Abstract: The present invention provides a receptor of musclin and a screening system for an agonist and/or antagonist of the receptor by means of the interaction of musclin and the receptor. Hence, provided is a screening method for a substance that alters the bindability (i) a protein containing the same or substantially the same amino acid sequence as the amino acid sequence shown by SEQ ID NO:2 or a partial peptide thereof or a salt thereof and (ii) musclin or a partial peptide thereof or a salt thereof, containing using both.

Abstract: A method of suppressing the differentiation of an adipocite and/or lipid accumulation in an adipocyte, which comprises contacting the adipocyte with a protein comprising the amino acid sequence of SEQ ID NO: 2 or a salt thereof, or with a polynucleotide comprising a sense strand sequence encoding a protein comprising the amino acid sequence of SEQ ID NO: 2.

Abstract: The present invention provides a novel secretory or membrane protein expressed specifically in skeletal muscles, a nucleic acid encoding the same, an antibody against the same, useful as a prophylactic/therapeutic agent or diagnostic agent for a disease associated with an abnormality of differentiation of skeletal muscle cell or metabolism function, or as a tool for screening a drug-candidate compound effective for the prophylaxis/treatment of the disease.

Abstract: The present invention provides a novel secretory/membrane protein associated with adipocyte differentiation and/or metabolism function, specifically, an adipocyte-derived secretory/membrane protein containing amino acid sequence which is the same or substantially the same as an amino acid sequence represented by SEQ ID NOS: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 or 22, a nucleic acid encoding it, an antibody therefor, a method of screening prophylactic and/or therapeutic agents for diseases involving abnormality of adipocyte differentiation/metabolism function using it and/or a kit for the screening, a prophylactic and/or therapeutic agent for the diseases or a diagnostic agent containing the membrane protein.

Abstract: The present invention provides a protein containing the same or substantially the same amino acid sequence as the amino acid sequence starting at Amino Acid No. 1 in the amino acid sequence shown by SEQ ID NO:2 or 4, the nucleic acid that encodes it, a method of screening a prophylactic/therapeutic substance for a disease involved in differentiation of skeletal muscle cell and/or metabolic abnormality, which uses the protein or a nucleic acid that encodes it, and the like.

Abstract: The present invention provides a novel secretory/membrane protein associated with adipocyte differentiation and/or metabolism function, specifically, an adipocyte-derived secretory/membrane protein containing amino acid sequence which is the same or substantially the same as an amino acid sequence represented by SEQ ID NOS: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 or 22, a nucleic acid encoding it, an antibody therefor, a method of screening prophylactic and/or therapeutic agents for diseases involving abnormality of adipocyte differentiation/metabolism function using it and/or a kit for the screening, a prophylactic and/or therapeutic agent for the diseases or a diagnostic agent containing the membrane protein.