Interleukin-9 induces tyrosine phosphorylation of insulin receptor substrate-1 via JAK tyrosine kinases

Obesity and Leukemia: Biological Mechanisms, Perspectives, and Challenges

PURPOSE OF REVIEW

To examine the epidemiological data on obesity and leukemia; evaluate the effect of obesity on leukemia outcomes in childhood acute lymphoblastic leukemia (ALL) survivors; assess the potential mechanisms through which obesity may increase the risk of leukemia; and provide the effects of obesity management on leukemia. Preventive (diet, physical exercise, obesity pharmacotherapy, bariatric surgery) measures, repurposing drugs, candidate therapeutic agents targeting oncogenic pathways of obesity and insulin resistance in leukemia as well as challenges of the COVID-19 pandemic are also discussed.

RECENT FINDINGS

Obesity has been implicated in the development of 13 cancers, such as breast, endometrial, colon, renal, esophageal cancers, and multiple myeloma. Leukemia is estimated to account for approximately 2.5% and 3.1% of all new cancer incidence and mortality, respectively, while it represents the most frequent cancer in children younger than 5 years. Current evidence indicates that obesity may have an impact on the risk of leukemia. Increased birthweight may be associated with the development of childhood leukemia. Obesity is also associated with worse outcomes and increased mortality in leukemic patients. However, there are several limitations and challenges in meta-analyses and epidemiological studies. In addition, weight gain may occur in a substantial number of childhood ALL survivors while the majority of studies have documented an increased risk of relapse and mortality among patients with childhood ALL and obesity. The main pathophysiological pathways linking obesity to leukemia include bone marrow adipose tissue; hormones such as insulin and the insulin-like growth factor system as well as sex hormones; pro-inflammatory cytokines, such as IL-6 and TNF-α; adipocytokines, such as adiponectin, leptin, resistin, and visfatin; dyslipidemia and lipid signaling; chronic low-grade inflammation and oxidative stress; and other emerging mechanisms. Obesity represents a risk factor for leukemia, being among the only known risk factors that could be prevented or modified through weight loss, healthy diet, and physical exercise. Pharmacological interventions, repurposing drugs used for cardiometabolic comorbidities, and bariatric surgery may be recommended for leukemia and obesity-related cancer prevention.

Engineering the IL-4/IL-13 axis for targeted immune modulation

The structurally and functionally related interleukin-4 (IL-4) and IL-13 cytokines play pivotal roles in shaping immune activity. The IL-4/IL-13 axis is best known for its critical role in T helper 2 (Th2) cell-mediated Type 2 inflammation, which protects the host from large multicellular pathogens, such as parasitic helminth worms, and regulates immune responses to allergens. In addition, IL-4 and IL-13 stimulate a wide range of innate and adaptive immune cells, as well as non-hematopoietic cells, to coordinate various functions, including immune regulation, antibody production, and fibrosis. Due to its importance for a broad spectrum of physiological activities, the IL-4/IL-13 network has been targeted through a variety of molecular engineering and synthetic biology approaches to modulate immune behavior and develop novel therapeutics. Here, we review ongoing efforts to manipulate the IL-4/IL-13 axis, including cytokine engineering strategies, formulation of fusion proteins, antagonist development, cell engineering approaches, and biosensor design. We discuss how these strategies have been employed to dissect IL-4 and IL-13 pathways, as well as to discover new immunotherapies targeting allergy, autoimmune diseases, and cancer. Looking ahead, emerging bioengineering tools promise to continue advancing fundamental understanding of IL-4/IL-13 biology and enabling researchers to exploit these insights to develop effective interventions.

The immuno-oncological implications of insulin

Emerging evidence has implicated insulin in regulating the phenotypes of various immune cells through canonical downstream signalling effectors of insulin, namely, the PI3K/Akt/mTOR pathway. Notably, these signalling components also exhibit crosstalk with other immune signalling pathways, such as the JAK/STAT pathway (activated by cytokines and growth factors), and, importantly, are also negatively regulated by the immune checkpoint blockers (ICBs), PD-1 and CTLA-4. Here, we point out recent findings, suggesting that insulin may promote a pro-inflammatory phenotype with potential implications on ICB therapy. As an example, the contemporary paradigm holds that, while T cell receptor recognition of distinct MHC-expressed epitopes ensures specificity, co-activation of CD28 along with signal inputs form various cytokines and insulin operates to 'fine-tune' the immune response via PI3K and other downstream signalling molecules. These considerations highlight the urgent need for focused investigations into the role of insulin in regulating immune cell function in the context of ICB therapies.

Cloning and functional testing of rhesus macaque (Macaca mulatta) IL-9 and IL-33

BACKGROUND

IL-9 and IL-33 can profoundly influence immune responses. As a necessary first step toward defining their impact in the rhesus macaque model, we confirmed their endogenous expression and sequence identity and generated expression vectors for the recombinant expression of rhesus IL-9 and IL-33.

METHODS

RT-PCR and Sanger sequencing was used to define the expression and sequences for rhesus IL-9 and IL-33. The resulting recombinant cytokines were tested by ELISA and proliferation assays.

RESULTS

Full-length rhesus IL-9 and the mature form of rhesus IL-33 share 78% and 73% nucleotide similarity, respectively, with humans. Both cytokines are expressed in lymphocytes, with IL-9 expression also evident in CD4+ T cells. Recombinantly expressed rhesus IL-9 and IL-33 were each biologically active in vitro, including enhancing the proliferation of a rhesus B cell line.

CONCLUSIONS

The recombinant rhesus IL-9 and IL-33 constructs produce biologically active cytokines that can act upon rhesus B cells.

