Antigen and carbachol mobilize calcium by similar mechanisms in a transfected mast cell line (RBL-2H3 cells) that expresses ml muscarinic receptors

Oksoon Hong Choi, Jong Hwa Lee, Tatiana Kassessinoff, Jose R. Cunha-Melo, S. V.Penelope Jones, Michael A. Beaven

Research output: Contribution to journalArticlepeer-review

57 Scopus citations

Abstract

Because of unresolved questions about the mechanism of Ag-stimulated Ca2+ influx, Ca2+ mobilization in response to carbachol and Ag was compared in transfected rat basophilic RBL-2H3(ml) cells that expressed both Fcε and ml muscarinic receptors. Although the stimulants activated phospholipase C via different coupling mechanisms, a G protein for carbachol or a tyrosine kinase for Ag, they released Ca2+ from the same intracellular pool and used the same or very similar mechanisms for influx of Ca2+ as indicated by the similar patterns of inhibition of uptake of 45Ca2+ by various cations. With both stimulants, influx and sustained increases in free cytosolic Ca2+ ([Ca2+]i) were associated with relatively small increases in inositol 1,4,5-trisphosphate (IP3). Blockade of Ca2+ influx resulted in rapid decline in [Ca2+]i to basal levels; resumption of influx caused a substantial "spike" in [Ca2+]i before [Ca2+]i reequilibrated at the same former steady-state levels but without perturbing levels of IP3. Thus, the refilling and discharge of Ca2+ from IP3-sensitive stores might occur synchronously on resumption of influx, or asynchronously during sustained influx and elevation of [Ca2+]i. Together, the results suggested that influx of Ca2+ in response to stimulation via Fcε receptors occurred through a pathway, analogous to that observed with other types of stimulants, in which Ca2+ influx follows emptying of intracellular Ca2+ stores by IP3. Also, secretion was highly dependent on this IP3-dependent pathway.

Original languageEnglish (US)
Pages (from-to)5586-5595
Number of pages10
JournalJournal of Immunology
Volume151
Issue number10
StatePublished - Nov 15 1993
Externally publishedYes

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology

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