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Original Article |
/ßregulated Developmental Transitions
Correspondence to: Kristin M. Abraham, Department of Microbiology and Immunology, BRB 13-045, University of Maryland School of Medicine, 655 W. Baltimore St., Baltimore, MD 21201-1559. Tel:410-706-4126 Fax:410-706-2129 E-mail:kabraham{at}umaryland.edu.
Maturational changes at the CD4-CD8- double negative (DN) to CD4+CD8+ double positive (DP) transition are dependent on signals generated via the preT cell receptor (TCR) and the nonreceptor protein tyrosine kinase p56lck (Lck). How Lck activities are stimulated or relayed after pre-TCR formation remains obscure. Our structurefunction mapping of Lck thymopoietic properties reveals that the noncatalytic domains of Lck are specialized to signal efficient cellular expansion at DN to DP transition. Moreover, although substitution of the Lck catalytic domain with FynT sequences minimally impacts DP development, single positive thymocytes are most efficiently produced in the presence of kinases containing both the NH2-terminal and catalytic regions of Lck. These findings demonstrate that the Lck structure is uniquely adapted to mediate signals at both major transitions in thymopoiesis.
Key Words: thymus, signal transduction, cellular differentiation, protein kinases, lymphocytes
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