Proteasome Lactacystin

Whereas standard proteases use serine, cysteine, aspartate, or metals to cleave peptide bonds, the proteasome employs an unusual catalytic mechanism. N-terminal threonine residues are generated by self-removal of short peptide extensions from the active yS-subunits and act as nucleophiles during peptide-bond hydrolysis [23]. Given its unusual catalytic mechanism, it is not surprising that there are highly specific inhibitors of the proteasome. The fungal metabolite lactacystin and the bacterial product epoxomicin covalently modify the active-site threonines and in-... 

Fenteany, G. et al. Inhibition of proteasome activities and subunit-specific amino-terminal threonine modification by lactacystin. Science 1995, 268, 726-731. 

Fig. 10.7. Inh ibitor binding to individual active sites of the yeast 20S proteasome. The inhibitors lactacystin (A), epoxomicin (B) and TMC95A (C) are colored green and are shown in stereo mode together with their unbiased electron densities. The active-site Thrl is highlighted in black. (A) Covalent binding of the Streptomyces metabolite lactacystin to the active site of 5. The SI pockets of the active subunits and differ from that of 5 and are not suitably constructed to bind the inhibitor. As discussed in the text, Met45 (black), which is located at the bottom of the 5-Sl pocket, makes the difference for inhibitor...

Fenteany, G., Standaert, R. F., Lane, W. S., Choi, S., Corey, E. J., and Schreiber, S. L. Inhibition of proteasome activities and subunit-spedfic amino-terminal threonine modification by lactacystin. Science 1995, 268, 726-731. 

Moreover, an UCH (Ap-uch) that interacts with the proteasome was found to be induced by 5-HT, the neurotransmitter that induced long-term facilitation. Ap-uch was found to be critical for the induction of longterm facilitation. Subsequently, Chain et al showed that at sensory-motor neuron synapses, injection of lactacystin, a specific proteasome inhibitor blocked induction of long-term facilitation. Since R subunit inhibits the activity of C subunits of PKA, the results were interpreted to suggest that the ubiquitin-proteasome pathway operates to remove inhibitory constraints on the formation of long-term memory. This has been... 

Proteasome inhibition by lactacystin and Bz-LLL-COCHO (benzol-Leu-Leu-Leu-glyoxal) causes a significant increase of ABP and cell death by altering APP processing at the y-secretase site (406). Resveratrol does not inhibit ABP production because it has no effect on 3-, or y-secretases, but promotes instead intracellular degradation of ABP via a mechanism that involves the proteasome. The resveratrol-induced decrease of ABP can be effectively prevented by several selective proteasome inhibitors and by small interfering RNA-directed silencing on the proteasome subunit P5 (407). 

Synthesis of the Proteasome Inhibitors Salinosporamide A, Omuralide and Lactacystin... 

The structurally-related 7-lactams salinosporamide A 1, omuralide 2 and lactacystin 3, of bacterial origin, inhibit proteasome activity, and so are of interest as lead compounds for the development of anticancer agents. Barbara . M. Potts of Nereus Pharmaceuticals in San Diego has reported (J. Med. Chem. 2005,48,3684) a detailed structure-activity studies in this series, and E.J. Corey of Harvard University has prepared (J. Am. Chem. Soc. 2005,127, 8974, 15386) several interesting structural analogues. Susumi Hatakeyama of Nagasaki University, building on previous work in this area, has reported (J. Org. Chem. 2004, 69,7765) a synthesis of 2 and 3 from Tris. 

A specific inhibitor of the major proteasomal activities is lactacystin, a compound formed by Streptomyces. Lactacystin is converted reversibly, by loss of N-acetyl-cysteine, into a P-lactone known as c/asto-lactacystin. The N-terminal amino group attacks the reactive four-membered ring of the lactone (Eq. 12-22)358/359... 

Lactacystin is a Streptomyces metabolite that selectively modifies the fiS subunit of the mammalian proteasome and irreversibly blocks its activity. Other proteolytic sites of the proteasome are also modified and reversibly inhibited, but at much slower rates [45, 46). 

Craiu, a., Gaczynska, M., Akopian, T, Gramm, C. F., Fenteany, G., Goldberg, A.L., Rock, K. L., Lactacystm and dasto-lactacystin beta-lactone modify multiple proteasome beta-subunits and inhibit intracellular protein degradation and major histocompatibility complex class 1 antigen presentation. J. Biol. Chem. 1997,... 

Corey EJ, Li WD, Nagamitsu T, Fenteany G. The structural requirements for inhibition of proteasome function by the lactacystin-derived f -lactone and synthetic analogs. Tetrahedron 1999 55 3305-3316. 

Biochemical Studies Epolactaene promoted neurite outgrowth and arrested cell-cycle progression at the GO/Gl phase in the neuroblastoma cell line [1]. Different from lactacystin, a compound that promotes neurite outgrowth and arrests cell cycle in both the GO/Gl and G2/M phases in mouse neuroblastoma Neuro2A cells, epolactaene did not inhibit the proteasome peptidase activities... 

Proteins in the human body have a limited lifetime. They are earmarked for degradation with a marker ubiquitin and hydrolysed by proteasomes. Though this is a natural and necessary sequence of events it can get out of hand and proteasome inhibitors could provide treatments for heart diseases, asthma, and arthritis. Lactacystin 112 is a proteasome inhibitor from a soil micro-organism. 

Lactacystin proteasome inhibitor (inhibits protein degradation)... 

The catalytic role of the N-terminal threonine of ft subunits was soon extended to eukaryotic proteasomes by the observation that binding of lactacystin, a Streptomyces metabolite, to the mammalian /1-type subunit /15/X irreversibly inhibits its proteolytic activity... 

The potently cytotoxic proteasome inhibitor salinosporamide A (26, NPI-0052) was isolated from a new genus of marine bacteria called Salinispora The bicyclic (/3-lactam-7-lactam) core structure of salinosporamide A is also found in the activated form of lactacystin known as r/iMto-lactacystin /3-lactone (24, omuralide). While structurally similar to omuralide, salinosporamide A (26) is pharmacologically and mechanistically distinct/ Unlike omuralide, chloride displacement from the chlorinated side chain in salinosporamide A... 

Since the proteasome mediates the oxygen-dependent degradation of HIE-lct protein, natural product-based proteasome inhibitors have become important tools to probe HIE-1 regulation. Salceda and Caro found that inhibition of the ubiquitin-proteasome system with lactacystin (23) caused HIE-lct accumulation, indicating that HIE-lct protein is rapidly degraded by the ubiquitin-proteasome under normoxic conditions and that redox-induced biochemical modification mediates the changes in HIE-lct protein stability... 

Discovery and application in cell biology of Lactacystin, a proteasome inhibitor 00YZ935. 

K. Worowski, Lactacystin, a specific inhibitor of the proteasome, inhibits human platelet lysosomal cathepsin A-like enzyme, Biochem. Biophys. Res. Commun. 1997, 234, 729-732. 

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