Protein-Degradation Inhibitors

A method of controlling malaria and related disorders using asymmetrical amidinyl diphenylurea derivatives as modulators of cellular pathways in eukaryotes is described. 

1-Thiocarbonyldiimidazole (0.8 mmol) dissolved in 5 ml nitromethane was cooled to 4°C, then treated dropwise with methyl triflate (1.6 mmol). The reaction was 

Entry Structure Anti- plasmodial activity2 (3D7) Anti- plasmodial activity (Dd2) Human proteasome inhibition0 

For the determination of the antiplasmodial activity of the compounds, the multi-resistant Dd2 strain of Plasmodium falciparum was used and [8-3H]-hypoxanthine incorporated into the parasitic nucleic acids measured. The plasmodia were incubated with 0.3% parasitemia and an erythrocyte hematocrit of 2.5% in the presence of different concentrations of selected experimental agents in a final volume of 200 xl. The medium employed was RPMI 1640 containing 10% of heat-treated human serum and 3 mg/1 of gentamycin. In the incubations, the concentrations of the compounds varied from 0.3 to 100 xM. After 48 hours, each batch was treated with 50 xl [8-3H]hypoxanthine and incubated additional 18 hours. Testing results are provided in Table 1. 

Antiplasmodial Activity Against the 3D7 Chloroquine-sensitive Strain Antiplasmodial activity against the 3D7 chloroquine-sensitive strain of P. falciparum was determined using the method of Wright (1). Testing results are provided in Table 1. 

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Rehner This suggestion is not sufficient to explain your results with cycloheximide. If cycloheximide is added, the inhibitor should already have been made. In this case the timing can only work if a protein degradation system is switched on on time in the absence of protein synthesis. 

Yoshimori T, Yamamoto A, Moriyama Y, Futai M, Tashiro Y. Bafilomycin Al, a specific inhibitor of vacuolar-type H(+)-ATPase, inhibits acidification and protein degradation in lysosomes of cultured cells. J Biol Chem 1991 266(26) 17707-17712. 

Lee DH, Goldberg AL (1996) Selective inhibitors of the proteasome-dependent and vacuolar pathways of protein degradation in Saccharomyces cerevisiae. J Biol Chem 271 27280-27284... 

Blocking of Protein Degradation of HaloTag-CL1 by a Proteasome Inhibitor MG132... 

In contrast to cAMP, a stimulation of PKC with phorbol esters (TPA) has been shown to play an important role in the downregulation of gap junctional coupling [Yancey et al., 1982]. Since reestablishment of intercellular coupling was not seen after wash out of TPA in the presence of the protein synthesis inhibitor, puromycin [Fitzgerald et al., 1983], the phorbol ester probably induces the elimination of junctional channels under these conditions. Thus, it might be possible that PKC is involved in the regulation of channel degradation. 

The mechanisms whereby GH and other factors modulate receptor levels is not known. In medium- or long-term experiments use of protein synthesis inhibitors usually blocks such modulation, suggesting that de novo synthesis of receptors may be required, although involvement of other short-lived proteins cannot be ruled out. Rapid increase in receptor levels probably does not require synthesis of new receptors, and may be achieved by insertion of receptors that were previously stored in-tracellulqrly into the plasma membrane, and/or by activation of receptor proteins already in the plasma membrane in an inactive form. Down-regulation of receptors probably involves endocytosis, possibly followed by degradation [18]. 

Protease inhibitors, which prevent proteolytic protein degradation. 

Elucidation of the role of the 205 proteasome in protein degradation and as a target for cancer chemotherapy could not have been achieved without small molecule inhibitors, some of which have served strictly as research tools, while others have progressed through preclinical development and clinical trials.18,28,29 These molecules represent a variety of structural classes, including peptide boronic acids such as bortezomib and CEP-187 70,30 epoxyketones (e.g. carfilzomib)31 and the y-lactam-(3-lactone family of inhibitors (Figure 12.1). 

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