Use of intracellular Ca2+ stores from rat basophilic leukemia cells to study the molecular mechanism leading to quantal Ca2+ release by inositol 1,4,5-trisphosphate. Academic Article uri icon

Overview

abstract

  • Quantal Ca2+ release is a novel motif for the mediation of signal transduction in which the amplitude of a biological response following multiple stepwise increases in agonist concentration is retained. The release of Ca2+ from permeabilized cells in response to the second messenger inositol 1,4,5-trisphosphate (InsP3) proceeds in this fashion. The mechanisms leading to quantal Ca2+ release are unknown. InsP3 releases 50-90% of the Ca2+ sequestered within the intracellular stores of mammalian cells permeabilized with saponin. However, preparation of microsomes results in the loss of this sensitivity. In this report, functionally intact intracellular Ca2+ stores were isolated from rat basophilic leukemia (RBL) cells by osmotic lysis followed by differential and sucrose density gradient centrifugation. From this preparation, 64% of the stored Ca2+ is released by InsP3. We demonstrate that quantal Ca2+ release is retained by isolated Ca2+ stores and is identical to that observed in permeabilized cells. Addition of a subsaturating (28 nM) concentration of InsP3 to permeabilized cells at 37 degrees C results in the release of only a small fraction of the sequestered Ca2+. When the cells are cooled to 11 degrees C, the remaining Ca2+ is rapidly released. Hence, the mechanism leading to the quantal nature of Ca2+ release is reversible and is thus not likely to be the result of a covalent modification of the channel protein or of the Ca2+ store.(ABSTRACT TRUNCATED AT 250 WORDS)

publication date

  • February 9, 1993

Research

keywords

  • Calcium
  • Inositol 1,4,5-Trisphosphate
  • Leukemia, Basophilic, Acute

Identity

Scopus Document Identifier

  • 0027340478

Digital Object Identifier (DOI)

  • 10.1021/bi00056a011

PubMed ID

  • 8448137

Additional Document Info

volume

  • 32

issue

  • 5