Activation of cGMP-dependent protein kinase Iβ inhibits interleukin 2 release and proliferation of T cell receptor-stimulated human peripheral T cells

Several major functions of type I cGMP-dependent protein kinase (cGK I) have been established in smooth muscle cells, platelets, endothelial cells, and cardiac myocytes, Here we demonstrate that cGK I beta is endogenously expressed in freshly purified human peripheral blood T lymphocytes and inhibits their proliferation and interleukin 2 release. Incubation of human T cells with the NO donor, sodium nitroprusside, or the mem brane-permeant cGMP analogs PET-cGMP and 8-pCPT-cGMP, activated cGK I and produced (i) a distinct pattern of phosphorylation of vasodilator-stimulated phosphoprotein, (ii) stimulation of the mitogen-activated protein kinases ERK1/2 and p38 kinase, and, upon anti-CD3 stimulation, (iii) inhibition of interleukin 2 release and (iv) inhibition of cell proliferation. cGK I was lost during in vitro culturing of primary T cells and was not detectable in transformed T cell lines. The proliferation of these cGK I-deficient cells was not inhibited by even high cGMP concentrations indicating that cGK I, but not cGMP-regulated phosphodiesterases or channels, cAMP-dependent protein kinase, or other potential cGMP mediators, was responsible for inhibition of T cell proliferation, Consistent with this, overexpression of cGK I beta, but not an inactive cGK I beta mutant, restored cGMP-dependent inhibition of cell proliferation of Jurkat cells, Thus, the NO/cGMP/cGK signaling system is a negative regulator of T cell activation and proliferation and of potential significance for counteracting inflammatory or lymphoproliferative processes.