Structural and functional characterization of the human T lymphocyte receptor for insulin-like growth factor I in vitro.
Growth factor receptors for T lymphocytes, such as interleukin 2 and insulin, are present on activated but not resting T lymphocytes. We sought to determine if insulin-like growth factor I (IGF-I) could act as a growth factor for human T cells and to characterize its receptor on resting and activated cells. Recombinant IGF-I induced two separate functions. It was chemotactic for and increased incorporation of tritiated thymidine into both unactivated (resting) and mitogen-activated T cells. High-affinity 125I-IGF-I binding to human T cells was saturable with an apparent Kd of 1.2 +/- .6 X 10(-10) M for binding to activated T cells and 1.2 +/- .9 X 10(-10) for unactivated T cells. The calculated binding for activated cells was 330 +/- 90 and for resting cells 45 +/- 9 high-affinity receptor sites per cell. Affinity cross-linking of 125I-IGF-I to resting or activated T cells revealed a radioligand-receptor complex of 360,000 mol wt when analyzed by SDS-PAGE without reduction and complexes of 270,000 and 135,000 mol wt upon reduction; prior incubation with excess unlabeled IGF-I prevented formation of the 125I-IGF-I receptor complex. Our data suggest that both resting and activated T lymphocytes bear functional IGF-I receptors similar to those found in other tissues. These receptors may mediate T cell growth and chemotaxis.
Tapson
V F
VF
Pulmonary Center, Boston University School of Medicine, Massachusetts 02118.
Boni-Schnetzler
M
M
Pilch
P F
PF
Center
D M
DM
Berman
J S
JS
D000345:Affinity Labels; D001667:Binding, Competitive; D002634:Chemotaxis, Leukocyte / Q000187:drug effects; D003432:Cross-Linking Reagents; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000302:isolation & purification / Q000502:physiology*; D007399:Interphase / Q000187:drug effects; D008213:Lymphocyte Activation / Q000187:drug effects; D011948:Receptors, Antigen, T-Cell / Q000302:isolation & purification / Q000502:physiology*; D013002:Somatomedins / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism
D000345:Affinity Labels; D003432:Cross-Linking Reagents; D011948:Receptors, Antigen, T-Cell; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013936:Thymidine