EAT-2 links SLAM-family receptors with PLCγ1 to activate human NK cells (116.8)

Abstract

Abstract Cell surface receptors are important mediators of pathogen recognition and intercellular communication. The SLAM-family receptors are a group of Immunoglobulin Superfamily receptors that signal through the small SH2 domain-containing adapters SAP and EAT-2. These adapters promote cellular activation through interactions with Src-family kinases and PKC-θ, though putative inhibitory signaling can be found under some conditions. Our laboratory previously reported a novel interaction between the adapter protein EAT-2 and PLCγ1, suggesting a potent activating potential for EAT-2 in NK cells. Subsequent experiments have demonstrated that EAT-2 phosphorylated on Tyr-127 specifically recruits PLCγ1 but not PLCγ2. By shRNA-mediated knockdown of human NK cell gene expression, we determined that activation of cytotoxicity through SLAM-family receptors was critically dependent on PLCγ1. Importantly, cytotoxicity through other receptors such as CD2 or NKp30 was unaffected by the absence of PLCγ1. While mouse studies have implicated PLCγ2 as a primary mediator of NK cell activation, our study indicates parallel pathways for induction of calcium flux, and demonstrates the importance of the EAT-2/PLCγ1 pathway in human NK cell activity. Further experiments to measure the individual contributions of SAP and EAT-2 have revealed important roles for these proteins in NK cell cytotoxicity.