The Lifeact-EGFP mouse is a translationally controlled fluorescent reporter of T cell activation
Jorge Luis Galeano Niño, Szun S. Tay, Jacqueline L.E. Tearle, Jianling Xie, Matt Govendir, Daryan Kempe, Jessica K. Mazalo, Alexander P. Drew, Feyza Colakoglu, Sarah Kummerfeld, Christopher G. Proud, Maté Biro
Abstract
ABSTRACT It has become increasingly evident that T cell functions are subject to translational control in addition to transcriptional regulation. Here, by using live imaging of CD8+ T cells isolated from the Lifeact-EGFP mouse, we show that T cells exhibit a gain in fluorescence intensity following engagement of cognate tumour target cells. The GFP signal increase is governed by Erk1/2-dependent distal T cell receptor (TCR) signalling and its magnitude correlates with IFN-γ and TNF-α production, which are hallmarks of T cell activation. Enhanced fluorescence was due to increased translation of Lifeact-EGFP protein, without an associated increase in its mRNA. Activation-induced gains in fluorescence were also observed in naïve and CD4+ T cells from the Lifeact-EGFP reporter, and were readily detected by both flow cytometry and live cell microscopy. This unique, translationally controlled reporter of effector T cell activation simultaneously enables tracking of cell morphology, F-actin dynamics and activation state in individual migrating T cells. It is a valuable addition to the limited number of reporters of T cell dynamics and activation, and opens the door to studies of translational activity and heterogeneities in functional T cell responses in situ.