Regulation of inositol 1,4,5-trisphosphate receptors in rat basophilic leukemia cells. II. Modulation of the receptor in permeabilized cells by the cytosolic compartment

Panda E C Hershey, Isaac N Pessah, Frederick C Mohr

Research output: Contribution to journalArticle

3 Scopus citations


Engagement of the IP3 receptor by its ligand releases Ca2+ from intracellular stores of the rat basophilic leukemia (RBL) cell. The IP3 receptor in washed permeabilized cells has high affinity (Kd = 1.2±0.3 nM) for [3H]IP3 and is not sensitive to physiological concentrations of Ca2+. Moreover, washed permeabilized cells only release small amounts of Ca2+ when stimulated with IP3. When [3H]IP3 binding to permeabilized cells is performed in the presence of cytosolic constituents (unwashed cells), the IP3 receptor has a lower affinity for [3H]IP3 (Kd from 20 to 100 nM) and has enhanced Ca2+ release. Cytosolic supernatant, prepared by centrifugation of permeabilized cells and added back to washed permeabilized cells, decreases [3H]IP3 binding in a dose-dependent manner and increases the amount of Ca2+ released by IP3. Depletion of either MgATP or IP3 in the cytosolic supernatant does not affect the supernatant's ability to decrease [3H]IP3 binding. Though MgATP competitively inhibits [3H]IP3 binding, it cannot fully account for the shift in Kd or the modulation of IP3-stimulated Ca2+ release in the presence of cytosol. These findings suggest that components present in the cytosolic supernatant modulate the function of the IP3 receptor by maintaining it in a low affinity state capable of promoting Ca2+ release.

Original languageEnglish (US)
Pages (from-to)115-124
Number of pages10
JournalBBA - Biomembranes
Issue number1
StatePublished - Apr 8 1993



  • Calcium store
  • Inositol 1,4,5-trisphosphate
  • Intracellular calcium regulation
  • Mast cell
  • RBL cell

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Cell Biology

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