Exocytosis in response to antigen (Ag) only occurs when intracellular free ionized calcium is elevated in a single mucosal mast cell. Secretion of serotonin from individual secretory granules is shown by the amperometric current spikes (lower trace). Intracellular calcium in the same cell (upper trace) was detected photometrically, using the calcium-sensitive fluorescent probe indo-1.
Research Interests: Calcium as a second messenger in non-excitable cells, protein kinase C, exocytosis proteins, ion channels in mast cells.
Biophysical and pharmacological approaches are being used to study stimulus-response coupling in cells in the immune system and the role of Ca2+ in this process. We are characterizing the immunoglobulin E receptor-activated signal transduction pathway in mucosal mast cells, and in particular the role of Ca2+ and protein kinase C. Techniques include measurements of intracellular Ca2+ and membrane potential using fluorescent probes and quantitative image-enhanced fluorescence microscopy. Collaborative studies are also under way to identify the exocytosis protein that acts as the Ca2+ sensor in mast cells.
Indo-1 photometry and constant-potential amperometry are being used to monitor intracellular Ca2+ and serotonin secretion at the single-cell level, with high temporal resolution. The ion channels in both resting and stimulated mast cells are being characterized using a variety of techniques, including patch-clamp electrophysiology. Using these approaches we are now characterizing the relationship between release of Ca2+ from intracellular stores, ion channel activation, oscillations in cytoplasmic Ca2+ and the individual exocytotic events occurring in a single cell.