Interleukin-17 (IL-17)-secreting T cells of the T helper 17 (TH17) lineage play a pathogenic role in multiple inflammatory and autoimmune conditions and thus represent a highly attractive target for therapeutic intervention. We report that inhibition of acetyl-CoA carboxylase 1 (ACC1) restrains the formation of human and mouse TH17 cells and promotes the development of anti-inflammatory Foxp3(+) regulatory T (Treg) cells. We show that TH17 cells, but not Treg cells, depend on ACC1-mediated de novo fatty acid synthesis and the underlying glycolytic-lipogenic metabolic pathway for their development. Although TH17 cells use this pathway to produce phospholipids for cellular membranes, Treg cells readily take up exogenous fatty acids for this purpose. Notably, pharmacologic inhibition or T cell-specific deletion of ACC1 not only blocks de novo fatty acid synthesis but also interferes with the metabolic flux of glucose-derived carbon via glycolysis and the tricarboxylic acid cycle. In vivo, treatment with the ACC-specific inhibitor soraphen A or T cell-specific deletion of ACC1 in mice attenuates TH17 cell-mediated autoimmune disease. Our results indicate fundamental differences between TH17 cells and Treg cells regarding their dependency on ACC1-mediated de novo fatty acid synthesis, which might be exploited as a new strategy for metabolic immune modulation of TH17 cell-mediated inflammatory diseases.

In response to stress, the heart undergoes extensive cardiac remodeling that results in cardiac fibrosis and pathological growth of cardiomyocytes (hypertrophy), which contribute to heart failure. Alterations in microRNA (miRNA) levels are associated with dysfunctional gene expression profiles associated with many cardiovascular disease conditions; however, miRNAs have emerged recently as paracrine signaling mediators. Thus, we investigated a potential paracrine miRNA crosstalk between cardiac fibroblasts and cardiomyocytes and found that cardiac fibroblasts secrete miRNA-enriched exosomes. Surprisingly, evaluation of the miRNA content of cardiac fibroblast-derived exosomes revealed a relatively high abundance of many miRNA passenger strands ("star" miRNAs), which normally undergo intracellular degradation. Using confocal imaging and coculture assays, we identified fibroblast exosomal-derived miR-21_3p (miR-21*) as a potent paracrineacting RNA molecule that induces cardiomyocyte hypertrophy. Proteome profiling identified sorbin and SH3 domain-containing protein 2 (SORBS2) and PDZ and LIM domain 5 (PDLIM5) as miR-21* targets, and silencing SORBS2 or PDLIM5 in cardiomyocytes induced hypertrophy. Pharmacological inhibition of miR-21* in a mouse model of Ang II-induced cardiac hypertrophy attenuated pathology. These findings demonstrate that cardiac fibroblasts secrete star miRNA-enriched exosomes and identify fibroblast-derived miR-21* as a paracrine signaling mediator of cardiomyocyte hypertrophy that has potential as a therapeutic target.

Three ionotropic glutamate receptor subunits, designated GluRIIA, GluRIIB, and GluRIII, have been identified at neuromuscular junctions of Drosophila. Whereas GluRIIA and GluRIIB are redundant for viability, it was shown recently that GluRIII is essential for both the synaptic localization of GluRIIA and GluRIIB and the viability of Drosophila. Here we identify a fourth and a fifth subunit expressed in the neuromuscular system, which we name GluRIID and GluRIIE. Both new subunits we show to be necessary for survival. Moreover, both GluRIID and GluRIIE are required for the synaptic expression of all other glutamate receptor subunits. All five subunits are interdependent for receptor function, synaptic receptor expression, and viability. This indicates that synaptic glutamate receptors incorporate the GluRIII, GluRIID, and GluRIIE subunit together with either GluRIIA or GluRIIB at the Drosophila neuromuscular junction. At this widely used model synapse, the assembly of four different subunits to form an individual glutamate receptor channel may thus be obligatory. This study opens the way for a further characterization of in vivo glutamate receptor assembly and trafficking using the efficient genetics of Drosophila.

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The neurotransmitter serotonin (5-HT) plays an important role in the regulation of multiple events in the CNS. We demonstrated recently a coupling between the 5-HT 4 receptor and the heterotrimeric G13-protein resulting in RhoA-dependent neurite retraction and cell rounding (Ponimaskin et al., 2002). In the present study, we identified G12 as an additional G-protein that can be activated by another member of serotonin receptors, the 5-HT 7 receptor. Expression of 5-HT 7 receptor induced constitutive and agonist-dependent activation of a serum response element-mediated gene transcription through G12-mediated activation of small GTPases. In NIH3T3 cells, activation of the 5-HT 7 receptor induced filopodia formation via a Cdc42-mediated pathway correlating with RhoA-dependent cell rounding. In mouse hippocampal neurons, activation of the endogenous 5-HT 7 receptors significantly increased neurite length, whereas stimulation of 5-HT 4 receptors led to a decrease in the length and number of neurites. These data demonstrate distinct roles for 5-HT 7 R/G12 and 5-HT 4 R/G13 signaling pathways in neurite outgrowth and retraction, suggesting that serotonin plays a prominent role in regulating the neuronal cytoarchitecture in addition to its classical role as neurotransmitter.

