Specific binding sites for inositol 1,3,4,5-tetrakisphosphate are located predominantly in the plasma membranes of human platelets.
In the present study we describe the characterization and localization of Ins(1,3,4,5)P4-binding sites in human platelet membranes. Specific binding sites for Ins(1,3,4,5)P4 have been identified on mixed, plasma and intracellular membranes from neuraminidase-treated platelets using highly purified carrier-free [32P]Ins(1,3,4,5)P4. The displacement of Ins(1,3,4,5)P4 from these sites by Ins(1,4,5)P3 and InsP6 occurs at greater than two orders of magnitude higher concentrations and with Ins(1,3,4,5,6)P5 at about 40-fold higher concentrations than with Ins(1,3,4,5)P4. The membranes were further separated by free-flow electrophoresis into plasma and intracellular membranes. The Ins(1,3,4,5)P4-binding sites separated with plasma membranes, and showed similar affinities and specificities as mixed membranes, whereas Ins(1,4,5)P3-binding sites were predominantly in the intracellular membranes. These results suggest a predominantly plasma membrane location for putative Ins(1,3,4,5)P4 receptors in human platelets.
Cullen
P J
PJ
AFRC Babraham Institute, Babraham, Cambridge, U.K.
Patel
Y
Y
Kakkar
V V
VV
Irvine
R F
RF
Authi
K S
KS
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001792:Blood Platelets / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism*; D006801:Humans; D007295:Inositol Phosphates / Q000097:blood*; D010761:Phosphorus Radioisotopes; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*
D007295:Inositol Phosphates; D010761:Phosphorus Radioisotopes; D018160:Receptors, Cytoplasmic and Nuclear; C061107:inositol-1,3,4,5-tetrakisphosphate receptor; C081655:inositol-1,3,4,5-tetrakisphosphate