Association of phosphatidylinositol kinase and phosphatidylinositol 4‐phosphate kinase activities with the cytoskeleton in human platelets

Abstract

The inositol lipid kinases were investigated in the cytoskeletons of human platelets. In the absence of added lipids the kinases were only barely detectable in the Triton-soluble fractions and undetectable in cytoskeletons of resting cells. However at least 30% of the total phosphatidylinositol kinase was present in the cytoskeleton as revealed by saturation of the enzyme. Phosphatidylinositol 4-phosphate kinase was also found in significant amounts in the cytoskeletons. On the other hand, both enzymes being only recovered in the particulate fraction of the cells, we suggest that inositol lipid kinases may be present near the anchoring points of the cytoskeletons at the membranes.

Phosphoinositide kinase, diacylglycerol kinase, and phospholipase C activities associated to the cytoskeleton: effect of epidermal growth factor.

“…In this paper we demonstrate that PtdIns 4-kinase, PtdIns- As such these data are in agreement with the findings that the phosphoinositide kinases are associated to the membrane skeleton of platelets and erythrocytes (11,26) . In addition also traces of PtdIns-(3)P were found in cytoskeletons of A431 cells, indicating the presence of a PtdIns 3-kinase even if under our experimental conditions its activity is much lower than the PtdIns 4-kinase .…”

Monoclonal antibodies to phosphatidylinositol 4-phosphate 5-kinase: distribution and intracellular localization of the C isoform

“…Bazenet et al (1990) have previously purified the human homologue of PtdIns4P 5-kinase C (which they call type II PtdIns4P 5-kinase) from both cytosol and membrane fractions of human erythrocytes. Interestingly, addition of the purified type II enzyme to stripped erythrocyte membranes yielded very low activity compared with the activity obtained with the type I isoform, suggesting that other components may be required for full activation of the type II enzyme in vivo: both in A431 cells stimulated with epidermal growth factor and in platelets stimulated with thrombin, there is an increase in the PtdIns4P 5-kinase activity associated with the cytoskeleton (Nahas et al, 1989;Grondin et al, 1991;Payrastre et al, 1991). It is an exciting possibility that the increase in PtdIns4P 5-kinase activity is due to interaction with cytoskeletal components, leading to activation of the enzyme.…”

Association of Phosphatidylinositol 4-Kinase with the Plant Cytoskeleton

“…However, recent studies have indicated that enzymes of the polyphosphoinositide signaling pathway are also associated with the cytoskeleton of animal cells. The enzymes include Ptdlns 4-kinase, Ptdlns 3-kinase, Ptdlns(4)P 5-kinase, phospholipase C, and DG kinase (Nahas et al, 1989;Grondinetal., 1991;Payrastreetal., 1991). In our experiments,…”

“…A role of ABPs in controlling the availability of polyphosphoinositides for second messenger production is now becoming evident, and an intriguing three-way interaction between polyphosphoinositide pools, components of the cytoskeleton (such as ABPs), and the phosphorylation status of phosphoinositidase C isozymes appears to exist in many mammalian cell types (Goldschmidt-Clermont et al, 1990, 1991. Furthermore, severa1 phosphoinositide cycle enzymes have been demonstrated to be associated with the detergent-insolu ble cytoskeleton isolated from different animal cell lines (Nahas et al, 1989;Grondin et al, 1991;Payrastre et al, 1991). Our aim in this investigation has been to establish whether a similar set of interactions might exist in plant cells.…”