A novel cDNA encoding a 1436 aa protein was cloned using a PCR system with degenerate primers. This new gene, hPTP-J, was found to encode a PTP protein consisting of an extracellular region containing an MAM (meprin, A5, mu)-like domain, an immunoglobulin-like domain, four fibronectin type-III repeats, a transmembrane region, and a cytoplasmic region containing two tandemly repeated PTP domains hPTP-J is thus considered to be a new member of the type II receptor PTP (RPTP) subfamily, like RPTP mu and RPTP kappa. hPTP-J gene expression was strongly detected in skeletal muscle and moderately detected in the prostate, pancreas, placenta, and heart, but was only weakly detected in the peripheral blood lymphocytes, thymus, and spleen even though gene expression was relatively high in the Jurkat T lymphoma cell line. Moreover, hPTP-J gene expression was down-regulated after Jurkat cells were stimulated by either PMA or calcium ionophore. Based on these findings, it is suggested that some signaling pathways mediated by PMA and/or intracellular calcium are involved in the regulation of hPTP-J gene expression in Jurkat cells.