Lung-restricted inhibition of Janus kinase 1 is effective in rodent models of asthma

Preclinical and clinical evidence indicates that a subset of asthma is driven by type 2 cytokines such as interleukin-4 (IL-4), IL-5, IL-9, and IL-13. Additional evidence predicts pathogenic roles for IL-6 and type I and type II interferons. Because each of these cytokines depends on Janus kinase 1 (JAK1) for signal transduction, and because many of the asthma-related effects of these cytokines manifest in the lung, we hypothesized that lung-restricted JAK1 inhibition may confer therapeutic benefit. To test this idea, we synthesized iJak-381, an inhalable small molecule specifically designed for local JAK1 inhibition in the lung. In pharmacodynamic models, iJak-381 suppressed signal transducer and activator of transcription 6 activation by IL-13. Furthermore, iJak-381 suppressed ovalbumin-induced lung inflammation in both murine and guinea pig asthma models and improved allergen-induced airway hyperresponsiveness in mice. In a model driven by human allergens, iJak-381 had a more potent suppressive effect on neutrophil-driven inflammation compared to systemic corticosteroid administration. The inhibitor iJak-381 reduced lung pathology, without affecting systemic Jak1 activity in rodents. Our data show that local inhibition of Jak1 in the lung can suppress lung inflammation without systemic Jak inhibition in rodents, suggesting that this strategy might be effective for treating asthma.

An Update on Interleukin-9: From Its Cellular Source and Signal Transduction to Its Role in Immunopathogenesis

Interleukin-9 (IL-9) is a pleiotropic cytokine and was primarily studied in the context of T helper 2 (T_H2)-associated immuno-pathological conditions such as asthma and parasitic infections. There was a paradigm shift in the biology of IL-9 after the recent discovery of T_H9 cells, a new subtype of T_H cells which secrete IL-9 in copious amounts. This has resulted in renewed interest in this cytokine, which was neglected since discovery because it was considered it to be just another T_H2 cytokine. Recent studies have shown that it has multiple cellular sources and is critically involved in the immune-pathogenesis of inflammatory diseases and in guarding immune tolerance. In this review, we will discuss its discovery, gene organization, cellular sources, and signaling pathways. Especially, we will give an update on the recent development regarding its relevance in the immune pathogenesis of human diseases.

Features and roles of T helper 9 cells and interleukin 9 in immunological diseases

T helper 9 (T_H9) cells are considered as newly classified helper T cells that have an important role in the regulation of immune responses. Since these cells preferentially produce IL-9, these cells are termed T_H9 cells. Recently, the role of T_H9 and its signature cytokine (IL-9) has been investigated in a wide range of diseases, including autoimmunity, allergy, infections, cancer and immunodeficiency. Herein, we review the most recent data concerning T_H9 cells and IL-9 as well as their roles in disease. These insights suggest that T_H9 cells are a future target for therapeutic intervention.

Insulin Substrate Receptor (IRS) proteins in normal and malignant hematopoiesis

The insulin receptor substrate (IRS) proteins are a family of cytoplasmic proteins that integrate and coordinate the transmission of signals from the extracellular to the intracellular environment via transmembrane receptors, thus regulating cell growth, metabolism, survival and proliferation. The PI3K/AKT/mTOR and MAPK signaling pathways are the best-characterized downstream signaling pathways activated by IRS signaling (canonical pathways). However, novel signaling axes involving IRS proteins (noncanonical pathways) have recently been identified in solid tumor and hematologic neoplasm models. Insulin receptor substrate-1 (IRS1) and insulin receptor substrate-2 (IRS2) are the best-characterized IRS proteins in hematologic-related processes. IRS2 binds to important cellular receptors involved in normal hematopoiesis (EPOR, MPL and IGF1R). Moreover, the identification of IRS1/ABL1 and IRS2/JAK2V617F interactions and their functional consequences has opened a new frontier for investigating the roles of the IRS protein family in malignant hematopoiesis. Insulin receptor substrate-4 (IRS4) is absent in normal hematopoietic tissues but may be expressed under abnormal conditions. Moreover, insulin receptor substrate-5 (DOK4) and insulin receptor substrate-6 (DOK5) are linked to lymphocyte regulation. An improved understanding of the signaling pathways mediated by IRS proteins in hematopoiesis-related processes, along with the increased development of agonists and antagonists of these signaling axes, may generate new therapeutic approaches for hematological diseases. The scope of this review is to recapitulate and review the evidence for the functions of IRS proteins in normal and malignant hematopoiesis.

The Common Cytokine Receptor γ Chain Family of Cytokines

Interleukin (IL)-2, IL-4, IL-7, IL-9, IL-15, and IL-21 form a family of cytokines based on their sharing the common cytokine receptor γ chain (γc), which was originally discovered as the third receptor component of the IL-2 receptor, IL-2Rγ. The IL2RG gene is located on the X chromosome and is mutated in humans with X-linked severe combined immunodeficiency (XSCID). The breadth of the defects in XSCID could not be explained solely by defects in IL-2 signaling, and it is now clear that γc is a shared receptor component of the six cytokines noted above, making XSCID a disease of defective cytokine signaling. Janus kinase (JAK)3 associates with γc, and JAK3-deficient SCID phenocopies XSCID, findings that served to stimulate the development of JAK3 inhibitors as immunosuppressants. γc family cytokines collectively control broad aspects of lymphocyte development, growth, differentiation, and survival, and these cytokines are clinically important, related to allergic and autoimmune diseases and cancer as well as immunodeficiency. In this review, we discuss the actions of these cytokines, their critical biological roles and signaling pathways, focusing mainly on JAK/STAT (signal transducers and activators of transcription) signaling, and how this information is now being used in clinical therapeutic efforts.

IL-9 Signaling Pathway: An Update

Since the discovery of IL-9 almost three decades back as a growth factor, we have come a long way to understand its pleiotropic functions in the immune system. Despite its many functions, IL-9 still remains as an understudied cytokine. In the last decade, renewed emphasis has been provided to understand the biology of IL-9. Any growth factor or cytokine signals via its cognate receptor to mediate biological functions. In this chapter, we discuss the IL-9 signal transduction in different cell types, which would then exert its distinct functions.

Experimental analysis of risk factors for ulcerative dermatitis in mice

Ulcerative dermatitis (UD) is a severe inflammatory skin disorder with an unknown aetiology. Recently, insulin receptor substrate 1 KO mice were shown to be fully resistant to UD. In this study, we showed that high-fat diet (HFD) feeding significantly increased incidence of UD in wild type (WT) C57BL/6 mice, as did lithium-mediated inhibition of GSK3-β, which is a key negative regulator of IRS1. In contrast to WT mice, resistance to UD was fully preserved in HFD-fed Irs1-KO mice. Our results identify IRS1 as a key determinant of UD pathogenesis and establish a direct link between diet composition, obesity-induced inflammation and chronic ulceration.

