Alternative Receptor Research Articles

Breaking the Convention: Sialoglycan Variants, Coreceptors, and Alternative Receptors for Influenza A Virus Entry.

The influenza A virus (IAV) envelope protein hemagglutinin binds α2,6- or α2,3-linked sialic acid as a host cell receptor. Bat IAV subtypes H17N10 and H18N11 form an exception to this rule and do not bind sialic acid but enter cells via major histocompatibility complex (MHC) class II. Here, we review current knowledge on IAV receptors with a focus on sialoglycan variants, protein coreceptors, and alternative receptors that impact IAV attachment and internalization beyond the well-described sialic acid binding.

T-cell co-stimulation in combination with targeting FAK drives enhanced anti-tumor immunity.

Focal Adhesion Kinase (FAK) inhibitors are currently undergoing clinical testing in combination with anti-PD-1 immune checkpoint inhibitors. However, which patients are most likely to benefit from FAK inhibitors, and what the optimal FAK/immunotherapy combinations are, is currently unknown. We identify that cancer cell expression of the T-cell co-stimulatory ligand CD80 sensitizes murine tumors to a FAK inhibitor and show that CD80 is expressed by human cancer cells originating from both solid epithelial cancers and some hematological malignancies in which FAK inhibitors have not been tested clinically. In the absence of CD80, we identify that targeting alternative T-cell co-stimulatory receptors, in particular OX-40 and 4-1BB in combination with FAK, can drive enhanced anti-tumor immunity and even complete regression of murine tumors. Our findings provide rationale supporting the clinical development of FAK inhibitors in combination with patient selection based on cancer cell CD80 expression, and alternatively with therapies targeting T-cell co-stimulatory pathways.

The muscarinic receptor antagonist tolterodine inhibits voltage-dependent K+ channels in rabbit coronary arterial smooth muscle cells

We explored the effect of the muscarinic receptor antagonist tolterodine on voltage-dependent K+ (Kv) channels using the patch-clamp technique in coronary arterial smooth muscle cells freshly isolated from rabbits. Tolterodine inhibited Kv channels in a concentration-dependent manner, with an IC50 of 1.71 ± 0.33 μM and Hill coefficient of 0.69 ± 0.03. Tolterodine accelerated the decay rate of Kv channel inactivation. The apparent rate constants of association and dissociation for tolterodine were 1.79 ± 0.13 μM−1s−1, and 3.13 ± 0.96 s−1, respectively. Although 3 μM tolterodine had no effect on the steady-state activation of the Kv current, it shifted the steady-state inactivation curve towards a negative potential. Application of consecutive train steps (1 or 2 Hz) progressively decreased the Kv current and promoted its inhibition. Furthermore, the recovery time constant was augmented in the presence of tolterodine, indicating that tolterodine-induced Kv channel blockade is use (state) dependent. Pretreatment with inhibitors of the Kv1.5, Kv2.1, and Kv7 subtypes (DPO-1, guangxitoxin, and linopirdine) partially reduced the inhibitory effect of tolterodine on Kv channels. The alternative muscarinic receptor antagonist atropine did not inhibit the Kv current nor influence tolterodine-induced inhibition of the Kv current. Tolterodine induced vasoconstriction and membrane depolarization. Based on these results, we conclude that tolterodine inhibits Kv channels in concentration-, time-, and use (state)-dependent manners, irrespective of its antagonism of muscarinic receptors.

Electrophysiological responses to sugars and amino acids in the nucleus of the solitary tract of type 1 taste receptor double-knockout mice.

