ShcA Mediates the Dominant Pathway to Extracellular Signal-Regulated Kinase Activation during Early Thymic Development

Abstract

During thymic development, the β selection checkpoint is regulated by pre-T-cell receptor-initiated signals. Progression through this checkpoint is influenced by phosphorylation and activation of the serine/threonine kinases extracellular signal-regulated kinase 1 (ERK1) and ERK2, but the in vivo relevance of specific upstream players leading to ERK activation is not known. Here, using mice with a conditional loss of the shc1 gene or expressing mutants of ShcA, we demonstrate that the adapter protein ShcA is responsible for up to 70% of ERK activation in double-negative (DN) thymocytes in vivo and ex vivo. We also identify two specific tyrosines on ShcA that promote ERK phosphorylation in vivo, and mice expressing ShcA with mutations of these tyrosines show impaired DN thymocyte development. This work provides the first in vivo demonstration of the relative requirement of upstream adapters in controlling ERK activation during β selection and suggests a dominant role for ShcA.

Supplemental material for this article may be found at http://mcb.asm.org/.

We thank Tim Bender and Ulrike Lorenz for discussions and suggestions, Chris Wilson for the lck-Cre transgenic mouse line, and the FACS core facility at the University of Virginia for assistance. We also thank the members of the Ravichandran lab for helpful discussions.

This work was supported by a grant from the National Institutes of Health (GM55761 to K.S.R.).