Catalytic specificity of human protein tyrosine kinases revealed by Peptide substrate profiling

Out of the 90 human protein tyrosine kinases, 81 were assayed with short peptides derived from well-characterized [CDK1(Tyr15), IRS1(Tyr983), and JAK1(Tyr1023)] or generic [polyGlu:Tyr(4:1) and poly-Glu:Ala:Tyr(1:1:1)] substrates. As expected, the CDK1 peptide is a substrate for all Src family kinases. On the other hand, some of the activities are novel and lead to a better understanding of the function of certain kinases. Specifically, the CDK1 peptide is a substrate for many of the Eph family members. Interestingly, profiling of nearly all the human protein tyrosine kinases revealed a distinct pattern of selectivity towards the CDK1 and IRS1 peptides.

A brief history of IL-9

IL-9 was first described in the late 1980s as a member of a growing number of cytokines that had pleiotropic functions in the immune system. Although many biological functions have been attributed to IL-9, it remains an understudied cytokine. A resurgence of interest in IL-9 has been spurred by recent work demonstrating a role for IL-9 in regulating inflammatory immunity and defining the transcription factors that activate the Il9 gene in cells that most efficiently produce IL-9. In this review, we summarize the characterization of IL-9 biological activities, highlight roles for the cytokine that are clearly defined, and outline questions regarding IL-9 functions that still require further exploration.

IL-9: basic biology, signaling pathways in CD4+ T cells and implications for autoimmunity

CD4(+) T cell subsets play an important role in the adaptive immune response in human autoimmune diseases and in animal models of autoimmunity. In recent years, our knowledge of CD4(+) T cell differentiation has increased significantly, and new subsets continue to be recognized. Of significant importance is the recent discovery of Th9 cells, the CD4 + T cell subset that produces Interleukin-9. IL-9 has largely been regarded as a Th2 cytokine; however, it is now known that under specific conditions, Tregs, Th1, Th17 and the Th9 subset of T cells also produce IL-9. The STAT family of proteins plays a major role in the signaling pathways of these CD4(+)T subsets. Biological actions of IL-9 and the STATs signaling pathways in autoimmune diseases are continuing to be clarified. Investigation of IL-9-producing CD4(+)T cells, and elucidation of the mechanisms of IL-9-induced STATs signaling, in concert with other transcription factors, will provide a better understanding of the pathogenesis of various autoimmune diseases.

The Interleukin (IL)‐2 Family Cytokines: Survival and Proliferation Signaling Pathways in T Lymphocytes

Lymphocyte populations in the immune system are maintained by a well-organized balance between cellular proliferation, cellular survival and programmed cell death (apoptosis). One of the primary functions of many cytokines is to coordinate these processes. In particular, the interleukin (IL)-2 family of cytokines, which consists of six cytokines (IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21) that all share a common receptor subunit (gammac), plays a major role in promoting and maintaining T lymphocyte populations. The details of the molecular signaling pathways mediated by these cytokines have not been fully elucidated. However, the three major pathways clearly involved include the JAK/STAT, MAPK and phosphatidylinositol 3-kinase (P13K) pathways. The details of these pathways as they apply to the IL-2 family of cytokines is discussed, with a focus on their roles in proliferation and survival signaling.

Type I IL-4Rs selectively activate IRS-2 to induce target gene expression in macrophages

Although interleukin-4 (IL-4) and IL-13 participate in allergic inflammation and share a receptor subunit (IL-4Ralpha), they have different functions. We compared cells expressing type I and II IL-4Rs with cells expressing only type II receptors for their responsiveness to these cytokines. IL-4 induced highly efficient, gammaC-dependent tyrosine phosphorylation of insulin receptor substrate 2 (IRS-2), whereas IL-13 was less effective, even when phosphorylation of signal transducer and activator of transcription 6 (STAT6) was maximal. Only type I receptor, gammaC-dependent signaling induced efficient association of IRS-2 with the p85 subunit of phosphoinositide 3-kinase or the adaptor protein growth factor receptor-bound protein 2. In addition, IL-4 signaling through type I IL-4Rs induced more robust expression of a subset of genes associated with alternatively activated macrophages than did IL-13. Thus, IL-4 activates signaling pathways through type I IL-4Rs qualitatively differently from IL-13, which cooperate to induce optimal gene expression.

Ligands to the (IRAP)/AT4 receptor encompassing a 4-hydroxydiphenylmethane scaffold replacing Tyr2

Analogues of the hexapeptide angiotensin IV (Ang IV, Val(1)-Tyr(2)-Ile(3)-His(4)-Pro(5)-Phe(6)) encompassing a 4-hydroxydiphenylmethane scaffold replacing Tyr(2) and a phenylacetic or benzoic acid moiety replacing His(4)-Pro(5)-Phe(6) have been synthesized and evaluated in biological assays. The analogues inhibited the proteolytic activity of cystinyl aminopeptidase (CAP), frequently referred to as the insulin-regulated aminopeptidase (IRAP), and were found less efficient as inhibitors of aminopeptidase N (AP-N). The best Ang IV mimetics in the series were approximately 20 times less potent than Ang IV as IRAP inhibitors. Furthermore, it was found that the ligands at best exhibited a 140 times lower binding affinity to the membrane-bound IRAP/AT4 receptor than Ang IV. Although the best compounds still exert lower activities than Ang IV, it is notable that these compounds comprise only two amino acid residues and are considerably less peptidic in character than the majority of the Ang IV analogues previously reported as IRAP inhibitors in the literature.

Regulation of the human leukocyte-derived arginine aminopeptidase endoplasmic reticulum-aminopeptidase 2 gene by interferon-?

The leukocyte-derived arginine aminopeptidase (L-RAP) is the second aminopeptidase localized in the endoplasmic reticulum (ER) processing antigenic peptides presented to major histocompatibility complex (MHC) class I molecules. In this study, the genomic organization of the gene encoding human L-RAP was determined and the regulatory mechanism of its expression was elucidated. The entire genomic structure of the L-RAP gene is similar to both placental leucine aminopeptidase (P-LAP) and adipocyte-derived leucine aminopeptidase (A-LAP) genes, confirming the close relationship of these three enzymes. Interferon (IFN)-gamma up-regulates the expression of the L-RAP gene. Deletion and site-directed mutagenic analyses of the 5'-flanking region of the L-RAP gene and electrophoretic mobility shift assay indicated that while interferon regulatory factor (IRF)-2 is important in the basal condition, IRF-1 is the primary regulator of IFN-gamma-mediated augmentation of the gene expression. In addition, PU.1, a member of the E26 transformation-specific family of transcription factors, also plays a role in the regulation of gene expression. The maximum expression of the gene was achieved by coexpression of IRF-1 and PU.1 in HEK293 cells and IRF-2 suppressed the IRF-1-mediated enhancement of gene expression, suggesting that IFN-gamma-induced L-RAP gene expression is cooperatively regulated by IRFs and PU.1 transcription factors.

