GTP-activated communication between distinct inositol 1,4,5-trisphosphate-sensitive and -insensitive calcium pools

Tarun K. Ghosh, Julienne M. Mullaney, Fahmy I. Tarazi, Donald Gill

Research output: Contribution to journalArticlepeer-review

174 Scopus citations


INOSITOL 1,4,5-trisphosphate (InsP3) is an established mediator of intracellular Ca2+ signals but little is known of the nature and organization of Ca2+ regulatory organelles responsive to InsP3. Here we derive new information from the study of Ca2+ movements induced both by InsP3 and a specific GTP-activated Ca2+ translocation process. The latter mechanism is clearly distinct from that activated by InsP3 (ref. 4) and may involve the translocation of Ca2+ between compartments without its release into the cytosol. This idea is supported by the fact that GTP activates Ca2+ movement into the InsP3-releasable pool. In the light of this evidence we postulated that there are two intracellular Ca2+ pools distinguishable by InsP3-sensitivity and oxalate-permeability, and that movement between them is activated by GTP. We report here direct evidence for the existence and separation of two distinct Ca2+-pumping compartments with properties coinciding with those predicted. Of these, the InsP3-sensitive Ca2+ pool is identified within a purified rough endoplasmic reticulum fraction, an observation consistent with recent InsP3 receptor-localization studies. Ca2+ translocation between pools may reflect function of a class of small GTP-binding proteins known to mediate interorganelle transfer in eukaryotic cells.

Original languageEnglish (US)
Pages (from-to)236-239
Number of pages4
Issue number6230
StatePublished - Jan 1 1989

All Science Journal Classification (ASJC) codes

  • General


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