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The atypical MAPK ERK3 controls positive selection of thymocytes.

Sirois J, Daudelin JF, Boulet S, Marquis M, Meloche S, Labrecque N

Maisonneuve-Rosemont Hospital Research Centre, Montreal, QC, Canada; Department of Microbiology, Infection and Immunology, University of Montreal, Montreal, QC, Canada.

Extracellular signal-regulated kinase 3 (ERK3 )is an atypical member of the mitogen-activated protein kinase (MAPK) family. We have previously shown that ERK3 is expressed during thymocyte differentiation and that its expression is induced in mature peripheral T cells following activation of ERK1/2 by T-cell receptor (TCR) signalling. Herein, we have investigated whether ERK3 expression is required for proper T-cell selection. Using a knock-in mouse model in which the coding sequence of ERK3 is replaced by the gene encoding for the β-galactosidase reporter, we show that ERK3 is expressed by double-positive (DP) thymocytes undergoing positive selection. In ERK3-deficient mice with a polyclonal TCR repertoire, we observe a decrease in positive selection. This reduction in positive selection was also observed when ERK3-deficient mice were backcrossed to class I- and class II-restricted TCR transgenic mice. Furthermore, the response of DP thymocytes to in vitro TCR stimulation was strongly reduced in ERK3-deficient mice. Together, these results show that ERK3 expression following TCR signalling is critical for proper thymic positive selection.

Immunology 2015;145(1):161-9.

Pubmed ID: 25521218

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