Roles of the N and C terminal domains of the interleukin-3 receptor alpha chain in receptor function.
The interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor, and IL-5 receptor alpha chains are each composed of three extracellular domains, a transmembrane domain and a short intracellular region. Domains 2 and 3 constitute the cytokine receptor module (CRM), typical of the cytokine receptor superfamily; however, the function of the N-terminal domain is not known. We have investigated the functions of the N-terminal and C-terminal domains of the IL-3 receptor (IL-3R) alpha chain. We find that cells transfected with the receptor beta chain (h beta c) and a truncated IL-3R alpha that is devoid of the intracellular region fail to proliferate or to activate STAT5 in response to human IL-3, despite binding the IL-3 with affinity indistinguishable from that of full-length receptor. In addition, IL-3-induced phosphorylation of h beta c was not detected. Thus, the IL-3R alpha intracellular region does not contribute detectably to stabilization of the receptor/ligand complex, but is essential for signal propagation. In contrast, a truncated IL-3R alpha with the N-terminal domain deleted interacts functionally with the beta chain; mouse cells transfected with these receptor chains proliferate in response to human IL-3 and STAT5 transcription factor is activated. High- and low-affinity binding sites are retained, although the affinity for IL-3 is decreased 15-fold, indicating a significant role for the N-terminal domain in IL-3 binding.
Barry
S C
SC
Hanson Centre for Cancer Research, Adelaide, Australia.
Korpelainen
E
E
Sun
Q
Q
Stomski
F C
FC
Moretti
P A
PA
Wakao
H
H
D'Andrea
R J
RJ
Vadas
M A
MA
Lopez
A F
AF
Goodall
G J
GJ
D000595:Amino Acid Sequence; D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D019556:COS Cells; D003593:Cytoplasm / Q000737:chemistry / Q000502:physiology; D007424:Intracellular Fluid / Q000737:chemistry / Q000502:physiology; D016296:Mutagenesis; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016185:Receptors, Interleukin-3 / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D015398:Signal Transduction
D019138:Antibodies, Blocking; D000911:Antibodies, Monoclonal; D016185:Receptors, Interleukin-3