Somatostatin increases mitogen- induced IL-2 secretion and proliferation of human Jurkat T cells via sst3 receptor isotype.
The neuropeptide somatostatin (SRIF) modulates normal and leukemia T cell proliferation. However, neither molecular isotypes of receptors nor mechanisms involved in these somatostatin actions have been elucidated as yet. Here we show by using RT-PCR approach that mitogen-activated leukemia T cells (Jurkat) express mRNA for a single somatostatin receptor, sst3. This mRNA is apparently translated into protein since specific somatostatin binding sites (K11 = 78 +/- 3 pM) were detected in semipurified plasma membrane preparations by using 125I-Tyr1-SRIF14 as a radioligand. Moreover, somatostatin inhibits adenylyl cyclase activity with similar efficiency (IC50 = 23 +/- 4 pM) thus strongly suggesting a functional coupling of sst3 receptor to this transduction pathway. The involvement of sst3 receptor in immuno-modulatory actions of somatostatin was assessed by analysis of neuropeptide effects on IL-2 secretion and on proliferation of mitogen-activated Jurkat cells. Our data show that in the concentrations comprised between 10 pM and 10 nM, somatostatin potentiates IL-2 secretion. This effect is correlated with somatostatin-dependent increase of Jurkat cell proliferation since the EC50 concentrations for both actions were almost identical (EC50 = 22 +/- 9 pM and EC50 = 12 +/- 1 pM for IL-2 secretion and proliferation, respectively). Altogether, these data strongly suggest that in mitogen-activated Jurkat cells, somatostatin increases cell proliferation through the increase of IL-2 secretion via a functional sst3 receptor negatively coupled to the adenylyl cyclase pathway.[1]References
- Somatostatin increases mitogen-induced IL-2 secretion and proliferation of human Jurkat T cells via sst3 receptor isotype. Cardoso, A., el Ghamrawy, C., Gautron, J.P., Horvat, B., Gautier, N., Enjalbert, A., Krantic, S. J. Cell. Biochem. (1998) [Pubmed]
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