Screening methods for biologically active ligands

A method of identifying a ligand that can bind to at least one of two or more kinds of receptors, wherein said method comprises the steps of:

• (i) providing a composition comprising cells expressing two or more kinds of chimeric receptors, each of said chimeric receptors comprising:
• (a) a common signal-transducing domain derived from a receptor selected from the group consisting of hematopoietic factor receptor family, cytokine receptor family, tyrosine kinase-type receptor family, serine/threonine kinase-type receptor family, TNF receptor family, G protein-coupled receptor family, GPI-anchored receptor family, tyrosine phosphatase-type receptor family, cell adhesion receptor family, and hormone receptor family, and
• (b) an extracellular domain or ligand-binding portion thereof derived from a receptor selected from the group consisting of hematopoietic factor receptor family, cytokine receptor family, tyrosine kinase-type receptor family, serine/threonine kinase-type receptor family, TNF receptor family, G protein-coupled receptor family, GPI-anchored receptor family, tyrosine phosphatase-type receptor family, cell adhesion receptor family, and hormone receptor family,
• wherein, in each kind of chimeric receptor, said extracellular domain or ligand-binding portion thereof derives from a different receptor, and binding of a ligand to the extracellular domain or ligand-binding portion thereof induces signal transduction through the signal-transducing domain,
• (ii) contacting said composition with a test sample, and
• (iii) detecting binding of said test sample to at least one of said two or more kinds of receptors by detecting a change in a detection marker selected from the group consisting of proliferation activity of the cells, phosphorylation of the receptor or downstream substrate proteins, dephosphorylation of the receptor or downstream substrate proteins, change in cAMP level, change in Ca2+ level, and induction of downstream gene expression, wherein said change is induced by signal transduction through said common signal-transducing domain.

A method of screening for a ligand that can bind to at least one of two or more kinds of receptors, wherein said method comprises the steps of:

• (i) providing a composition comprising cells expressing two or more kinds of receptors, each of said receptors comprising (a) a common signal-transducing domain derived from a receptor selected from the group consisting of EPO receptor, G-CSF receptor, TPO receptor, and EGF receptor, and (b) a ligand-binding domain derived from a receptor selected from the group consisting of EPO receptor, G-CSF receptor, TPO receptor, insulin receptor, Flt-3 receptor, PDGF receptor, IFN-α or -β receptor, GH receptor, IL-10 receptor, IGF-I receptor, LIF receptor, and CNTF receptor, wherein in each of said kinds of receptors, said ligand-binding domain derives from a different receptor, and binding of a ligand to the ligand-binding domain induces signal transduction through the signal-transducing domain;
• (ii) contacting a test sample with said composition comprising cells expressing two or more kinds of receptors;
• and
• (iii) detecting binding of said test sample to at least one of said two or more kinds of receptors by detecting a change in proliferation activity of the cells, wherein said change is induced by signal transduction through said common signal-transducing domain.

A method of identifying a ligand that can bind to at least one of two or more kinds of receptors, wherein said method comprises the steps of:

• (i) providing a composition comprising cells expressing two or more kinds of chimeric receptors, each of said chimeric receptors comprising:
• (a) a common signal-transducing domain derived from a receptor selected from the group consisting of EPO receptor, G-CSF receptor, TPO receptor, and EGF receptor, and
• (b) an extracellular domain or ligand-binding portion thereof derived from a receptor selected from the group consisting of EPO receptor, G-CSF receptor, TPO receptor, insulin receptor, Flt-3 receptor, PDGF receptor, IFN-α or β-receptor, leptin receptor, GH receptor, IL-10 receptor, IGF-I receptor, LIF receptor, and CNTF receptor,
• wherein, in each kind of chimeric receptor, said extracellular domain or ligand-binding portion thereof derives from a different receptor, and binding of a ligand to the extracellular domain or ligand-binding portion thereof induces signal transduction through the signal-transducing domain,
• (ii) contacting said composition with a test sample, and
• (iii) detecting binding of said test sample to at least one of said two or more kinds of receptors by detecting a change in proliferation activity of the cells, wherein said change is induced by signal transduction through said common signal-transducing domain.