title: Molecular and functional characterization of a CS1 (CRACC) splice variant expressed in human NK cells that does not contain immunoreceptor tyrosine-based switch motifs.
abstract: CS1 (CRACC, novel Ly9) is a novel member of the CD2 family expressed on natural killer (NK), T and stimulated B cells. Although the cytoplasmic domain of CS1 contains immunoreceptor tyrosine-based switch motifs (ITSM), which enables to recruite signaling lymphocyte activation molecule (SLAM)-associated protein (SAP/SH2D1A), it activates NK cells in the absence of a functional SAP. CS1 is a self ligand and homophilic interaction of CS1 regulates NK cell cytolytic activity. Here we have identified a novel splice variant of CS1 (CS1-S), which lacks ITSM. Human NK cells express mRNA for both wild-type CS1 (CS1-L) and CS1-S and their expression level remained steady upon various stimulations. To determine the function of each isoform, cDNA for CS1-L and CS1-S were transfected into the rat NK cell line RNK-16 and functionally tested using redirected cytotoxicity assays and calcium flux experiments. CS1-L was able to mediate redirected cytotoxicity of P815 target cells in the presence of monoclonal antibody against CS1 and a rise in intracellular calcium within RNK-16 cells, suggesting that CS1-L is an activating receptor, whereas CS1-S showed no effects. Interestingly, SAP associated with unstimulated CS1-L and dissociated upon pervanadate stimulation. These results indicate that CS1-L and CS1-S may differentially regulate human NK cell functions.
authors.affiliation: Department of Molecular Biology and Immunology and Institute for Cancer Research, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, USA.
authors.forename: Jae Kyung
authors.initials: JK
authors.lastname: Lee
authors.forename: Kent S
authors.initials: KS
authors.lastname: Boles
authors.forename: Porunelloor A
authors.initials: PA
authors.lastname: Mathew
mesh_terms: D020816:Amino Acid Motifs / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D003602:Cytotoxicity, Immunologic; D004274:DNA, Recombinant; D005434:Flow Cytometry; D015723:Gene Library; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology*; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D011971:Receptors, Immunologic / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071176:Signaling Lymphocytic Activation Molecule Family; D014162:Transfection; D014443:Tyrosine / Q000276:immunology
chemical_list: D004274:DNA, Recombinant; D020033:Protein Isoforms; D012333:RNA, Messenger; D011971:Receptors, Immunologic; C448987:SLAMF7 protein, human; D000071176:Signaling Lymphocytic Activation Molecule Family; D014443:Tyrosine