Strong evidence supports a major role for heterodimers of the type 1 taste receptor (T1R) family in the taste transduction of sugars (T1R2+T1R3) and amino acids (T1R1+T1R3), but there are also neural and behavioral data supporting T1R-independent mechanisms. Most neural evidence for alternate mechanisms comes from whole nerve recordings in mice with deletion of a single T1R family member, limiting conclusions about the functional significance and T1R independence of the remaining responses. To clarify these issues, we recorded single-unit taste responses from the nucleus of the solitary tract in T1R double-knockout (double-KO) mice lacking functional T1R1+T1R3 [KO1+3] or T1R2+T1R3 [KO2+3] receptors and their wild-type background strains [WT; C57BL/6J (B6), 129X1/SvJ (S129)]. In both double-KO strains, responses to sugars and a moderate concentration of an monosodium glutamate + amiloride + inosine 5'-monophosphate cocktail (0.1 M, i.e., umami) were profoundly depressed, whereas a panel of 0.6 M amino acids were mostly unaffected. Strikingly, in contrast to WT mice, no double-KO neurons responded selectively to sugars and umami, precluding segregation of this group of stimuli from those representing other taste qualities in a multidimensional scaling analysis. Nevertheless, residual sugar responses, mainly elicited by monosaccharides, persisted as small "sideband" responses in double-KOs. Thus other receptors may convey limited information about sugars to the central nervous system, but T1Rs appear critical for coding the distinct perceptual features of sugar and umami stimuli. The persistence of amino acid responses supports previous proposals of alternate receptors, but because these stimuli affected multiple neuron types, further investigations are necessary.NEW & NOTEWORTHY The type 1 taste receptor (T1R) family is crucial for transducing sugars and amino acids, but there is evidence for T1R-independent mechanisms. In this study, single-unit recordings from the nucleus of the solitary tract in T1R double-knockout mice lacking T1R1+T1R3 or T1R2+T1R3 receptors revealed greatly reduced umami synergism and sugar responses. Nevertheless, residual sugar responses persisted, mainly elicited by monosaccharides and evident as "sidebands" in neurons activated more vigorously by other qualities.

A Single-Step, High-Dose Selection Scheme Reveals Distinct Mechanisms of Acquired Resistance to Oncogenic Kinase Inhibition in Cancer Cells.

Despite the remarkable clinical efficacy demonstrated by molecularly targeted cancer therapeutics, the benefits are typically temporary due to the emergence of acquired drug resistance. This has spurred a massive effort by the cancer research community to identify mechanisms used by cancer cells to evade treatment. Among the various methodologies developed and employed to identify such mechanisms, the most commonly used approach has been to model acquired resistance by exposing cancer cells in culture to gradually increasing concentrations of drug over an extended period of time. Here, we employed a less commonly used variation on this approach, wherein resistant cells are selected by immediately exposing cancer cells to a continuous, high concentration of drug. Using this approach, we isolated clones representing three distinct mechanisms of resistance to inhibition of MET kinase activity from a single clonally derived cancer cell line. The emergent clones had acquired resistance through engagement of alternative receptor tyrosine kinases either through upregulation of FGF3 or HBEGF or increased MAPK signaling through an activating V600E mutation in BRAF. Importantly, these mechanisms were not identified using the conventional "ramp-up" approach in previous studies that employed the same cell line. These results suggest that the particular nature of the selection scheme employed in cell culture modeling studies can determine which potential resistance mechanisms are identified and which ones may be missed, highlighting the need for careful consideration of the specific approach used to model resistance in cultured cells. SIGNIFICANCE: Through modeling resistance to MET kinase inhibition in cultured cancer cells using single-step, high-dose selection, these findings highlight that the specific nature of the selection protocol impacts which resistance mechanisms are identified.See related commentary by Floros et al., p. 25.

Integrating complement into the molecular pathogenesis of Hidradenitis Suppurativa.

