TY - JOUR
T1 - Regulation of inositol 1,4,5-trisphosphate receptors in rat basophilic leukemia cells. I. Multiple conformational states of the receptor in a microsomal preparation
AU - Mohr, Frederick C
AU - Hershey, Panda E C
AU - Zimányi, Ildikó
AU - Pessah, Isaac N
PY - 1993/4/8
Y1 - 1993/4/8
N2 - A detailed characterization of the inositol 1,4,5-trisphosphate (IP3) receptor in rat basophilic leukemia (RBL) cells, a neoplastic mast cell line, has been possible through the growth of solid RBL cell tumors which provide a rich source of IP3 receptor. Equilibrium binding studies show a 1.6 ± 0.1 pmol/mg of protein maximal binding capacity for [3H]IP3 at optimal Ca2+ (10 μM). The specificity of the RBL cell IP3 receptor towards phosphoinositides, ATP and heparin parallels those previously described with excitable and nonexcitable tissues. [3H]IP3 binding is slightly enhanced from < 1 nM to 10 μM Ca2+ and inhibited by > 10 μM Ca2+. Kinetic and equilibrium studies provide evidence for at least two classes or conformational states of binding sites with pico- and nanomolar affinities. At nM concentrations of IP3, neither binding to the IP3 receptor nor IP3-induced Ca2+ efflux from permeabilized cells demonstrates cooperativity. In contrast, at pM concentrations, IP3 binding kinetics deviate from simple mass action suggesting a complex interaction among binding sites for IP3 on the receptor-channel oligomer. The mechanism that regulate [3H]IP3 binding in RBL cells are unique when compared to what has been reported in other cells.
AB - A detailed characterization of the inositol 1,4,5-trisphosphate (IP3) receptor in rat basophilic leukemia (RBL) cells, a neoplastic mast cell line, has been possible through the growth of solid RBL cell tumors which provide a rich source of IP3 receptor. Equilibrium binding studies show a 1.6 ± 0.1 pmol/mg of protein maximal binding capacity for [3H]IP3 at optimal Ca2+ (10 μM). The specificity of the RBL cell IP3 receptor towards phosphoinositides, ATP and heparin parallels those previously described with excitable and nonexcitable tissues. [3H]IP3 binding is slightly enhanced from < 1 nM to 10 μM Ca2+ and inhibited by > 10 μM Ca2+. Kinetic and equilibrium studies provide evidence for at least two classes or conformational states of binding sites with pico- and nanomolar affinities. At nM concentrations of IP3, neither binding to the IP3 receptor nor IP3-induced Ca2+ efflux from permeabilized cells demonstrates cooperativity. In contrast, at pM concentrations, IP3 binding kinetics deviate from simple mass action suggesting a complex interaction among binding sites for IP3 on the receptor-channel oligomer. The mechanism that regulate [3H]IP3 binding in RBL cells are unique when compared to what has been reported in other cells.
KW - Calcium store
KW - Inositol 1,4,5-trisphosphate
KW - Intracellular calcium regulation
KW - Mast cell
KW - RBL cell
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U2 - 10.1016/0005-2736(93)90320-Y
DO - 10.1016/0005-2736(93)90320-Y
M3 - Article
C2 - 8385492
AN - SCOPUS:0027512103
VL - 1147
SP - 105
EP - 114
JO - Biochimica et Biophysica Acta - Biomembranes
JF - Biochimica et Biophysica Acta - Biomembranes
SN - 0005-2736
IS - 1
ER -