Protein kinase A inhibitors

Opposite modulation of opiate withdrawal behaviors on microinfusion of a protein kinase A inhibitor versus activator into the locus coeruleus or periaqueductal gray. J Neurosci 1997 17 8520-8527. 

Ferry DR, Smith A, Malkhandi J, F e DW, deTakats PG, Anderson D, Baker J, Kerr DJ (1996) Phase 1 clinical trial of the flavonoid quercetin pharmacokinetics and evidence for in vivo tyrosine kinase inhibition. Clin Cancer Res 2 659-668 Findik D, Song Q, Hidaka H, Lavin M (1995) Protein kinase A inhibitors enhance radiation-induced apoptosis. J Cell Biochem 57 12-21 Fine RL, Patel J, Chabner BA (1988) Phorbol esters induce multidrug resistance in human breast cancer cells. Proc Natl Acad Sci USA, 85 582-586 Finkenzeller G, Marme D, Hug H (1992) Inducible overexpression of human protein kinase C in NIH 3T3 fibroblasts results in growth abnormalities. Cell Signall 4 163-177... 

De la Rosa, L.A., Vilarino, N., Vieytes, M.R., and Botana, L.M. 2001b. Modulation of thapsigargin-induced calcium mobilisation by cyclic AMP-elevating agents in human lymphocytes is insensitive to the action of the protein kinase A inhibitor H-89. Cell Signal 13, 441 49. 

Fig. 3. Effect of oxytocin (0,1,10 or 100 ng/mL medium) (O) and oxytocin (0,1,10 or 100 ng/mL medium) in combination with protein kinase A inhibitor Rp-cAMPS ( 1 imo ) on prostaglandin (PG)E release by isolated and cultured porcine ovarian follicles. Values are means + SEM. Significant differences (P< 0.05) between cells cultured with and without exogenous oxytocin. Methods of isolation and culture of ovarian follicles, as well as the prostaglandin E radioimmunoassay are described in (8). 

Incubation of rat heart mitochondria with ATP resulted in the phosphorylation of two mitochondrial membrane proteins, one with a of 6 kDA consistent with the NDUFAl (MWFE), and one at 18 kDa consistent with either NDUSF4 (AQDQ) or NDUFB7 (B18) (Raha et al. 2002). Phosphorylation of both sununits was enhanced by cAMP derivatives and protein kinase A and was inhibited by protein kinase A inhibitors. When mitochondrial membranes were incubated with pyruvate dehydrogenase kinase, phosphorylation of an 18 kDa protein but not a 6 kDa protein was observed, NADH cytochrome c reductase activity was decreased and superoxide production rates with NADH as substrate were increased. On the other hand, with protein kinase A-driven phosphorylation, NADH cytochrome c reductase was increased and superoxide production decreased. Overall there was a 4-fold variation in electron transport rates observable at the extremes of these phosphorylation events. This suggests... 

Mazur A, Roden DM, Anderson ME (1999) Systemic administration of calmodulin antagonist W-7 or protein kinase A inhibitor H-8 prevents torsade de pointes in rabbits. Circulation 100 2437-2442... 

Protein Folding Problem Protein Kinase Protein Kinase A Protein Kinase C Protein Kinase Inhibitors Protein Phosphatases Protein Sorting... 

In the total synthesis of the protein kinase C inhibitors calphostins 146, the orf/zo-substituted intermediates, which are either obtained from photolysis or from reaction of the dienyl carbene complex 144 with tert-butyl isocyanide, were oxidised to yield the 1,2-benzoquinone 145 as a common product [81] (Scheme 61). 

Pindur U., Lemster T. Recent Advances in the Synthesis of Carbazoles and Anellated Indoles With Antitumor Activity DNA-Binding Ligands and Protein Kinase C Inhibitors Recent Res. Dev. Org. Bioorg. Chem. 1997 1 33-54 Keywords Diels-Alder reactions of a 4,7-dioxo-indole with carbodienophiles... 

Figure 6. A hypothetical scheme for the control of the number of active crossbridges in smooth muscle. Following the activation of a smooth muscle by an agonist, the concentrations of intermediates along the main route begins to build up transiently. This is shown by the thickened arrows. Also, cAMP is generated which is universally an inhibitor in smooth muscle. Cyclic AMP in turn combines with protein kinase A, which accounts for most of its action. The downstream mechanisms, however, are not well worked out and at least three possibilities are likely in different circumstances. First, protein kinase A is known to catalyze the phosphorylation of MLCK, once phosphorylated MLCK has a relatively lower affinity for Ca-calmodulin so that for a given concentration of Ca-calmodulin, the activation downstream is reduced. The law of mass action predicts that this inhibition should be reversed at high calcium concentrations. Other cAMP inhibitory mechanisms for which there is evidence include interference with the SR Ca storage system, and activation of a MLC phosphatase.

Regioselective Beckmann rearrangements were used as key steps in the synthesis of phosphonoalkyl azepinones (Scheme 36) [43b] and in a formal total synthesis of the protein kinase C inhibitor balanol (Scheme 37) the optically active azide 197 derived from cyclohexadiene mono-oxide was converted into ketone 198 in several steps. After preparation of the oxime tosylates 199 (2.3 1 mixture), a Lewis acid mediated regioselective Beckmann rearrangement gave the lactams 200 and 201 in 66% and 9% yield, respectively. Lactam 201 underwent a 3-e im-ination to give additional 200, which served as a key intermediate in a balanol precursor synthesis (Scheme 37) [43 cj. 

