PTEN restricts IL-21R signaling in GC B cells and suppresses their differentiation to plasma cells.

The germinal center (GC) reaction is essential for generating high-quality humoral memory. Positively selected GC B cells must decide whether to remain in the GC for further affinity maturation or differentiate into memory or plasma cells (PCs). Previously, we identified IL-21R and CD40 signaling as critical promoters of GC B cell effector differentiation.

The phospholipid kinase PIKFYVE is essential for Th17 differentiation.

T helper 17 (Th17) cells are effector cells that mediate inflammatory responses to bacterial and fungal pathogens. While the cytokine signaling inputs required to generate Th17s are established, less is known about intracellular pathways that drive Th17 differentiation. Our previously published phosphoproteomic screen identifies that PIKFYVE, a lipid kinase that generates the phosphatidylinositol PtdIns(3,5)P2, is activated during Th17 differentiation.

CD91-mediated reprogramming of DCs by immunogenic heat shock proteins requires the kinases AXL and Fgr.

Immune responses to tumors, comprising adaptive T cells and innate NK cells, arise very early in tumorigeneses and prior to detection of palpable tumors or before tissue pathology is evident. Yet, how nascent tumors evoke dendritic cell maturation and the resulting cytokine responses that are necessary for these effector anti-tumor immune responses is unknown. We have previously shown that CD91 expression on dendritic cells is important for immune surveillance, specifically for generating T cell and NK cell responses to nascent tumors.

Role of the CCL5 and Its Receptor, CCR5, in the Genesis of Aldosterone-Induced Hypertension, Vascular Dysfunction, and End-Organ Damage.

Background: Aldosterone has been described to initiate cardiovascular diseases by triggering exacerbated sterile vascular inflammation. The functions of CCL5 (C-C motif chemokine ligand 5) and its receptor CCR5 (C-C motif chemokine receptor 5) are well known in infectious diseases, their contributions to aldosterone-induced vascular injury and hypertension remain unknown.

Methods: We analyzed the vascular profile, blood pressure, and renal damage in wild-type (CCR5) and CCR5 knockout (CCR5) mice treated with aldosterone (600 µg/kg per day for 14 days) while receiving 1% saline to drink.

Synergistic and additive interactions between receptor signaling networks drive the regulatory T cell versus T helper 17 cell fate choice.

CD4+ T cells differentiate into subsets that promote immunity or minimize damage to the host. T helper 17 cells (Th17) are effector cells that function in inflammatory responses. T regulatory cells (Tregs) maintain tolerance and prevent autoimmunity by secreting immunosuppressive cytokines and expressing check point receptors.

Transforming growth factor β (TGF-β) receptor signaling regulates kinase networks and phosphatidylinositol metabolism during T-cell activation.

The cytokine content in tissue microenvironments shapes the functional capacity of a T cell. This capacity depends on the integration of extracellular signaling through multiple receptors, including the T-cell receptor (TCR), co-receptors, and cytokine receptors. Transforming growth factor β (TGF-β) signals through its cognate receptor, TGFβR, to SMAD family member proteins and contributes to the generation of a transcriptional program that promotes regulatory T-cell differentiation.

Germinal center B cells selectively oxidize fatty acids for energy while conducting minimal glycolysis.

Germinal center B cells (GCBCs) are critical for generating long-lived humoral immunity. How GCBCs meet the energetic challenge of rapid proliferation is poorly understood. Dividing lymphocytes typically rely on aerobic glycolysis over oxidative phosphorylation for energy.

Cutting Edge: TCR Signal Strength Regulates Acetyl-CoA Metabolism via AKT.

TCR signaling activates kinases including AKT/mTOR that engage metabolic networks to support the energetic demands of a T cell during an immune response. It is realized that CD4 T cell subsets have different metabolic requirements. Yet, how TCR signaling is coupled to the regulation of intermediate metabolites and how changes in metabolite flux contribute to T cell differentiation are less established.

The Alzheimer's Disease-Associated Protein BACE1 Modulates T Cell Activation and Th17 Function.

