Smad3 is essential for TGF-beta 1 to suppress IL-2 production and TCR-induced proliferation, but not IL-2-induced proliferation.
Transforming growth factor-beta1 is essential to maintain T cell homeostasis, as illustrated by multiorgan inflammation in mice deficient in TGF-beta1 signaling. Despite the physiological importance, the mechanisms that TGF-beta1 uses to regulate T cell expansion remain poorly understood. TGF-beta1 signals through transmembrane receptor serine/threonine kinases to activate multiple intracellular effector molecules, including the cytosolic signaling transducers of the Smad protein family. We used Smad3(-/-) mice to investigate a role for Smad3 in IL-2 production and proliferation in T cells. Targeted disruption of Smad3 abrogated TGF-beta1-mediated inhibition of anti-CD3 plus anti-CD28-induced steady state IL-2 mRNA and IL-2 protein production. CFSE labeling demonstrated that TGF-beta1 inhibited entry of wild-type anti-CD3 plus anti-CD28-stimulated cells into cycle cell, and this inhibition was greatly attenuated in Smad3(-/-) T cells. In contrast, disruption of Smad3 did not affect TGF-beta1-mediated inhibition of IL-2-induced proliferation. These results demonstrate that TGF-beta1 signals through Smad3-dependent and -independent pathways to inhibit T cell proliferation. The inability of TGF-beta1 to inhibit TCR-induced proliferation of Smad3(-/-) T cells suggests that IL-2 is not the primary stimulus driving expansion of anti-CD3 plus anti-CD28-stimulated T cells. Thus, we establish that TGF-beta1 signals through multiple pathways to suppress T cell proliferation.
McKarns
Susan C
SC
Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI 48824 USA. smckarns@niaid.nih.gov
Schwartz
Ronald H
RH
Kaminski
Norbert E
NE
D000818:Animals; D002455:Cell Division / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017353:Gene Deletion; D006131:Growth Inhibitors / Q000502:physiology*; D007376:Interleukin-2 / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology*; D008213:Lymphocyte Activation / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010766:Phosphorylation; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D011948:Receptors, Antigen, T-Cell / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000502:physiology; D015398:Signal Transduction / Q000276:immunology*; D051899:Smad2 Protein; D051900:Smad3 Protein; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D015534:Trans-Activators / Q000172:deficiency / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000502:physiology*; D053773:Transforming Growth Factor beta1
D004268:DNA-Binding Proteins; D006131:Growth Inhibitors; D007376:Interleukin-2; D012333:RNA, Messenger; D011948:Receptors, Antigen, T-Cell; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; C508961:Tgfb1 protein, mouse; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1