Sidney Pestka

Interferons, interferon-like cytokines, and their receptors

Summary:  Recombinant interferon‐α (IFN‐α) was approved by regulatory agencies in many countries in 1986. As the first biotherapeutic approved, IFN‐α paved the way for the development of many other cytokines and growth factors. Nevertheless, understanding the functions of the multitude of human IFNs and IFN‐like cytokines has just touched the surface. This review summarizes the history of the purification of human IFNs and the key aspects of our current state of knowledge of human IFN genes, proteins, and receptors. All the known IFNs and IFN‐like cytokines are described [IFN‐α, IFN‐β, IFN‐ε, IFN‐κ, IFN‐ω, IFN‐δ, IFN‐τ, IFN‐γ, limitin, interleukin‐28A (IL‐28A), IL‐28B, and IL‐29] as well as their receptors and signal transduction pathways. The biological activities and clinical applications of the proteins are discussed. An extensive section on the evolution of these molecules provides some new insights into the development of these proteins as major elements of innate immunity. The overall structure of the IFNs is put into perspective in relation to their receptors and functions.

Identification and functional characterization of a second chain of the interleukin-10 receptor complex.

Interleukin‐10 (IL‐10) is a pleiotropic cytokine which signals through a specific cell surface receptor complex. Only one chain, that for ligand binding (IL‐10Rα or IL‐10R1), was identified previously. We report here that, although human IL‐10 binds to the human IL‐10R1 chain expressed in hamster cells, it does not induce signal transduction. However, the co‐expression of CRFB4, a transmembrane protein of previously unknown function belonging to the class II cytokine receptor family, together with the IL‐10R1 chain renders hamster cells sensitive to IL‐10. The IL‐10:CRFB4 complex was detected by cross‐linking to labeled IL‐10. In addition, the IL‐10R1 chain was able to be co‐immunoprecipitated with anti‐CRF antibody when peripheral blood mononuclear cells were treated with IL‐10. These results demonstrate that the CRFB4 chain is part of the IL‐10 receptor signaling complex. Thus, the CRFB4 chain, which we designate as the IL‐10R2 or IL‐10Rβ chain, serves as an accessory chain essential for the active IL‐10 receptor complex and to initiate IL‐10‐induced signal transduction events.

Tumor Cell Responses to IFNγ Affect Tumorigenicity and Response to IL-12 Therapy and Antiangiogenesis

Expression of a dominant negative mutant IFNgammaR1 in murine SCK and K1735 tumor cells rendered them relatively unresponsive to IFNgamma in vitro and more tumorigenic and less responsive to IL-12 therapy in vivo. IL-12 induced histologic evidence of ischemic damage only in IFNgamma-responsive tumors, and in vivo Matrigel vascularization assays revealed that while IFNgamma-responsive and -unresponsive tumor cells induced angiogenesis equally well, IL-12 and its downstream mediator IFNgamma only inhibited angiogenesis induced by the responsive cells. IL-12 induced angiogenesis inhibitory activity in the responsive cells, which may be attributable to production of the chemokine IP-10. Thus, IL-12 and IFNgamma inhibit tumor growth by inducing tumor cells to generate antiangiogenic activity.

The Interferons: 50 Years after Their Discovery, There Is Much More to Learn

The interferons (IFNs) and their receptors represent a subset of the class 2 α-helical cytokines that have been in chordates for millions of years. This brief review focuses on the discovery and purification of interferons, cloning of human IFN-α and IFN-β, interferon receptors, activities and therapeutic uses of interferons, and the side effects of interferons.

Identification and sequence of an accessory factor required for activation of the human interferon γ receptor

Abstract Human chromosomes 6 and 21 are both necessary to confer sensitivity to human interferon γ (Hu-IFN-γ), as measured by induction of class I human leukocyte antigen (HLA) and protection against encephalomyocarditis virus (EMCV) infection. Whereas human chromosome 6 encodes the Hu-IFN-γ receptor, human chromosome 21 encodes accessory factors for generating biological activity through the Hu-IFN-γ receptor. Probes from a genomic clone were used to identity cDNA clones expressing a species-specific accessory factor. These cDNA clones are able to substitute for human chromosome 21 to reconstitute the Hu-IFN-γ receptor-mediated induction of class I HLA antigens. However, the factor encoded by the cDNA does not confer full antiviral protection against EMCV, confirming that an additional factor encoded on human chromosome 21 is required for reconstitution of antiviral activity against EMCV. We conclude that this accessory factor belongs to a family of such accessory factors responsible for different actions of IFN-γ.

Cloning, expression and initial characterisation of interleukin-19 (IL-19), a novel homologue of human interleukin-10 (IL-10)

Interleukin-10 (IL-10) is a pleiotropic cytokine with important immunoregulatory functions whose actions influence activities of many of the cell-types in the immune system. We report here identification and cloning of a gene and corresponding cDNAs encoding a novel homologue of IL-10, designated IL-19. IL-19 shares 21% amino acid identity with IL-10. The exon/intron structure of IL-19 is similar to that of the human IL-10 gene, comprising five exons and four introns within the coding region of the IL-19 cDNA. There are at least two distinct IL-19 mRNA species that differ in their 5′-sequences, suggesting the existence of an intron in the 5′-sequences of coding portion of the IL-19 gene. The longer 5′-sequence contains an alternative initiating ATG codon that is in-frame with the rest of the coding sequence. The expression of IL-19 mRNA can be induced in monocytes by LPS-treatment. The appearance of IL-19 mRNA in LPS-stimulated monocytes was slightly delayed compared to expression of IL-10 mRNA: significant levels of IL-10 mRNA were detectable at 2 h post-stimulation, whereas IL-19 mRNA was not detectable until 4 h. Treatment of monocytes with IL-4 or IL-13 did not induce de novo expression of IL-19, but these cytokines did potentiate IL-19 gene expression in LPS-stimulated monocytes. In addition, GM-CSF was capable of directly inducing IL-19 gene expression in monocytes. IL-19 does not bind or signal through the canonical IL-10 receptor complex, suggesting existence of an IL-19 specific receptor complex, the identity of which remains to be discovered.

The human homologue of the yeast proteins Skb1 and Hsl7p interacts with Jak kinases and contains protein methyltransferase activity.

To expand our understanding of the role of Jak2 in cellular signaling, we used the yeast two-hybrid system to identify Jak2-interacting proteins. One of the clones identified represents a human homologue of the Schizosaccaromyces pombe Shk1 kinase-binding protein 1, Skb1, and the protein encoded by theSaccharomyces cerevisiae HSL7 (histone synthetic lethal 7) gene. Since no functional motifs or biochemical activities for this protein or its homologues had been reported, we sought to determine a biochemical function for this human protein. We demonstrate that this protein is a protein methyltransferase. This protein, designated JBP1 (Jak-binding protein 1), and its homologues contain motifs conserved among protein methyltransferases. JBP1 can be cross-linked to radiolabeled S-adenosylmethionine (AdoMet) and methylates histones (H2A and H4) and myelin basic protein. Mutants containing substitutions within a conserved region likely to be involved in AdoMet binding exhibit little or no activity. We mapped the JBP1 gene to chromosome 14q11.2–21. In addition, JBP1 co-immunoprecipitates with several other proteins, which serve as methyl group acceptors and which may represent physiological targets of this methyltransferase. Messenger RNA for JBP1 is widely expressed in human tissues. We have also identified and sequenced a homologue of JBP1 in Drosophila melanogaster. This report provides a clue to the biochemical function for this conserved protein and suggests that protein methyltransferases may have a role in cellular signaling.

Identification, Cloning, and Characterization of a Novel Soluble Receptor That Binds IL-22 and Neutralizes Its Activity

With the use of a partial sequence of the human genome, we identified a gene encoding a novel soluble receptor belonging to the class II cytokine receptor family. This gene is positioned on chromosome 6 in the vicinity of the IFNGR1 gene in a head-to-tail orientation. The gene consists of six exons and encodes a 231-aa protein with a 21-aa leader sequence. The secreted mature protein demonstrates 34% amino acid identity to the extracellular domain of the IL-22R1 chain. Cross-linking experiments demonstrate that the protein binds IL-22 and prevents binding of IL-22 to the functional cell surface IL-22R complex, which consists of two subunits, the IL-22R1 and the IL-10R2c chains. Moreover, this soluble receptor, designated IL-22-binding protein (BP), is capable of neutralizing IL-22 activity. In the presence of the IL-22BP, IL-22 is unable to induce Stat activation in IL-22-responsive human lung carcinoma A549 cells. IL-22BP also blocked induction of the suppressors of cytokine signaling-3 (SOCS-3) gene expression by IL-22 in HepG2 cells. To further evaluate IL-22BP action, we used hamster cells expressing a modified IL-22R complex consisting of the intact IL-10R2c and the chimeric IL-22R1/γR1 receptor in which the IL-22R1 intracellular domain was replaced with the IFN-γR1 intracellular domain. In these cells, IL-22 activates biological activities specific for IFN-γ, such as up-regulation of MHC class I Ag expression. The addition of IL-22BP neutralizes the ability of IL-22 to induce Stat activation and MHC class I Ag expression in these cells. Thus, the soluble receptor designated IL-22BP inhibits IL-22 activity by binding IL-22 and blocking its interaction with the cell surface IL-22R complex.

Jak-Stat signal transduction pathway through the eyes of cytokine class II receptor complexes

Cells of the immune system communicate with each other to initiate, establish and maintain immune responses. The communication occurs through cell-to-cell contact or through a variety of intercellular mediators that include cytokines, chemokines, growth factors and hormones. In the case of cytokines, the signal is transmitted from the outside to the inside of a cell through cell surface receptors specific for each cytokine. At this step the signal is also decoded and amplified: ligand binding causes recruitment and/or activation of numerous cytoplasmic proteins. One cytokine can activate a number of signal transduction pathways leading to regulation of a wide array of biological activities. One of these pathways, the Jak-Stat pathway, is briefly reviewed here with respect to the class II cytokine receptors. Signal transduction through receptors for interferons Type I (IFN-α, IFN-β, IFN-ω) and Type II (IFN-γ), and interleukin 10 (IL-10) is described in detail. In addition, a complex between tissue factor (TF) and coagulation factor VIIa, and two new receptors related to the class II cytokine receptor family are discussed.

Genomic structure, chromosomal localization and expression profile of a novel melanoma differentiation associated ( mda -7) gene with cancer specific growth suppressing and apoptosis inducing properties

Abnormalities in cellular differentiation are frequent occurrences in human cancers. Treatment of human melanoma cells with recombinant fibroblast interferon (IFN-β) and the protein kinase C activator mezerein (MEZ) results in an irreversible loss in growth potential, suppression of tumorigenic properties and induction of terminal cell differentiation. Subtraction hybridization identified melanoma differentiation associated gene-7 (mda-7), as a gene induced during these physiological changes in human melanoma cells. Ectopic expression of mda-7 by means of a replication defective adenovirus results in growth suppression and induction of apoptosis in a broad spectrum of additional cancers, including melanoma, glioblastoma multiforme, osteosarcoma and carcinomas of the breast, cervix, colon, lung, nasopharynx and prostate. In contrast, no apparent harmful effects occur when mda-7 is expressed in normal epithelial or fibroblast cells. Human clones of mda-7 were isolated and its organization resolved in terms of intron/exon structure and chromosomal localization. Hu-mda-7 encompasses seven exons and six introns and encodes a protein with a predicted size of 23.8 kDa, consisting of 206 amino acids. Hu-mda-7 mRNA is stably expressed in the thymus, spleen and peripheral blood leukocytes. De novo mda-7 mRNA expression is also detected in human melanocytes and expression is inducible in cells of melanocyte/melanoma lineage and in certain normal and cancer cell types following treatment with a combination of IFN-β plus MEZ. Mda-7 expression is also induced during megakaryocyte differentiation induced in human hematopoietic cells by treatment with TPA (12-O-tetradecanoyl phorbol-13-acetate). In contrast, de novo expression of mda-7 is not detected nor is it inducible by IFN-β+MEZ in a spectrum of additional normal and cancer cells. No correlation was observed between induction of mda-7 mRNA expression and growth suppression following treatment with IFN-β+MEZ and induction of endogenous mda-7 mRNA by combination treatment did not result in significant intracellular MDA-7 protein. Radiation hybrid mapping assigned the mda-7 gene to human chromosome 1q, at 1q 32.2 to 1q41, an area containing a cluster of genes associated with the IL-10 family of cytokines. Mda-7 represents a differentiation, growth and apoptosis associated gene with potential utility for the gene-based therapy of diverse human cancers.