Novel role for JNK as a stress-activated Bcl2 kinase.
Interleukin (IL)-3-induced Bcl2 phosphorylation at Ser(70) may be required for its full and potent antiapoptotic activity. However, in the absence of IL-3, increased expression of Bcl2 can also prolong cell survival. To determine how Bcl2 may be functionally phosphorylated following IL-3 withdrawal, a stress-activated Bcl2 kinase (SAK) was sought. Results indicate that anisomycin, a potent activator of the stress kinase JNK/SAPK, can induce Bcl2 phosphorylation at Ser(70) and that JNK1 can be latently activated following IL-3 withdrawal to mediate Bcl2 phosphorylation. JNK1 directly phosphorylates Bcl2 in vitro, co-localizes with Bcl2, and collaborates with Bcl-2 to mediate prolonged cell survival in the absence of IL-3 or following various stress applications. Dominant-negative (DN)-JNK1 can block both anisomycin and latent IL-3 withdrawal-induced Bcl2 phosphorylation (>90%) and potently enhances cell death. Furthermore, low dose okadaic acid (OA), a potent protein phosphatase 1 and 2A inhibitor, can activate the mitogen-activated protein kinases JNK1 and ERK1/2, but not p38 kinase, to induce Bcl2 phosphorylation and prolong cell survival in factor-deprived cells. Since PD98059, a specific MEK inhibitor, can only partially inhibit OA-induced Bcl2 phosphorylation but completely blocks OA-induced Bcl2 phosphorylation in cells expressing DN-JNK1, this supports the conclusion that OA may stimulate Bcl2 phosphorylation via a mechanism involving both JNK1 and ERK1/2. Collectively, these findings indicate a novel role for JNK1 as a SAK and may explain, at least in part, how functional phosphorylation of Bc12 can occur in the absence of growth factor.
Deng
X
X
University of Florida Shands Cancer Center, Gainesville, Florida 32610-0232, USA.
Xiao
L
L
Lang
W
W
Gao
F
F
Ruvolo
P
P
May
W S
WS
D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D017209:Apoptosis; D054713:Bryostatins; D002460:Cell Line; D002470:Cell Survival; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D007377:Interleukin-3 / Q000494:pharmacology; D007783:Lactones / Q000494:pharmacology; D018942:Macrolides; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009154:Mutation; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D011493:Protein Kinase C / Q000378:metabolism; D054645:Protein Phosphatase 1; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological
D054713:Bryostatins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007377:Interleukin-3; D007783:Lactones; D018942:Macrolides; D019253:Proto-Oncogene Proteins c-bcl-2; D019319:Okadaic Acid; C046785:bryostatin 1; D000841:Anisomycin; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one