Vangrevelinghe E, Zimmermann K, Schoepfer J, Portmann R, Fabbro D, Furet P. Discovery of a potent and selective protein kinase CK2 inhibitor by high-throughput docking. J Med Chem 2003 46 2656-62. 

Recent evidence indicates that the 5-HT transporter is subject to post-translational regulatory changes in much the same way as neurotransmitter receptors (Blakeley et al. 1998). Protein kinase A and protein kinase C (PKC), at least, are known to be involved in this process. Phosphorylation of the transporter by PKC reduces the Fmax for 5-HT uptake and leads to sequestration of the transporter into the cell, suggesting that this enzyme has a key role in its intracellular trafficking. Since this phosphorylation is reduced when substrates that are themselves transported across the membrane bind to the transporter (e.g. 5-HT and fi -amphetamine), it seems that the transport of 5-HT is itself linked with the phosphorylation process. Possibly, this process serves as a homeostatic mechanism which ensures that the supply of functional transporters matches the demand for transmitter uptake. By contrast, ligands that are not transported (e.g. cocaine and the selective serotonin reuptake inhibitors (SSRIs)) prevent the inhibition of phosphorylation by transported ligands. Thus, such inhibitors would reduce 5-HT uptake both by their direct inhibition of the transporter and by disinhibition of its phosphorylation (Ramamoorthy and Blakely 1999). 

Chmura SJ, Dolan ME, Cha A, Mauceri HJ, Kufe DW, Weichselbaum RR. In vitro and in vivo activity of protein kinase C inhibitor chelerythrine chlorise induces tumor cell toxicity and growth delay in vivo. Clin Cancer Res 2000 6 737-742. 

Rotenberg, S.A., Calogeropoulou, T., Jaworski, J., Weinstein, I.B., and Rideout, D.A. (1991) Self-assembling protein kinase C inhibitor. Proc. Natl. Acad. Sci. USA 88, 2490-2494. 

Bebchuk, J. M., Arfken, C. L., Dolan-Manji, S. et al. A preliminary investigation of a protein kinase C inhibitor in the treatment of acute mania. Arch. Gen. Psych. 57 95-97, 2000. 

Pharmacological approaches to finding antidotes for cyanide are also under investigation. Maduh et al. (1995) examined the effects of a protein kinase C inhibitor, l-5-(isoquinolinesulfonyl)-2 methylpiperazine (H-7), on cellular energy depletion caused by sodium cyanide. They reported that H-7 partially prevented cellular energy depletion and increased the number of surviving cells. 

Maduh EU, Nealley EW, Song H, et al. 1995. A protein kinase C inhibitor attenuates cyanide toxicity in vivo. Toxicology 100 129-137. 

Figure 6.14. Kinetics of 02 secretion by activated neutrophils. Neutrophil suspensions (5 x 10s/ml) were suspended in RPMI 1640 medium containing 75 /JM cytochrome c. In (b) and (d), suspensions contained 100 nM staurosporine. At time zero, suspensions in (a) and (b) were stimulated by the addition of 1 /iM fMet-Leu-Phe, whilst suspensions in (c) and (d) were stimulated by the addition of 0.1 fi g/ml PM A. Reference cuvettes were identical to the sample cuvettes, but additionally contained 30 jUg/ml SOD. The bar marker represents a A4 of 0.03 in (a) and (b), or 0.08 in (c) and (d). Similar results were obtained using the more specific protein kinase C inhibitor, bisindolylmaleimide.

It is known that protein kinase C can phosphorylate a number of key oxidase components, such as the two cytochrome b subunits and the 47-kDa cytoplasmic factor. This process is prevented by protein kinase C inhibitors such as staurosporine (although it is now recognised that this inhibitor is not specific for protein kinase C), which also inhibits the respiratory burst activated by agonists such as PMA. However, when cells are stimulated by fMet-Leu-Phe, translocation of pAl-phox to the plasma membrane can occur even if protein kinase C activity is blocked - that is, phosphorylation is not essential for the translocation of this component in response to stimulation by this agonist. Similarly, the kinetics of phosphorylation of the cytochrome subunits do not follow the kinetics of oxidase activation, and protein kinase C inhibitors have no effect on oxidase activity elicited by some agonists -for example, on the initiation of the respiratory burst elicited by agonists such as fMet-Leu-Phe (Fig. 6.14). Furthermore, the kinetics of DAG accumulation do not always follow those of oxidase activity. Hence, whilst protein kinase C is undoubtedly involved in oxidase activation by some agonists, oxidase function is not totally dependent upon the activity of this kinase. 

Figure 6.15. Structures of some protein kinase C inhibitors. Staurosporine is a potent inhibitor of protein kinase C, but is not selective. Some derivatives of protein kinase C, such as Ro31-8220 and Ro31-8425, retain a potency similar to that of the parent molecule in protein kinase C inhibition, but are much more specific.

Zhang W, Law RE, Hinton DR, Couldwell WT. (1997). Inhibition of human malignant glioma cell motility and invasion in vitro by hypericin, a potent protein kinase C inhibitor. Cancer Lett. 120(1) 31-8. 

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