Opiates are widely used analgesics in anesthesiology, but they have serious adverse effects such as depression of breathing. This is caused by direct inhibition of rhythm-generating respiratory neurons in the Pre-Boetzinger complex (PBC) of the brainstem. We report that serotonin 4(a) [5-HT4(a)] receptors are strongly expressed in respiratory PBC neurons and that their selective activation protects spontaneous respiratory activity. Treatment of rats with a 5-HT4 receptor-specific agonist overcame fentanyl-induced respiratory depression and reestablished stable respiratory rhythm without loss of fentanyl's analgesic effect. These findings imply the prospect of a fine-tuned recovery from opioid-induced respiratory depression, through adjustment of intracellular adenosine 3',5'-monophosphate levels through the convergent signaling pathways in neurons.

Influenza virus matrix protein (M1), a critical protein required for virus assembly and budding, is presumed to interact with viral glycoproteins on the outer side and viral ribonucleoprotein on the inner side. However, because of the inherent membrane-binding ability of M1 protein, it has been difficult to demonstrate the specific interaction of M1 protein with hemagglutinin (HA) or neuraminidase (NA), the influenza virus envelope glycoproteins. Using Triton X-100 (TX-100) detergent treatment of membrane fractions and floatation in sucrose gradients, we observed that the membrane-bound M1 protein expressed alone or coexpressed with heterologous Sendai virus F was totally TX-100 soluble but the membrane-bound M1 protein expressed in the presence of HA and NA was predominantly detergent resistant and floated to the top of the density gradient. Furthermore, both the cytoplasmic tail and the transmembrane domain of HA facilitated binding of M1 to detergent-resistant membranes. Analysis of the membrane association of M1 in the early and late phases of the influenza virus infectious cycle revealed that the interaction of M1 with mature glycoproteins which associated with the detergent-resistant lipid rafts was responsible for the detergent resistance of membrane-bound M1. Immunofluorescence analysis by confocal microscopy also demonstrated that, in influenza virus-infected cells, a fraction of M1 protein colocalized with HA and associated with the HA in transit to the plasma membrane via the exocytic pathway. Similar results for colocalization were obtained when M1 and HA were coexpressed and HA transport was blocked by monensin treatment. These studies indicate that both HA and NA interact with influenza virus M1 and that HA associates with M1 via its cytoplasmic tail and transmembrane domain.Influenza viruses, enveloped RNA viruses containing singlestranded, segmented RNA of negative polarity, assemble and bud from the plasma membrane of virus-infected cells into the outside environment. Complete virions are usually not observed inside the cell in the productive infectious cycle. Furthermore, in polarized epithelial cells, influenza viruses bud asymmetrically, i.e., predominantly from the apical plasma membrane (30). For virus budding to occur, two processes are obligatory (27). Firstly, all viral structural components, namely, the matrix protein (M1), the viral nucleocapsid (viral ribonucleoprotein [vRNP]) containing vRNA, nucleoprotein (NP), polymerase proteins (PB1, PB2, and PA), and NS2 (NEP) as well as the viral envelope containing the host lipids and three transmembrane proteins (hemagglutinin [HA], neuraminidase [NA], and M2) must be transported and targeted either individually or as complex subviral components to the assembly site at the plasma membrane. Secondly, these viral proteins and/or subviral components must interact with each other to initiate the budding processes leading to morphogenesis of virus particles and release of virions.Influenza virus M1, the most abundant protein in the virus particle,...

A method for spectral analysis of Förster resonance energy transfer (FRET) signals is presented, taking into consideration both the contributions of unpaired donor and acceptor fluorophores and the influence of incomplete labeling of the interacting partners. It is shown that spectral analysis of intermolecular FRET cannot yield accurate values of the Förster energy transfer efficiency E, unless one of the interactors is in large excess and perfectly labeled. Instead, analysis of donor quenching yields a product of the form Ef(d)p(a), where f(d) is the fraction of donor-type molecules participating in donor-acceptor complexes and p(a) is the labeling probability of the acceptor. Similarly, analysis of sensitized emission yields a product involving Ef(a). The analysis of intramolecular FRET (e.g., of tandem constructs) yields the product Ep(a). We use our method to determine these values for a tandem construct of cyan fluorescent protein and yellow fluorescent protein and compare them with those obtained by standard acceptor photobleaching and fluorescence lifetime measurements. We call the method lux-FRET, since it relies on linear unmixing of spectral components.