Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

Antibodies for serotonin transporter (SERT) were used to assess expression of SERT in neuronal and non-neuronal cells, and to investigate trancriptional and post-tranlational regulations of this gene. Immunoblotting of NMB and COS-7 cells transfected with pCMV-rSERT revealed two immunoreactive bands, 83±3 and 110±3 kDa, that were larger than the two bands of human placental JAR cells (75±3 and 95±3 kDa), expressing the transporter constitutively. The inhibitor of N-linked glycosylation tunicamycin decreased by 40% the size of SERT in both NMB- and COS-7-transfected cells, and in JAR cells. It is well known that a short treatment with TPA decreases serotonin uptake. Whether TPA also has a long-term effect on serotonin transport, possibly at the transcriptional level, was studied. TPA treatment for 24-72 hr increased 3H-5HT uptake in JAR cells in a time- and dose-dependent way, and Lineweaver-Burk analysis indicated an increase of 2-3 folds in Vmax, with no effect on Km. Phorbol analogues that do not activate protein kinase C did not increase 3H-5HT uptake. As expected, 30 min treatment with TPA had no effect on SERT protein level, whereas 48 hr treatment increased SERT immunoreactivity. The cyclic-AMP phosphodiesterase inhibitor IBMX, like cholera toxin, increased 3H-5HT uptake. Interestingly, the effect of long-term co-treatment with cholera toxin and TPA was not additive. RT-PCR analysis showed that the glucocorticoid hormone dexamethasone inhibited the long-term effect of TPA on SERT mRMA level. Whether transcription factors such as AP-1 proteins participate in modulating expression of SERT gene is discussed.

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Presentation Number SAdus0133
Keywords: depression, protein kinase, steroids, neurotransmitter, PCR