Biomedical subjects

P Gual

Publications and source records attributed to P Gual.

5 recordsLinked to original sources

PubMed1998

Interaction of Janus kinases JAK-1 and JAK-2 with the insulin receptor and the insulin-like growth factor-1 receptor.

Insulin and insulin-like growth factor-1 (IGF-1) treatment of cells overexpressing the insulin receptor or the IGF-1 receptor promotes phosphorylation and activation of Janus kinases JAK-1 and JAK-2 but not of TYK-2. With insulin, we observed maximal phosphorylation of JAK-1 within 2 min (5.2 +/- 0.6-fold) and maximal phosphorylation of JAK-2 within 10 min (2.4 +/- 0.6-fold). In cells incubated with IGF-1, we found maximal phosphorylation of JAK-2 within 2 min (1.9 +/- 0.2-fold) and of JAK-1 within 5 min (4.5 +/- 0.4-fold). The JAKs from insulin- or IGF-1-stimulated cells were activated, as shown by their autophosphorylation in vitro. Moreover, they were able to phosphorylate in vitro native insulin receptor substrate (IRS)-1 and a fragment of IRS-2 (GST-IRS-2591-786). Comparison of 32P-peptide maps of IRS-1 phosphorylated in vitro by the insulin receptor vs. JAK-1 showed the occurrence of different phosphopeptides, suggesting that different sites are likely to be phosphorylated by the two kinases. Finally, coprecipitation of receptors and JAK-1 was seen, and phosphorylation of both receptors was found to be necessary for receptor binding to JAK-1. Two domains of JAK- 1 are involved in the formation of the complex between receptor and JAK-1, i.e. the N-terminal portion containing JH7 and JH6 domains, and the C-terminal kinase domain (JH1 domain). Taking our data together, we conclude that: 1) insulin and IGF-1 lead to phosphorylation and activation of JAK-1 and JAK-2 in intact cells; 2) phosphorylation of IRS-I by JAK-1 seems to occur on sites different from those phosphorylated by the insulin receptor; 3) JAK-1 interacts directly with phosphorylated insulin and IGF-1 receptors; and 4) the JH7-JH6 and JH1 domains of JAK-1 are responsible for the interaction with insulin and IGF-1 receptors.

3T3 Cells↗

PubMed1996

Role of the insulin receptor C-terminal acidic domain in the modulation of the receptor kinase by polybasic effectors.

Basic polymers such as polylysine have been found to activate insulin receptor autophosphorylation and kinase activity toward substrates. It was suggested that acidic receptor domains may be involved in the interaction of the receptor with these basic effectors. In a previous study, we have shown that the receptor acid-rich C-terminal sequence, including residues 1270-1280, is involved in the regulation of the receptor kinase activity. Moreover, this domain may be the site of interaction with histone, which is a modulator of the receptor kinase. In this study, we investigated whether the insulin receptor domain comprising amino acids 1270-1280 is involved in the interaction with polybasic effectors. We used anti-peptide serum directed to this sequence, and basic activators such as polylysine, polyarginine and protamine sulfate. Our antibodies inhibit polylysine-induced receptor autophosphorylation, whereas they have no effect on receptor phosphorylation stimulated by concanavalin A which is a non-basic activator of the insulin receptor. Polylysine-induced receptor aggregation was blocked by the antibodies (Fab fragments or whole Ig), indicating that competition occurs between the antibody and polylysine at the level of their binding site to the receptor. Finally, we observed a direct interaction of the 125I-peptide corresponding to receptor sequence 1270-1280 with the basic polymers in dot-blot experiments. Interestingly, the peptide did not bind spermine, a basic molecule which is not an activator of the insulin receptor kinase. Our data indicate that the insulin receptor C-terminal acidic domain including residues 1270-1280 is involved in the interaction of polylysine and other polybasic molecules with the receptor. Since this receptor region has been implicated in the regulation of the receptor kinase activity, we propose that interaction of basic effectors with this domain may be responsible for their activating properties.

Antibodies↗

PubMed1996

Insulin receptor-induced phosphorylation of cellular and synthetic substrates is regulated by the receptor beta-subunit C-terminus.

The transmembrane beta-subunits of the insulin receptor possess hormone-sensitive tyrosine kinase activity. To study the role of the C-terminus domain, a rabbit antipeptide antibody directed to the 1294-1317 domain was produced. The antipeptide antibody inhibited the receptor-induced phosphorylation of poly (Glu, Tyr) and synthetic peptides corresponding to the receptor autophosphorylation sites. In contrast, the same antibody did not inhibit receptor autophosphorylation. The kinetic parameters of the poly(Glu, Tyr) phosphorylation reaction indicated that the antibody interfered with the receptor enzymatic site. Concerning the insulin receptor cellular substrates, the anti-(1294-1317) antibody inhibited Src homology/collagen and IRS-1 phosphorylation. The extent of inhibition was 52% for Src homology/collagen phosphorylation and 30% for IRS-1 phosphorylation. From our data, we conclude that a similar regulation of insulin receptor-induced phosphorylation of artificial and cellular insulin receptor substrates can be generated at the level of the receptor beta-subunit C-terminus.

Amino Acid Sequence↗

PubMed1995

A conformational change in the beta-subunit of the insulin-like growth factor I receptor identified by antipeptide antibodies.

Insulin-like growth factor I (IGF-I) binding to its receptor results in receptor autophosphorylation and phosphorylation of several cellular substrates. The mechanism by which binding of the ligand to the extracellular receptor domain activates the intracellular kinase remains to be defined. Using polyclonal antibodies against four regions of the IGF-I receptor, we searched for putative conformational changes occurring in purified receptors. We studied the ability of the antipeptide antibodies to immunoprecipitate the native, ligand-occupied, or autophosphorylated IGF-I receptor. We found that the antipeptide antibody directed to the sequence 985-998 of the kinase domain immunoprecipitated the phosphorylated receptor, but not the native or the ligand-occupied receptor. By contrast, the antibody against the sequence 950-957 of the juxtamembrane domain immunoprecipitated the three receptor forms. The difference between phosphorylated receptors and unphosphorylated receptors was not observed in Western blot experiments, indicating that the conformational modification of the receptors is not detected upon unfolding. These data demonstrate that the IGF-I receptor undergoes an autophosphorylation-induced conformational change detectable in the kinase domain. Our work provides evidence that conformational changes induced by autophosphorylation may be a common activation mechanism for tyrosine kinase receptors.

3T3 Cells↗

PubMed1989

[Anorexia nervosa: study method and sleep analysis].

By studying anorexia nervosa with an Integrated Inventory and the quality and the quantity of sleep applying Hauri's scale for the analysis of dream contents, the sleeping habits of 50 anorexic patients who were under treatment have been studied. The results show that sleep in these patients is similar and sometimes better in quantity and quality than those in the control group. Their dreams are characterized by an almost total absence of sexual, aggressive and alimentary contents, and that reality, active participation, unpleasant feelings and sensory-perceptive elements are predominant.

Adolescent↗