Nerve-mast cell (RBL) interaction: RBL membrane ruffling occurs at the contact site with an activated neurite

Mast cell-neurite interaction serves as a model for neuroimmune interaction. We have shown that neurite-mast cell communication can occur via substance P interacting with neurokinin (NK)-1 receptors on the mucosal mast cell-like cell, the rat basophilic leukemia (RBL) cell. Neurite (murine superior cervical ganglia) and RBL cell [expressing the granule-associated antigen CD63-green fluorescent protein (GFP) conjugate] cocultures were established and stimulated with bradykinin (BK; 10 nM) or scorpion venom (SV; 10 pg/ml), both of which activate only neurites. Cell activation was assessed by confocal imaging of Ca2+ (cells preloaded with fluo 3), and analyses of RBL CD63-GFP+ granule movement were conducted. Neurite activation by BK or SV was followed by RBL Ca2+ mobilization, which was inhibited by an NK-1 receptor antagonist (NK-1 RA). Moreover, membrane ruffling was observed on RBL pseudopodial extensions in contact with the activated neurite, but not on noncontacting pseudopodia. RBL membrane ruffling was inhibited by NK-1 RA, but not NK-2 RA, and was accompanied by a significant increase in granule movement (0.13 +/- 0.04 vs. 0.05 +/- 0.01 microm/s) that was most evident at the point of neurite contact: many of the granules moved toward the plasmalemma. This is the first documentation of such precise (restricted to the membrane's contact site) transfer of information between nerves and mast cells that could allow for very subtle in vivo communication between these two cell types.