β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) is best known for its role in Alzheimer's disease amyloid plaque formation but also contributes to neurodegenerative processes triggered by CNS injury. In this article, we report that BACE1 is expressed in murine CD4 T cells and regulates signaling through the TCR. BACE1-deficient T cells have reduced IL-17A expression under Th17 conditions and reduced CD73 expression in Th17 and inducible T regulatory cells.

The Lysophosphatidylcholine Transporter MFSD2A Is Essential for CD8 Memory T Cell Maintenance and Secondary Response to Infection.

Access to nutrients is critical for an effective T cell immune response to infection. Although transporters for sugars and amino acids have previously been described in the context of the CD8 T cell immune response, the active transport of exogenous fatty acids has remained enigmatic. In this study, we discovered that the sodium-dependent lysophosphatidylcholine (LPC) transporter major facilitator superfamily domain containing 2A (MFSD2A) is upregulated on activated CD8 T cells and is required for memory T cell maintenance.

T cells transduce T-cell receptor signal strength by generating different phosphatidylinositols.

T-cell receptor (TCR) signaling strength is a dominant factor regulating T-cell differentiation, thymic development, and cytokine signaling. The molecular mechanisms by which TCR signal strength is transduced to downstream signaling networks remains ill-defined. Using computational modeling, biochemical assays, and imaging flow cytometry, we found here that TCR signal strength differentially generates phosphatidylinositol species.

Histone acetyltransferase CBP is critical for conventional effector and memory T-cell differentiation in mice.

Compared with naïve T cells, memory CD8 T cells have a transcriptional landscape and proteome that are optimized to generate a more rapid and robust response to secondary infection. Additionally, rewired kinase signal transduction pathways likely contribute to the superior recall response of memory CD8 T cells, but this idea has not been experimentally confirmed. Herein, we utilized an MS approach to identify proteins that are phosphorylated on tyrosine residues in response to -induced T-cell receptor (TCR) stimulation in both naïve and memory CD8 T cells from mice and separated by fluorescence- and flow cytometry-based cell sorting.

14-3-3z sequesters cytosolic T-bet, upregulating IL-13 levels in T2 and CD8 lymphocytes from patients with scleroderma.

Background: IL-13-producing CD8 T cells have been implicated in the pathogenesis of type 2-driven inflammatory human conditions. We have shown that CD8IL-13 cells play a critical role in cutaneous fibrosis, the most characteristic feature of systemic sclerosis (SSc; scleroderma). However, the molecular mechanisms underlying production of IL-13 and other type 2 cytokines by CD8 T cells remain unclear.

TCR Signal Strength Regulates Akt Substrate Specificity To Induce Alternate Murine Th and T Regulatory Cell Differentiation Programs.

The Akt/mTOR pathway is a key driver of murine CD4 T cell differentiation, and induction of regulatory T (Treg) cells results from low TCR signal strength and low Akt/mTOR signaling. However, strong TCR signals induce high Akt activity that promotes Th cell induction. Yet, it is unclear how Akt controls alternate T cell fate decisions.

Cutting Edge: Differential Regulation of PTEN by TCR, Akt, and FoxO1 Controls CD4+ T Cell Fate Decisions.

Signaling via the Akt/mammalian target of rapamycin pathway influences CD4(+) T cell differentiation; low levels favor regulatory T cell induction and high levels favor Th induction. Although the lipid phosphatase phosphatase and tensin homolog (PTEN) suppresses Akt activity, the control of PTEN activity is poorly studied in T cells. In this study, we identify multiple mechanisms that regulate PTEN expression.

An immunology primer for computational modelers.

The immune system is designed to protect an organism from infection and damage caused by a pathogen. A successful immune response requires the coordinated function of multiple cell types and molecules in the innate and adaptive immune systems. Given the complexity of the immune system, it would be advantageous to build computational models to better understand immune responses and develop models to better guide the design of immunotherapies.

Modeling the T cell immune response: a fascinating challenge.

