The present invention relates to a screening method/screening kit for screening a compound or its salt that changes the binding properties of (a) a protein containing the same or substantially the same amino acid sequence as the amino acid sequence represented by SEQ ID NO: 1 or SEQ ID NO: 19, its partial peptides, or salts thereof, and (b) a ligand capable of binding specifically to the protein; compounds obtained by the screening or salts thereof; pharmaceuticals comprising the compounds or salts thereof; a protein containing the same or substantially the same amino acid sequence as the amino acid sequence represented by SEQ ID NO: 19; etc. The compounds obtained by the screening of the present invention are useful as agents for the prevention/treatment of, for example, neurodegenerative diseases, immunological diseases, edema, acid indigestion, etc.