Correlating Ca2+ responses and secretion in individual RBL-2H3 mucosal mast cells

Area of Science:

• Cellular Biology
• Immunology
• Biochemistry

Background:

• The precise role of intracellular calcium (Ca2+) in stimulus-response coupling within nonexcitable cells remains largely unclear.
• Individual cell Ca2+ responses are highly variable, featuring oscillations, but the specific signal characteristics essential for cellular function are unknown.

Purpose of the Study:

• To investigate the temporal relationship between intracellular Ca2+ changes and serotonin secretion in RBL-2H3 mucosal mast cells.
• To determine the critical features of Ca2+ signals that regulate stimulus-secretion coupling in nonexcitable cells.

Main Methods:

• Utilized simultaneous indo-1 photometry and constant potential amperometry for single-cell analysis.
• Employed thapsigargin to investigate the role of Ca2+ stores and influx in secretion.

Main Results:

• Serotonin secretion requires elevated intracellular Ca2+ and does not occur during initial Ca2+ oscillations.
• Exocytosis is associated with Ca2+ oscillation peaks and sustained Ca2+ elevations.
• Ca2+ influx, independent of store release, can trigger secretion, indicating store-associated microdomains are not essential.

Conclusions:

• Ca2+ influx is a critical determinant for stimulus-secretion coupling in nonexcitable mast cells.
• The amplitude of the Ca2+ signal, rather than oscillatory patterns alone, is important for triggering cellular responses.