Suresh Koduru

IL-21R is essential for epicutaneous sensitization and allergic skin inflammation in humans and mice

Atopic dermatitis (AD) is a common allergic inflammatory skin disease caused by a combination of intense pruritus, scratching, and epicutaneous (e.c.) sensitization with allergens. To explore the roles of IL-21 and IL-21 receptor (IL-21R) in AD, we examined skin lesions from patients with AD and used a mouse model of allergic skin inflammation. IL-21 and IL-21R expression was upregulated in acute skin lesions of AD patients and in mouse skin subjected to tape stripping, a surrogate for scratching. The importance of this finding was highlighted by the fact that both Il21r-/- mice and WT mice treated with soluble IL-21R-IgG2aFc fusion protein failed to develop skin inflammation after e.c. sensitization of tape-stripped skin. Adoptively transferred OVA-specific WT CD4+ T cells accumulated poorly in draining LNs (DLNs) of e.c. sensitized Il21r-/- mice. This was likely caused by both DC-intrinsic and nonintrinsic effects, because trafficking of skin DCs to DLNs was defective in Il21r-/- mice and, to a lesser extent, in WT mice reconstituted with Il21r-/- BM. More insight into this defect was provided by the observation that skin DCs from tape-stripped WT mice, but not Il21r-/- mice, upregulated CCR7 and migrated toward CCR7 ligands. Treatment of epidermal and dermal cells with IL-21 activated MMP2, which has been implicated in trafficking of skin DCs. These results suggest an important role for IL-21R in the mobilization of skin DCs to DLNs and the subsequent allergic response to e.c. introduced antigen.

Vaccinia virus inoculation in sites of allergic skin inflammation elicits a vigorous cutaneous IL-17 response

Eczema vaccinatum (EV) is a complication of smallpox vaccination occurring in patients with atopic dermatitis. In affected individuals, vaccinia virus (VV) spreads through the skin, resulting in large primary lesions and satellite lesions, and infects internal organs. BALB/c mice inoculated with VV at sites of Th2-biased allergic skin inflammation elicited by epicutaneous ovalbumin (OVA) sensitization exhibited larger primary lesions that were erosive, more satellite lesions, and higher viral loads in skin and internal organs than mice inoculated in saline-exposed skin, unsensitized skin, or skin sites with Th1-dominant inflammation. VV inoculation in OVA-sensitized skin induced marked local expression of IL-17 transcripts and massive neutrophil infiltration compared to VV inoculation in saline-exposed skin. Treatment with anti-IL-17 decreased the size of primary lesions, numbers of satellite lesions, and viral loads. Addition of IL-17 promoted VV replication in skin explants. These results suggest that IL-17 may be a potential therapeutic target in EV.

WIP is critical for T cell responsiveness to IL-2.

The Wiskott-Aldrich syndrome (WAS) interacting protein (WIP) stabilizes the WAS protein (WASP), the product of the gene mutated in WAS. WIP-deficient T cells have low WASP levels, limiting the usefulness of WIP KO mice in defining the role of WIP in T cell function. To define this role, we compared WIP/WASP double KO (DKO) mice to WASP KO mice on DO11.10 background. T cell development was normal in both strains, but peripheral T cell numbers were significantly decreased in DKO mice. WASP KO T cells proliferated and secreted IL-2 normally in response to OVA peptide (OVAp). In contrast, T cells from DKO mice proliferated poorly in response to OVAp in vitro, and cutaneous hapten hypersensitivity was deficient in these mice. DKO T cells up-regulated CD25 expression and secreted normal amounts of IL-2 after antigen stimulation, but had defective response to IL-2, evidenced by failure to further up-regulate CD25 expression, phosphorylate STAT5, and induce expression of STAT5-dependent genes. DKO, but not WASP KO, T cells had a disrupted subcortical actin cytoskeleton and impaired actin polymerization after T cell antigen receptor (TCR) ligation. These results indicate that WIP is essential for IL-2 signaling and responsiveness in T cells, possibly because of its critical role in TCR-triggered actin cytoskeletal reorganization.

HS3ST2 modulates breast cancer cell invasiveness via MAP kinase- and Tcf4 (Tcf7l2)-dependent regulation of protease and cadherin expression

