Reconstitution studies of lipid effects on insulin-receptor kinase activation.
Eur J Biochem
; 213(1): 277-84, 1993 Apr 01.
Article
en En
| MEDLINE
| ID: mdl-8386623
ABSTRACT
Insulin receptors extracted from human placenta were reconstituted by dialysis into well-characterized lipid vesicles. For all types of lipids studied, vesicles were shown to be unilamellar, about 120 nm in diameter. The incorporation of lectin-purified insulin receptors was assessed by cosedimentation of 125I-insulin binding and [32P]phospholipids in a sucrose gradient. The insulin-binding activity was not modified by the composition of the lipid vesicles. However, tyrosine kinase activation appeared to be more sensitive to its lipid environment. Mixtures of phosphatidylcholine/phosphatidylserine or phospholipids/phosphatidylserine, in ratios of 1-4, increased the insulin-induced tyrosine kinase activation in a dose-dependent manner. In contrast, experiments performed in the presence of phosphatidylinositol showed a decrease in the enzyme stimulation. These results indicate an opposing involvement of these two anionic phospholipids in the kinase activation. Inclusion of cholesterol (10-30%) into phosphatidylcholine vesicles reduced kinase activation, which was drastically inhibited by 30% cholesterol. The effect of a total extract of brain gangliosides was biphasic, stimulatory at low concentration (5-10%), but with a reverse effect at higher concentrations. These results stress the importance of the lipid environment for insulin-receptor signaling, particularly for the insulin-induced activation of its beta-subunit kinase.
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Banco de datos:
MEDLINE
Asunto principal:
Proteínas Tirosina Quinasas
/
Lípidos
Límite:
Animals
/
Humans
Idioma:
En
Revista:
Eur J Biochem
Año:
1993
Tipo del documento:
Article
País de afiliación:
Francia