MicroRNAs (miRNAs) exert powerful effects on immune function by tuning networks of target genes that orchestrate cell behavior. We sought to uncover miRNAs and miRNA-regulated pathways that control the TH2 responses that drive pathogenic inflammation in asthma. Profiling miRNA expression in human airway-infiltrating T cells revealed miR-19a elevation in asthma. Modulating miR-19 activity altered TH2 cytokine production in both human and mouse T cells, and TH2 cell responses were markedly impaired in cells lacking the entire miR-17∼92 cluster. miR-19 promotes TH2 cytokine production and amplifies PI(3)K, JAK-STAT, and NF-κB signaling by direct targeting of PTEN, SOCS1, and A20. Thus, miR-19a up regulation in asthma may be an indicator and a cause of increased TH2 cytokine production in the airways.

Summary Many nociceptors detect mechanical cues, but the ion channels responsible for mechanotransduction in these sensory neurons remain obscure. Using in vivo recordings and genetic dissection, we identified the DEG/ENaC protein, DEG-1, as the major mechanotransduction channel in ASH, a polymodal nociceptor in Caenorhabditis elegans. But, DEG-1 is not the only mechanotransduction channel in ASH: loss of deg-1 revealed a minor current whose properties differ from those expected of DEG/ENaC channels. This current was independent of two TRPV channels expressed in ASH. Although loss of these TRPV channels inhibits behavioral responses to noxious stimuli, we found that both mechanoreceptor currents and potentials were essentially wild-type in TRPV mutants. We propose that ASH nociceptors rely on two genetically-distinct mechanotransduction channels and that TRPV channels contribute to encoding and transmitting information. Because mammalian and insect nociceptors also co-express DEG/ENaCs and TRPVs, the cellular functions elaborated here for these ion channels may be conserved.

GLAST is the predominant glutamate transporter in the cerebellum and contributes substantially to glutamate transport in forebrain. This astroglial glutamate transporter quickly binds and clears synaptically released glutamate and is principally responsible for ensuring that synaptic glutamate concentrations remain low. This process is associated with a significant energetic cost. Compartmentalization of GLAST with mitochondria and proteins involved in energy metabolism could provide energetic support for glutamate transport. Therefore, we performed immunoprecipitation and co-localization experiments to determine if GLAST might co-compartmentalize with proteins involved in energy metabolism. GLAST was immunoprecipitated from rat cerebellum and subunits of the Na+/K+ ATPase, glycolytic enzymes, and mitochondrial proteins were detected. GLAST co-localized with mitochondria in cerebellar tissue. GLAST also co-localized with mitochondria in fine processes of astrocytes in organotypic hippocampal slice cultures. From these data, we hypothesized that mitochondria participate in a macromolecular complex with GLAST to support oxidative metabolism of transported glutamate. To determine the functional metabolic role of this complex, we measured CO2 production from radiolabeled glutamate in cultured astrocytes and compared it to overall glutamate uptake. Within 15 minutes, 9% of transported glutamate was converted to CO2. This CO2 production was blocked by inhibitors of glutamate transport and glutamate dehydrogenase, but not by an inhibitor of glutamine synthetase. Our data support a model in which GLAST exists in a macromolecular complex that allows transported glutamate to be metabolized in mitochondria to support energy production.

T helper (Th)17 cell responses orchestrate immunity against extracellular pathogens, but also underlie autoimmune disease pathogenesis. Here, we uncovered a distinct and critical role for miR-18a in limiting Th17 cell differentiation. miR-18a was the most dynamically upregulated miRNA of the miR-17∼92 cluster in activated T cells. miR-18a deficiency enhanced CCR6+RORγt+ Th17 cell differentiation in vitro and increased the number of tissue Th17 cells expressing CCR6, RORγt and IL-17A in airway inflammation models in vivo. Sequence-specific miR-18 inhibitors increased CCR6 and RORγt expression in both mouse and human CD4+ T cells, revealing functional conservation. miR-18a directly targeted Smad4, Hif1a, and Rora, all key transcription factors in the Th17 cell gene expression program. These findings indicate that activating signals influence the outcome of T helper cell differentiation via differential regulation of mature miRNAs within a common cluster.

SHORT ABSTRACT The Neon® next generation electroporation is an efficient method for transfecting human Th17 cells with small RNAs to alter gene expression and cell behavior. LONG ABSTRACT CD4+ T cells can differentiate into several subsets of effector T helper cells depending on the surrounding cytokine milieu. Th17 cells can be generated from naive CD4+ T cells in vitro by activating them in the presence of the polarizing cytokines IL-1β, IL-6, IL-23, and TGFβ. Th17 cells orchestrate immunity against extracellular bacteria and fungi, but their aberrant activity has also been associated with several autoimmune and inflammatory diseases. Th17 cells are identified by the chemokine receptor CCR6 and defined by their master transcription factor, RORγt, and characteristic effector cytokine, IL-17A. Optimized culture conditions for Th17 cell differentiation facilitate mechanistic studies of human T cell biology in a controlled environment. They also provide a setting for studying the importance of specific genes and gene expression programs through RNA interference or the introduction of microRNA (miRNA) mimics or inhibitors. This protocol provides an easy to use, reproducible, and highly efficient method for transient transfection of differentiating primary human Th17 cells with small RNAs using the Neon® next generation electroporation device.

CD4+ T cells can differentiate into several subsets of effector T helper cells depending on the surrounding cytokine milieu. Th17 cells can be generated from naïve CD4 + T cells in vitro by activating them in the presence of the polarizing cytokines IL-1β, IL-6, IL-23, and TGFβ. Th17 cells orchestrate immunity against extracellular bacteria and fungi, but their aberrant activity has also been associated with several autoimmune and inflammatory diseases. Th17 cells are identified by the chemokine receptor CCR6 and defined by their master transcription factor, RORγt, and characteristic effector cytokine, IL-17A. Optimized culture conditions for Th17 cell differentiation facilitate mechanistic studies of human T cell biology in a controlled environment. They also provide a setting for studying the importance of specific genes and gene expression programs through RNA interference or the introduction of microRNA (miRNA) mimics or inhibitors. This protocol provides an easy to use, reproducible, and highly efficient method for transient transfection of differentiating primary human Th17 cells with small RNAs using a next generation electroporation device.