Three genes encoding secretory membrane proteins have been successfully isolated from an osteoblast-like cell line by a method for specifically cloning secretory membrane proteins. One of these genes encodes a novel receptor protein. The protein has only the extracellular region, binds to the cell membrane via a GPI anchor, and carries therein a cysteine-rich, repetitive region commonly conserved in the TNF receptor super family. Overexpression of this protein in osteoblast-like cell line cells suppresses cell proliferation, changes cell morphology, and increases alkaline phosphatase activity, which is one of markers for differentiation of osteoblasts.