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Y Yarden

Publications and source records attributed to Y Yarden.

At least 91 records · Page 5Linked to original sources
PubMed1994

Convergence of signaling by interleukin-3, granulocyte-macrophage colony-stimulating factor, and mast cell growth factor on JAK2 tyrosine kinase.

Mast cell growth factor (MGF) (also called stem cell factor) synergizes with several lymphokines, including interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF), to promote proliferation and differentiation of certain hemopoietic progenitor cells. Although similar patterns of tyrosine-phosphorylated proteins characterize cells stimulated by MGF, IL-3, and GM-CSF, only the MGF receptor is a tyrosine kinase, and the heterodimeric receptors for IL-3 and GM-CSF share a common beta subunit that is devoid of enzymatic activity. Here we show that signaling pathways utilized by all three cytokines include the cytoplasmic tyrosine kinase JAK2. Analysis of several factor-dependent myeloid cell lines indicated that JAK2 is physically associated with the common beta subunit and with MGF receptor (c-Kit) even prior to ligand binding. However, each of the ligands induced elevated tyrosine phosphorylation of JAK2 and a consequent increase in its catalytic activity. These results demonstrate for the first time the convergence within the same myeloid cells of signaling pathways originating in two distinct lymphokine receptors and a tyrosine kinase receptor on activation of a cytoplasmic tyrosine kinase.

Amino Acid Sequence↗
PubMed1994

Brain neurons and glial cells express Neu differentiation factor/heregulin: a survival factor for astrocytes.

Neu differentiation factor (NDF, also called heregulin) was isolated from mesenchymal cells on the basis of its ability to elevate phosphorylation of ErbB proteins. Earlier in situ hybridization analysis showed that NDF was transcribed predominantly in the central nervous system during embryonic development. To gain insights into the role of NDF in brain we analyzed its distribution by immunohistochemistry and in situ hybridization. Late-gestation (day 17) rat embryos displayed high NDF immunoreactivity in both motor (e.g., putamen) and limbic (e.g., septum) regions. Lower levels of the factor were exhibited by adult brain, except for the cerebellum, where NDF expression was increased postnatally. Both neurons and glial cells were identified by immunohistochemistry as NDF-producing cells (e.g., pyramidal neurons in the cerebral cortex and glial cells in the corpus callosum). By establishment of primary cultures of rat brain cells we confirmed that NDF was expressed in neurons as well as in astrocytes. In addition, by using such primary cultures we observed that NDF treatment exerted only a limited mitogenic effect, which was accompanied by significant acceleration of astrocyte maturation. Furthermore, long-term incubation with the factor specifically protected astrocytes from apoptosis, implying that NDF functions in brain as a survival and maturation factor for astrocytes.

Animals↗
PubMed1994

A single autophosphorylation site confers oncogenicity to the Neu/ErbB-2 receptor and enables coupling to the MAP kinase pathway.

The transforming potential of the Neu/ErbB-2 receptor tyrosine kinase undergoes inactivation by deletion of the non-catalytic C-terminal tail, which contains five autophosphorylation sites. To determine which site is essential for oncogenicity, we tailed the C-terminally-deleted mutant with individual autophosphorylation sites. Complete restoration of the transforming action in vitro and in vivo was conferred by a stretch of 12 amino acids that contained the most C-terminal tyrosine autophosphorylation site (Y1253). Reconstitution of transformation was specific to this amino acid sequence because none of the other autophosphorylation sites, when grafted individually, caused transformation, and replacement of the tyrosine with a phenylalanine residue significantly reduced the oncogenic potential of both the full-length and the tailed proteins. When present alone the most C-terminal sequence enabled coupling to a biochemical pathway that includes Ras, MAP kinase and transactivation of Jun. These results indicate that the multiplicity of autophosphorylation sites on a receptor tyrosine kinase is not essential for transformability, and implicate the MAP kinase pathway in transduction of the oncogenic signal of Neu/ErbB-2.

Animals↗
PubMed1994

The Heregulin gene can be included in the 8p12 amplification unit in human breast cancer.

The Heregulin (HGL) gene, encoding a ligand for a member of the ERBB receptor family, is located at 8p12-p22, in or close to a region frequently amplified in breast carcinoma. Amplification of HGL was detected in three of 83 (3.6%) cases of breast tumors. No overexpression of the gene was observed in the amplified tumors. This and the low incidence of amplification suggest that HGL is not the key gene of the 8p12 amplification but may be used as a marker of large amplification units.

Breast Neoplasms↗
PubMed1994

Steel factor and c-kit protooncogene: genetic lessons in signal transduction.

Despite extensive research on the molecular mechanisms of signal transduction by growth factors and their oncogenic receptor tyrosine kinases, the physiological relevance of these pathways, especially in mammals, remains largely unknown. A unique exception is the Steel factor (SLF) and its c-kit-encoded receptor, because many natural germ line mutations of both the ligand and the receptor exist in mice. The protooncogene c-kit encodes a cell surface receptor that belongs to the immunoglobulin gene family and carries an intrinsic tyrosine kinase activity in its cytoplasmic portion. The precursor of the Kit ligand, SLF, is also a transmembrane protein that exists as a soluble factor as well as a cell surface protein. The interaction of Kit with SLF leads to receptor dimerization, kinase activation, and tyrosine phosphorylation of cytoplasmic proteins that contain Src homology 2 motifs. Various mutations in Kit and SLF result in a defective signaling pathway and underly the complex phenotypes of W and Sl mice, respectively. The early development of at least four cell lineages is affected. These are erythrocytes, melanocytes, germ cells, and mast cells. Correlation between the behavior of these lineages and specific mutations uncovered interesting physiological aspects of the mechanism of signal transduction by a polypeptide growth factor. These include the different degrees of severity of affected lineages, indications for distinct functions during early embryonic development and at late phases, the significance of synergy between a growth factor and lymphokines, the interaction between mutant and wild-type proteins in heterozygous animals, and the possibility that a surface-anchored ligand may act differently than a soluble factor. Predictably, the lessons learned with Kit and Sl mice will be widely relevant to other pairs of ligands and receptors that control the function of different cell lineages and physiological processes.

Animals↗
PubMed1994

Neu differentiation factors: a family of alternatively spliced neuronal and mesenchymal factors.

The Neu proto-oncogene (also called ErbB-2 and HER-2) encodes a tyrosine kinase transmembrane receptor homologous to the epidermal growth factor receptor (EGF-R). Overexpression, a point-mutation, and co-expression with EGF-R activate the oncogenic potential of the Neu protein by permanent coupling to signal transducing pathways. The search for ligands that elevate tyrosine phosphorylation of Neu led to the discovery of a 44-kDa glycoprotein that acts either as a differentiation factor or as a mitogen for mammary tumor cells. This protein, termed Neu differentiation factor (NDF), is derived from a transmembrane precursor that contains an EGF-like motif and an immunoglobulin-like domain. Alternative splicing generates a dozen NDF-related proteins that are expressed in a variety of mesenchymal and neuronal tissues. This unprecedented multiplicity raises the possibility that different isoforms fulfill distinct biological roles.

Alternative Splicing↗
PubMed1994

Protein kinase C-dependent release of a functional whole extracellular domain of the mast cell growth factor (MGF) receptor by MGF-dependent human myeloid cells.

The mast cell growth factor (MGF) affects migration, proliferation and differentiation of erythroid and myeloid progenitor cells by binding to a transmembrane receptor tyrosine kinase encoded by the c-Kit proto-oncogene. By using MGF-dependent human myeloid cell lines (M-07e and TF-1), here we show that a Kit-related 100 kDa protein is associated with the cell but it undergoes release into the medium upon treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C. Immunological analysis with a series of antibodies to Kit indicated that the released protein (p100Kit) contains the whole glycosylated extracellular portion of the transmembrane Kit protein (p145Kit). The secreted protein retained the ability to specifically bind MGF. Moreover, p100Kit was able to block the mitogenic effect of MGF on cultured M-07e cells, suggesting that the soluble protein may function as a physiological antagonist of MGF.

Animals↗
PubMed1994

Expression of the erbB-2 family of growth factor receptors and their ligands in breast cancers. Implication for tumor biology and clinical behavior.

Transmembrane receptor tyrosine kinases that bind to growth factors transmit signals that are essential to growth and differentiation. These receptors can be classified into groups based on their structure. One group implicated in the pathogenesis of breast cancer contains receptors belonging to the erbB family. This group includes the epidermal growth factor receptors, the HER-2/neu (erbB-2), HER-3, and HER-4. Despite the structural similarity of these receptors, HER-2/neu, HER-4, and HER-3 do not bind to any ligand of the epidermal growth factor receptor. However, a 44-kD glycoprotein called neu differentiation factor (neu differentiation factor/heregulin) has been isolated. This ligand phosphorylates the HER-2/neu receptor and binds directly to HER-4 and HER-3. The abundance of erbB receptors and their ligands in breast cancers points to their functional importance in the pathogenesis and biological behavior of breast cancers. Furthermore, these receptors and ligands may hold a promise for targeted therapy for breast cancer in the future.

Breast Neoplasms↗
PubMed1994

Medullary carcinoma is associated with expression of intercellular adhesion molecule-1. Implication to its morphology and its clinical behavior.

The histological hallmarks for the diagnosis of medullary breast cancer are circumscription, syncytial architecture, diffuse inflammatory infiltrate, and highly atypical nuclei. The biological and prognostic implication is a lower propensity to metastasize. We studied 19 medullary carcinomas for expression of the intercellular adhesion molecule-1 and lymphocyte-function-associated antigen-1, Neu differentiation factor, tumor necrosis factor-alpha, and the expression of HER-2/neu, HER-4, and HER-3 receptors. Our study revealed that all of the 19 medullary carcinomas expressed the intercellular adhesion molecule-1 and lymphocyte function associated antigen. Eighteen of 19 cancers expressed Neu differentiation factor and tumor necrosis factor-alpha. All medullary cancers expressed the HER-2/neu receptor, however, in the majority of the cases, the staining was confined to the cytoplasm. Only 4 of 12 cancers expressed HER-4 and none of the eight medullary cancers tested expressed HER-3. By comparison, in a control group of infiltrating ductal carcinomas, expression of intercellular adhesion molecule-1, lymphocyte function associated antigen-1, and Neu differentiation factor was positive in about 25 to 30% of the cases, HER-4 was expressed in 75% and HER-3 in 95% of the cases. Taken together, our observations suggest that the expression of intercellular adhesion molecule-1, lymphocyte function associated antigen, Neu differentiation factor, and tumor necrosis factor-alpha as factors that may affect the special morphology and the biological behavior that characterizes medullary carcinomas.

Breast Neoplasms↗
PubMed1993

Targeting of T lymphocytes to Neu/HER2-expressing cells using chimeric single chain Fv receptors.

Cell surface molecules essential for the transformed phenotype or growth of malignant cells are attractive targets for anticancer immunotherapy. Antibodies specific to Neu/HER2, a human adenocarcinoma-associated growth factor receptor, were demonstrated to have tumor-inhibitory capacity. Yet, the inefficient accessibility of antibodies to solid tumors limits their clinical use. To redirect effector lymphocytes to adenocarcinomas, we constructed and functionally expressed in T cells chimeric single chain receptor genes incorporating both the Ag-binding domain of anti-Neu/HER2 antibodies and the zeta-signal-transducing subunit of the TCR/CD3 complex or the gamma-signal-transducing subunit of the Ig Fc receptor complex. Surface expression of the anti-Neu/HER2 chimeric genes in cytotoxic T cell hybridomas endowed them with specific Neu/HER2 recognition enabling their activation for IL-2 production and lysis of transformed cells overexpressing Neu/HER2. These chimeric genes hold promise for the immunotherapy of cancer.

Animals↗
PubMed1993

Neural expression and chromosomal mapping of Neu differentiation factor to 8p12-p21.

Neu differentiation factor (NDF/heregulin) is a 44-kDa glycoprotein that interacts with the Neu/ErbB-2 receptor tyrosine kinase to increase its phosphorylation on tyrosine residues. In vitro NDF promotes differentiation of certain mammary tumor cell lines to milk-producing cells. As a first step toward understanding the physiological role of NDF, we performed in situ hybridization analyses to determine mRNA distribution in the mouse embryo and to map the gene to human karyotypes. In 14.5-day-postcoitum mouse embryos, NDF expression is confined predominantly to the central and peripheral nervous system, including the neuroepithelium that lines the lateral ventricles of the brain, the ventral horn of the spinal cord, and the intestinal as well as dorsal root ganglia. Other tissues that contain NDF transcripts are the adrenal gland, liver, and distinct cell layers of the dermis and germinal ridge. In situ hybridization of a 3H-labeled probe to human metaphase spreads localized the NDF gene to the short arm of chromosome 8 at bands p12-p21.

Animals↗
PubMed1993

Soluble c-kit proteins and antireceptor monoclonal antibodies confine the binding site of the stem cell factor.

The binding of the stem cell factor (SCF) to the c-kit-encoded receptor tyrosine kinase stimulates a variety of biochemical responses that culminate in cellular proliferation, migration, or survival. The extracellular domain of p145kit consists of five immunoglobulin-like domains. To confine the ligand binding site to this portion of the receptor we generated a panel of murine monoclonal antibodies (mAbs) to the Kit protein and identified two mAbs that efficiently displaced receptor-bound SCF and also inhibited proliferation of SCF-dependent human megakaryocytes. To map the epitopes of these mAbs we constructed and expressed soluble portions of the extracellular domain of Kit, which included either the two amino-terminal Ig-like domains (denoted Kit 1-2), three Ig-like domains (Kit 1-2-3), or the entire extracellular portion (Kit-X). All three recombinant proteins were recognized by the ligand inhibitory mAbs, suggesting that the SCF binding site resides in the amino-terminal half of the ecto-domain. Consistent with this conclusion, all of the soluble proteins inhibited SCF binding to Kit-expressing cells, and they also underwent specific covalent cross-linking to the radiolabeled ligand. However, whereas Kit 1-2-3 and Kit-X displayed comparable ligand affinities, deletion of the third Ig-like domain, in Kit 1-2, involved significant reduction in SCF binding. Hence, the binding site of SCF probably includes Ig-like domains 1 and 2, but structural determinants distal to this portion may also participate in ligand recognition.

Animals↗
PubMed1993

Neu and its ligands: from an oncogene to neural factors.

Transmembrane receptor tyrosine kinases that bind to peptide factors transmit essential growth and differentiation signals. A growing list of orphan receptors, of which some are oncogenic, holds the promise that many unknown ligands may be discovered by tracking the corresponding surface molecules. The neu gene (also called erbB-2 and HER-2) encodes such a receptor tyrosine kinase whose oncogenic potential is released in the developing rodent nervous system through a point mutation. Amplification and overexpression of neu are thought to contribute to malignancy of certain human adenocarcinomas. The search for soluble factors that interact with the Neu receptor led to the discovery of a 44 kDa glycoprotein that induces phenotypic differentiation of cultured mammary tumor cells to growth-arrested and milk-producing cells. The Neu differentiation factor (NDF or heregulin), however, also acts as a mitogen for epithelial, Schwann and glial cells. Multiple forms of the factor are produced by alternative splicing and their expression is confined predominantly to the central and to the peripheral nervous systems. One identified neuronal function of this family of polypeptides is to control the formation of neuromuscular junctions, but their physiological role in secretory epithelia is still unknown. Other open questions relate to the transmembrane topology of various precursors, the identity of a putative coreceptor, the possible existence of additional ligands of Neu and the functional significance of the interaction between Neu and at least three highly related receptor tyrosine kinases.

Amino Acid Sequence↗
PubMed1993

Cell-type specific interaction of Neu differentiation factor (NDF/heregulin) with Neu/HER-2 suggests complex ligand-receptor relationships.

