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L F Parada

Publications and source records attributed to L F Parada.

At least 91 records · Page 5Linked to original sources
PubMed1991

High-affinity NGF binding requires coexpression of the trk proto-oncogene and the low-affinity NGF receptor.

Nerve growth factor (NGF) interacts with two different low-affinity receptors that can be distinguished by affinity crosslinking. Reconstitution experiments by membrane fusion and transient transfection into heterologous cells indicate that high-affinity NGF binding requires coexpression and binding to both the low-affinity NGF receptor and the tyrosine kinase trk gene product. These studies reveal a new growth factor receptor-mediated mechanism of cellular differentiation involving trk and the low-affinity NGF receptor.

Animals↗
PubMed1991

Tyrosine phosphorylation and tyrosine kinase activity of the trk proto-oncogene product induced by NGF.

Nerve growth factor (NGF) is a neurotrophic factor responsible for the differentiation and survival of sympathetic and sensory neurons as well as selective populations of cholinergic neurons. NGF binds to specific cell-surface receptors but the mechanism for transduction of the neurotrophic signal is unknown. Several experiments using the NGF-responsive pheochromocytoma cell line, PC12, have implicated tyrosine phosphorylation in NGF-mediated responses, although no NGF-specific tyrosine kinases have been identified. Here we show that NGF induces tyrosine phosphorylation and tyrosine kinase activity of the trk proto-oncogene product, a tyrosine kinase receptor whose expression is restricted in vivo to neurons of the sensory spinal and cranial ganglia of neural crest origin. Tyrosine phosphorylation of trk by NGF is rapid, specific and occurs with picomolar quantities of factor, indicating that the response is mediated by physiological amounts of NGF. Activation of the trk tyrosine kinase receptor provides a possible mechanism for signal transduction by NGF.

Blotting, Northern↗
PubMed1991

Embryonic RNA expression patterns of the c-kit receptor and its cognate ligand suggest multiple functional roles in mouse development.

Mutations at the dominant white spotting (W) and Steel (Sl) loci in mouse exert deleterious effects on three migratory cell lineages (primordial germ cells, melanocytes and hematopoietic stem cells) resulting in loss of pigmentation, reduced fertility and anemia. The W locus encodes the c-kit protein tyrosine kinase (TK) receptor. More recently, the Sl locus has been shown to encode a ligand for c-kit, which is variously known as mast cell growth factor (MGF), stem cell growth factor and c-kit ligand. Here we report an in situ hybridization analysis comparing the expression profiles of MGF and c-kit transcripts during mouse embryogenesis. The data are consistent with the c-kit receptor-ligand complex providing a homing mechanism during stem cell migration in early development and in stem cell proliferation, differentiation, or survival in late development. In the nervous system, an unexpected and complex pattern of expression is uncovered that suggests involvement of the W and Sl gene products in the organization of the neural tube and brain.

Animals↗
PubMed1990

The trkB tyrosine protein kinase gene codes for a second neurogenic receptor that lacks the catalytic kinase domain.

We previously identified two tyrosine protein kinase genes, designated trk and trkB, that code for putative neurogenic cell surface receptors. In this study, we report that the mouse trkB locus codes for at least two classes of receptor-like molecules. These trkB proteins, designated gp145trkB and gp95trkB, have identical extracellular and transmembrane domains, suggesting that they might recognize the same ligand(s). However, only gp145trkB contains a long cytoplasmic region, which includes a catalytic tyrosine protein kinase domain. trkB transcripts coding for this protein were observed in the cerebral cortex and the pyramidal cell layer of the hippocampus. In contrast, transcripts coding for the noncatalytic gp95trkB molecule were found in the ependymal linings of the cerebral ventricles and in the choroid plexus. These results illustrate that a tyrosine protein kinase locus can code for two structurally and functionally distinct cellular receptors.

Amino Acid Sequence↗
PubMed1990

Expression of the trk proto-oncogene is restricted to the sensory cranial and spinal ganglia of neural crest origin in mouse development.

We have cloned and characterized the mouse homolog of the human trk proto-oncogene, a member of the protein tyrosine kinase (TK) receptor gene family. Here, we present the first report of a trk-encoded mRNA species in vivo. In situ hybridization analysis in the mouse embryo reveals a striking temporal and spatial regulation of trk transcription, with expression confined to the sensory cranial (trigeminal, superior, jugular) and dorsal root ganglia (DRG) of neural crest origin. Recent reports have shown that TK receptors can play regulatory roles in embryonic development. Thus, the developmental mutations W in mouse and torso and sevenless in Drosophila represent genes that code for defective TK receptors. Our data show that trk, a gene associated with malignancy in humans, is a specific marker for a set of neural crest-derived sensory neurons, and are consistent with the hypothesis that this proto-oncogene may have an important role in the development or phenotype of the neurons where it is expressed.

Animals↗
PubMed1990

Germ line transmission of an inactive N-myc allele generated by homologous recombination in mouse embryonic stem cells.

We have disrupted one allele of the N-myc locus in mouse embryonic stem (ES) cells by using homologous recombination techniques and have obtained germ line transmission of null N-myc ES cell lines with transmission of the null N-myc allele to the offspring. The creation of mice with a deficient N-myc allele will allow the generation of offspring bearing null N-myc alleles in both chromosomes and permit study of the role that this proto-oncogene plays in embryonic development.

Alleles↗
PubMed1990

Expression of the tyrosine kinase receptor gene trkB is confined to the murine embryonic and adult nervous system.

We have examined the expression of the trkB gene, which encodes a member of the family of protein tyrosine kinase (TK) transmembrane receptors, during mouse embryogenesis using in situ hybridization and Northern analysis. Transcripts were first detected in the neuroepithelium and in the neural crest of 9.5 day embryos with regions of high expression in the neural folds and at the lateral neuroepithelium. However, during the process of cephalization and development of the peripheral nervous system, transcripts were detected in most neural tissues, including the brain, spinal cord, cranial and spinal ganglia, and along the pathways of axonal tracts extending peripherally. In the adult brain, expression continues in a complex pattern that is confined to specific regions or neuron types. The expression of trkB, a TK receptor, in early embryogenesis, and specifically in neural tissues, is consistent with the notion that this gene plays a role in the events that regulate the development of the nervous system.

Animals↗
PubMed1989

trkB, a novel tyrosine protein kinase receptor expressed during mouse neural development.

We have isolated a novel member of the tyrosine protein kinase family of cell surface receptors. This gene, designated trkB, is highly related to the human trk proto-oncogene. At the amino acid level, their respective products share a 57% homology in their extracellular regions including 9 of the 11 cysteines present in the trk proto-oncogene. This homology increases to 88% within their respective tyrosine kinase catalytic domains. Both trk and trkB are equally distantly related to the other members of this gene family of receptors. A biologically active cDNA clone of trkB can direct the synthesis of gp145trkB, a glycoprotein of 145 kd of which only 93 kd correspond to its polypeptide backbone. In adult mice, trkB is preferentially expressed in brain tissue, although significant levels of trkB RNA have also been observed in lung, muscle and ovaries. In addition, trkB transcripts can be detected in mid and late gestation embryos. The trkB locus exhibits a complex pattern of transcription. At least seven RNA species ranging in size from approximately 9 kb to 2 kb have been identified in brain. However, only a subset of these transcripts appears to be expressed in the other tissues. In situ hybridization analysis of 14 and 18 day old mouse embryos indicates that trkB transcripts are localized in the central (CNS) and peripheral (PNS) nervous systems, including brain, spinal cord, spinal and cranial ganglia, paravertebral trunk of the sympathetic nervous system and various innervation pathways. These results suggest that trkB may code for a novel cell surface receptor involved in neurogenesis.

Amino Acid Sequence↗
PubMed1986

Behavior of myc and ras oncogenes in transformation of rat embryo fibroblasts.

