Regulation of inositol 1,4,5-trisphosphate 3-kinases by calcium and localization in cells

Samantha M. Lloyd-Burton, Jowie C.H. Yu, Robin F. Irvine, Michael J. Schell

Research output: Contribution to journalArticle

Abstract

Inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) 3-kinases (IP 3Ks) are a group of calmodulin-regulated inositol polyphosphate kinases (IPKs) that convert the second messenger Ins(1,4,5)P3 into inositol 1,3,4,5-tetrakisphosphate. However, what they contribute to the complexities of Ca2+ signaling, and how, is still not fully understood. In this study, we have used a simple Ca2+ imaging assay to compare the abilities of various Ins (1,4,5)P3-metabolizing enzymes to regulate a maximal histamine-stimulated Ca2+ signal in HeLa cells. Using transient transfection, we overexpressed green fluorescent protein-tagged versions of all three mammalian IP3K isoforms, including mutants with disrupted cellular localization or calmodulin regulation, and then imaged the Ca2+ release stimulated by 100 μM histamine. Both localization to the F-actin cytoskeleton and calmodulin regulation enhance the efficiency of mammalian IP3Ks to dampen the Ins (1,4,5)P 3-mediated Ca2+ signals. We also compared the effects of the these IP3Ks with other enzymes that metabolize Ins(1,4,5)P 3, including the Type I Ins(1,4,5)P3 5-phosphatase, in both membrane-targeted and soluble forms, the human inositol polyphosphate multikinase, and the two isoforms of IP3K found in Drosophila. All reduce the Ca2+ signal but to varying degrees. We demonstrate that the activity of only one of two IP3K isoforms from Drosophila is positively regulated by calmodulin and that neither isoform associates with the cytoskeleton. Together the data suggest that IP3Ks evolved to regulate kinetic and spatial aspects of Ins (1,4,5)P3 signals in increasingly complex ways in vertebrates, consistent with their probable roles in the regulation of higher brain and immune function.

Original languageEnglish (US)
Pages (from-to)9526-9535
Number of pages10
JournalJournal of Biological Chemistry
Volume282
Issue number13
DOIs
StatePublished - Mar 30 2007

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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