Polyglutamine aggregates stimulate ER stress signals and caspase-12 activation.
Accumulation of unfolded and malfolded proteins causes endoplasmic reticulum (ER) stress, stimulating unfolded protein response (UPR) and c-Jun N-terminal kinase (JNK) activation and activating caspase-12 located on the ER. Little is known about the relationship between the ER stress and polyglutamine [poly(Q)] aggregates. Poly(Q)72 repeats [poly(Q)(72)] induced the stimulation of ER stress signals such as JNK activation, upregulation of Grp78/Bip and caspase-12 activation in C2C5 cells. We prepared antiserum against the cleavage site of mouse caspase-12 at D(318) (anti-m12D318), and showed that poly(Q)(72) with perinuclear aggregates, cytoplasmic inclusions and nuclear inclusions stimulated JNK activation and anti-m12D318 immunoreactivity, but poly(Q)(72) with dispersed aggregates and small nuclear aggregates showed a significantly less effect. Poly(Q)(72) and poly(Q)(11) dispersed in cytoplasm did not. Anti-m12D318-positive cells showed apoptotic features. Unlike anti-m8D387 immunoreactivity, the anti-m12D318 immunoreactivity was not coaggregated with poly(Q). Ac-IETD-fmk (caspase-8 inhibitor) and Ac-DEVD-CHO (caspase-3 inhibitor) did not prevent the anti-m12D318 immunoreactivity induced by poly(Q)(72) aggregates. Anti-m12D318 immunoreactivity was detected in caspase-8(-/-) and caspase-3(-/-) mouse embryonic fibroblasts expressing poly(Q)(72) aggregates. Thus, caspase-12 was activated by poly(Q)(72) aggregates via a pathway independent of caspase-8 and caspase-3 activation, and caspase-12 activation was closely associated with poly(Q) aggregate-mediated cell death. Stimulation of ER stress signals may be involved in the pathogenesis of neurodegenerative disorders with poly(Q) expansion.
Kouroku
Yoriko
Y
Division of Development and Differentiation, National Institute of Neuroscience, 4-1-1 Ogawahigashi-machi, Kodaira, Tokyo 187-8502, Japan.
Fujita
Eriko
E
Jimbo
Atsushi
A
Kikuchi
Tateki
T
Yamagata
Takanori
T
Momoi
Mariko Y
MY
Kominami
Eiki
E
Kuida
Keisuke
K
Sakamaki
Kazuhiro
K
Yonehara
Shin
S
Momoi
Takashi
T
D000818:Animals; D017209:Apoptosis; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism; D053454:Caspase 12; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D004789:Enzyme Activation; D016758:Genes, jun; D006360:Heat-Shock Proteins; D015151:Immunoblotting; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D018832:Molecular Chaperones; D010455:Peptides; C097188:polyglutamine; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C506440:Casp12 protein, mouse; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053454:Caspase 12; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases