2 E). orchestrated by the cosignaling network, which is involved in all stages of the T cell response (Croft, 2003; Zhu et al., 2011). The B7/CD28 family of Ig superfamily (IGSF) and several members of TNF receptor superfamily are the major groups of T cell cosignaling molecules (Chen and Flies, 2013). The importance of these cosignaling pathways has been emphasized in a variety of human diseases, including graft versus host disease, autoimmunity, infection, and cancer (Rosenblum et al., 2012; Yao et al., 2013; Drake et al., 2014). Poliovirus receptor (PVR)Clike proteins are a newly emerging group of IGSF with T cell cosignaling functions (Chan et al., 2012; Pauken and Wherry, 2014). This group of molecules share PVR signature motifs in the first Ig variableClike (IgV) domain and are originally known AZD5438 to mediate epithelial cellCcell contacts (Takai et al., 2008; Yu et al., 2009). The two ligands, CD155 (PVR/Necl-5) and CD112 (PVRL2/nectin-2), interact with CD226 (DNAM-1) to costimulate T cells, and they also inhibit T cell response through another coinhibitory receptor, T cell Ig and immunoreceptor tyrosine-based inhibitory motif (ITIM) domain (TIGIT; Yu et al., 2009). CD155 seems to be the predominant ligand in this ligand/receptor network because the interaction between CD112 and TIGIT is very weak (Yu et al., 2009). Adding to the complexity of this network, CD155, but not CD112, interacts with CD96, another PVR-like protein present on T cells and NK cells, though the function of this interaction is still unclear (Fuchs et al., 2004; Seth et al., 2007; Chan et al., 2014). In addition to its intrinsic inhibitory function, TIGIT exerts its T cell inhibitory effects AZD5438 through ligating CD155 on DCs to increase IL-10 secretion or competes with the costimulatory receptor CD226 for ligand interaction (Yu et al., 2009; Lozano et al., 2012; Stengel et al., 2012). Although the molecular and functional relationship between CD226 and TIGIT is still unclear, this novel cosignaling pathway represents important immunomodulators of T cell responses, as well as valuable targets for future immunotherapy (Joller et al., 2011, 2014; Levin et al., 2011; Johnston et al., 2014; Zhang et al., 2014; AZD5438 Chauvin et al., 2015). In this study, we identified CD112R as a new coinhibitory receptor of the PVR family for human T cells. RESULTS AND DISCUSSION Charactering CD112R as a new receptor of the PVR family We performed an extensive genome-wide search to look for genes that are both preferentially expressed on human T cells and encode transmembrane proteins with a single IgV extracellular domain. We discovered a candidate human gene previously named PVR-related Ig domain containing (PVRIG; NCBI Nucleotide database accession no. {“type”:”entrez-nucleotide”,”attrs”:{“text”:”BC073861″,”term_id”:”49522665″}}BC073861). We renamed it as the receptor for CD112 (CD112R) to reflect its strong interaction with CD112 as described in this study. The CD112R gene encodes a putative single transmembrane protein, which is composed of a single extracellular IgV domain, one transmembrane domain, and AZD5438 a long intracellular domain (Fig. 1 A). Notably, the intracellular domain of human CD112R contains two tyrosine residues, one within an ITIM-like motif that is a potential docking site for phosphatases (Billadeau and Leibson, 2002). The extracellular domain sequence of human and mouse CD112R have 65.3% Rabbit polyclonal to ZNF300 similarity (Fig. 1 B). Phylogenic tree analysis of the first IgV of the PVR family reveals that CD112R is close to PVR-like proteins (Fig. 1 C). Alignment of the amino acid sequence indicates that the IgV domain of CD112R contains residues conserved among the PVR family (Fig. 1 D). These residues constitute at least three main motifs shared among the PVR family: Val, Ile-Ser, and Thr-Gln at position 72C74 aa of CD112R, Ala89-X6-Gly96, and Tyr139 or Phe139-Pro140-X-Gly142 (Yu et al., 2009). Using the first IgV domain of PVRL4 as a template, we constructed a structural model of CD112R. CD112R seems to adapt a V-set Ig fold consisting of a series of sheets (Fig. 1 E). Open in a separate window Figure 1. Characterization of human CD112R protein. (A) Protein sequence encoded by the human CD112R gene. Predicted extracellular IgV-like and transmembrane domains are highlighted.