Heparan sulfate 3‐O‐sulfotransferase 2 (HS3ST2), an enzyme mediating 3‐O‐sulfation of heparan sulfate (HS), is silenced by hypermethylation in breast cancer. As HS has an important co‐receptor function for numerous signal transduction pathways, the phenotypical changes due to HS3ST2 reexpression were investigated in vitro using high and low invasive breast cancer cell lines. Compared to controls, highly invasive HS3ST2‐expressing MDA‐MB‐231 cells showed enhanced Matrigel invasiveness, transendothelial migration and motility. Affymetrix screening and confirmatory real‐time PCR and Western blotting analysis revealed increased expression of several matrix metalloproteinases, cadherin‐11, E‐cadherin and CEACAM‐1, while protease inhibitor and annexin A10 expression were decreased. Low invasive HS3ST2 ‐expressing MCF‐7 cells became even less invasive, with no change in gelatinolytic MMP activity. HS3ST2 expression increased HS‐dependent basal and FGF2‐specific signaling through the constitutively active p44/42 MAPK pathway in MDA‐MB‐231 cells. Increased MAPK activation was accompanied by upregulation of ß‐catenin in MDA‐MB‐231, and of the transcription factor Tcf4 in both cell lines. Dysregulation of Tcf4‐regulated ion transporters and increased cytosolic acidification were observed in HS3ST2‐expressing MDA‐MB‐231 cells, which is a possible underlying cause of increased chemosensitivity towards doxorubicine and paclitaxel in these cells. This study provides the first in vitro evidence of the involvement of HS3ST2 in breast cancer cell invasion and chemosensitivity.

Cdc42 interacting protein 4 (CIP4) is essential for integrin-dependent T-cell trafficking

The F-BAR domain containing protein CIP4 (Cdc42 interacting protein 4) interacts with Cdc42 and WASP/N-WASP and is thought to participate in the assembly of filamentous actin. CIP4−/− mice had normal T- and B-lymphocyte development but impaired T cell-dependent antibody production, IgG antibody affinity maturation, and germinal center (GC) formation, despite an intact CD40L–CD40 axis. CIP4−/− mice also had impaired contact hypersensitivity (CHS) to haptens, and their T cells failed to adoptively transfer CHS. Ovalbumin-activated CD4+ effector T cells from CIP4−/−/OT-II mice migrated poorly to antigen-challenged skin. Activated CIP4−/− T cells exhibited impaired adhesion and polarization on immobilized VCAM-1 and ICAM-1 and defective arrest and transmigration across murine endothelial cell monolayers under shear flow conditions. These results demonstrate an important role for CIP4 in integrin-dependent T cell-dependent antibody responses and GC formation and in integrin-mediated recruitment of effector T cells to cutaneous sites of antigen-driven immune reactions.

The early vertebrate Danio rerio Mr 46000 mannose-6-phosphate receptor: biochemical and functional characterisation

Mannose-6-phosphate receptors (MPRs) have been identified in a wide range of species from humans to invertebrates such as molluscs. A characteristic of all MPRs is their common property to recognize mannose-6-phosphate residues that are labelling lysosomal enzymes and to mediate their targeting to lysosomes in mammalian cells by the corresponding receptor proteins. We present here the analysis of full-length sequences for MPR 46 from zebrafish (Danio rerio) and its functional analysis. This is the first non-mammalian MPR 46 to be characterised. The amino acid sequences of the zebrafish MPR 46 displays 70% similarity to the human MPR 46 protein. In particular, all essential cysteine residues, the transmembrane domain as well as the cytoplasmic tail residues harbouring the signals for endocytosis and Golgi-localizing, γ-ear-containing, ARF-binding protein (GGA)-mediated sorting at the trans-Golgi network, are highly conserved. The zebrafish MPR 46 has the arginine residue known to be essential for mannose-6-phosphate binding and other additional characteristic residues of the mannose-6-phosphate ligand-binding pocket. Like the mammalian MPR 46, zebrafish MPR 46 binds to the multimeric mannose-6-phosphate ligand phosphomannan and can rescue the missorting of lysosomal enzymes in mammalian MPR-deficient cells. The conserved C-terminal acidic dileucine motif (DxxLL) in the cytoplasmic domain of zebrafish MPR 46 essential for the interaction of the GGAs with the receptor domains interacts with the human GGA1-VHS domain. Interestingly, the serine residue suggested to regulate the interaction between the tail and the GGAs in a phosphorylation-dependent manner is substituted by a proline residue in fish.

Binding of WIP to actin is essential for T cell actin cytoskeleton integrity and tissue homing.

ABSTRACT The Wiskott-Aldrich syndrome protein (WASp) is important for actin polymerization in T cells and for their migration. WASp-interacting protein (WIP) binds to and stabilizes WASp and also interacts with actin. Cytoskeletal and functional defects are more severe in WIP−/− T cells, which lack WASp, than in WASp−/− T cells, suggesting that WIP interaction with actin may be important for T cell cytoskeletal integrity and function. We constructed mice that lack the actin-binding domain of WIP (WIPΔABD mice). WIPΔABD associated normally with WASp but not F-actin. T cells from WIPΔABD mice had normal WASp levels but decreased cellular F-actin content, a disorganized actin cytoskeleton, impaired chemotaxis, and defective homing to lymph nodes. WIPΔABD mice exhibited a T cell intrinsic defect in contact hypersensitivity and impaired responses to cutaneous challenge with protein antigen. Adoptively transferred antigen-specific CD4+ T cells from WIPΔABD mice had decreased homing to antigen-challenged skin of wild-type recipients. These findings show that WIP binding to actin, independently of its binding to WASp, is critical for the integrity of the actin cytoskeleton in T cells and for their migration into tissues. Disruption of WIP binding to actin could be of therapeutic value in T cell-driven inflammatory diseases.

