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J Exp Med. 2007 Jul 9;204(7):1703-15. Epub 2007 Jul 2.

Distinct roles for Syk and ZAP-70 during early thymocyte development.

Author information

1
Department of Medicine, the Rosalind Russell Medical Research Center for Arthritis, University of California-San Francisco, San Francisco, CA 94143, USA.

Abstract

The spleen tyrosine kinase (Syk) and zeta-associated protein of 70 kD (ZAP-70) tyrosine kinases are both expressed during early thymocyte development, but their unique thymic functions have remained obscure. No specific role for Syk during beta-selection has been established, and no role has been described for ZAP-70 before positive selection. We show that Syk and ZAP-70 provide thymocytes with unique and separable fitness advantages during early development. Syk-deficient, but not ZAP-70-deficient, thymocytes are specifically impaired in initial pre-TCR signaling at the double-negative (DN) 3 beta selection stage and show reduced cell-cycle entry. Surprisingly, and despite overlapping expression of both kinases, only ZAP-70 appears to promote sustained pre-TCR/TCR signaling during the DN4, immature single-positive, and double-positive stages of development before thymic selection occurs. ZAP-70 promotes survival and cell-cycle progression of developing thymocytes before positive selection, as also shown by in vivo anti-CD3 treatment of recombinase-activating gene 1-deficient mice. Our results establish a temporal separation of Syk family kinase function during early thymocyte development and a novel role for ZAP-70. We propose that pre-TCR signaling continues during DN4 and later stages, with ZAP-70 dynamically replacing Syk for continued pre-TCR signaling.

PMID:
17606633
PMCID:
PMC2118636
DOI:
10.1084/jem.20070405
[Indexed for MEDLINE]
Free PMC Article

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