Nerve growth factor blocks thapsigargin-induced apoptosis at the level of the mitochondrion via regulation of Bim.
This study examined how the neurotrophin, nerve growth factor (NGF), protects PC12 cells against endoplasmic reticulum (ER) stress-induced apoptosis. ER stress was induced using thapsigargin (TG) that inhibits the sarcoplasmic/ER Ca2+-ATPase pump (SERCA) and depletes ER Ca2+ stores. NGF pre-treatment inhibited translocation of Bax to the mitochondria, loss of mitochondrial transmembrane potential, cytochrome c release, activation of caspases (-3, -7 and -9) and apoptosis induction by TG. Notably, TG also caused a marked induction of BimEL mRNA and protein, and knockdown of Bim with siRNA protected cells against TG-induced apoptosis. NGF delayed the induction and increased the phosphorylation of BimEL. NGF-mediated protection was dependent on phosphatidylinositol-3 kinase (PI3K) signalling since all above apoptotic events, including expression and phosphorylation status of BimEL protein, could be reverted by the PI3K inhibitor LY294002. In contrast, NGF had no effect on the TG-mediated induction of the unfolded protein response (increased expression of Grp78, GADD34, splicing of XBP1 mRNA) or ER stress-associated pro-apoptotic responses (induction of C/EBP homologous protein [CHOP], induction and processing of caspase-12). These data indicate that NGF-mediated protection against ER stress-induced apoptosis occurs at the level of the mitochondria by regulating induction and activation of Bim and mitochondrial translocation of Bax.
Szegezdi
E
E
Department of Biochemistry, National University of Ireland, Galway, Ireland.
Herbert
K Reed
KR
Kavanagh
E T
ET
Samali
A
A
Gorman
A M
AM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D000072224:Bcl-2-Like Protein 11; D001693:Biological Transport, Active / Q000187:drug effects; D053454:Caspase 12 / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D008954:Models, Biological; D020932:Nerve Growth Factor / Q000494:pharmacology*; D016716:PC12 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017510:Protein Folding / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013312:Stress, Physiological / Q000187:drug effects; D019284:Thapsigargin / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; C494828:Bax protein, rat; D000072224:Bcl-2-Like Protein 11; C000606778:Bcl2l11 protein, rat; D017931:DNA Primers; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051028:bcl-2-Associated X Protein; D019284:Thapsigargin; D020932:Nerve Growth Factor; D019869:Phosphatidylinositol 3-Kinases; C506443:Casp12 protein, rat; D053454:Caspase 12