The immune system is designed to protect the organism from infection and to repair damaged tissue. An effective response requires recognition of the threat, the appropriate effector mechanism to clear the pathogen and a return to homeostasis with minimal damage to self-tissues. T cells play a central role in orchestrating the immune response at all stages of the response and have been the subject of intense study by both experimental immunologists and modelers.

TCR scanning of peptide/MHC through complementary matching of receptor and ligand molecular flexibility.

Although conformational changes in TCRs and peptide Ags presented by MHC protein (pMHC) molecules often occur upon binding, their relationship to intrinsic flexibility and role in ligand selectivity are poorly understood. In this study, we used nuclear magnetic resonance to study TCR-pMHC binding, examining recognition of the QL9/H-2L(d) complex by the 2C TCR. Although the majority of the CDR loops of the 2C TCR rigidify upon binding, the CDR3β loop remains mobile within the TCR-pMHC interface.

Peptide modulation of class I major histocompatibility complex protein molecular flexibility and the implications for immune recognition.

T cells use the αβ T cell receptor (TCR) to recognize antigenic peptides presented by class I major histocompatibility complex proteins (pMHCs) on the surfaces of antigen-presenting cells. Flexibility in both TCRs and peptides plays an important role in antigen recognition and discrimination. Less clear is the role of flexibility in the MHC protein; although recent observations have indicated that mobility in the MHC can impact TCR recognition in a peptide-dependent fashion, the extent of this behavior is unknown.

Structural and dynamic control of T-cell receptor specificity, cross-reactivity, and binding mechanism.

Over the past two decades, structural biology has shown how T-cell receptors engage peptide/major histocompatibility complex (MHC) complexes and provided insight into the mechanisms underlying antigen specificity and cross-reactivity. Here we review and contextualize our contributions, which have emphasized the influence of structural changes and molecular flexibility. A repeated observation is the presence of conformational melding, in which the T-cell receptor (TCR), peptide, and in some cases, MHC protein cooperatively adjust in order for recognition to proceed.

Cutting edge: Evidence for a dynamically driven T cell signaling mechanism.

T cells use the αβ TCR to bind peptides presented by MHC proteins (pMHC) on APCs. Formation of a TCR-pMHC complex initiates T cell signaling via a poorly understood process, potentially involving changes in oligomeric state, altered interactions with CD3 subunits, and mechanical stress. These mechanisms could be facilitated by binding-induced changes in the TCR, but the nature and extent of any such alterations are unclear.

Structure-based mechanism of ADP-ribosylation by sirtuins.

Sirtuins comprise a family of enzymes found in all organisms, where they play a role in diverse processes including transcriptional silencing, aging, regulation of transcription, and metabolism. The predominant reaction catalyzed by these enzymes is NAD(+)-dependent lysine deacetylation, although some sirtuins exhibit a weaker ADP-ribosyltransferase activity. Although the Sir2 deacetylation mechanism is well established, much less is known about the Sir2 ADP-ribosylation reaction.

Structural insights into intermediate steps in the Sir2 deacetylation reaction.

Sirtuin enzymes comprise a unique class of NAD(+)-dependent protein deacetylases. Although structures of many sirtuin complexes have been determined, structural resolution of intermediate chemical steps are needed to understand the deacetylation mechanism. We report crystal structures of the bacterial sirtuin, Sir2Tm, in complex with an S-alkylamidate intermediate, analogous to the naturally occurring O-alkylamidate intermediate, and a Sir2Tm ternary complex containing a dissociated NAD(+) analog and acetylated peptide.

Molecular evolution of the actin family.

Members of the actin family have well-characterized cytoskeletal functions, but actin and actin-related proteins (ARPs) have also been implicated in nuclear activities. Previous analyses of the actin family have identified four conserved subfamilies, but many actin-related proteins (ARPs) do not fall into these groups. A new systematic phylogenetic analysis reveals that at least eight ARP subfamilies are conserved from humans to yeast, indicating that these ARPs are part of the core set of eukaryotic proteins.