Complement inhibition has been identified as a potential therapeutic target for multiple inflammatory disorders including Hidradenitis Suppurativa (HS). It is currently unclear how complement integrates into our current model of molecular pathogenesis in HS and whether it represents a central component of pathogenesis, or a neutrophil-associated bystander. Levels of C5a in serum and tissue correlate with disease activity and degree of neutrophilic infiltrates in HS. C5a has been associated with Th17 immune axis activation in psoriasis, rheumatoid arthritis and Crohn's disease with strong similarities to TH17 activation in HS. Porphyromonas species (which are identified in the HS microbiome) are able to cleave inactive C5 into C5a implicating the cutaneous microbiome as an activator of complement. C3a and C5a are associated with activation of the NLRP3 inflammasome, implicated in the inflammatory drive in HS. Complement receptors are present upon dendritic cells, monocytes, fibroblasts and adipocytes, which may broaden the potential contribution of complement to multiple aspects of HS pathogenesis. Dysregulation of complement receptor pathways has been documented in obesity, insulin resistance and polycystic ovarian syndrome leading to the possibility that complement may explain the epidemiological associations between these conditions and HS. The therapeutic potential of complement inhibitors in HS may be related to the therapeutic target (complement receptor or complement subunit) and the presence of alternate receptors (such as C5aR2) or ligands (including C3a, PAMPs and DAMPs). Integrating complement into the known pathogenesis of HS may aid in explaining the contradictory results between Phase 2 studies of C5a antagonists. It also allows for the identification of existing knowledge gaps to target further clinical investigation and research.

CSIG-31. ALTERNATIVE RECEPTOR TYROSINE KINASE SIGNALING AS A RESISTANCE MECHANISM TO ERK INHIBITION IN HIGH-GRADE GLIOMAS

Abstract Pediatric High-Grade Gliomas (PHGG), which include Diffuse Midline Gliomas (DMG), are a leading cause of brain tumor death in children. Our recent work has identified extracellular signal-regulated kinase 5 (ERK5) as a critical mediator of cell survival in PHGG. Suppression of ERK5 genetically or pharmacologically leads to decreased cell proliferation and increased apoptosis both in vitro and in vivo in multiple PHGG and H3K27M mutant DMG cell lines. Mechanistically, we show that ERK5 directly stabilizes the proto-oncogene MYC at the protein level, providing rationale to clinically target ERK5. ERK5 contains both a kinase domain (KD) and a transactivation domain (TAD), unlike all other ERKs. Unexpectedly, we found that our ERK5 depleted cells could be partially rescued by an ERK5 kinase domain dead (ERK5-KDD) but TAD intact construct. Additionally, persistent ERK5 depletion does not result in complete growth inhibition and therefore we set out to determine potential adaptation or resistance mechanisms in response to ERK5 loss. To address this, we performed RNA sequencing of DMG cells, comparing control cells to ERK5 knockdown cells, and performed gene-ontology (GO) pathway analysis to identify transcriptional changes that occur in response to ERK5 depletion. We identified 105 differentially expressed genes, and GO analysis identified alternative receptor tyrosine kinase (RTK) gene-expression as one of the top biological processes upregulated in response to ERK5 loss. We validated our top targets at the RNA and the protein level. Our top targets were Erb-B2 Receptor Tyrosine Kinase 4 (ERBB4) and Discoidin Domain Receptor Tyrosine Kinase 2 (DDR2), both clinically actionable targets. Our future work will focus on functional validation of these RTKs as potential resistance mechanisms to ERK5 loss. Identification of resistance mechanisms to ERK5 loss will have both biological and translational relevance and may lead to effective therapeutic combinations.

Interconversion between Anticipatory and Active GID E3Ubiquitin Ligase Conformations via Metabolically Driven Substrate Receptor Assembly.

Cells respond to environmental changes by toggling metabolic pathways, preparing for homeostasis, andanticipating future stresses. For example, in Saccharomyces cerevisiae, carbon stress-induced gluconeogenesis is terminated upon glucose availability, a process that involves the multiprotein E3 ligase GIDSR4 recruiting N termini and catalyzing ubiquitylation of gluconeogenic enzymes. Here, genetics, biochemistry, and cryoelectron microscopy define molecular underpinnings of glucose-induced degradation. Unexpectedly, carbon stress induces an inactive anticipatory complex (GIDAnt), which awaits a glucose-induced substrate receptor to form the active GIDSR4. Meanwhile, other environmental perturbations elicit production of an alternative substrate receptor assembling into a related E3 ligase complex. The intricate structure of GIDAnt enables anticipating and ultimately binding various N-degron-targeting (i.e., "N-end rule") substrate receptors, while the GIDSR4 E3 forms a clamp-like structure juxtaposing substrate lysines with the ubiquitylation active site. The data reveal evolutionarily conserved GID complexes as a family of multisubunit E3 ubiquitin ligases responsive to extracellular stimuli.

