TYROSINE KINASE-ACTIVITY OF A CHIMERIC INSULIN-LIKE-GROWTH-FACTOR-1 RECEPTOR-CONTAINING THE INSULIN-RECEPTOR C-TERMINAL DOMAIN - COMPARISONWITH THE TYROSINE KINASE-ACTIVITIES OF THE INSULIN AND INSULIN-LIKE-GROWTH-FACTOR-1 RECEPTORS USING A CELL-FREE SYSTEM
I. Mothe et al., TYROSINE KINASE-ACTIVITY OF A CHIMERIC INSULIN-LIKE-GROWTH-FACTOR-1 RECEPTOR-CONTAINING THE INSULIN-RECEPTOR C-TERMINAL DOMAIN - COMPARISONWITH THE TYROSINE KINASE-ACTIVITIES OF THE INSULIN AND INSULIN-LIKE-GROWTH-FACTOR-1 RECEPTORS USING A CELL-FREE SYSTEM, European journal of biochemistry, 228(3), 1995, pp. 842-848
In a previous study, we showed that a chimeric insulin-like-growth-fac
tor-l (IGF-1) receptor, with the beta subunit C-terminal part of the i
nsulin receptor was more efficient in stimulating glycogen synthesis a
nd p44(mapk) activity compared to the wild-type IFG-1 receptor [Tartar
e, S., Mothe, I., Kowalski-Chauvel, A., Breittmayer, J.-P., Ballotti,
R. and Van Obberghen, E. (1994) J. Biol. Chem. 269, 11449-11455]. Thes
e data indicate that the receptor C-terminal domain plays an important
role in the transmission of biological effects. To understand the mol
ecular basis of the differences in receptor specificity, we studied th
e characteristics of insulin, IGF-1 and chimeric receptor tyrosine kin
ase activities in a cell-free system. We found that, compared to wild-
type insulin and IGF-1 receptors, the chimeric receptor showed a decre
ase in (a) autophosphorylation, (b) tyrosine kinase activity towards i
nsulin receptor substrate-1 and the insulin receptor-(1142-1158)-pepti
de, and (c) the ability to activate phosphatidylinositol 3-kinase. How
ever, for all the effects measured in a cell-free system, the chimeric
receptor displayed an increased response td IGF-1 compared to the nat
ive IGF-1 receptor. Concerning the cation dependence of the tyrosine k
inase activity, we showed that, at 10 mM Mg2+, the Ligand-stimulated p
hosphorylation of poly(Glu(80)Tyr(20)) by both insulin receptor and ch
imeric receptor was increased by Mn2+. Conversely at 50 mM Mg2+, the c
himeric receptor behaved like the IGF-1 receptor, since the presence o
f Mn2+ decreased the stimulatory effect of IGF-1 on their kinase activ
ity. Furthermore, the K-m of the chimeric receptor for ATP was increas
ed compared to the wild-type receptors. These data demonstrate that th
e replacement of the C-ter,oma; tail of the IGF-1 receptor by that of
the insulin receptor has changed the receptor characteristics studied
in a cell-free system. Our findings indicate that the C-terminal domai
n of the insulin receptor beta subunit plays a key role in regulation
of the tyrosine kinase activity. The fine-tuning of the tyrosine kinas
e by the C-terminal tail could participate in the receptor specificity
.