title: Expression of the p56(Lck) Y505F mutation in CD45-deficient mice rescues thymocyte development.
abstract: Mice deficient in the transmembrane protein tyrosine phosphatase CD45 exhibit a block in thymocyte development. To determine whether the block in thymocyte development was due to the inability to dephosphorylate the inhibitory phosphorylation site (Y505) in p56(lck) (Lck), we generated CD45-deficient mice that express transgenes for the Lck Y505F mutation and the DO11.10 T-cell antigen receptor (TCR). CD4 single-positive T cells developed and accumulated in the periphery. Treatment with antigen resulted in thymocyte apoptosis and the loss of transgenic-TCR-bearing cells. Peripheral CD45-deficient T cells from the mice expressing both transgenes responded to antigen by increasing CD69 expression, interleukin-2 production, and proliferation. These results indicate that thymocyte development requires the dephosphorylation of the inhibitory site in Lck by CD45.
mesh_terms: D000818:Animals; D017209:Apoptosis; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism; D003433:Crosses, Genetic; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D015151:Immunoblotting; D017493:Leukocyte Common Antigens / Q000502:physiology*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D010770:Phosphotransferases / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D013154:Spleen / Q000378:metabolism; D013950:Thymus Gland / Q000254:growth & development*; D013997:Time Factors