HER-Family Ligands Promote Acquired Resistance to Trastuzumab in Gastric Cancer.

Despite the clinical benefit of trastuzumab, eventually all HER2-amplified gastric cancer tumors develop drug resistance. We aimed to identify molecular mechanisms of acquired resistance to trastuzumab in gastric cancer by using well-established cell line-based preclinical models, as well as samples from patients with HER2-positive gastric cancer treated with trastuzumab. We studied trastuzumab resistance in NCI-N87 and OE19, two gastric cancer cell lines that overexpress HER2 receptor and are trastuzumab sensitive. Differences at protein, DNA, and RNA levels between the parental and resistant cells were characterized and functional studies were performed. Paired pre- and post-trastuzumab blood and tissue samples from patients with gastric cancer treated with trastuzumab were analyzed. We found that resistant cells were associated with increased activation of MAPK/ERK and PI3K/mTOR pathways driven by SRC activation. Upstream, resistant cells showed increased coexpression of multiple HER-family ligands that allowed for compensatory activation of alternative HER receptors upon HER2 blockade. Simultaneous inhibition of EGFR, HER2, and HER3 by the novel antibody mixture, Pan-HER, effectively reverted trastuzumab resistance in vitro and in vivo Similarly, an increase in HER-family ligands was observed in serum and tumor from patients with gastric cancer after trastuzumab therapy. We propose that trastuzumab resistance in gastric cancer is mediated by HER-family ligand upregulation that allows a compensatory activation of HER receptors and maintains downstream signaling activation despite trastuzumab therapy. Resistance is reverted by simultaneous inhibition of EGFR, HER2, and HER3, thereby revealing a potential therapeutic strategy to overcome trastuzumab resistance in patients with gastric cancer.

Expression of the checkpoint receptors LAG-3, TIM-3 and VISTA in peripheral T cell lymphomas

AimsPeripheral T cell lymphomas represent approximately 10%–15% of non-Hodgkin lymphomas and are characterised by an aggressive clinical courses and poor outcomes. Ligands provided by constituents of the tumour microenvironment engage...

Non-canonical Estrogen Signaling in Endocrine Resistance.

Breast cancer is one of the leading causes of cancer related deaths in women worldwide. The disease is extremely heterogenous. A large percentage of the breast cancers are dependent on estrogen signaling and hence respond to endocrine therapies which essentially block the estrogen signaling. However, many of these tumors emerge as endocrine resistant tumors. Many mechanisms have been proposed to explain the emergence of endocrine resistance, which include mutations in the estrogen receptors, cross-talk with other signaling pathways, cancer stem cells etc. This review is focused on the role of non-canonical estrogen receptor signaling in endocrine resistance. Most of the therapeutics which are used currently are targeting the major receptor of estrogen namely ER-α. Last two decades has witnessed the discovery of alternate forms of ER-α, as well as other receptors for estrogen such as ERRgamma, GPER-1 as well as ER-β, which are activated not only by estrogen, but also by the therapeutic agents such as tamoxifen that are routinely used in treatment of breast cancer. However, when the alternate receptors are activated, they result in activation of membrane signaling which subsequently activates pathways such as MAPK and GPCR leading to cell-proliferation. This renders the anticipated anti-estrogenic effects of tamoxifen less effective or ineffective. Future research in this area has to focus on the alternate mechanisms and develop a combinatorial strategy, which can complement the existing therapeutics to get better outcome of endocrine therapies.

Antibody-mediated targeting of TNFR2 activates CD8+ T cells in mice and promotes antitumor immunity.

