A screening strategy based on differential binding of ligand to receptor and to binding proteins: Screening for compounds interacting with corticotrophin-releasing factor-binding protein

The ligand-receptor interaction has been commonly used in development of hi gh throughput screening assays for new drugs, In some cases, an endogenous ligand interacts not: only with membrane receptors but also with soluble bi nding proteins, Corticotrophin-releasing factor (CRF) is an important stres s neurotransmitter/hormone involved in both the central and peripheral nerv ous systems. CRF exerts its function by interacting with CRFR1 and CRFR2 re ceptors, In addition, CRF-binding protein (CRF-BP) binds CRF with high affi nity. Accordingly, CRF-BP has been suggested to play an important role in m odulating CRF function, Based on the potential involvement of CRF-BP in man y neurological disorders, it is desirable to develop a screening assay to l ook for drugs that either mimic or interfere with CRF binding to CRF-BP, An assay was developed to monitor the interactions of radiolabeled CRF with h uman/rat CRF-BP and the mouse CRFR1 (mCRFR1) receptor, By carefully examini ng the binding characteristics of radiolabeled CRF to mCRFR1, the assay was able to identify compounds that bind to CRF-BP with high affinity and have little or no affinity for mCRFR1 receptors, Based on a mathematical model, we have verified the screening system with several well-characterized CRF ligands that all have different affinities for CRF receptors and CRF-BP.