Human skeletal muscle cell differentiation is associated with changes in myogenic markers and enhanced insulin-mediated MAPK and PKB phosphorylation

AIM

We hypothesized that myogenic differentiation of HSMC would yield a more insulin responsive phenotype.

METHODS

We assessed expression of several proteins involved in insulin action or myogenesis during differentiation of primary human skeletal muscle cultures (HSMC).

RESULTS

Differentiation increased creatine kinase activity and expression of desmin and myocyte enhancer factor (MEF)2C. No change in expression was observed for big mitogen-activated protein kinase (BMK1/ERK5), MEF2A, insulin receptor (IR), hexokinase II, and IR substrates 1 and 2, while expression of glycogen synthase, extracellular signal-regulated kinase 1 and 2 (ERK1/2 MAP kinase) and the insulin responsive aminopeptidase increased after differentiation. In contrast to protein kinase B (PKB)a, expression of (PKB)b increased, with differentiation. Both basal and insulin-stimulated PI 3-kinase activity increased with differentiation. Insulin-mediated phosphorylation of PKB and ERK1/2 MAP kinase increased after differentiation.

CONCLUSION

Components of the insulin-signalling machinery are expressed in myoblast and myotube HSMC; however, insulin responsiveness to PKB and ERK MAP kinase phosphorylation increases with differentiation.

Genetics of lactase persistence and lactose intolerance

The enzyme lactase that is located in the villus enterocytes of the small intestine is responsible for digestion of lactose in milk. Lactase activity is high and vital during infancy, but in most mammals, including most humans, lactase activity declines after the weaning phase. In other healthy humans, lactase activity persists at a high level throughout adult life, enabling them to digest lactose as adults. This dominantly inherited genetic trait is known as lactase persistence. The distribution of these different lactase phenotypes in human populations is highly variable and is controlled by a polymorphic element cis-acting to the lactase gene. A putative causal nucleotide change has been identified and occurs on the background of a very extended haplotype that is frequent in Northern Europeans, where lactase persistence is frequent. This single nucleotide polymorphism is located 14 kb upstream from the start of transcription of lactase in an intron of the adjacent gene MCM6. This change does not, however, explain all the variation in lactase expression.

Regulatory role of membrane-bound peptidases in the progression of gynecologic malignancies

Membrane-bound peptidases play a key role in the control of growth, differentiation, and signal transduction of many cellular systems by degrading bioactive peptides. Thus, abnormal changes in their expression pattern and catalytic function result in altered peptide activation, which contributes to neoplastic transformation or progression. In this review, we describe our recent findings along with work from other groups on the expression and biological functions of membrane-bound peptidases in cancer, focusing on the regulatory roles of three peptidases, aminopeptidase A (APA), neutral endopeptidase (NEP) and placental leucine aminopeptidase (P-LAP), in the progression of gynecologic malignancies. APA, NEP and P-LAP are differentially expressed and localized in various gynecologic malignancies including cervical cancer, endometrial cancer, ovarian cancer and choriocarcinoma in a tumor-type specific pattern. The expression levels are up- or down-regulated depending on histological grade or disease progression. These peptidases play regulatory roles in tumor cell proliferation, invasion or angiogenesis via degradation/inactivation of target peptides such as angiotensin II, endothelin-1 and oxytocin, which act on cancer cells as stimulatory or inhibitory factors. Thus, membrane-bound peptidases may become not only a new diagnostic/prognostic marker, but also a novel molecular target for the treatment of gynecologic malignancies.

Expression of placental leucine aminopeptidase and adipocyte-derived leucine aminopeptidase in human normal and malignant invasive trophoblastic cells

We recently identified two novel aminopeptidases, placental leucine aminopeptidase (P-LAP) and adipocyte-derived leucine aminopeptidase (A-LAP). Enzymatically, P-LAP degrades oxytocin, vasopressin, and angiotensin III, while A-LAP degrades angiotensin II and kallidin. In this study we investigated the expression and localization of P-LAP and A-LAP in human trophoblastic cells in the normal placenta (n = 26), gestational choriocarcinoma (n = 8), and placental site trophoblastic tumor (n = 3). On immunoblot analysis both P-LAP and A-LAP proteins were detected in normal placenta and five choriocarcinoma tissues, as well as in two choriocarcinoma cell lines. Immunohistochemical staining of normal placental tissues demonstrated that P-LAP was not only localized in villous syncytiotrophoblasts but also highly expressed in extravillous trophoblasts (EVTs) invading the decidua or maternal spiral arteries. The expression level of P-LAP on these invasive EVTs reached a maximum during the late first to second trimesters of pregnancy, and it decreased in the third trimester. Similarly, A-LAP was strongly expressed in EVTs invading the decidua or spiral arteries in the second trimester of pregnancy, while it was weakly or moderately expressed in villous cytotrophoblasts or EVTs located in the cell columns. These two aminopeptidases were more strongly expressed in all eight choriocarcinomas and three placental site trophoblastic tumors and mainly localized to the intermediate-type trophoblastic tumor cells invading the uterine myometrium or stromal vessels. In summary P-LAP and A-LAP were predominantly expressed in the invasive phenotype of EVTs during placentation, as well as in the invasive tumor cells of trophoblastic neoplasms. These results suggest the involvement of these aminopeptidases in invasiveness of both normal and malignant intermediate-type trophoblasts possibly through degradation of specific peptide substrates.