Tumor necrosis factor receptor 2 (TNFR2) is the alternate receptor for TNF and can mediate both pro- and anti-inflammatory activities of T cells. Although TNFR2 has been linked to enhanced suppressive activity of regulatory T cells (Tregs) in autoimmune diseases, the viability of TNFR2 as a target for cancer immunotherapy has been underappreciated. Here, we show that new murine monoclonal anti-TNFR2 antibodies yield robust antitumor activity and durable protective memory in multiple mouse cancer cell line models. The antibodies mediate potent Fc-dependent T cell costimulation and do not result in significant depletion of Tregs Corresponding human agonistic monoclonal anti-TNFR2 antibodies were identified and also had antitumor effects in humanized mouse models. Anti-TNFR2 antibodies could be developed as a novel treatment option for patients with cancer.

Once-weekly semaglutide for patients with type 2 diabetes: a cost-effectiveness analysis in the Netherlands

ObjectiveChoosing therapies for type 2 diabetes that are both effective and cost-effective is vital as healthcare systems worldwide aim to maximize health of the population. The present analysis assessed the...

Virus-Receptor Interactions: Structural Insights For Oncolytic Virus Development.

Recent advancements in oncolytic virotherapy commend a special attention to developing new strategies for targeting cancer cells with oncolytic viruses (OVs). Modifications of the viral envelope or coat proteins serve as a logical mean of repurposing viruses for cancer treatment. In this review, we discuss how detailed structural knowledge of the interactions between OVs and their natural receptors provide valuable insights into tumor specificity of some viruses and re-targeting of alternate receptors for broad tumor tropism or improved tumor selectivity.

Dual Recognition of Sialic Acid and αGal Epitopes by the VP8* Domains of the Bovine Rotavirus G6P[5] WC3 and of Its Mono-reassortant G4P[5] RotaTeq Vaccine Strains.

Group A rotaviruses, an important cause of severe diarrhea in children and young animals, initiate infection via interactions of the VP8* domain of the VP4 spike protein with cell surface sialic acids (SAs) or histo-blood group antigens (HBGAs). Although the bovine G6P[5] WC3 strain is an important animal pathogen and is also used in the bovine-human reassortant RotaTeq vaccine, the receptor(s) for the VP8* domain of WC3 and its reassortant strains have not yet been identified. In the present study, HBGA- and saliva-binding assays showed that both G6P[5] WC3 and mono-reassortant G4P[5] strains recognized the αGal HBGA. The infectivity of both P[5]-bearing strains was significantly reduced in αGal-free MA-104 cells by pretreatment with a broadly specific neuraminidase or by coincubation with the α2,6-linked SA-specific Sambucus nigra lectin, but not by the α2,3-linked specific sialidase or by Maackia amurensis lectin. Free NeuAc and the αGal trisaccharide also prevented the infectivity of both strains. This indicated that both P[5]-bearing strains utilize α2,6-linked SA as a ligand on MA104 cells. However, the two strains replicated in differentiated bovine small intestinal enteroids and in their human counterparts that lack α2,6-linked SA or αGal HBGA, suggesting that additional or alternative receptors such as integrins, hsp70, and tight-junction proteins bound directly to the VP5* domain can be used by the P[5]-bearing strains to initiate the infection of human cells. In addition, these data also suggested that P[5]-bearing strains have potential for cross-species transmission.IMPORTANCE Group A rotaviruses initiate infection through the binding of the VP8* domain of the VP4 protein to sialic acids (SAs) or histo-blood group antigens (HBGAs). Although the bovine G6P[5] WC3 strain is an important animal pathogen and is used as the backbone in the bovine-human reassortant RotaTeq vaccine, the receptor(s) for their P[5] VP8* domain has remained elusive. Using a variety of approaches, we demonstrated that the WC3 and bovine-human mono-reassortant G4P[5] vaccine strains recognize both α2,6-linked SA and αGal HBGA as ligands. Neither ligand is expressed on human small intestinal epithelial cells, explaining the absence of natural human infection by P[5]-bearing strains. However, we observed that the P[5]-bearing WC3 and G4P[5] RotaTeq vaccine strains could still infect human intestinal epithelial cells. Thus, the four P[5] RotaTeq vaccine strains potentially binding to additional alternative receptors may be efficient and effective in providing protection against severe rotavirus disease in human.

