Correlating Ca2+ responses and secretion in individual RBL-2H3 mucosal mast cells.
The role of Ca2+ in stimulus-response coupling in nonexcitable cells is still not well understood. The Ca2+ responses of individual cells are extremely diverse, often displaying marked oscillations, and almost nothing is known about the specific features of these Ca2+ signals that are important for the functional response of a cell. Using the RBL-2H3 mucosal mast cell as a model, we have studied the temporal relationship between changes in intracellular Ca2+ and serotonin secretion at the single-cell level using simultaneous indo-1 photometry and constant potential amperometry. Secretion in response to antigen never occurs until intracellular Ca2+ is elevated, nor is it seen during the first few oscillations in Ca2+. Exocytotic events tend to be clustered around the peaks of oscillations, but excellent secretion is also seen in cells with sustained elevations in Ca2+. Ca2+ release from stores in the absence of influx fails to elicit secretion. If refilling and continued release of Ca2+ from stores is prevented with thapsigargin, Ca2+ influx can still trigger secretion, suggesting that store-associated microdomains of Ca2+ are not required for exocytosis. Our findings demonstrate the importance of an amplitude-encoded Ca2+ signal and Ca2+ influx for stimulus-secretion coupling in these nonexcitable cells.
Kim
T D
TD
Department of Pharmacology, Cornell University, Ithaca, New York 14853, USA.
Eddlestone
G T
GT
Mahmoud
S F
SF
Kuchtey
J
J
Fewtrell
C
C
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002460:Cell Line; D005089:Exocytosis / Q000502:physiology*; D008407:Mast Cells / Q000378:metabolism*; D008954:Models, Biological; D009092:Mucous Membrane / Q000166:cytology; D051381:Rats; D017455:Receptors, IgE / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
D017455:Receptors, IgE; D002118:Calcium