Differential Function of Themis CABIT Domains during T Cell Development

Toshiyuki Okada,Hiroyo Oda,Harumi Suzuki,Kentaro Kaji,Akiko Takashima,Takeshi Nitta,Tadashi Okamura,Norimasa Tamehiro,Michael S Patrick,Motohito Goto,Jon C D Houtman

doi:10.1371/journal.pone.0089115

Toshiyuki Okada, Hiroyo Oda + Show 9 more

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https://doi.org/10.1371/journal.pone.0089115

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Journal: PloS one	Publication Date: Feb 21, 2014
Citations: 10	License type: CC BY 4.0

Affiliation: National Center for Global Health and Medicine

Abstract

Themis (also named Gasp) is a newly identified Grb2-binding protein that is essential for thymocyte positive selection. Despite the possible involvement of Themis in TCR-mediated signal transduction, its function remains unresolved and controversial. Themis contains two functionally uncharacterized regions called CABIT (cysteine-containing, all-β in Themis) domains, a nuclear localization signal (NLS), and a proline-rich sequence (PRS). To elucidate the role of these motifs in Themis’s function in vivo, we established a series of mutant Themis transgenic mice on a Themis−/− background. Deletion of the highly conserved Core motif of CABIT1 or CABIT2 (Core1 or Core2, respectively), the NLS, or the PRS abolished Grb2-association, as well as TCR-dependent tyrosine-phosphorylation and the ability to induce positive selection in the thymus. The NLS and Core1 motifs were required for the nuclear localization of Themis, whereas Core2 and PRS were not. Furthermore, expression of ΔCore1- but not ΔCore2-Themis conferred dominant negative-type inhibition on T cell development. Collectively, our current results indicate that PRS, NLS, CABIT1, and CABIT2 are all required for positive selection, and that each of the CABIT domains exerts distinct functions during positive selection.

Highlights

T cells develop through positive and negative selection in the thymus to become either class II MHC-restricted helper CD4+CD82 [CD4-single positive (CD4SP)] or class I MHCrestricted cytotoxic CD42CD8+ (CD8SP) cells [1]
We found that the proline-rich sequence (PRS), Core1, and Core2 motifs were all required for Grb2-binding and TCR-dependent tyrosine-phosphorylation, as well as for positive selection in the thymus
As has been reported [9], introduction of a CD2-driven wildtype Themis transgene into Themis2/2 mice successfully recovered defective positive selection in the knockout (Fig. 2A), proving that this transgenic approach is useful to evaluate the function of Themis mutant proteins in vivo

Summary

Introduction

T cells develop through positive and negative selection in the thymus to become either class II MHC-restricted helper CD4+CD82 [CD4-single positive (CD4SP)] or class I MHCrestricted cytotoxic CD42CD8+ (CD8SP) cells [1]. Themis (thymocyte-expressed molecule involved in selection) was identified as a novel mandatory factor for positive selection by five independent groups in 2009 [2,3-4,5-6]. Themis knockout mice exhibited significantly reduced numbers of CD4SP and CD8SP T cells both in the thymus and periphery [2,3-4,5-6]. Inhibitory effects of Themis deficiency on negative selection and T cell activation were controversial among the reports [2,3-4,5], they were much slighter than that for positive selection. Since Themis-deficient mice did not exhibit inflammatory bowel disease or autoimmune diseases observed in Tregdeficient mice, functional requirements for Themis in Tregs could be different between rat and mouse

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