BSA-based sample clean-up columns for ochratoxin A determination in wine: Method development and validation

Analytical chromatographic techniques for mycotoxins control are well established, but they often depend on costly immunoaffinity sample clean-up. Serum albumins, particularly that from bovine origin (BSA), have stable binding affinity towards some mycotoxins, and can be cheaper alternative receptors for sample clean-up due to their wide availability. Thus, this work used BSA immobilized in agarose beads as a novel solid-phase extraction method for quantification of ochratoxin A (OTA) in wine. Constructed BSA-agarose columns could extract OTA efficiently from red wine after its dilution (4-fold) in 0.1 M Tris pH 8.0. The method was linear (R2 = 0.9999) in the OTA concentration range studied (0.05 to 3.0 μg L−1), with recovery rates above 98%. It also showed low detection (0.017 μg L−1) and quantification (0.051 μg L−1) limits. The efficacy of the BSA-based method was further validated by direct comparison with commercial immunoaffinity columns. Portuguese wines analyzed by both methods had agreeing results.

Abstract 1017: Novel inhibitors of AR-v7 nuclear import: new therapeutic opportunities for CRPC

Abstract Reactivation of androgen receptor (AR) signaling by active splice variants (AR-Vs) is one of key drivers of castration resistant prostate cancer (CRPC). AR-v7 is the most prevalent AR-V and its expression has been clinically associated with poor overall survival, resistance to the AR inhibitors enzalutamide and abiraterone, as well as taxane resistance. Given that treatment with AR inhibitors and taxanes are the only effective therapeutic modalities in CRPC, development of specific AR-v7 inhibitors is urgently needed. Mechanistically, AR-v7 re-activates AR signaling by being constitutively active in the nucleus. While taxane chemotherapy inhibits the nuclear import of AR which is significantly associated with clinical outcomes in CRPC, it has no effect on AR-v7 nuclear localization and activity. Mechanistically, AR-v7 lacks the microtubule-binding domain and—unlike AR—does not utilize the canonical importin-α/β pathway, or RanGTP for nuclear import. Using wheat germ agglutinin to block active protein nuclear uptake resulted in AR-v7 cytoplasmic sequestration, indicating a requirement for an alternative transport receptor. Further, mutation of AR-v7 dimerization domain (D-box) led to its cytoplasmic sequestration, indicating that the D-box is also required for nuclear import. As inhibition of AR nuclear import is a clinically validated therapeutic strategy, we developed a novel drug discovery platform to identify compounds that specifically inhibit AR-v7 nuclear import. Using cells stably expressing inducible AR-v7 in conjunction with an enzyme complementation assay we tested 166,000 compounds by high throughput screening (HTS). The robust HTS performance (Z>0.8) together with subsequent counter screens including confirmation and compound titration, cell toxicity, a tertiary imaging based screen, led to identification of lead compounds that inhibit AR-v7 nuclear import. The lead compounds share structural features, across two main chemotypes, which are amenable to structure-activity relationship studies to identify the most desirable compound for in vivo studies. Using newly synthesized compounds from each of the two chemotypes, we showed specific dose-dependent inhibition of AR-v7 nuclear import. Currently, we are testing these compounds, on inhibition of AR-v7 transcriptional activity across several cell models including enzalutamide-resistant cells as well as inhibition of tumor growth in AR-v7 xenograft models. In parallel we are testing the lead compound for potential direct binding to the AR-v7 dimerization domain or to candidate alternative nuclear transport receptors. Further development of our lead small molecules will yield novel chemotypes, with desirable pharmacological properties that target the unique AR-v7 nuclear import pathway and can be clinically combined with existing AR therapies. Note: This abstract was not presented at the meeting. Citation Format: Seaho Kim, Mohd Azrin Jamalruddin, Eiman Mukhtar, Michael Miller, Leigh Baxt, Stacia Kargman, Andrew Stamford, Peter Meinke, Paraskevi Giannakakou. Novel inhibitors of AR-v7 nuclear import: new therapeutic opportunities for CRPC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1017.

