Functional association of Fc epsilon RI gamma with Arginine(632) of pairedimmunoglobulin-like receptor (PIR)-A3 in murine macrophages

Paired immunoglobulin-like receptors (PIR) are expressed on B cells and mac rophages and include inhibitory and putative activating receptors referred to as PIR B and PIR-A, respectively. Although PIR-B's inhibitory pathway ha s been described, it is unknown whether PIR-A receptors can deliver activat ion signals to macrophages, and if so, through what mechanism. Here we use chimeric receptors to address the mechanisms of PIR-A signaling. Cotransfec tion of chimeric receptors comprised of the extracellular region of human C D4 and the transmembrane and cytoplasmic domains of murine PIR-A3 showed th e ability of PIR-A3 to physically interact with the Fc epsilon Rl gamma cha in in 293T cells. This interaction is dependent on Arg(632) within the PIR- A3 transmembrane domain. We also demonstrate PIR-A3 interaction with the en dogenous Fc epsilon Rl gamma of the ANA-1 macrophage cell line, again in an Arg(632)-dependent manner. Furthermore, we show that crosslinking of these chimeric receptors synergizes with IFN-gamma in the production of nitric o xide. Our data are the first to show the potential of PIR-A3 to deliver act ivation signals to macrophages and establish its dependence on Arg632. Thes e findings suggest that further study of the PIR-A receptors should be aggr essively pursued toward a complete understanding of the intricate regulatio n of macrophage biology. This is a US government work. There are no restric tions on its use.