The requirements for transformation of rat embryo fibroblasts (REFs) by transfected ras and myc oncogenes were explored. Under conditions of dense monolayer culture, neither oncogene was able to transform REFs on its own. However, the introduction of a ras oncogene together with a selectable neomycin resistance marker into REFs allowed killing of the normal nontransfected cells and the outgrowth of colonies of ras transformants, 10% of which survived crisis and became tumorigenic. These cells expressed greater than 10-fold-higher levels of ras p21 than tumorigenic cells cotransfected with ras and myc oncogenes. The myc oncogene similarly was unable to induce tumorigenic conversion of REFs unless especially refractile colonies of oncogene-bearing cells, produced by use of a cotransfected selectable marker, were picked and subcultured. Tumorigenic conversion of REFs by single transfected oncogenes appears to require special culture conditions and high levels of gene expression.

Animals↗
PubMed1983

Cellular oncogenes and multistep carcinogenesis.

Two dozen cellular proto-oncogenes have been discovered to date through the study of retroviruses and the use of gene transfer. They form a structurally and functionally heterogeneous group. At least five distinct mechanisms are responsible for their conversion to active oncogenes. Recent work provides experimental strategies by which many of these oncogenes, as well as oncogenes of DNA tumor viruses, may be placed into functional categories. These procedures may lead to definition of a small number of common pathways through which the various oncogenes act to transform cells.

Gene Expression Regulation↗
PubMed1983

The HL-60 transforming sequence: a ras oncogene coexisting with altered myc genes in hematopoietic tumors.

The oncogene of the HL-60 human promyelocytic leukemia cell line has been passed serially through NIH/3T3 mouse fibroblasts. Oncogene-specific probes prepared from the resulting tertiary transfectants by molecular cloning have been used to show that loss of the transfected oncogene from NIH/3T3 cells correlates with reversion to nontransformed morphology. Analysis of cells transfected by the oncogenes of other tumors and tumor cell lines indicates that the transforming gene of the HL-60 leukemia cell line is closely related to oncogenes of a Burkitt's lymphoma, an acute myelogenous leukemia, an adenocarcinoma of the colon, a neuroblastoma, and two sarcomas. This oncogene is distantly related to the viral oncogenes of Kirsten and Harvey sarcoma viruses. It has been termed N-ras. The active N-ras oncogene coexists with altered versions of the myc oncogene in the HL-60 and AW Ramos human tumors. This suggests a multistep mechanism involving both ras and myc genes in the creation of these tumors.

Animals↗
PubMed1982

Human EJ bladder carcinoma oncogene is homologue of Harvey sarcoma virus ras gene.

Examination of homologies between retroviral oncogenes and transforming sequences defined by transfection reveals that the human bladder carcinoma (EJ) oncogene is homologous to the Harvey sarcoma virus oncogene (ras). Structural analysis limits the region of homology to a 3.0-kilobase SacI fragment of the EJ oncogene. Both EJ and ras DNA probes detect similar transcripts in transfectants derived from bladder carcinoma cell lines.

Animals↗
PubMedDate not supplied

Trks: signal transduction and intracellular pathways.

The neurotrophin family of growth factors supports survival and differentiation of neurons in the developing vertebrate nervous system by binding activating receptor tyrosine kinases, the Trks. Activation of Trk receptors leads to stimulation of a number of intracellular signaling cascades including, among others, the ras/extracellular regulated kinase (erk) and the phosphatidylinositol-3 kinase (PI 3 kinase) cascades. Over the past several years, work in several neurotrophin responsive systems has begun to identify the role each of these signaling cascades plays in the cellular response to neurotrophins. It now appears that neurotrophins, in particular nerve growth factor (NGF), mediate their multiple effects through a number of distinct intracellular signaling cascades. In this review, we will overview the evidence implicating specific signaling cascades in aspects of the cellular response to the neurotrophins, specifically in response to activation of TrkA by NGF.

Animals↗