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G Uze

Publications and source records attributed to G Uze.

7 recordsLinked to original sources
PubMed2000

A dual role for the kinase-like domain of the tyrosine kinase Tyk2 in interferon-alpha signaling.

Tyrosine kinases of the Janus kinase family initiate cellular responses through their association with receptors for alpha-helical cytokines. In addition to a tyrosine kinase domain, these enzymes possess a kinase-like (KL) domain, whose function remains elusive. To investigate the role of the KL domain of Tyk2 in interferon-alpha/beta signaling, we transfected a library of Tyk2 cDNAs containing random point mutations in KL into Tyk2-negative cells and selected for loss-of-function Tyk2 mutants. Four such mutants, V584D, G596V, H669P, and R856G, were identified through this screen. Like the wild-type Tyk2, the mutant proteins were able to sustain the level of IFNAR1 receptor protein. However, all four mutants were incapable of restoring high-affinity interferon-alpha binding in Tyk2-negative cells and were also catalytically impaired, even when transiently overexpressed. Interferon-alpha induced phosphorylation, and gene expression could be detected in V584D- or G596V-expressing cells, but not in H669P- or R856G-expressing cells. Furthermore, H669P and R856G proteins were constitutively highly phosphorylated. All together, our findings demonstrate that an intact KL domain is essential for the intrinsic catalytic activity of Tyk2 and for the establishment of a high-affinity interferon-alpha receptor complex.

Cell Line↗
PubMed1998

Type I interferons: expression and signalization.

Type I interferon (IFN-A and IFN-B) genes encode a large family of multifunctional secreted proteins involved in antiviral defence, cell growth regulation and immune activation. These cytokines, as a consequence of their biological activities, have been established as effective therapeutic molecules for malignant and viral diseases. Virus infection is the main inducer leading to transient expression of type I IFN (A and B) and the antiviral response appears to proceed through a two-step pathway requiring, first, induction of type I IFN gene expression and, second, transcriptional activation by the synthesized IFN proteins, binding to their specific cell surface receptors, of a large number of genes. The proteins they encode are responsible, in part, for the pleiotropic multiple biological activities of the IFN. In this two-step pathway, the virus-induced IFN genes and the IFN-stimulated gene (ISG) expression seem to share common factors. Even if IFN-A genes are structurally related and very often coordinately induced in virus-infected cells, differences in the expression of the individual IFN-A messenger RNAs of the multigenic IFN-A gene family are observed in human as well as in murine cells, reflecting, in a particular cell type, the transcriptional activity of the corresponding promoter regions. Important studies on interferon regulatory factors and ISG factors have been made in the last decade. However, some factors involved in IFN-A gene regulation remain to be identified. Our goal has been to review the factors involved in the control of the type I IFN gene expression to understand the mechanisms of induction and repression of their transcription and to explain the properties of these cytokines through their signal transduction pathway.

Animals↗
PubMed1991

Linkage mapping of highly informative DNA polymorphisms within the human interferon-alpha receptor gene on chromosome 21.

Two polymorphic loci within the interferon-alpha receptor (IFNAR) gene on human chromosome 21 have been identified and mapped by linkage analysis in 40 CEPH families. These markers are (1) a multiallelic RFLP with an observed heterozygosity of 0.72 and (2) a variable (AT3)n short sequence repeat at the poly(A) tail of an Alu sequence (AluVpA) with an observed heterozygosity of 0.83. This locus is close to D21S58 (theta = 0.02, zeta = 36.76) and D21S17 (theta = 0.02, Zeta = 21.76) with chromosomal band 21q22.1. Multipoint linkage analysis suggests the most likely locus order to be 21cen-D21S58-IFNAR-D21S17-21qter. Given its high heterozygosity, the IFNAR gene can be used as an index marker on human chromosome 21.

Base Sequence↗
PubMed1988

Interferon removes its own receptors as it blocks the division of Daudi cells.

The Burkitt-derived line, Daudi, whose proliferation is inhibited by human alpha-interferon (IFN-alpha), was treated with 125I-labelled recombinant human IFN-alpha A. After separation from unbound ligand, cell-bound IFN was extracted with the detergent digitonin yielding soluble and insoluble complexes of IFN and receptor, together with a certain amount of uncomplexed IFN. 1. Soluble complexes were stable enough to be separated from uncomplexed IFN by permeation chromatography. Treatment of soluble complexes with the bifunctional reagent, disuccinimidyl suberate, yielded a radioactive product separating with an Mr of 130,000 on electrophoresis in sodium dodecyl sulphate. Similar complexes could be recovered with sodium dodecyl sulphate from the digitonin-insoluble residue, treated with the bi-functional reagent. 2. The total (soluble and insoluble) of complexed IFN obtained after digitonin extraction was a constant fraction (0.62) of the total cell-bound radioactivity, being independent of the concentration of IFN added to the cells (less than pM to greater than nM), and of the time of incubation (1 min to 20 h). However, between 30 min and 3 h of incubation, the insoluble complex increased, at the expense of the soluble complex, and there appeared a cellular pool of degraded ligand. From 3 h to 20 h the distribution of ligand-derived radioactivity remained constant while the total amount decreased to less than 10% of its value at 30 min. This decrease in binding was matched by the appearance of an equivalent quantity of radiolabelled fragments in the culture medium. 3. The inhibition of cellular division due to IFN was shown to be coincident with the disappearance of cellular binding and with the cell-mediated degradation of receptor-complexed IFN. We propose that IFN removes its own receptor and, in doing so, blocks a linked function necessary for the stimulated growth of Daudi cells.

Binding Sites↗
PubMed1988

Electrostatic interactions in the cellular dynamics of the interferon-receptor complex.

Using membrane preparations of the interferon receptor, prepared from cells of the Burkitt line, Daudi, we have examined the binding of three human recombinant alpha-interferons. 1. We discovered a binding titration of the interferons IFN-alpha A and IFN-alpha D in the pH range 6-9. Receptor binding, negligible at pH 6, rises to a maximum close to pH 9. We have shown that binding of IFN-alpha A at basic pH is to the same receptors as at neutrality and that IFN-receptor complexes extracted with digitonin are more stable at basic pH than they are at neutrality. 2. The recombinant interferon, IFN-alpha B, shows little change of binding in the pH range 6-9. At its basic optimum the binding of IFN-alpha A approaches that of IFN-alpha B, while at neutral pH the binding of IFN-alpha A is 3-4 times less. This difference at neutral pH is seen on intact cells as well as on membrane preparations. The specific activity of IFN-alpha B is close to that of IFN-alpha A, both of which are 10-20 times more active than IFN-alpha D; and the binding titration is, therefore, independent of the initial binding affinities. 3. Using hybrid IFNs constructed from the DNA sequences of alpha D and alpha B, we have isolated the sequence responsible for the binding titration to the segment comprising amino acids 61-92. Examination of these sequences reveals that Lys-84 is present in all the IFN-alpha except IFN-alpha B where it is replaced by Glu; and Tyr-90, present in most of the common IFN-alpha including alpha A and alpha D, is replaced by Asp in IFN-alpha B. Lys and Tyr would normally titrate in the pH range 6-9. We conclude that the binding titration is due to an electrostatic interaction and we propose that the interaction is between IFN-receptor complexes. The role of the interaction in the binding losses that accompany the antiproliferative effects of IFN is discussed.

Amino Acids↗
PubMed1984

Receptor mediated pathways for interferon action: in vivo implications.

High affinity receptors for human interferon (IFN) are a common surface component of human nucleated cells. A model culture system has been used to mark the activation of surface receptors by IFN as the first step in several, possibly separate, pathways of action, some of which depend on the continued presence of IFN. Two types of equilibrium binding can be seen: an initial one of short duration corresponding to receptor activation and a second of longer duration corresponding to activation of a second site by IFN. Various different responses to IFN are seen to be determined by one or other of these equilibria. In vivo, implications are discussed in terms of the pharmacokinetic distribution of IFN, with particular reference to intravenous injection. Desensitization of target cells with respect to late equilibrium effects is seen as a possible consequence of receptor activation against the background of changing IFN concentration in vivo. A modulating effect of combined IFN species is proposed.

Cell Division↗