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We studied the effects of 12-O-tetradecanoylphorbol 13-acetate (TPA), a protein kinase C (PKC) activator, and calyculin A (CLA), an inhibitor of type 1 and 2A serine/threonine phosphatases, on serotonin uptake by a human placenta choriocarcinoma cell line (BeWo) and COS-7 cells expressing recombinant serotonm transporter (SET). In BeWo cells, treatment with TPA decreased imipramine-sensitive serotonin uptake with a reduction in Vrnax without affecting K,,~. CLA also decreased imipramine-sensitive serotonin uptake in a manner similar to that of TPA. TPA and CLA also decreased the uptake activity of recombinant SET expressed in COS-7 cells as seen in BeWo cells. These effects of TPA and CLA were reversed by staurosporine, a protein kinase inhibitor. To elucidate whether the inhibitory effects of TPA and CLA were due to direct phosphorylation of SET by PKC, site-directed mutagenesis of five putative PKC phosphorylation sites in SET was performed. Serotonin uptake was also down-regulated by TPA and CLA in all nine mutants, suggesting that these inhibitory modulation of SET activity did not act via direct phosphorylation of SET by PKC. Key Words: Serotonin transporter-Phorbol ester-Calyculin A-BeWo cell-Site-directed mutagenesis-Protein kinase C.

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Wereport a case of spontaneousremission of a massive CNSlesion with eosinophilic infiltrate. This 69-yearold man had eosinophilia without any systemic disorder or laboratory evidence of the most common causes of hypereosinophilia. MRIof the brain suggested an infiltrating neoplasm, but histological examination of a nee-