Abstract
RasGRP1 is a guanine nucleotide exchange factor for Ras that is required for the efficient production of both CD4 and CD8 single-positive thymocytes. We found that RasGRP1 expression is rapidly up-regulated in double-negative thymocytes following pre-TCR ligation. Transgenic overexpression of RasGRP1 compensated for deficient pre-TCR signaling in vivo, enabling recombinase-activating gene 2(-/-) double-negative thymocytes to mature to the double-positive stage. RasGRP1 transgenic mice had a 4-fold increase in CD8 single-positive thymocytes, most of which had atypically low levels of CD3. The RasGRP1 transgene lowered the threshold of TCR signaling needed to initiate proliferation of single-positive thymocytes, with this effect being particularly evident among CD8 single-positive cells. In 3-day cultures, TCR stimulation via anti-CD3 caused a 10-fold increase in the ratio of CD8 to CD4 thymocytes among RasGRP1 transgenic vs nontransgenic thymocytes. These results demonstrate that in addition to driving the double-negative to double-positive transition, increased expression of RasGRP1 selectively increases CD8 single-positive thymocyte numbers and enhances their responsiveness to TCR signaling.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adjuvants, Immunologic / biosynthesis
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Adjuvants, Immunologic / genetics
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Adjuvants, Immunologic / physiology*
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Amino Acid Sequence
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Animals
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CD8 Antigens / biosynthesis*
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CD8 Antigens / genetics
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CD8-Positive T-Lymphocytes / cytology*
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CD8-Positive T-Lymphocytes / immunology
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CD8-Positive T-Lymphocytes / metabolism
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Cell Differentiation / genetics
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Cell Differentiation / immunology
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Cell Division / genetics
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Cell Division / immunology
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Crosses, Genetic
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DNA-Binding Proteins / biosynthesis*
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DNA-Binding Proteins / genetics*
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DNA-Binding Proteins / physiology
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Guanine Nucleotide Exchange Factors*
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Humans
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Lymphocyte Count
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Mice
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Mice, Inbred C57BL
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Mice, Inbred DBA
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Mice, Knockout
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Mice, Transgenic
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Molecular Sequence Data
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Nuclear Proteins
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Receptors, Antigen, T-Cell / immunology
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Receptors, Antigen, T-Cell / metabolism
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Receptors, Antigen, T-Cell / physiology
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T-Lymphocyte Subsets / cytology
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T-Lymphocyte Subsets / immunology
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T-Lymphocyte Subsets / metabolism
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T-Lymphocytes / cytology*
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T-Lymphocytes / immunology*
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T-Lymphocytes / metabolism
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Thymus Gland / cytology*
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Thymus Gland / immunology
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Thymus Gland / metabolism
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Transgenes / immunology
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Up-Regulation / genetics
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Up-Regulation / immunology
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ras Proteins / physiology
Substances
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Adjuvants, Immunologic
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CD8 Antigens
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DNA-Binding Proteins
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Guanine Nucleotide Exchange Factors
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Nuclear Proteins
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RAG2 protein, human
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RASGRP1 protein, human
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Rag2 protein, mouse
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Rasgrp1 protein, mouse
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Receptors, Antigen, T-Cell
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V(D)J recombination activating protein 2
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ras Proteins