MG132

MG-132 displays >1000 times more activity than ZLLal in inhibiting the ZLLL-MCA-degrading activity of 20S proteasome with IC50 of 100 nM versus 110 μM. This compound also inhibits calpain with IC50 of 1.2 μM. This chemical induces neurite outgrowth in PC12 cells at an optimal concentration of 20 nM, displaying 500 times more potency than ZLLal. ^[1] This compound (10 μM) potently inhibits TNF-α-induced NF-κB activation, interleukin-8 (IL-8) gene transcription, and IL-8 protein release in A549 cells by inhibition of proteasome-mediated IκBα degradation. ^[2] This chemical treatment potently induces p53-dependent apoptosis in KIM-2 cells by 26S proteasome inhibition. ^[3] Unlike BzLLLCOCHO or PS-341, this compound treatment results in weak inhibition of the chymotrypsinlike (CT-L) and peptidylglutamyl peptide hydrolysing (PGPH) activities of the 26S proteasome, whereas multiple myeloma cells (U266 and OPM-2) are more sensitive to induction of apoptosis by this chemical than BzLLLCOCHO. ^[4] This compound (1 μM) sensitizes TRAIL-resistant prostate cancer cells by activating the AP-1 family members c-Fos and c-Jun, which, in turn, repress the antiapoptotic molecule c-FLIP(L). ^[5] This chemical significantly enhances the ability of inositol hexakisphosphate (IP6) to reduce cellular metabolic activity in both PC3 and DU145 androgen-independent prostate cancer (AIPCa) cell lines. ^[6]

Administration of MG-132 effectively rescues the expression levels and plasma membrane localization of dystrophin, β-dystroglycan, α-bdystroglycan, and α-sarcoglycan in skeletal muscle fibers from mdx mice, reduces muscle membrane damage, and ameliorates the histopathological signs of muscular dystrophy. ^[7] Treatment with this compound significantly reduces immobilization-induced skeletal muscle atrophy in mice, by downregulating the muscle-specific ubiquitin ligases atrogin-1/MAFbx and MuRF-1 mRNA. ^[8]

• Measurement of inhibitory activities of MG-132 against 20S proteasome

  The reaction mixture for the 20S proteasome inhibitory assay contains 0.1 M Tris-acetate, pH 7.0, 20S proteasome, MG-132, and 25 μM substrate dissolved in dimethyl sulfoxide in a final volume of 1 mL. After incubation at 37 °C for 15 minutes, the reaction is stopped by the addition of 0.1 mL of 10% SDS and 0.9 mL of 0.1M Tris acetate, pH 9.0. The fluorescence of the reaction products is measured. To determine the IC50 against 20S proteasome, various concentrations of this compound are included in the assay mixture.

• Cell lines

  KIM-2, HC11, and ES

• Concentrations

  Dissolved in DMSO, final concentrations ~25 μM

• Incubation Time

  24 and 48 hours

• Method

  Cells are exposed to various concentrations of MG-132 for 24, and 48 hours. Supernatant and monolayer cells are harvested by centrifugation and fixed in 70% ethanol in PBS for staining with acridine orange. Equal volumes of cells and acridine orange (5 mg/mL in PBS) are mixed on a microscope slide and examined by fluorescence microscopy. For annexin V analysis, cells are harvested by centrifugation and stained with annexin V and propidium iodide. For cell cycle analysis, cells are rehydrated in PBS at room temperature for 10 minutes, followed by staining with propidium iodide (5 mg/mL). All samples are analyzed using a Coulter Epics XL flow cytometer.

• Animal Models

  Male mdx (C57BL/10ScSn DMD mdx) mice

• Dosages

  ~10 μg/kg/day

• Administration

  Injection