MURINE DEP-1, A RECEPTOR PROTEIN-TYROSINE-PHOSPHATASE, IS EXPRESSED IN MACROPHAGES AND IS REGULATED BY CSF-1 AND LPS

The spectrum of protein tyrosine phosphatases (PTPs) expressed in bone marrow-derived murine macrophages (BMMs) was examined using reverse t ranscriptase-polymerase chain reaction. Ten different PTP cDNAs were i solated and in this study we focus on mDEP-1, a type III receptor PTP. Three mDEP-1 transcripts were expressed in primary macrophages and ma crophage cell lines and were induced during macrophage differentiation of M1 myeloid leukemia cells. A valiant mRNA Tvas identified that enc odes an alternate carboxyl-terminus and 3' UTR. The expression of mDEP -1 was down-regulated by CSF-1 (macrophage colony-stimulating factor) and up-regulated by bacterial lipopolysaccharide, an important physiol ogical regulator of macrophage function that opposes CSF-1 action. Who le mount irt situ hybridization, and immunolocalization of the protein , confirmed that mDEP-1 is expressed by a subset of embryonic macropha ges in the liver and mesenchyme. mDEP-1 was also detected in the eye a nd peripheral nervous system of the developing embryo. Attempts to exp ress mDEP-1 constitutively in the macrophage cell line RAW264 were uns uccessful, with results suggesting that the gene product inhibits cell proliferation.