Epidermal growth factor-induced depletion of the intracellular Ca2+ store fails to activate capacitative Ca2+ entry in a human salivary cell line

Bin Xian Zhang, Xiuye Ma, Chih Ko Yeh, Meyer D. Lifschitz, Michael X. Zhu, Michael S. Katz

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Epidermal growth factor (EGF) is a multifunctional factor known to influence proliferation and function of a variety of cells. The actions of EGF are mediated by EGF receptor tyrosine kinase pathways, including stimulation of phospholipase Cγ and mobilization ofintracellular Ca2+ ([Ca2+]i). Generally, agonist-mediated Ca2+ mobilization involves both Ca2+ release from internal stores and Ca2+ influx activated by store depletion (i.e. capacitative or storeoperated Ca2+ influx). However, the role of capacitative Ca2+ entry in EGF-mediated Ca2+ mobilization is still largely unknown. In this study, we compared [Ca2+]i signals elicited by EGF with those induced by agents (the muscarinic receptor agonist carbachol and thapsigargin (Tg)) known to activate capacitative Ca2+ entry. Unlike carbachol and Tg, EGF (5 nM) elicited a transient [Ca2+]i signal without a plateau phase in the presence of extracellular Ca2+ and also failed to accelerate Mn2+ entry. Repletion of extracellular Ca2+ to cells stimulated with EGF in the absence of Ca2+ elicited an increase in [Ca2+]i, indicating that EGF indeed stimulates Ca2+ infux. However, the influx was activated at lower EGF concentrations than those required to stimulate Ca2+ release. Interestingly, the phospholipase C inhibitor U73122 completely inhibited Ca2+ release induced by both EGF and carbachol and also reduced Ca2+ influx responsive to carbachol but had no effect on Ca2+ influx induced by EGF. EGF-induced Ca2+ influx was potentiated by low concentrations (<5 ng/ml) of oligomycin, a mitochondrial inhibitor that blocks capacitative Ca2+ influx in other systems. Transient expression of the hTRPC3 protein enhanced Ca2+ influx responsive to carbachol but did not increase EGF-activated Ca2+ influx. Both EGF and carbachol depleted internal Ca2+ stores. Our results demonstrate that EGF-induced Ca2+ release from internal stores does not activate capacitative Ca2+ influx. Rather, EGF stimulates Ca2+ influx via a mechanism distinct from capacitative Ca2+ influx induced by carbachol and Tg.

Original languageEnglish (US)
Pages (from-to)48165-48171
Number of pages7
JournalJournal of Biological Chemistry
Volume277
Issue number50
DOIs
StatePublished - Dec 13 2002

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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