CysLT2 receptors interact with CysLT1 receptors and down-modulate cysteinyl leukotriene-dependent mitogenic responses of mast cells

Cysteinyl leukotrienes (cys-LTs) induce inflammation through 2 G protein-coupled receptors (GPCRs), CysLT(1) and CysLT(2), which are coexpressed by most myeloid cells. Cys-LTs induce proliferation of mast cells (MCs), transactivate c-Kit, and phosphorylate extracellular signal-regulated kinase (ERK). Although MCs express CysLT(2), their responses to cys-LTs are blocked by antagonists of CysLT(1). We demonstrate that CysLT(2) interacts with CysLT(1), and that knockdown of CysLT(2) increases CysLT1 surface expression and CysLT(1)-dependent proliferation of cord blood-derived human MCs (hMCs). Cys-LT-mediated responses were absent in MCs from mice lacking CysLT(1) receptors, but enhanced by the absence of CysLT(2) receptors. CysLT(1) and CysLT(2) receptors colocalized to the plasma membranes and nuclei of a human MC line, LAD2. Antibody-based fluorescent lifetime imaging microscopy confirmed complexes containing both receptors based on fluorescence energy transfer. Negative regulation of CysLT(1)-induced mitogenic signaling responses of MCs by CysLT(2) demonstrates physiologically relevant functions for GPCR heterodimers on primary cells central to inflammation.