Binding of the WASP/N-WASP-Interacting Protein WIP to Actin Regulates Focal Adhesion Assembly and Adhesion

ABSTRACT The actin cytoskeleton is essential for cell adhesion and migration, functions important for tumor invasion. In addition to binding N-WASP/WASP, WIP binds and stabilizes F-actin. WIP−/− fibroblasts were used to test the role of WIP in F-actin function. WIP−/− cells had defective focal adhesion (FA), stress fiber assembly, and adherence to substrates, functions that were restored by transduction of wild-type WIP. Protein and mRNA levels of several FA constituents regulated by the myocardin-related transcription factor (MRTF)–serum response factor (SRF) transcription factor complex were reduced in WIP−/− fibroblasts. The level of G-actin, which sequesters MRTF in the cytoplasm, was increased, and nuclear localization of MRTF-A and SRF was reduced, in WIP−/− fibroblasts. Transfection of an MRTF-A mutant that constitutively translocates to the nucleus or transfection of constitutively active SRF restored FA and stress fiber assembly. Fibroblasts from knock-in mice expressing a WIP mutant that fails to bind actin phenocopied WIP−/− fibroblasts. Thus, WIP is a novel regulator of FA assembly and cell adhesion.

Mast cells regulate CD4+ T-cell differentiation in the absence of antigen presentation

Background: Given their unique capacity for antigen uptake, processing, and presentation, antigen‐presenting cells (APCs) are critical for initiating and regulating innate and adaptive immune responses. We have previously shown the role of nicotinamide adenine dinucleotide (NAD+) in T‐cell differentiation independently of the cytokine milieu, whereas the precise mechanisms remained unknown. Objective: The objective of this study is to further dissect the mechanism of actions of NAD+ and determine the effect of APCs on NAD+‐mediated T‐cell activation. Methods: Isolated dendritic cells and bone marrow–derived mast cells (MCs) were used to characterize the mechanisms of action of NAD+ on CD4+ T‐cell fate in vitro. Furthermore, NAD+‐mediated CD4+ T‐cell differentiation was investigated in vivo by using wild‐type C57BL/6, MC−/−, MHC class II−/−, Wiskott‐Aldrich syndrome protein (WASP)−/−, 5C.C7 recombination‐activating gene 2 (Rag2)−/−, and CD11b‐DTR transgenic mice. Finally, we tested the physiologic effect of NAD+ on the systemic immune response in the context of Listeria monocytogenes infection. Results: Our in vivo and in vitro findings indicate that after NAD+ administration, MCs exclusively promote CD4+ T‐cell differentiation, both in the absence of antigen and independently of major APCs. Moreover, we found that MCs mediated CD4+ T‐cell differentiation independently of MHC II and T‐cell receptor signaling machinery. More importantly, although treatment with NAD+ resulted in decreased MHC II expression on CD11c+ cells, MC‐mediated CD4+ T‐cell differentiation rendered mice resistant to administration of lethal doses of L monocytogenes. Conclusions: Collectively, our study unravels a novel cellular and molecular pathway that regulates innate and adaptive immunity through MCs exclusively and underscores the therapeutic potential of NAD+ in the context of primary immunodeficiencies and antimicrobial resistance.

Lysosomal Enzyme Sorting Receptors—Where Did They First Appear in the Animal Kingdom?

Two distinct but homologous mannose 6-phosphate receptors (MPRs) designated as the cation-independent mannose 6-phosphate/IGF-II receptor (MPR300, Mr 300 kDa) and the cation-dependent mannose 6-phosphate receptor (MPR46, Mr 46 kDa) are evolutionarily conserved proteins that transport lysosomal enzymes to lysosomes in the vertebrates. MPR300 alone has also been shown to be an endocytic receptor and it also binds human IGF-II. To further understand the evolution of the MPRs, we extended our studies to the invertebrate species by initially identifying one of their interacting partners, such as α-fucosidase. In the highly evolved invertebrate, starfish (echinodermata) and unio (mollusca) lysosomal enzyme activities were detected and an α-fucosidase has been affinity purified. Additionally, both putative receptors were also affinity purified from these species. In Biomphalaria glabrata (snail cells), the MPR300 protein has been shown to be involved in lysosomal enzyme targeting. Below the molluscs, in the Drosophila melanogaster we could discover only a truncated form of the MPR300 protein which lacks the ability to bind multivalent phosphomannan like the other known receptors. No MPR 46 protein was detected in this species. Furthermore, in species such as the prawn (arthropoda) and the earthworm (annelidae), that fall below the mollusca only MPR 300-like polypeptides were detectable and no MPR 46 protein was identified. In comparison to molluscs, the lysosomal activities detectable were in the order arthropoda greater than annelidae. Our data strongly suggests that the functional MPRs started appearing in the animal kingdom from the mollusc onwards