The Neu/HER-2 receptor tyrosine kinase is overexpressed in some types of human adenocarcinomas, including tumors of the breast and the ovary. A 44 kDa glycoprotein that elevates tyrosine phosphorylation of Neu has been isolated and named Neu differentiation factor (NDF), or heregulin. Here we show that NDF affects tyrosine phosphorylation of Neu in human tumor cells of breast, colon and neuronal origin, but not in ovarian cells that overexpress the receptor. By using monoclonal antibodies (mAbs) to Neu, we found that the ovarian receptor is immunologically and biochemically similar to the mammary p185neu. Nevertheless, unlike breast-derived Neu, the ovarian protein did not display covalent cross-linking to radiolabeled NDF, and was devoid of ligand-induced association with phosphatidylinositol 3'-kinase. Direct binding analysis showed that NDF binds with high affinity (Kd approximately 10(-9) M) to mammary cells, but its weak association with ovarian cells is probably mediated by heparin-like molecules. Similar to the endogenous receptor, the ectopically overexpressed Neu of mammary cells, but not of ovarian and fibroblastic cells, exhibited elevated levels of NDF-induced phosphorylation and covalent cross-linking of the radiolabeled factor. Taken together, our results imply that NDF binding to cells requires both Neu and an additional cellular component, whose identity is still unknown, but its tissue distribution is more restricted than the expression of the neu gene.

Animals↗
PubMed1993

Structure-function analyses of the kit receptor for the steel factor.

Binding of the Steel factor (SLF) to the product of the c-kit proto-oncogene stimulates the receptor's intrinsic tyrosine kinase that phosphorylates a set of cytoplasmic signaling molecules. Germ-line mutations in the genes that encode the receptor or the ligand result in remarkably similar phenotypes that affect melanogenesis, erythropoiesis and gametogenesis in mice. We concentrated on the initial events of the signal transduction pathway that underlies these processes. The extracellular portion of Kit is comprised of five immunoglobulin-(Ig)-like domains. Ligand binding to this domain induces rapid and extensive dimerization of the receptor molecules in a mechanism that involves monovalent binding of the dimeric ligand, followed by an increase in receptors' affinity and gradual stabilization of the dimers. It thus appears that Kit has at least two functions: ligand binding and ligand-induced receptor dimerization, in addition to the kinase activity. Both functions are independent of the transmembrane and cytoplasmic domains, as a recombinant soluble ectodomain retained high affinity to SLF and ligand-dependent dimerization. In order to correlate these functions with specific structures, we employed ligand-competitive monoclonal antibodies, soluble deletion mutants of the ectodomain and chimeric human-mouse Kit proteins. These approaches indicated that the N-terminal three Ig-like domains constitute the binding site, whose core is the second domain. Further experiments suggested that a putative dimerization site is distinct from the binding cleft and may be located on the fourth Ig-like domain.

Animals↗
PubMed1993

Interspecies molecular chimeras of kit help define the binding site of the stem cell factor.

The extracellular portion of the kit-encoded receptor for the stem cell factor (SCF) comprises five immunoglobulin (Ig)-like domains. To localize the ligand recognition site, we exploited the lack of binding of human SCF to the murine receptor by using human-mouse hybrids of Kit and species-specific monoclonal antibodies (MAbs) that inhibit ligand binding. Replacement of the three N-terminal Ig-like domains of the murine Kit with the corresponding portion of the human receptor conferred upon the chimeric receptor high-affinity binding of the human ligand as well as of human-specific ligand-inhibitory MAbs. By constructing five chimeric murine Kit proteins which individually contain each of these three human Ig-like units or pairs of them, we found that the second human domain confers upon the mouse Kit high-affinity binding of the human ligand and also binding of species-specific SCF-competitive MAbs. Nevertheless, the flanking Ig-like domains also affect high-affinity recognition of SCF. Moreover, it appears that the determinants that define ligand specificity of the murine and the human receptors do not structurally coincide. This observation allowed us to identify a chimeric receptor that displayed a dual specificity; namely, it bound with high affinity either the human or the murine SCF molecules and reacted with mouse- as well as human-specific ligand-inhibitory MAbs. Conversely, another chimera, which included all of the five Ig-like domains, bound neither ligand. In conclusion, interdomain packing involving the second Ig-like domain of human Kit and noncontiguous structural motifs of the receptor are involved in SCF recognition.

Animals↗