Interleukin-9 influences chemokine release in airway smooth muscle: role of ERK

Interleukin (IL)-9 is a pleiotropic cytokine that has been proposed as a candidate gene for asthma. As IL-9 expression is correlated with airway hyperresponsiveness in animals, we examined the effects of IL-9 on cultured human airway smooth muscle (HASM) cells. IL-9 alone had no effect on IL-8 release, but at concentrations of > or =30 ng/ml, IL-9 significantly increased IL-8 release induced by TNF-alpha. IL-9 increased phosphorylation of extracellular signal-regulated protein kinase (ERK, p42 and p44) in a concentration- and time-dependent fashion, and U-0126 (10 micro M), which inhibits ERK phosphorylation, abolished the synergism between TNF-alpha and IL-9 on IL-8 release. IL-9 alone had no effect on eotaxin release into HASM cell supernatants but at concentrations of > or =10 ng/ml caused an approximately 50% increase in release of eotaxin evoked by IL-13 (10 ng/ml). U-0126 blocked the synergism between IL-9 and IL-13 on eotaxin release. IL-9 had no effect on cyclooxygenase-2 (COX-2) expression or PGE(2) release and did not augment the COX-2 expression that was induced by IL-1beta. Our results indicate that airway smooth muscle is a target for IL-9 and that IL-9 amplifies the potential for these cells to recruit eosinophils and neutrophils into the airways by a mechanism involving ERK.

Involvement of the V2 receptor in vasopressin-stimulated translocation of placental leucine aminopeptidase/oxytocinase in renal cells

The placental leucine aminopeptidase (P-LAP)/oxytocinase is a membrane-bound enzyme thought to play an important role during pregnancy. In this study, we identified the presence of P-LAP protein in the renal distal tubules and collecting ducts. In rat NRK52E cells derived from renal tubules, P-LAP was localized mainly in the intracellular compartment. Upon the treatment of cells with 8-arginine-vasopressin (AVP), a significant increase in the surface level of P-LAP was observed. [deamino-Cys1, d-Arg8]-vasopressin (DDAVP), a specific V2 receptor agonist, increased the surface level of P-LAP, while [adamantaneacetyl1, O-Et-d-Tyr2, Val4, aminobutyryl6, Arg8,9]-vasopressin (AEAVP), a potent V2 receptor antagonist, blocked the AVP-stimulated enhancement. Moreover, reagents known to enhance the intracellular level of cAMP have also been shown to increase the surface level of P-LAP. When we examined the colocalization of P-LAP with the cell surface water channel aquaporin-2 (AQP-2) that is regulated by AVP, the P-LAP-containing vesicles had a relatively higher density than the AQP-2-containing vesicles, suggesting that P-LAP and AQP-2 are differently distributed in NRK52E cells. These results suggest that AVP induces the translocation of P-LAP via V2 receptor and P-LAP plays a role in the regulation of excessive AVP level in the renal collecting duct, acting as a negative feedback mechanism for the AVP action of regulating water reabsorption.

Modulation of intestinal muscle contraction by interleukin-9 (IL-9) or IL-9 neutralization: correlation with worm expulsion in murine nematode infections

Immune responses associated with intestinal nematode infections are characterized by the activation of T-helper 2 (Th2) cells. Previous studies demonstrated that during Trichinella spiralis infection, Th2 cells contribute to the development of intestinal muscle hypercontractility and to worm eviction from the gut, in part through signal transducer and activator of transcription factor 6 (Stat6). Interleukin-9 (IL-9), a Th2-cell-derived cytokine, has pleiotropic activities on various cells that are not mediated through Stat6. In this study, we investigated the role of IL-9 in the generation of enteric muscle hypercontractility in mice infected with the intestinal parasite T. spiralis and the cecal parasite Trichuris muris. Treatment of mice with IL-9 enhanced infection-induced jejunal muscle hypercontractility and accelerated worm expulsion in T. spiralis infection. These effects were associated with an up-regulation of IL-4 and IL-13 production from in vitro-stimulated spleen cells. In addition, increases in the level of intestinal goblet cells and in the level of mouse mucosal mast cell protease 1 (MMCP-1) in serum were observed in infected mice following IL-9 administration. However, the neutralization of IL-9 by anti-IL-9 vaccination or by anti-IL-9 antibody had no significant effect on worm expulsion or muscle contraction in T. spiralis-infected mice. In contrast, the neutralization of IL-9 significantly attenuated T. muris infection-induced colonic muscle hypercontractility and inhibited worm expulsion. The attenuated expulsion of the parasite by IL-9 neutralization was not accompanied by changes in goblet cell hyperplasia or the MMCP-1 level. These findings suggest that IL-9 contributes to intestinal muscle function and to host protective immunity and that its importance and contribution may differ depending on the type of nematode infection.

Tip60 is a co-repressor for STAT3

Tip60 (Tat-interactive protein, 60 kDa), a cellular protein with intrinsic histone acetyltransferase activity, is involved in DNA damage repair and apoptosis. Recent studies have suggested that Tip60 acts either as a co-activator or a co-repressor to modulate transcription. In this study, we demonstrate that Tip60 represses reporter gene expression when it is fused to the Gal4 DNA binding domain. We also show that Tip60 associates with histone deacetylase 7 (HDAC7) through its N-terminal zinc finger-containing region and that HDAC7 activity is required for the repressive effect of Tip60. Because endogenous Tip60 interacts with STAT3, we hypothesized that Tip60 might complex with STAT3 and HDAC7 and modulate STAT3-mediated trans-activation. Consistent with this hypothesis, the overexpression of Tip60 represses STAT3-driven reporter gene expression, which can be further potentiated by the co-transfection of HDAC7. Furthermore, interleukin-9-induced c-myc expression, which depends on STAT3 activity, is abrogated by exogenous expression of Tip60. This is the first demonstration of which Tip60 represses STAT3 activity in part through the recruitment of HDAC7.

MAP kinase activation by interleukin-9 in lymphoid and mast cell lines

Interleukin-9 (IL-9) stimulates the proliferation of mast cells and lymphocytes. In the present study, we showed that IL-9 induced a transient phosphorylation of MEK, ERK2 and p90/RSK in murine lymphoid and mast cell lines. ERK2 in vitro kinase activity was also increased upon IL-9 stimulation. Similar results were obtained with IL-4, which had not been previously reported to activate these kinases in hematopoietic cells. Analysis of IL-9 receptor mutants showed that activation of the pathway was correlated with proliferation and with phosphorylation of the adaptor protein SHC, but not IRS2 or GAB2. The MEK inhibitor PD98059 reduced the mitogenic response to IL-4 and IL-9. In addition, expression of a dominant-negative RAS variant blocked ERK phosphorylation and significantly decreased Ba/F3 cell growth in the presence of IL-9, but did not affect expression of pim-1, a STAT target gene. In summary, these results indicate that IL-9 can transiently activate the mitogen-activated protein kinase pathway, which contributes to growth stimulation of hematopoietic cell lines.

