p110β and p110δ Phosphatidylinositol 3-Kinases Up-regulate FcεRI-activated Ca2+ Influx by Enhancing Inositol 1,4,5-Trisphosphate Production

Alexander J. Smith, Zurab Surviladze, Elizabeth A. Gaudet, Jonathan M. Backer, Christina A. Mitchell, Bridget S. Wilson

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

FcεRI-induced Ca2+ signaling in mast cells is initiated by activation of cytosolic tyrosine kinases. Here, in vitro phospholipase assays establish that the phosphatidylinositol 3-kinase (PI 3-kinase) lipid product, phosphatidylinositol 3,4,5-triphosphate, further stimulates phospholipase Cγ2 that has been activated by conformational changes associated with tyrosine phosphorylation or low pH. A microinjection approach is used to directly assess the consequences of inhibiting class IA PI 3-kinases on Ca 2+ responses after FcεRI cross-linking in RBL-2H3 cells. Injection of antibodies to the p110β or p110δ catalytic isoforms of PI 3-kinase, but not antibodies to p110α, lengthens the lag time to release of Ca2+ stores and blunts the sustained phase of the calcium response. Ca2+ responses are also inhibited in cells microinjected with recombinant inositol polyphosphate 5-phosphatase I, which degrades inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), or heparin, a competitive inhibitor of the Ins(1,4,5)P3 receptor. This indicates a requirement for Ins(1,4,5)P3 to initiate and sustain Ca2+ responses even when PI 3-kinase is fully active. Antigen-induced cell ruffling, a calcium-independent event, is blocked by injection of p110β and p110δ antibodies, but not by injection of 5-phosphatase I, heparin, or anti-p110α antibodies. These results suggest that the p110β and p110δ isoforms of PI 3-kinase support FcεRI-induced calcium signaling by modulating Ins(1,4,5)P3 production, not by directly regulating the Ca2+ influx channel.

Original languageEnglish (US)
Pages (from-to)17213-17220
Number of pages8
JournalJournal of Biological Chemistry
Volume276
Issue number20
DOIs
StatePublished - May 18 2001

Fingerprint

Phosphatidylinositol 3-Kinase
Inositol 1,4,5-Trisphosphate
Phosphatidylinositol 3-Kinases
Up-Regulation
Phospholipases
Antibodies
Calcium
Phosphoric Monoester Hydrolases
Injections
Heparin
Protein Isoforms
Polyphosphates
Phosphorylation
Calcium Signaling
Microinjections
Inositol
Mast Cells
Protein-Tyrosine Kinases
Tyrosine
Anti-Idiotypic Antibodies

ASJC Scopus subject areas

  • Biochemistry

Cite this

p110β and p110δ Phosphatidylinositol 3-Kinases Up-regulate FcεRI-activated Ca2+ Influx by Enhancing Inositol 1,4,5-Trisphosphate Production. / Smith, Alexander J.; Surviladze, Zurab; Gaudet, Elizabeth A.; Backer, Jonathan M.; Mitchell, Christina A.; Wilson, Bridget S.

In: Journal of Biological Chemistry, Vol. 276, No. 20, 18.05.2001, p. 17213-17220.

Research output: Contribution to journalArticle

Smith, Alexander J. ; Surviladze, Zurab ; Gaudet, Elizabeth A. ; Backer, Jonathan M. ; Mitchell, Christina A. ; Wilson, Bridget S. / p110β and p110δ Phosphatidylinositol 3-Kinases Up-regulate FcεRI-activated Ca2+ Influx by Enhancing Inositol 1,4,5-Trisphosphate Production. In: Journal of Biological Chemistry. 2001 ; Vol. 276, No. 20. pp. 17213-17220.
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AB - FcεRI-induced Ca2+ signaling in mast cells is initiated by activation of cytosolic tyrosine kinases. Here, in vitro phospholipase assays establish that the phosphatidylinositol 3-kinase (PI 3-kinase) lipid product, phosphatidylinositol 3,4,5-triphosphate, further stimulates phospholipase Cγ2 that has been activated by conformational changes associated with tyrosine phosphorylation or low pH. A microinjection approach is used to directly assess the consequences of inhibiting class IA PI 3-kinases on Ca 2+ responses after FcεRI cross-linking in RBL-2H3 cells. Injection of antibodies to the p110β or p110δ catalytic isoforms of PI 3-kinase, but not antibodies to p110α, lengthens the lag time to release of Ca2+ stores and blunts the sustained phase of the calcium response. Ca2+ responses are also inhibited in cells microinjected with recombinant inositol polyphosphate 5-phosphatase I, which degrades inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), or heparin, a competitive inhibitor of the Ins(1,4,5)P3 receptor. This indicates a requirement for Ins(1,4,5)P3 to initiate and sustain Ca2+ responses even when PI 3-kinase is fully active. Antigen-induced cell ruffling, a calcium-independent event, is blocked by injection of p110β and p110δ antibodies, but not by injection of 5-phosphatase I, heparin, or anti-p110α antibodies. These results suggest that the p110β and p110δ isoforms of PI 3-kinase support FcεRI-induced calcium signaling by modulating Ins(1,4,5)P3 production, not by directly regulating the Ca2+ influx channel.

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