MURINE HIP L29 IS A HEPARIN-BINDING PROTEIN WITH A RESTRICTED PATTERNOF EXPRESSION IN ADULT TISSUES/

Heparin/heparan sulfate (Hp/HS)-binding proteins are implicated in a v ariety of cell biological processes including cell adhesion, modulatio n of blood coagulation, and cytokine/growth factor action. Hp/HS-inter acting protein (HIP) has been identified in various adult tissues in h umans. HIP supports high affinity, selective binding to Hp/HS, promote s cell adhesion, and modulates blood coagulation activities via Hp/HS- dependent mechanisms. Herein, a murine ortholog of human HIP is descri bed that is 78.8% identical to human HIP and 99.8% identical at the cD NA level and identical at the aminoacid level to a previously describe d murine ribosomal protein, L29, Western blot analyses and immunohisto logical staining with affinity-purified antibodies generated against t wo distinct peptide sequences of murine HIP/L29 indicate that HIP/L29 is differentially expressed in adult murine tissues and cell types. In the normal murine mammary epithelial cell line, NMuMG, HIP/L29 is enr iched in the 100,000 x g particulate fraction. HIP/L29 can be solubili zed from the 100,000 x g particulate fraction with 0.8 M NaCl, suggest ing that it is a peripheral membrane protein. HIP/L29 directly binds I -125-Hp in gel overlay assays and requires 0.75 M NaCl for elution fro m Hp-agarose. In addition, recombinant murine HIP expressed in Escheri chia coli binds Hp in a saturable and highly selective manner, compare d with other glycosaminoglycans including dermatan sulfate, chondroiti n sulfate, keratan sulfate, and hyaluronic acid. Collectively, these d ata indicate that murine HIP/L29, Like its human ortholog, is a Hp-bin ding protein expressed in a restricted manner in adult tissues.