling complex

Deficiency of Antigen Presenting Cell Invariant Chain Reduces Atherosclerosis in Mice

August 25, 2010Background: Adaptive immunity and innate immunity play important roles in atherogenesis. Invariant chain (CD74) mediates antigen-presenting cell antigen presentation and T-cell activation. This study tested the hypothesis that CD74-deficient mice have reduced numbers of active T cells and resist atherogenesis. Methods and Results: In low-density lipoprotein receptor–deficient (Ldlr[superscript −/−]) mice, CD74 deficiency (Ldlr[superscript −/−]Cd74[superscript −/−]) significantly reduced atherosclerosis and CD25+-activated T cells in the atheromata. Although Ldlr[superscript −/−]Cd74[superscript −/−] mice had decreased levels of plasma immunoglobulin (Ig) G1, IgG2b, and IgG2c against malondialdehyde-modified LDL (MDA-LDL), presumably as a result of impaired antigen-presenting cell function, Ldlr[superscript −/−]Cd74[superscript −/−] mice showed higher levels of anti–MDA-LDL IgM and IgG3. After immunization with MDA-LDL, Ldlr[superscript −/−]Cd74[superscript −/−] mice had lower levels of all anti–MDA-LDL Ig isotypes compared with Ldlr[superscript −/−] mice. As anticipated, only Ldlr[superscript −/−] splenocytes responded to in vitro stimulation with MDA-LDL, producing Th1/Th2 cytokines. Heat shock protein-65 immunization enhanced atherogenesis in Ldlr[superscript −/−] mice, but Ldlr[superscript −/−] Cd74[superscript −/−] mice remained protected. Compared with Ldlr[superscript −/−] mice, Ldlr[superscript −/−]Cd74[superscript −/−] mice had higher anti–MDA-LDL autoantibody titers, fewer lesion CD25+-activated T cells, impaired release of Th1/Th2 cytokines from antigen-presenting cells after heat shock protein-65 stimulation, and reduced levels of all plasma anti–heat shock protein-65 Ig isotypes. Cytofluorimetry of splenocytes and peritoneal cavity cells of MDA-LDL– or heat shock protein-65–immunized mice showed increased percentages of autoantibody-producing marginal zone B and B-1 cells in Ldlr[superscript −/−]Cd74[superscript −/−] mice compared with Ldlr[superscript −/−] mice. Conclusions: Invariant chain deficiency in Ldlr[superscript −/−] mice reduced atherosclerosis. This finding was associated with an impaired adaptive immune response to disease-specific antigens. Concomitantly, an unexpected increase in the number of innate-like peripheral B-1 cell populations occurred, resulting in increased IgM/IgG3 titers to the oxidation-specific epitopes

Searching for transcriptional regulators of Ang II–induced vascular pathology

Ang II plays a key role in cardiovascular regulation and participates in vascular pathobiology, including inflammation and remodeling. Whether these tissue effects are mediated by direct Ang II actions or indirectly as a result of its influence on hemodynamics is being debated. In vitro data have shown that Ang II induces vascular cellular transcriptional activation and gene expression, but the mechanisms explaining its long-term tissue effects in vivo are relatively unknown. Do the multiple in vivo vascular activities elicited by Ang II (such as inflammation, fibrosis, and vascular cell hypertrophy/proliferation) occur via independent pathways, or do common transcription mechanisms mediate these multiple effects? In this issue, Zhan et al. identify Ets-1 as a critical downstream transcriptional mediator of vascular inflammation and remodeling in vivo; their data suggest that Ets-1 may be a common denominator of a complex process that involves multiple pathways previously considered to be mechanistically independent. Characterization of the critical transcription programs activated by Ang II in vivo and determination of the hierarchy of responses are vital to the understanding of the mechanism of vascular disease and to the development of therapies targeted at inhibiting the common transcription effectors of vascular pathology

The Angiotensin II Type I Receptor-associated Protein, ATRAP, Is a Transmembrane Protein and a Modulator of Angiotensin II Signaling

Our group identified angiotensin II type 1 (AT1) receptor-associated protein (ATRAP) in a yeast two-hybrid screen for proteins that bind to the carboxyl-terminal cytoplasmic domain of the AT1. In this work, we characterize ATRAP as a transmembrane protein localized in intracellular trafficking vesicles and plasma membrane that functions as a modulator of angiotensin II-induced signal transduction. ATRAP contains three hydrophobic domains at the amino-terminal end of the protein, encompassing the amino acid residues 14–36, 55–77, and 88–108 and a hydrophilic cytoplasmic carboxyl-terminal tail from residues 109–161. Endogenous and transfected ATRAP cDNA shows a particulate distribution; electron microscopy reveals the presence of ATRAP in prominent perinuclear vesicular membranes; and colocalization analysis by immunofluorescence shows that ATRAP colocalizes in an intracellular vesicular compartment corresponding to endoplasmic reticulum, Golgi, and endocytic vesicles. Real-time tracking of ATRAP vesicles shows constitutive translocation toward the plasma membrane. Using epitope-tagged forms of ATRAP at either the amino or carboxyl end of the molecule, we determined the orientation of the amino end as being outside the cell. Mutant forms of ATRAP lacking the carboxyl end are unable to bind to the AT1 receptor, leading to the formation of prominent perinuclear vesicle clusters. Functional analysis of the effects of ATRAP on angiotensin II-induced AT1 receptor signaling reveals a moderate decrease in the generation of inositol lipids, a marked decrease in the angiotensin II-stimulated transcriptional activity of the c-fos promoter luciferase reporter gene, and a decrease in cell proliferation

Determination of the healing effect of Piper aduncum (spiked pepper or matico) on human fibroblasts

Objectives. To evaluate the healing effect of a Piper aduncum ethanol-water extract on an adult human dermal fibroblast cell line (hDFa). Materials and Methods. After obtaining the extract via solid-liquid extraction, concentration, and lyophilization, extract proteins were purified using reverse phase high-performance liquid chromatography, identified using tandem mass spectrometry of tryptic peptides, and analyzed using MALDI-TOF-TOF on an ABSciex4800 mass spectrometer. Half maximum effective concentration values (EC50), half maximum inhibiting concentration (IC50), and percentages of cell proliferation were determined using tetrazolium salt assays. Cell migration was evaluated using a “scratch assay”. Growth factor expression in cells was analyzed via quantitative real-time reverse transcription polymerase chain reaction. Results. Against the hDFa cell line, the extract had an IC50 of 200 μg/mL and EC50 of 103.5 μg/mL. In the proliferation assay, protein K2 (obtained from the extract) exhibited increased proliferative activity relative to other treatments (1 μg/mL); this agent also exhibited increased activity (50 μg/mL) in the fibroblast migration assay. Furthermore, the relative expression of platelet-derived growth factor increased by 8.6-fold in the presence of K2 protein relative to the control. Conclusions. The hydroethanolic extract of Piper aduncum and its component proteins increased the proliferation and migration of hDFa and increased the expression of growth factors involved in the healing process