Agonistic and antagonistic variants of ciliary neurotrophic factor (CNTF) reveal functional differences between membrane-bound and soluble CNTF alpha-receptor.
Ciliary neurotrophic factor (CNTF) drives the sequential assembly of a receptor complex containing the ligand-specific alpha-receptor subunit (CNTFR) and the signal-transducing beta-subunits gp130 and leukemia inhibitory factor receptor-beta (LIFR). CNTFR can function in either membrane-bound or soluble forms. The membrane-bound form mediates the neuronal actions of CNTF, whereas the soluble form serves to confer cytokine responsiveness to non-neuronal cells expressing gp130 and LIFR. The objective of this work was to analyze whether the two receptor isoforms differ in their ability to interact functionally with CNTF and related proteins. Two new types of CNTF variants, characterized by weakened interactions with either CNTFR or both LIFR and gp130, were developed, and the biological activities of these and other mutants were determined in non-neuronal versus neuronal cells, as well as in non-neuronal cells transfected with an expression vector for CNTFR. Membrane anchoring of CNTFR was found to render the CNTF receptor complex relatively insensitive to changes in agonist affinity for either alpha- or beta-receptor subunits and to promote a more efficient interaction with a gp130-depleting antagonistic variant of CNTF. As a result of this phenomenon, which can be rationalized in terms of the multivalent nature of CNTF receptor interaction, CNTF variants display striking changes in receptor selectivity.
Di Marco
A
A
Istituto di Ricerche di Biologia Molecolare P. Angeletti (IRBM), Pomezia, Rome, Italy.
Gloaguen
I
I
Demartis
A
A
Saggio
I
I
Graziani
R
R
Paonessa
G
G
Laufer
R
R
D015703:Antigens, CD / Q000737:chemistry / Q000378:metabolism*; D001681:Biological Assay; D020934:Ciliary Neurotrophic Factor; D050822:Cytokine Receptor gp130; D004305:Dose-Response Relationship, Drug; D006131:Growth Inhibitors; D006801:Humans; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; D053680:Leukemia Inhibitory Factor Receptor alpha Subunit; D008222:Lymphokines; D008562:Membrane Glycoproteins / Q000819:agonists / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins; D008956:Models, Chemical; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000494:pharmacology*; D011485:Protein Binding; D020794:Receptor Protein-Tyrosine Kinases / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020801:Receptor, Ciliary Neurotrophic Factor; D018121:Receptors, Cytokine / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017475:Receptors, Nerve Growth Factor / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D053606:Receptors, OSM-LIF; D011994:Recombinant Proteins / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D012995:Solubility
D015703:Antigens, CD; D020934:Ciliary Neurotrophic Factor; D006131:Growth Inhibitors; C494199:IL6ST protein, human; D015850:Interleukin-6; C507837:LIF protein, human; C507840:LIFR protein, human; D053605:Leukemia Inhibitory Factor; D053680:Leukemia Inhibitory Factor Receptor alpha Subunit; D008222:Lymphokines; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D020801:Receptor, Ciliary Neurotrophic Factor; D018121:Receptors, Cytokine; D017475:Receptors, Nerve Growth Factor; D053606:Receptors, OSM-LIF; D011994:Recombinant Proteins; D050822:Cytokine Receptor gp130; D020794:Receptor Protein-Tyrosine Kinases