Publications

The biological activity of interleukin-2 receptors (IL-2R) is dependent on the functional coupling of IL-2R beta molecules to intracellular enzymes such as protein tyrosine kinase. The serine-rich, S-domain within the cytosolic portion of IL-2R beta plays an essential role in transduction of the IL-2 proliferative signal. Cells bearing either wild type IL-2R beta (Baf alpha/beta) or deletions within the S-domain (Baf alpha/beta SD1) were used to evaluate the importance of the S-domain in linking ligand binding to protein tyrosine kinase induction. Multiparameter, side by side comparisons showed that only those cells that expressed wild type IL-2R beta responded to IL-2 by increased cellular proliferation, accumulation of the c-myc proto-oncogene, and activation of protein tyrosine kinase. Activation of protein tyrosine kinase was, in turn, linked to increased tyrosine phosphorylation and activation of phosphatidylinositol-3-kinase. These findings indicate that the S-domain of the IL-2R beta chain is an essential component in the signal transduction cascade that links IL-2 binding to tyrosine kinase and phosphatidylinositol-3-kinase activation.

Cannibidiol (CBD) has been shown to impair hepatic drug metabolism in several animal species and to markedly inhibit mouse hepatic microsomal delta 1-tetrahydrocannabinol (THC) metabolism by inactivating specific cytochrome P450s (P450) belonging to the 2C and 3A subfamilies. Elucidation of the mechanism of CBD-mediated P450 inhibition would be clinically very important for predicting its effect on metabolism of THC and the many other clinically important drugs known to be metabolized by P450s 2C and 3A. CBD-mediated inactivation of mouse hepatic microsomal P450s did not decrease hepatic microsomal heme content. However, [14C]CBD was found covalently bound to microsomal protein in an approximately equimolar ratio to P450 loss. Immunoprecipitation of microsomal protein with antibodies raised against either P450 2C or 3A revealed that approximately equal amounts of [14C]-CBD were bound to each of these P450s after CBD-mediated inactivation. Furthermore, this specific P450 binding was equivalent to P450 loss and accounted for nearly all of the microsomal [14C]CBD irreversible binding. Although > 80% of the enzyme activities attributed to P450s 2C and 3A were inactivated by CBD at the anticonvulsant dose of 120 mg/kg, P450 2C was approximately 3-fold more sensitive than P450 3A at the lower CBD doses tested. CBD analogs were synthesized in order to elucidate the chemical pathways for CBD-mediated P450 inactivation in vivo. Oxidations at allylic carbon positions or saturation of either the exocyclic double bond or both double bonds of the terpene moiety did not markedly affect the inhibitory properties of the analogs. Methylation of both phenolic groups of the resorcinol moiety completely blocked the P450-inhibitory properties of this analog, revealing the involvement of a free hydroxyl group in the inactivation process. Rotation of the resorcinol moiety in abnormal-CBD did not impair the inhibitory properties of the analog, suggesting that the position of the hydroxyl group relative to the terpene ring is unimportant. Further studies are required to fully understand the chemical basis of CBD-mediated P450 inactivation.