Latent TGF-beta binding protein-3 (LTBP-3) requires binding to TGF-beta for secretion

Latent transforming growth factor-beta (TGF-beta) binding protein (LTBP)-1, which is easily secreted, has been shown to enhance the secretion of TGF-beta. Here we show that another member of the LTBP family, LTBP-3, is not secreted by several cell types, but secretion occurs after coexpression with TGF-beta. The secretion of LTBP-3 requires complexing of LTBP-3 with Cys33 of the TGF-beta propeptide.

Specificity of interleukin-2 receptor gamma chain superfamily cytokines is mediated by insulin receptor substrate-dependent pathway

Interleukins 9 (IL-9) and 4 are cytokines within the IL-2 receptor gamma chain (IL-2R gamma) superfamily that possess similar and unique biological functions. The signaling mechanisms, which may determine cytokine specificity and redundancy, are not well understood. IRS proteins are tyrosine-phosphorylated following IL-9 and IL-4 stimulation, a process in part mediated by JAK tyrosine kinases (Yin, T. G., Keller, S. R., Quelle, F. W., Witthuhn, B. A., Tsang, M. L., Lienhard, G. E., Ihle, J. N., and Yang, Y. C. (1995) J. Biol. Chem. 270, 20497--20502). In the present study, we used 32D cells stably transfected with insulin receptor (32D(IR)), which do not express any IRS proteins, as a model system to study the requirement of different structural domains of IRS proteins in IL-9- and IL-4-mediated functions. Overexpression of IRS-1 and IRS-2, but not IRS-4, induced proliferation of 32D(IR) cells in response to IL-9. The pleckstrin homology (PH) domain of IRS proteins is required for IRS-mediated proliferation stimulated by IL-9. The phosphotyrosine binding and Shc and IRS-1 NPXY binding domains are interchangeable for IRS to transduce the proliferative effect of IL-4. Therefore, the PH domain plays different roles in coupling IRS proteins to activated IL-9 and IL-4 receptors. The role of IRS proteins in determining cytokine specificity was corroborated by their ability to interact with different downstream signaling molecules. Although phosphatidylinositol 3' -kinase (PI3K) and Grb-2 interact with tyrosine-phosphorylated IRS proteins, Shp-2 only binds to IRS proteins following IL-4, but not IL-9, stimulation. Although PI3K activity is necessary for the IRS-1/2-mediated proliferative effect of IL-9 and IL-4, Akt activation is only required for cell proliferation induced by IL-4, but not IL-9. These data suggest that IRS-dependent signaling pathways work by recruiting different signaling molecules to determine specificity of IL-2R gamma superfamily cytokines.

Ghrelin modulates the downstream molecules of insulin signaling in hepatoma cells

Ghrelin was identified in the stomach as an endogenous ligand specific for the growth hormone secretagogue receptor (GHS-R). GHS-R is found in various tissues, but its function is unknown. Here we show that GHS-R is found in hepatoma cells. Exposure of these cells to ghrelin caused up-regulation of several insulin-induced activities including tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1), association of the adapter molecule growth factor receptor-bound protein 2 with IRS-1, mitogen-activated protein kinase activity, and cell proliferation. Unlike insulin, ghrelin inhibited Akt kinase activity as well as up-regulated gluconeogenesis. These findings raise the possibility that ghrelin modulates insulin activities in humans.

IL-10 promotes survival of microglia without activating Akt

IL-10 is an anti-inflammatory cytokine that has recently been shown to promote survival of neurons and glia. Here we establish that IL-10 induces phosphorylation of Stat3 on Tyr(705) and serves as a survival factor for N13 microglial cells. Recombinant IL-10 (10 ng/ml) decreases growth factor withdrawal-induced apoptosis by 50%, as assessed by TUNEL. In contrast to IL-10, IGF-I increases enzymatic activity of PI 3-kinase and causes phosphorylation on serine(473) of Akt but does not prevent microglial apoptosis. These data establish that IL-10 activates Stat3 and inhibits the mitochondrial pathway of cell death without activating the Akt cell survival pathway.

Characterization of a secretase activity for placental leucine aminopeptidase

Placental leucine aminopeptidase (P-LAP) is believed to play an important role in the inactivation of small regulatory peptides. P-LAP exists in both membrane-bound and soluble forms and cDNA cloning has demonstrated that P-LAP is a type II membrane protein, which means that its soluble form is released by a specific proteolytic cleavage. In this report, we studied this process in COS7 cells. Inhibitors of serine or aspartic proteases did not affect the secretion of P-LAP, while EDTA and 1,10-phenanthroline inhibited it. In addition, we transfected P-LAP expression vectors that have point mutations of the cleavage site or deletion of the juxtamembrane stalk. Point mutations of the cleavage site resulted in significantly lower secretion of P-LAP. On the contrary, the distance to cleavage site showed no relation to P-LAP secretion. These results suggest that P-LAP secretase has a metalloprotease activity which depends on the amino acid sequence of the cleavage site.

Cytokine regulation of host defense against parasitic gastrointestinal nematodes: lessons from studies with rodent models

Studies with rodents infected with Trichinella spiralis, Heligmosomoides polygyrus, Nippostronglyus brasiliensis, and Trichuris muris have provided considerable information about immune mechanisms that protect against parasitic gastrointestinal nematodes. Four generalizations can be made: 1. CD4+ T cells are critical for host protection; 2. IL-12 and IFN-gamma inhibit protective immunity; 3. IL-4 can: (a) be required for host protection, (b) limit severity of infection, or (c) induce redundant protective mechanisms; and 4. Some cytokines that are stereotypically produced in response to gastrointestinal nematode infections fail to enhance host protection against some of the parasites that elicit their production. Host protection is redundant at two levels: 1. IL-4 has multiple effects on the immune system and on gut physiology (discussed in this review), more than one of which may protect against a particular parasite; and 2. IL-4 is often only one of multiple stimuli that can induce protection. Hosts may have evolved the ability to recognize features that characterize parasitic gastrointestinal nematodes as a class as triggers for a stereotypic cytokine response, but not the ability to distinguish features of individual parasites as stimuli for more specific protective cytokine responses. As a result, hosts deploy a set of defense mechanisms against these parasites that together control infection by most members of that class, even though a specific defense mechanism may not be required to defend against a particular parasite and may even damage a host infected with that parasite.

