Caspase-like activity

Cell mortality of this type appears to be related to the process of apoptosis described in multicellular systems. Apoptosis is mediated by a group of cysteine endopeptidases (EC 3.4.22.x), termed caspases, that cleave after aspartate residues. Thus, caspase activity (or what is better termed caspase-like activity, see Section 2.4.3.2) may prove to be a good marker of this form of cell mortality. 

Information gained from assays and future potential So far, few field measurements have been made of caspase-like activities (Berman-Frank et al., 2004 Vardi et al., 1999), but the assay methods appear to be sensitive enough to allow use in natural communities. As work using cultures proceeds, and our understanding of cell death processes improves, assays of capase-like activity may offer an important means to distinguish different forms of cell mortality. Aside from bulk in vitro assays, the availability of ceU-permeable substrates, coupled with flow cytometry will provide improved resolution and specificity (e.g. Bidle and Bender, 2008). 

Segovia, M., and Berges, J. A. (2005). Effect of inhibitors of protein synthesis and DNA replication on the induction of proteolytic activities, caspase-like activities and cell death in the unicellular chlorophyte Dunaliella tertiolecta. Eur.J. Phycol. 40, 21—30. 

Parameswaran, N. et al., Okadaic acid stimulates caspase-like activities and induces apoptosis of cultured rat mesangial cells. Mol. Cell. Biochem., 260, 7, 2004. 

G. A., Kessler, B.M., Overkleeft, H.S., and Kisselev, A.F. (2007) A cell-permeable inhibitor and activity-based probe for the caspase-like activity of the proteasome. Bioorg. Med. Chem. Lett, 17, 3402-3405. 

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... 

The catabolism of iNOS is also largely mediated by the ubiquitination-proteasome pathway (Kolodziejski et al. 2002 Musial and Eissa 2001). It is therefore possible that the caspase-sensitive step of flavopiridol-driven iNOS down-regulation occurs upstream the ubiquitination-proteasome pathway. Interestingly, a cell cycle-dependent caspase-like activity, termed KIPase, which is able to cleave the cdk inhibitor p27 P (Medina-Palazon et al. 2004), was recently identified as the pi subunit of the 20S proteasome (Tambyrajah et al. 2007). 

Medina-Palazon, C., Bernard, E., Frost, V., Morley, S., and Sinclair, A.J. (2004). KIPase activity is a novel caspase-like activity associated with cell proliferation. Fur J Biochem. 271,2716-2723. 

Tambyrajah, W.S., Bowler, L.D., Medina-Palazon, C., and Sinclair, AJ. (2007). Cell cycle-dependent caspase-like activity that cleaves p27(KIPl) is the beta(l) subunit of the 20S proteasome. Arch. Biochem. Biophys. 466, 186-193. 

The introduction of FRET pairs with improved properties allows the generation of probes suitable for the measurement of spatio-temporal activities in living cells and in vivo. One example is the imaging of caspase-3 activation in HeLa cells after inducing apoptosis. Previous fluorogenic substrates, such as DEVD-MCA, could not be used in living cells because the autofluorescence interfered with the low emission wavelength of the coumarin dye MCA [123], With the incorporation of the FRET pair 6-carboxydichlorofluorescein and 5-carboxytetramethylrhodamine into another peptide sequence cleavable by caspase-3, Mizukami et al. measured caspase-3-like activity in HeLa cells stimulated by an inducer of apoptosis [124],... 

Colquhoun and Schumacher [98] have shown that y-linolcnic acid and eicosapentaenoic acid, which inhibit Walker tumor growth in vivo, decreased proliferation and apoptotic index in these cells. Development of apoptosis was characterized by the enhancement of the formation of reactive oxygen species and products of lipid peroxidation and was accompanied by a decrease in the activities of mitochondrial complexes I, III, and IV, and the release of cytochrome c and caspase 3-like activation of DNA fragmentation. Earlier, a similar apoptotic mechanism of antitumor activity has been shown for the flavonoid quercetin [99], Kamp et al. [100] suggested that the asbestos-induced apoptosis in alveolar epithelial cells was mediated by iron-derived oxygen species, although authors did not hypothesize about the nature of these species (hydroxyl radicals, hydrogen peroxide, or iron complexes ). 

Constitutive activation of the P13-K - Akt/PKB survival signaling pathway is a likely mechanism by which many cancers become refractory to cytotoxic therapy. In LNCaP prostate cancer cells, the PTEN is inactivated, leading to constitutive activation of Akt/PKB and resistance to apoptosis. However, apoptosis and inactivation of Akt/PKB can be induced in these cells by treatment with P13-K inhibitors. Surprisingly, androgen, epidermal growth factor, or semm can protect these cells from apoptosis, even in the presence of P13-K inhibitors and without activation of Akt/PKB, indicating the activity of a novel, Akt/PKB-independent survival pathway. This pathway blocks apoptosis at a level prior to caspase 3 activation and release of cytochrome c from mitochondria (Carson et al, 1999)... 

Like many other proteases, the caspases are formed as inactive proenzymes of 30—50 kDa and are activated by proteolytic processing. The proenzymes have a prodomain and two cleavage sites for processing, which are consensus sites for the caspases, enabling activating by autoproteolysis. 

Jankowski-Hennig MA, Clegg MS, Oaston GP, Rogers JM, Keen CL (2000) Zinc-deficient rat embryos have increased caspase 3-like activity and apoptosis. Biochem Biophys Res Commun, 271(1) 250-256. 

Ouyang, Y. B., Tan, Y., Comb, M., Liu, C. L., Martone, M. E., Siesjo, B. K., and Hu, B. R. (1999). Survival- and death-promoting events after transient cerebral ischemia Phosphorylation of Akt, release of cytochrome C and Activation of caspase-like proteases. J. Cereb. Blood Flow Metab. 19, 1126-1135. 

In terms of structure and function, the 265 proteasome is an ATP-dependent multicatalytic enzyme complex comprising one or two 195 regulatory caps and a proteolytic 205 core particle within which protein degradation occurs.18,25,26 The 205 proteasome contains three pairs of proteolytic subunits, (35, (32 and (31, for which chymotrypsin-like (CT-L), trypsin-like (T-L) and caspase-like (C-L) activities have been ascribed, respectively, based on their substrate preferences.27... 

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