Characterization of a human sphingosine-1-phosphate receptor gene (S1P5) and its differential expression in LGL leukemia.

Large granular lymphocyte (LGL) leukemia is a lymphoproliferative disorder often associated with autoimmune disease. A central feature of this disease is dysregulation of apoptosis. In order to identify differentially expressed genes in LGL leukemia, microarray analysis was performed. We found many differentially expressed genes including several expression sequence tags (ESTs). As a systematic study, we selected one up-regulated EST (GenBank Accession number N47089) and further investigated. An LGL leukemia library was screened using this EST as a probe and a full-length sequence for a novel gene was identified. The deduced amino acid sequence revealed that the novel gene encodes a G-protein-coupled receptor gene that exhibits 86% identity with rat sphingosine-1-phosphate receptor (edg-8/nrg-1). This gene is present in brain, spleen, and peripheral blood mononuclear cells (PBMC) and is overexpressed in leukemic LGL.