Proteasome inhibition proteases

Several aryl esters of 6-chloromethyl-2-oxo-2//-l -benzopyran-3-carboxylic acid act as human Lon protease inhibitors (alternate substrate inhibitors)46 without having any effect on the 20S proteasome. Proteasomes are the major agents of protein turnover and the breakdown of oxidized proteins in the cytosol and nucleus of eukaryotic cells,47 whereas Lon protease seems to play a major role in the elimination of oxidatively modified proteins in the mitochondrial matrix. The coumarin derivatives are potentially useful tools for investigating the various biological roles of Lon protease without interfering with the proteasome inhibition. 

An WG, Hwang SG, Trepel JB, Blago-sklonny MV. 2000. Protease inhibitor-induced apoptosis accumulation of wt p53, p21WAFl/CIPl, and induction of apoptosis are independent markers of proteasome inhibition. Leukemia 14 1276-83... 

The inhibition of multifunctional enzymes can also have therapeutic interest. The 26S proteasome is a mul-ticatalytic intracellular protease complex expressed in eukaryotic cells. This complex is responsible for selective degradation of intracellular proteins that are responsible for cell proliferation, growth, regulation of apoptosis and transcription of genes. Thus, proteasome inhibition is a potential treatment option for cancer and diseases due to aberrant inflammation conditions. Bortezomib and PS-519 are the first proteasome inhibitors that have entered clinical trials. In multiple myeloma, both the FDA (United States... 

Both the 26S proteasome and the RC hydrolyze all four nucleotide triphosphates, with ATP and CTP preferred over GTP and UTP [58]. Although ATP hydrolysis is required for conjugate degradation, the two processes are not strictly coupled. Complete inhibition of the peptidase activity of the 26S proteasome by calpain inhibitor I has little effect on the ATPase activity of the enzyme. The nucleotidase activities of the RC and the 26S proteasome closely resemble those of E. coli Lon protease, which is composed of identical subunits that possess both proteolytic and nucleotidase activities in the same polypeptide chain. Like the regulatory complex and 26S proteasome, Lon hydrolyzes all four ribonucleotide triphosphates, but not ADP or AMP [18]. 

Peptide boronates are much more potent proteasome inhibitors than aldehydes [43[. Boronate-proteasome adducts have much more slower dissociation rates than proteasome-aldehyde adducts, and although boronates are considered reversible inhibitors, the inhibition is practically irreversible over a period of hours. In addition, PS-341 inhibits serine proteases 1000-fold weaker than it does the proteasome [43[. This combination of potency, selectivity and metabolic stability makes the peptide boronates better drug candidates than other classes of proteasome inhibitors. In vitro and mouse xenograft studies of PS-341 have shown anti-tumor activity in a variety of tumor types. DFLB and PS-273 are usefiil fluorescent active site probes binding of these inhibitors enhances the fluorescence of their environment-sensitive dansyl and naphthyl moieties [44]. 

Peptide vinyl sulfones are synthetic irreversible proteasome inhibitors that covalently modify its catalytic / subunits [47]. They are easier to synthesize than other irreversible proteasome inhibitors, and they do not inhibit serine proteases. 

Stehlik C, de Martin R, Kumabashiri I, Schmid JA, Binder BR, Lipp J (1998) Nuclear factor (NF)-kappaB-regulated X-chromosome-linked iap gene expression protects endothelial cells from tumor necrosis factor alpha-induced apoptosis. J Exp Med 188 211-216 Stennicke HR, Deveraux QL, Humke EW, Reed JC, Dixit VM, Salvesen GS (1999) Caspase-9 ctin be activated without proteolytic processing. J Biol Chem 274 8359-8362 Sun XM, Butterworth M, MacFarlane M, Dubiel W, Ciechanover A, Cohen GM (2004) Caspase activation inhibits proteasome function during apoptosis. Mol Cell 14 81-93 Suzuki Y, Imai Y, Nakayama H, Takahashi K, Takio K, Takahashi R (2001) A serine protease, HtrA2, is released from the mitochondria and interacts with XIAP, inducing cell death. Mol Cell 8 613-621... 

Lactacystin Cultured cells Neurite induction and protease inhibition Proteasome... 

As weU as age-related reductions in cell volume, there may also be contributions to macromolecular crowding from age-related decline in proteasomal activity. Decreases in protein degradation would result in increases in the concentration of all cytoplasmic proteins. It has been found that inhibition of proteasomal activity leads to the formation of a-synuclein inclusions without, however, significantly increasing the concentration of a-synuclein. Reduced protease activity has been measured in Parkinson s disease brains. Also protease activity in PC12 cells is known to be reduced by over-expression of a-synuclein. 

The proteasome inhibitors salinosporamide A and omuralide are both y-lactam-p-lactone bicy-clic compounds (Fig. 13.5) derived from natural sources. Salinosporamide A, also known as marizomib, is obtained from Salinospora tropica, a bacterium found in ocean sediments. The drug is an irreversible proteasome inhibitor that shows little effect on the caspase-like activity but inhibits chymotrypsin- and trypsin-like protease activities. Preclinical studies have demonstrated antitumor activity in models for multiple myeloma, hematologic malignancies, and solid tumors and, importantly, marizomib does not show cross-resistance with other proteasome inhibitors. Omuralide (clasto-lactacystin p-lactone p-clastolactacystin) is the active metabolite of... 

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