Cell type-specific localization of sphingosine kinase 1a in human tissues

Cell type-specific localization of sphingosine kinase 1a (SPHK1a) in tissue s was analyzed with a rabbit polyclonal antibody against the 16 C-terminal amino acids derived from the recently reported mouse cDNA sequence of SPHK1 a. This antibody (anti-SPHK1a antibody) can react specifically with SPHK1a of mouse, rat, and human tissues. Utilizing its crossreactivity to human SP HK1a, the cell-specific localization of SPHK1a in human tissues was histoch emically examined. Strong positive staining for SPHK1a was observed in the white matter in the cerebrum and cerebellum, the red nucleus and cerebral p eduncle in the midbrain, the uriniferous tubules in the kidney, the endothe lial cells in vessels of various organs, and in megakaryocytes and platelet s. The lining cells of sinusoids in the liver and splenic cords in the sple en showed moderate staining. Columnar epithelia in the intestine and Leydig 's cells in the testis showed weak staining patterns. In addition, TPA-trea ted HEL cells, a human leukemia cell line, showed a megakaryocytic phenotyp e accompanied with increases in immunostaining of both SPHK1a and SPHK enzy me activity, suggesting that SPHK1a may be a novel marker of megakaryocytic differentiation and that this antibody is also useful for in vitro study o f differentiation models.