Modulation of Serotonin Transporter Activity by a Protein Kinase C Activator and an Inhibitor of Type 1 and 2A Serine/Threonine Phosphatases
Open Access
- 1 June 1997
- journal article
- research article
- Published by Wiley in Journal of Neurochemistry
- Vol. 68 (6) , 2618-2624
- https://doi.org/10.1046/j.1471-4159.1997.68062618.x
Abstract
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 serotonin transporter (SET). In BeWo cells, treatment with TPA decreased imipramine‐sensitive serotonin uptake with a reduction in Vmax without affecting Km. 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.Keywords
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