The immunoglobulin-like module of gp130 is required for signaling by interleukin-6, but not by leukemia inhibitory factor.
The transmembrane protein gp130 is a shared component of the receptor complexes for the interleukin-6 (IL-6)-type cytokines, which include IL-6, leukemia inhibitory factor (LIF) and oncostatin M (OSM). In addition to its role in the generation of high affinity receptors, gp130 is required for signal transduction by these cytokines. In the present study we have examined the role of the N-terminal located, extracellular immunoglobulin (Ig)-like module of gp130 in signal transduction by IL-6 and LIF. We have expressed wild-type human gp130 or three mutants in murine myeloid M1-UR21 cells that lack functional endogenous gp130 but express the IL-6 receptor (IL-6R) and the LIF receptor (LIFR). By measuring cellular responses, such as morphological changes upon differentiation, soft agar colony formation, and induction of tyrosine phosphorylation of the signal transducer and activator of transcription, STAT3, we show that signaling by IL-6, but not LIF, is significantly reduced by mutations in the Ig-like module of gp130. However, the binding of 125I-labeled IL-6 or LIF is not affected by these mutations. We also present evidence that the Ig-like module forms part of the epitope of an anti-gp130 monoclonal antibody that neutralizes the bioactivity of IL-6, but not of LIF or OSM. The data suggest that gp130-activation by IL-6 and LIF requires different regions of gp130, that the Ig-like module of gp130 may be required for IL-6-induced gp130 dimerization, and that the stoichiometry of the high affinity IL-6 receptor-complex differs from those of the receptor-complexes for LIF and OSM.
Joint Protein Structure Laboratory, Ludwig Institute for Cancer Research (Melbourne Tumour Biology Branch) and The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia. hammacher@ludwig.edu.au
A
A
Hammacher
R T
RT
Richardson
J E
JE
Layton
D K
DK
Smith
L J
LJ
Angus
D J
DJ
Hilton
N A
NA
Nicola
J
J
Wijdenes
R J
RJ
Simpson
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D015703:Antigens, CD / Q000378:metabolism*; D001483:Base Sequence; D002460:Cell Line; D050822:Cytokine Receptor gp130; D017931:DNA Primers; D000939:Epitopes / Q000378:metabolism; D006131:Growth Inhibitors / Q000378:metabolism*; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism*; D015850:Interleukin-6 / Q000378:metabolism*; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D015398:Signal Transduction
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D017931:DNA Primers; D000939:Epitopes; D006131:Growth Inhibitors; C494199:IL6ST protein, human; C494200:Il6st protein, mouse; D007136:Immunoglobulins; D015850:Interleukin-6; C507837:LIF protein, human; D053605:Leukemia Inhibitory Factor; C507838:Lif protein, mouse; D008222:Lymphokines; D008562:Membrane Glycoproteins; D050822:Cytokine Receptor gp130