Phosphoinositides Isolation

Hajra, A. K., Fisher, S. K. and Agranoff, B. W. Isolation, separation and analysis of phosphoinositides from biological sources. In A. A. Boulton, G. B. Baker and L. A. Horrocks (eds), Neuromethods (Neurochemistry). Lipids and Related Compounds, vol. 8. Clifton, NJ Humana Press, 1987. 

The simplest type of phosphoinositide is represented by the phosphatide isolated from horse liver or dog liver by McKibbin.171 This consists only of glycerol, myo-inositol, phosphoric acid, and fatty acids it probably has structure LXXX. Similar inositides, differing only in the nature of the fatty acids, have been isolated from wheat germ,187 beef heart, 188 and beef liver.189 That the major portion of the fatty acids is attached to glycerol, not to myo-inositol, was shown by the isolation of a diglyceride on mild hydrolysis.189... 

We observed that the incubation of platelets or red blood cells in the presence of AlFx evoked changes in the phosphoinositide signaling system and a significant decrease of platelet [Ca2+]i [68, 64]. This response was not different in platelets isolated from the blood of AD patients as compared with healthy age-matched subjects or young healthy subjects. 

H. et al.. Mouse 3-phosphoinositide-dependent protein kinase-1 undergoes dimerization and franx-phosphorylation in the activation loop, J. Biol. Chem. 278, 42913 2919, 2003 Wu, S. and Kaufman, R.J., trans-auto-phosphorylation by the isolated kinase domain is not sufQcient for dimerization or activation of the dsRNA-activated protein kinase PKR, Biochemistry 43, 11027-11034, 2004. 

Activation of the chemokine receptor leads to rapid activation of phosphoinositide-spe-cific phospholipases, which leads to inositol-1,4,5-triphosphate formation and a transient rise in intracellular calcium (18). Phospholipase C (PLC) isoforms that are involved in chemokine receptor activation become activated by direct interaction with the J3y subunits. In addition to its interaction with PLCs, the j3y subunits also interact with the type phosphoinositol 3 kinase y (PISKy), and activation of this enzyme results in the formation of PtdIns(3,4,5)P3 (17). Mice that do not express PI3Ky have severely impaired chemo-kine-stimulated signal transduction, and PKB is not activated, suggesting an important role for this pathway in the chemotactic process (27-29). Although leukocytes isolated from these mice showed a decrease in cell chemo-taxis, the response is not completely lost, and under conditions of complete PI3Ky inhibition, neutrophils can still chemotax in response to chemokines (30). 

Trimucytin, a polypeptide/polysaccharide complex isolated from the venom of the viper Trimeresurus mucrosquamatus activates collagen receptors and causes aggregation mainly through phospholipase C-phosphoinositide pathway. Similar toxins found in the venom of related viper species. 

Preliminary data further suggest the involvement of phosphoinositides in G A3-induced synthesis and secretion of a-amylase in aleurone cells [13]. GA3 activation of protein kinase C-like enzyme has been shown in potato tubers [10]. The in vitro effect of 2,4-D on protein phosphorylation in a membrane fraction isolated from etiolated soybean hypocotyls may also be associated with this system [24]. Further investigation in this field may be valuable in the elucidation of molecular mechanism of phytohormone signal transduction and amplification. 

Phosphatidyl Inositols Inositol has been found to be a constituent of tubercle bacillus phospholipids (Anderson 1930) and soybean phospholipids (Klenk et al. 1939). A hydrolysate of brain lipids has also yielded inositol (Folch et al. 1942). In all instances the optically inactive myo-inositol was the only isomer of inositol that has been isolated from lipids. Inositol is an integral constituent of a group of different types of phosphoinositides a) monophosphoinositides, h) diphosphoino-sitides, and c) complex phosphoinositides,... 

AN AUXIN-MEDIATED CONTROL OF A RAPID PHOSPHOINOSITIDE RESPONSE IN ISOLATED PLANT CELL MEMBRANES... 

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