Defective thymocyte maturation by transgenic expression of a truncated form of the T lymphocyte adapter molecule and Fyn substrate, Sin.
Adapter molecules that promote protein-protein interactions play a central role in T lymphocyte differentiation and activation. In this study, we examined the role of the T lymphocyte-expressed adapter protein and Src kinase substrate, Sin, on thymocyte function using transgenic mice expressing an activated, truncated allele of Sin (SinDeltaC). We found that SinDeltaC expression led to reduced numbers of CD4(+) and CD8(+) single-positive cells and reduced thymic cellularity due to increased thymocyte apoptosis. Because the adapter properties of Sin are mediated by tyrosine-based motifs and given that Sin is a substrate for Src tyrosine kinases, we examined the involvement of these kinases in the inhibitory effects of SinDeltaC. We found that in transgenic thymocytes, SinDeltaC was constitutively phosphorylated by the Src kinase Fyn, but not by the related kinase Lck. Using SinDeltaC and fyn(-/-) animals, we also found that the expression of Fyn was required for the inhibitory effect of SinDeltaC on thymocyte apoptosis but not for SinDeltaC-mediated inhibition of T cell maturation. The inhibitory effect of SinDeltaC on thymocyte maturation correlated with defective activation of the mitogen-activated protein kinase extracellular signal-regulated kinase. Our results suggest that the Sin mutant inhibits thymocyte differentiation through Fyn-dependent and -independent mechanisms and that endogenous Sin may be an important regulator of thymocyte development.
Donlin
Laura T
LT
Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
Roman
Christopher A
CA
Adlam
Matthew
M
Regelmann
Adam G
AG
Alexandropoulos
Konstantina
K
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000276:immunology; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D002470:Cell Survival / Q000235:genetics / Q000276:immunology; D005260:Female; D005786:Gene Expression Regulation / Q000276:immunology; D006131:Growth Inhibitors / Q000235:genetics / Q000502:physiology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D018345:Mice, Knockout; D008822:Mice, Transgenic; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010750:Phosphoproteins / Q000096:biosynthesis / Q000235:genetics*; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D051076:Proto-Oncogene Proteins c-fyn; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D017384:Sequence Deletion; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D013950:Thymus Gland / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D019076:Transgenes / Q000276:immunology; D019061:src-Family Kinases / Q000502:physiology
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D002352:Carrier Proteins; D006131:Growth Inhibitors; C110810:LAT protein, human; C491734:Lat protein, mouse; D008565:Membrane Proteins; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D011948:Receptors, Antigen, T-Cell; C433810:SH3KBP1 protein, human; C494957:FYN protein, human; C494960:Fyn protein, mouse; D051076:Proto-Oncogene Proteins c-fyn; D019061:src-Family Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases