Paxillin Binding to the Cytoplasmic Domain of CD103 Promotes Cell Adhesion and Effector Functions for CD8+ Resident Memory T Cells in Tumors.

Ludiane Gauthier,Pierre Validire,Marie Boutet,Fathia Mami-Chouaib,Georges Bismuth,Gwendoline Gros,Stéphanie Corgnac

doi:10.1158/0008-5472.can-17-1487

Abstract

CD8+/CD103+ tissue-resident memory T cells (TRM cells) accumulate in several human solid tumors, where they have been associated with a favorable prognosis. However, the role of CD103, the α subunit of the integrin αEβ7 (also known as CD103), in the retention and functions of these TRM is undefined. In this report, we investigated the role of CD103 cytoplasmic domain and the focal adhesion-associated protein paxillin (Pxn) in downstream signaling and functional activities triggered through αE/CD103 chain. Binding to immobilized recombinant (r)E-cadherin-Fc of CD103 integrin expressed on tumor-specific CTL clones promotes phosphorylation of Pxn and Pyk2 and binding of Pxn to the αE/CD103 subunit tail. Inhibition of Pxn phosphorylation by the Src inhibitor saracatinib or its knockdown via shRNA dramatically altered adhesion and spreading of freshly isolated CD8+/CD103+ lung tumor-infiltrating lymphocytes and CD103+ tumor-specific CTL clones. Inhibition of Pxn phosphorylation with saracatinib in these CTL clones also severely compromised their functional activities toward autologous tumor cells. Using Jurkat T cells as a model to study CD103 integrin activation, we demonstrated a key role of serine residue S1163 of the αE chain intracellular domain in polarization of CD103 and recruitment of lysosomes and Pxn at the contact zone of T lymphocytes with rE-cadherin-Fc-coated beads. Overall, our results show how Pxn binding to the CD103 cytoplasmic tail triggers αEβ7 integrin outside-in signaling that promotes CD8+ T-cell migratory behavior and effector functions. These results also explain the more favorable prognosis associated with retention of TRM cells in the tumor microenvironment. Cancer Res; 77(24); 7072-82. ©2017 AACR.

Highlights

The aE(CD103)b7 integrin, hereafter referred to as CD103, plays a key role in cytotoxic immunological synapse (IS) formation and T-cell receptor (TCR)–mediated cytotoxicity toward epithelial tumor cells, through polarized exocytosis of their lytic granules at the IS [1, 2]
Using Jurkat T cells as a model to study CD103 integrin activation, we demonstrated a key role of serine residue S1163 of the aE chain intracellular domain in polarization of CD103 and recruitment of lysosomes and Pxn at the contact zone of T lymphocytes with rE-cadherin-Fc–coated beads
We show that the CD103 integrin is indispensable for TCR-mediated CD8þ/CD103þ TRM activities through the aE chain cytoplasmic domain, and that a phosphorylatable Ser at position 1163 in the ES1163IRKAQL motif of the subunit tail plays an important role in CD103 functions

Summary

Introduction

The aE(CD103)b7 integrin, hereafter referred to as CD103, plays a key role in cytotoxic immunological synapse (IS) formation and T-cell receptor (TCR)–mediated cytotoxicity toward epithelial tumor cells, through polarized exocytosis of their lytic granules at the IS [1, 2]. CD103 promotes CD8þ TIL activities by mediating T-cell recruitment within epithelial tumor islets, and initiating intratumoral early T-cell signaling [13] Each TCR microcluster is surrounded by an adhesion molecule structure, including leukocyte-function-associated antigen (LFA-1), the focal-adhesion–associated adaptor protein paxillin (Pxn) and proline-rich tyrosine kinase-2 (Pyk2) Disruption of these microstructures by downregulating both Pxn and Pyk inhibits T-cell activation and functions, indicating that these molecules are necessary for providing the outside-in signals required for optimal CTL responses [15, 16]. Pxn is a 68 kDa protein associated with actin binding and signaling proteins This adaptor molecule is activated through phosphorylation of several tyrosine (Tyr and Tyr118) and serine (Ser and Ser178) residues by different kinases, including focal adhesion kinase (FAK), Src kinase, JNK, and p38 MAPK [17,18,19]. The CD103-Pxn partnership is likely to represent a major outside-in signaling axis required for effector functions of CTL, including TRM, and thereby opens new avenues for the success of T-cell–based cancer immunotherapies

Materials and Methods

C Vehicle

Discussion

Disclosure of Potential Conflicts of Interest