Increased Protein Stability and Interleukin-2 Production of a LATG131D Variant With Possible Implications for T Cell Anergy

Mikel M Arbulo-Echevarria; Inmaculada Vico-Barranco; Isaac Narbona-Sánchez; Francisco García-Cózar; Arkadiusz Miazek; Enrique Aguado

doi:10.3389/fcell.2020.561503

Increased Protein Stability and Interleukin-2 Production of a LAT^G131D Variant With Possible Implications for T Cell Anergy

Front Cell Dev Biol. 2020 Sep 11:8:561503. doi: 10.3389/fcell.2020.561503. eCollection 2020.

Authors

Mikel M Arbulo-Echevarria¹, Inmaculada Vico-Barranco¹, Isaac Narbona-Sánchez¹, Francisco García-Cózar^{1

2}, Arkadiusz Miazek³, Enrique Aguado^{1

2}

Affiliations

¹ Institute of Biomedical Research Cadiz (INIBICA), Cádiz, Spain.
² Department of Biomedicine, Biotechnology and Public Health (Immunology), University of Cádiz and Puerto Real University Hospital Research Unit, Cádiz, Spain.
³ Department of Biochemistry and Molecular Biology, Wrocław University of Environmental and Life Sciences, Wrocław, Poland.

Abstract

The adaptor LAT plays a crucial role in the transduction of signals coming from the TCR/CD3 complex. Phosphorylation of some of its tyrosines generates recruitment sites for other cytosolic signaling molecules. Tyrosine 132 in human LAT is essential for PLC-γ activation and calcium influx generation. It has been recently reported that a conserved glycine residue preceding tyrosine 132 decreases its phosphorylation kinetics, which constitutes a mechanism for ligand discrimination. Here we confirm that a LAT mutant in which glycine 131 has been substituted by an aspartate (LAT^G131D) increases phosphorylation of Tyr132, PLC-γ activation and calcium influx generation. Interestingly, the LAT^G131D mutant has a slower protein turnover while being equally sensitive to Fas-mediated protein cleavage by caspases. Moreover, J.CaM2 cells expressing LAT^G131D secrete greater amounts of interleukin-2 (IL-2) in response to CD3/CD28 engagement. However, despite this increased IL-2 secretion, J.CaM2 cells expressing the LAT^G131D mutant are more sensitive to inhibition of IL-2 production by pre-treatment with anti-CD3, which points to a possible role of this residue in the generation of anergy. Our results suggest that the increased kinetics of LAT Tyr132 phosphorylation could contribute to the establishment of T cell anergy, and thus constitutes an earliest known intracellular event responsible for the induction of peripheral tolerance.

Keywords: IL-2 (interleukin-2); LAT; TCR; anergy; phosphorylation.