Interleukin-17 receptor D constitutes an alternative receptor for interleukin-17A important in psoriasis-like skin inflammation.

T helper 17 (TH17) cells and interleukin-17A (IL-17A) produced by them are critical in autoinflammatory diseases, such as psoriasis. IL-17A has been shown to signal through IL-17 receptor A/IL-17 receptor C (IL-17RA/IL-17RC) complex to drive inflammatory responses. However, in a psoriasis model, we found that Il17rc deficiency did not completely ameliorate the disease, suggesting another receptor. In search for another IL-17A-interacting receptor, we found that IL-17RD directly bound IL-17A but not IL-17F or IL-17A/F heterodimer and formed a heterodimer with IL-17RA. IL-17A-, but not IL-17F- or IL-17A/F-, mediated gene expression was defective in Il17rd-deficient keratinocytes. Il17rd deficiency in nonhemopoietic cells attenuated imiquimod-induced psoriasis-like skin inflammation. Although IL-17RC and IL-17RD differentially activated IL-17A-dependent signaling and gene expression, their compound mutation led to complete deficits in keratinocytes. IL-23 was found induced by IL-17A in keratinocytes, dependent on both IL-17RC and IL-17RD, suggesting feed-forward regulation of IL-23/IL-17 axis in psoriasis. Together, IL-17RD constitutes a second functional receptor for IL-17A and, together with IL-17RC, mediates the proinflammatory gene expression downstream of IL-17A.

Integrin β1 Promotes the Interaction of Murine IgG3 with Effector Cells.

Abs exert several of their effector functions by binding to cell surface receptors. For murine IgG3 (mIgG3), the identity of its receptors (and the very existence of a receptor) is still under debate, as not all mIgG3 functions can be explained by interaction with FcγRI. This implies the existence of an alternate receptor, whose identity we sought to pinpoint. We found that blockage of integrin β1 selectively hampered binding of mIgG3 to macrophages and mIgG3-mediated phagocytosis. Manganese, an integrin activator, increased mIgG3 binding to macrophages. Blockage of FcγRI or Itgb1 inhibited binding of different mIgG3 Abs to variable extents. Our results are consistent with the notion that Itgb1 functions as part of an IgG receptor complex. Given the more ancient origin of integrins in comparison with FcγR, this observation could have far-ranging implications for our understanding of the evolution of Ab-mediated immunity as well as in immunity to microorganisms, pathogenesis of autoimmune diseases, and Ab engineering.

Cooperation between T cell receptor and Toll-like receptor 5 signaling for CD4+ T cell activation.

CD4+ T cells recognize antigens through their T cell receptors (TCRs); however, additional signals involving costimulatory receptors, for example, CD28, are required for proper T cell activation. Alternative costimulatory receptors have been proposed, including members of the Toll-like receptor (TLR) family, such as TLR5 and TLR2. To understand the molecular mechanism underlying a potential costimulatory role for TLR5, we generated detailed molecular maps and logical models for the TCR and TLR5 signaling pathways and a merged model for cross-interactions between the two pathways. Furthermore, we validated the resulting model by analyzing how T cells responded to the activation of these pathways alone or in combination, in terms of the activation of the transcriptional regulators CREB, AP-1 (c-Jun), and NF-κB (p65). Our merged model accurately predicted the experimental results, showing that the activation of TLR5 can play a similar role to that of CD28 activation with respect to AP-1, CREB, and NF-κB activation, thereby providing insights regarding the cross-regulation of these pathways in CD4+ T cells.