Fes mediates the IL-4 activation of insulin receptor substrate-2 and cellular proliferation

Although Jak kinases are essential for initiating cytokine signaling, the role of other nonreceptor tyrosine kinases in this process remains unclear. We have examined the role of Fes in IL-4 signaling. Examination of Jak1-deficient cell lines demonstrates that Jak1 is required for the activation of Fes by IL-4. Experiments studying signaling molecules activated by IL-4 receptor suggest that IL-4 signaling can be subdivided into Fes-dependent and Fes-independent pathways. Overexpression of kinase-inactive Fes blocks the IL-4 activation of insulin receptor substrate-2, but not STAT6. Fes appears to be a downstream kinase from Jak1/Jak3 in this process. Further examination of downstream signaling demonstrates that kinase-inactive Fes inhibits the recruitment of phosphoinositide 3-kinase to the activated IL-4 receptor complex and decreases the activation of p70(S6k) kinase in response to IL-4. This inhibition correlates with a decrease in IL-4-induced proliferation. In contrast, mutant Fes does not inhibit the activation of Akt by IL-4. These data demonstrate that signaling pathways activated by IL-4 require different tyrosine kinases. This differential requirement predicts that specific kinase inhibitors may permit the disruption of specific IL-4-induced functions.

The insulin receptor substrate (IRS)-1 recruits phosphatidylinositol 3-kinase to Ret: evidence for a competition between Shc and IRS-1 for the binding to Ret

Tyrosine 1062 of Ret, which represents an intracytoplasmic docking site for multiple signaling molecules, is essential for Ret-mediated activation of phosphatidylinositol 3-Kinase (PI3-K). PI3-K, in turn, has been implicated in inducing cell survival and neoplastic transformation mediated by Ret. We have examined the mechanisms by which Ret stimulates PI3-K. Here we show that the Insulin Receptor Substrate-1 (IRS-1) is tyrosine phosphorylated and associated with the p85 regulatory subunit of PI3-K in response to Ret activation. IRS-1 coimmunoprecipitates with Ret and co-expression of IRS-1 results in the potentiation of Ret-mediated activation of Akt(PKB), a bona fide effector of PI3-K. The association with the PTB domain of IRS-1 depends on the phosphorylation of tyrosine 1062 of Ret. The deletion of asparagine 1059 (delN1059) and the substitution of leucine 1061 (L1061P), two Ret mutations identified in families affected by congenital megacolon (Hirschsprung's disease), impair the binding of IRS-1 to Ret as well as Ret-mediated Akt(PKB) stimulation. Finally, we show that Shc, which was previously identified as another ligand of Y1062 of Ret, competes with IRS-1 for the binding to Ret pY1062. All together, these findings suggest that IRS-1 is a component of the signaling pathway which leads to Ret-mediated PI3-K activation, a pathway which can be targeted by Hirschsprung-associated Ret mutations. The alternative binding of Shc and IRS-1 to Ret pY1062 can be a system to modulate the activation of different intracellular signaling pathways and to elicit different biological responses following Ret activation.

Characterization of IL-4 and IL-13 signals dependent on the human IL-13 receptor alpha chain 1: redundancy of requirement of tyrosine residue for STAT3 activation

IL-4 and IL-13 are pleiotropic cytokines whose biological activities overlap with each other. IL-13 receptor alpha chain 1 (IL-13R alpha 1) is necessary for binding to IL-13, and the heterodimer composed of IL-13R alpha 1 and IL-4R alpha chain transduces IL-13 and IL-4 signals; however, the functional mapping of the intracellular domain of IL-13R alpha 1 is not fully understood. In this study, we constructed wild and mutated types of human IL-13R alpha 1, and analyzed IL-4 and IL-13 signals using an IL-13R alpha 1-transfected human B cell line. Expression of IL-13R alpha 1 evoked STAT3 activation by IL-4 and IL-13, and in stimulated human B cells, on which IL-13R alpha 1 was highly expressed, IL-4 and IL-13 induced STAT3 activation. Replacement of the two tyrosine residues completely abolished STAT3 activation, although replacing either tyrosine residue alone retained it. Furthermore, we found that the Box1 region and the C-terminal tail of IL-13R alpha 1 were critical for binding to Tyk2, and activation of Jak1, Tyk2, the insulin receptor substrate-1 and STAT6 respectively. These results suggest that STAT3 activation is involved with IL-4 and IL-13 signals in human B cells along with the activation of STAT6, and that there is a unique sequence in IL-13R alpha 1 to activate STAT3.

Role of insulin receptor substrate-2 in interleukin-9-dependent proliferation

Interleukin-9 (IL-9) stimulation results in JAK, STAT and IRS1/2 phosphorylation. The role of IRS adaptor proteins in IL-9 signaling is not clear. We show that IL-9 induces IRS2 phosphorylation and association with phosphatidylinositol-3 kinase (PI 3-K) p85 subunit in TS1 cells and BaF/9R cells, which proliferate upon IL-9 stimulation. We observed a PI 3-K-dependent phosphorylation of protein kinase B (PKB) in TS1 cells, but not in BaF/9R, nor in other IL-9-dependent cell lines. Finally, 32D cells that were transfected with the IL-9 receptor but lack IRS expression survived in the presence of IL-9. Ectopic IRS1 expression allowed for IL-9-induced proliferation, in the absence of significant PKB phosphorylation.

