Inhibition versus induction of apoptosis by proteasome inhibitors depends on concentration.
We previously established that NF-kappaB DNA binding activity is required for Sindbis Virus (SV)-induced apoptosis. To investigate whether SV induces nuclear translocation of NF-kappaB via the proteasomal degradation pathway, we utilized MG132, a peptide aldehyde inhibitor of the catalytic subunit of the proteasome. 20 microM MG132 completely abrogated SV-induced NF-kappaB nuclear activity at early time points after infection. Parallel measures of cell viability 48 h after SV infection revealed that 20 microM MG132 induced apoptosis in uninfected cells. In contrast, a lower concentration of MG132 (200 nM) resulted in partial inhibition of SV-induced nuclear NF-kappaB activity and inhibition of SV-induced apoptosis without inducing toxicity in uninfected cells. The specific proteasomal inhibitor, lactacystin, also inhibited SV-induced death. Taken together, these results suggest that the pro-apoptotic and anti-apoptotic functions of peptide aldehyde proteasome inhibitors such as MG-132 depend on the concentration of inhibitor utilized and expand the list of stimuli requiring proteasomal activation to induce apoptosis to include viruses.
Lin
K I
KI
Department of Molecular Microbiology and Immunology, The Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD, USA.
Baraban
J M
JM
Ratan
R R
RR
D017209:Apoptosis; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007976:Leupeptins / Q000494:pharmacology*; D009097:Multienzyme Complexes / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D012845:Sindbis Virus / Q000502:physiology
D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D009097:Multienzyme Complexes; D016328:NF-kappa B; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde