Growth signal transduction by the human interleukin-2 receptor requires cytoplasmic tyrosines of the beta chain and non-tyrosine residues of the gamma c chain.
To evaluate the possible role for receptor-based tyrosine phosphorylation in growth signaling induced by interleukin-2 (IL-2), a series of substitution tyrosine mutants of the IL-2 receptor beta and gamma c chains was prepared and analyzed. Concurrent mutation of all six of the cytoplasmic tyrosines present in the beta chain markedly inhibited IL-2-induced growth signaling in both pro-B and T cell lines. Growth signaling in a pro-B cell line was substantially reconstituted when either of the two distal tyrosines (Tyr-392, Tyr-510) was selectively restored in the tyrosine-negative beta mutant, whereas reconstitution of the proximal tyrosines (Tyr-338, Tyr-355, Tyr-358, Tyr-361) did not restore this signaling function. Furthermore, at least one of the two cytoplasmic tyrosines that is required for beta chain function was found to serve as a phosphate acceptor site upon induction with IL-2. Studies employing a chimeric receptor system revealed that tyrosine residues of the beta chain likewise were important for growth signaling in T cells. In contrast, although the gamma c subunits is a target for tyrosine phosphorylation in vivo, concurrent substitution of all four cytoplasmic tyrosines of this chain produced no significant effect on growth signaling by chimeric IL-2 receptors. However, deletion of either the Box 1, Box 2, or intervening (V-Box) regions of gamma c abrogated receptor function. Therefore, tyrosine residues of beta but not of gamma c appear to play a pivotal role in regulating growth signal transduction through the IL-2 receptor, either by influencing cytoplasmic domain folding or by serving as sites for phosphorylation and subsequent association with signaling intermediates. These findings thus highlight a fundamental difference in the structural requirements for IL-2R beta and gamma c in receptor-mediated signal transduction.
Goldsmith
M A
MA
Gladstone Institute of Virology and Immunology, Department of Medicine, School of Medicine, University of California, San Francisco 94141-9100, USA.
Lai
S Y
SY
Xu
W
W
Amaral
M C
MC
Kuczek
E S
ES
Parent
L J
LJ
Mills
G B
GB
Tarr
K L
KL
Longmore
G D
GD
Greene
W C
WC
D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes; D002455:Cell Division; D003001:Cloning, Molecular; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017467:Receptors, Erythropoietin / Q000737:chemistry / Q000378:metabolism; D015375:Receptors, Interleukin-2 / Q000737:chemistry / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes; D014162:Transfection; D014443:Tyrosine
D007376:Interleukin-2; D046911:Macromolecular Substances; D017467:Receptors, Erythropoietin; D015375:Receptors, Interleukin-2; D011993:Recombinant Fusion Proteins; D014443:Tyrosine