Interleukin-9 enhances interleukin-5 receptor expression, differentiation, and survival of human eosinophils

Interleukin-9 (IL-9) has been implicated in the pathogenesis of allergic disorders. To examine the interaction between IL-9 and eosinophils, we evaluated mature peripheral blood eosinophils for their expression of the specific α-subunit of the IL-9 receptor (IL-9R–α). The expression of IL-9R–α by human eosinophils was detected at the messenger RNA (mRNA) and protein levels by reverse transcriptase–polymerase chain reaction (RT-PCR), flow cytometry, and immunocytochemical analysis, respectively. Functional analyses demonstrated that recombinant human (rh)IL-9 inhibited in vitro peripheral blood human eosinophil apoptosis in a concentration-dependent manner. We then examined the role of IL-9 in eosinophil differentiation using the human cord blood CD34+cells and human promyelocytic leukemia cells (HL-60). The addition of IL-9 to CD34+ cells cultured in IL-3 and IL-5 enhanced eosinophil development, and IL-9 alone induced the expression of IL-5R–α. IL-9 also up-regulated the IL-5R–α chain cell surface expression during terminal eosinophil differentiation of the HL-60 cell line. Our findings suggest that IL-9 may potentiate in vivo eosinophil function by increasing their survival and IL-5–mediated differentiation and maturation. Taken together, these results suggest a mechanism by which IL-9 potentiates airway and tissue eosinophilia.

Interleukin-9 enhances interleukin-5 receptor expression, differentiation, and survival of human eosinophils

Interleukin-9 (IL-9) has been implicated in the pathogenesis of allergic disorders. To examine the interaction between IL-9 and eosinophils, we evaluated mature peripheral blood eosinophils for their expression of the specific α-subunit of the IL-9 receptor (IL-9R–α). The expression of IL-9R–α by human eosinophils was detected at the messenger RNA (mRNA) and protein levels by reverse transcriptase–polymerase chain reaction (RT-PCR), flow cytometry, and immunocytochemical analysis, respectively. Functional analyses demonstrated that recombinant human (rh)IL-9 inhibited in vitro peripheral blood human eosinophil apoptosis in a concentration-dependent manner. We then examined the role of IL-9 in eosinophil differentiation using the human cord blood CD34+cells and human promyelocytic leukemia cells (HL-60). The addition of IL-9 to CD34+ cells cultured in IL-3 and IL-5 enhanced eosinophil development, and IL-9 alone induced the expression of IL-5R–α. IL-9 also up-regulated the IL-5R–α chain cell surface expression during terminal eosinophil differentiation of the HL-60 cell line. Our findings suggest that IL-9 may potentiate in vivo eosinophil function by increasing their survival and IL-5–mediated differentiation and maturation. Taken together, these results suggest a mechanism by which IL-9 potentiates airway and tissue eosinophilia.

Placental leucine aminopeptidase/oxytocinase in maternal serum and placenta during normal pregnancy

Placental leucine aminopeptidase (P-LAP), which is identical with cystine aminopeptidase as oxytocinase, was found to be homologous with rat insulin-regulated membrane aminopeptidase (IRAP) by sequence comparison. In the current study, we determined the P-LAP levels in maternal serum and placenta during healthy pregnancy. P-LAP activities in maternal serum increased with gestation and rose to the peak of 80 IU/ml at 38 weeks of gestation. Northern blot analysis revealed the increase of P-LAP mRNA levels in placenta in the third trimester compared to the first trimester. P-LAP protein and related activities could be detected in the conditioned medium of placental tissue, while they could not be detected in that of human umbilical vein endothelial cells. Immunohistochemically P-LAP was positively stained in the apical membrane of syncytiotrophoblast cells throughout the gestation. These results established the normal range of serum and tissue P-LAP levels during pregnancy and the possible source of serum P-LAP, which will be helpful to elucidate the physiological and clinical roles of P-LAP/oxytocinase/IRAP.

Association of insulin receptor substrate proteins with Bcl-2 and their effects on its phosphorylation and antiapoptotic function

Insulin receptor substrate (IRS) proteins are docking proteins that couple growth factor receptors to various effector molecules, including phosphoinositide-3 kinase, Grb-2, Syp, and Nck. Here we show that IRS-1 associates with the loop domain of Bcl-2 and synergistically up-regulates antiapoptotic function of Bcl-2. IRS-2 but not IRS-3 binds to Bcl-2, and IRS-1 associates with Bcl-XL but not with Bax or Bik. Overexpression of IRS-1 suppresses phosphorylation of Bcl-2 induced by stimulation with insulin, and the hypophosphorylation may lead to its enhanced antiapoptotic activity. The binding site for Bcl-2 is located on the carboxyl half-domain of IRS-1. IRS-3, which lacks the corresponding region, dominant-negatively abrogates the survival effects of IRS-1 and Bcl-2. For the antiapoptotic activity of IRS-1, binding to Bcl-2 is more critical than activating phosphoinositide-3 kinase. Our results indicate that IRS proteins transmit signals from the insulin receptor to Bcl-2, thus regulating cell survival probably through regulating phosphorylation of Bcl-2.

Biologic functions and signaling of the interleukin-4 receptor complexes

IL-4 is a pleiotropic cytokine which plays a pivotal role in shaping immune responses. The effects of IL-4 are mediated after binding to high affinity receptor complexes present on hematopoietic as well as non-hematopoietic cells. This review will summarize the current knowledge on the molecular structure of the different types of IL-4 receptor (IL-4R) complexes as well as the signal transduction mechanisms induced by IL-4 leading to cellular proliferation and / or gene activation. IL-4 effects are modulated by soluble forms of the respective receptor molecules which are produced by several immune cells in a regulated manner. The biological impact of recently described IL-4R allotypes of mice and humans as well as the results of studies with IL-4R knockout mice will be particularly emphasized.

Signaling pathways mediating insulin-stimulated glucose transport

A major action of insulin is to accelerate the rate of uptake of sugar into muscle and adipose cells following a meal. The biochemical mechanism by which this is accomplished has been a subject of intense experimentation, although elucidation of the pathways has remained elusive. In recent years, numerous signaling molecules and cascades modulated by insulin have been identified, although few have been definitively established as important to the metabolic actions of the hormone. An exception to this is the lipid kinase phosphatidylinositide 3'-kinase, which, under many conditions, appears absolutely required for insulin to stimulate hexose uptake into adipocytes. Akt/PKB, a serine/threonine protein kinase activated by insulin in a phosphatidylinositide 3'-kinase-dependent manner, has been implicated as a critical mediator of insulin's actions on metabolism and cell survival. Nonetheless, Akt/PKB's role in many insulin effects, particularly accelerated glucose transport, remains controversial. Interestingly, soluble analogues of ceramide antagonize both insulin's activation of Akt/PKB as well as its stimulation of glucose transport, consistent with a causal relationship between the two.