Wortmannin binding

T4. Thelen, M., Wymann, M. P., and Langen, H., Wortmannin binds specifically to 1-pho-sphatidylinositol 3-kinase while inhibiting guanine nucleotide-binding protein-coupled receptor signaling in neutrophil leukocytes. Proc. Natl. Acad. Sci. USA 91, 4960-4964 (1994). 

Wortmannin is a fungus-derived inhibitor of PI 3-kinase. The agent binds and inhibits the enzyme covalently and irreversibly. It is very potent and considered to be highly specific (IC5o in most cells in the low nanomolar range). 

Because wortmannin is hydrophobic (on the day of the experiment we dissolve an aliquot in DMSO and never keep it for more than a day or two, away from light) and used at very low concentrations, it should not be mixed with serum or other protein-rich media too long before the experiment. The DMSO solution should be added to the medium immediately before addition to the cells. If left in aqueous medium too long before addition, it will bind to the walls of the tube. 

As in the case of sstl, agonist binding to sst4 has and has not been shown to be sensitive to GTP and PTX similarly, inhibition of AC was and was not observed (Demchyshyn et al. 1993 Raynor et al. 1993a Kaupmann et al. 1994 Roosterman et al. 1997). In transfected cells, sst4 was functionally coupled, in a PTX-sensitive fashion, not only to inhibition of AC, but also to activation of arachidonate release and mitogen-activated protein kinase cascade (Bito et al. 1994 Shimizu et al. 1996). These effects were accompanied by the phosphorylation of 85-kDa cytosolic phospholipase A2 and were inhibited by the phosphatidylinositol-3-phosphate kinase inhibitor wortmannin. 

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