Inositol-1,3,4,5-tetrakisphosphate binding sites in control and ras-transformed NIH/3T3 fibroblasts.
Inositol-1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4) binding properties were investigated in NIH/3T3 fibroblasts and its ras-transformant (DT cells), in which inositol tetrakisphosphates induce Ca2+ influx. [3H]-Ins(1,3,4,5)P4 bound to membranes of both types of cells with Kd values of 10.6 and 8.6 nM, respectively. The rank order of inositol polyphosphates for displacing [3H]Ins(1,3,4,5)P4 in DT cells was Ins(1,3,4,5)P4 > inositol-1,3,4,5,6-pentakisphosphate > inositol hexakisphosphate > inositol-1,4,5-trisphosphate. This order is similar to that reported in two Ras-GTPase-activating proteins, GAP1IP4BP and GAP1m, which are also the Ins(1,3,4,5)P4 binding proteins. Northern blot analysis revealed that NIH/3T3 and DT cells expressed mRNA species that were hybridizable with GAP1m cDNA. These results suggest that parental and ras-transformed NIH/3T3 fibroblasts possess GAP1-like proteins, which may be responsible for triggering inositol tetrakisphosphate-dependent Ca2 influx.
Taketo
M
M
Department of Biophysics, Kanazawa University School of Medicine, Japan.
Yokoyama
S
S
Fukuda
M
M
Mikoshiba
K
K
Higashida
H
H
D016475:3T3 Cells; D000818:Animals; D001665:Binding Sites; D015152:Blotting, Northern; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins; D002461:Cell Line, Transformed; D020690:GTPase-Activating Proteins; D007295:Inositol Phosphates / Q000378:metabolism*; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D050857:Synaptotagmins; D020703:ras GTPase-Activating Proteins; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism
D002135:Calcium-Binding Proteins; D020690:GTPase-Activating Proteins; D007295:Inositol Phosphates; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D011506:Proteins; D018160:Receptors, Cytoplasmic and Nuclear; C061107:inositol-1,3,4,5-tetrakisphosphate receptor; D020703:ras GTPase-Activating Proteins; C081655:inositol-1,3,4,5-tetrakisphosphate; D050857:Synaptotagmins; D018631:ras Proteins; D002118:Calcium