scholarly journals UVB-mediated activation of p38 mitogen-activated protein kinase enhances resistance of normal human keratinocytes to apoptosis by stabilizing cytoplasmic p53

2002 ◽  
Vol 365 (1) ◽  
pp. 133-145 ◽  
Author(s):  
Nadine CHOUINARD ◽  
Kristoffer VALERIE ◽  
Mahmoud ROUABHIA ◽  
Jacques HUOT
Keyword(s):  
Adaptive Response ◽  
Human Keratinocytes ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Dominant Negative Mutant ◽  
Normal Human Keratinocytes ◽  
Mitogen Activated Protein ◽  
Normal Human ◽  
Induced Apoptosis ◽  
Negative Mutant

Human keratinocytes respond to UV rays by developing a fast adaptive response that contributes to maintaining their functions and survival. We investigated the role of the mitogen-activated protein kinase pathways in transducing the UV signals in normal human keratinocytes. We found that UVA, UVB or UVC induced a marked and persistent activation of p38, whereas c-Jun N-terminal kinase or extracellular signal-regulated kinase were less or not activated respectively. Inhibition of p38 activity by expression of a dominant-negative mutant of p38 or with SB203580 impaired cell viability and led to an increase in UVB-induced apoptosis. This sensitization to apoptosis was independent of caspase activities. Inhibition of p38 did not sensitize transformed HaCaT keratinocytes to UVB-induced apoptosis. In normal keratinocytes, expression of a dominant-negative mutant of p53 increased UVB-induced cell death, pointing to a role for p53. In these cells, UVB triggered a p38-dependent phosphorylation of p53 on Ser-15. This phosphorylation was associated with an SB203580-sensitive accumulation of p53, even in the presence of a serine phosphatase inhibitor. Accumulated p53 was localized mainly in the cytoplasm, independently of CRM1 nuclear export. In HaCaT cells, p53 was localized exclusively in the nucleus and its distribution and level were not affected by UVB or p38 inhibition. However, UVB induced an SB203580-insensitive phosphorylation on Ser-15 of mutated p53. Overall, our results suggest that, in normal human keratinocytes, protection against UVB depends on p38-mediated phosphorylation and stabilization of p53 and is tightly associated with the cytoplasmic sequestration of wild-type p53. We conclude that the p38/p53 pathway plays a key role in the adaptive response of normal human keratinocytes against UV stress.

scholarly journals JNK Regulates the Release of Proapoptotic Mitochondrial Factors in Reovirus-Infected Cells

2004 ◽  
Vol 78 (23) ◽  
pp. 13132-13138 ◽  
Author(s):  
Penny Clarke ◽  
Suzanne M. Meintzer ◽  
Yibing Wang ◽  
Lisa A. Moffitt ◽  
Sarah M. Richardson-Burns ◽  
...  
Keyword(s):  
Caspase 3 ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Reovirus Infection ◽  
Kinase C ◽  
Mitogen Activated Protein ◽  
Infected Cells ◽  
Induced Apoptosis ◽  
Factor C ◽  
Subsequent Onset

ABSTRACT Reovirus-induced apoptosis is associated with activation of the proapoptotic mitogen-activated protein kinase c-Jun N-terminal kinase (JNK) and the JNK-associated transcription factor c-Jun. Here we show that reovirus-induced apoptosis and activation of caspase 3 are inhibited in cells deficient in MEK kinase 1, an upstream activator of JNK in reovirus-infected cells. Inhibition of JNK activity following reovirus infection delays the release of proapoptotic mitochondrial factors and the subsequent onset of apoptosis. In contrast, reovirus-induced apoptosis is not blocked by infection with adenovirus expressing dominant-negative c-Jun, and c-Jun activation does not correlate with apoptosis in reovirus-infected cells. This is the first report demonstrating that JNK is associated with regulation of mitochondrial pathways of apoptosis following viral infection.

scholarly journals Coordinate Regulation of IκB Kinases by Mitogen-Activated Protein Kinase Kinase Kinase 1 and NF-κB-Inducing Kinase

1998 ◽  
Vol 18 (12) ◽  
pp. 7336-7343 ◽  
Author(s):  
Shino Nemoto ◽  
Joseph A. DiDonato ◽  
Anning Lin
Keyword(s):  
Protein Kinase ◽  
Interleukin 1 ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Dominant Negative Mutant ◽  
Necrosis Factor Alpha ◽  
Tnf Α ◽  
Ikk Complex ◽  
Mitogen Activated Protein ◽  
Protein Kinase Kinase

ABSTRACT IκB kinases (IKKα and IKKβ) are key components of the IKK complex that mediates activation of the transcription factor NF-κB in response to extracellular stimuli such as inflammatory cytokines, viral and bacterial infection, and UV irradiation. Although NF-κB-inducing kinase (NIK) interacts with and activates the IKKs, the upstream kinases for the IKKs still remain obscure. We identified mitogen-activated protein kinase kinase kinase 1 (MEKK1) as an immediate upstream kinase of the IKK complex. MEKK1 is activated by tumor necrosis factor alpha (TNF-α) and interleukin-1 and can potentiate the stimulatory effect of TNF-α on IKK and NF-κB activation. The dominant negative mutant of MEKK1, on the other hand, partially blocks activation of IKK by TNF-α. MEKK1 interacts with and stimulates the activities of both IKKα and IKKβ in transfected HeLa and COS-1 cells and directly phosphorylates the IKKs in vitro. Furthermore, MEKK1 appears to act in parallel to NIK, leading to synergistic activation of the IKK complex. The formation of the MEKK1-IKK complex versus the NIK-IKK complex may provide a molecular basis for regulation of the IKK complex by various extracellular signals.

scholarly journals TRAF2 Plays a Key, Nonredundant Role in LIGHT-Lymphotoxin β Receptor Signaling

2005 ◽  
Vol 25 (6) ◽  
pp. 2130-2137 ◽  
Author(s):  
You-Sun Kim ◽  
Sergei A. Nedospasov ◽  
Zheng-gang Liu
Keyword(s):  
Ectopic Expression ◽  
Wild Type Mouse ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Dominant Negative Mutant ◽  
Iκb Kinase ◽  
Mitogen Activated Protein ◽  
Β Receptor ◽  
Simplex Virus ◽  
Jnk Activation

ABSTRACT LIGHT is a member of the tumor necrosis factor (TNF) superfamily, and its function is mediated by at least two receptors, including lymphotoxin β receptor (LTβR) and herpes simplex virus entry mediator. However, the molecular mechanism of LIGHT signaling mediated by LTβR has not been clearly defined. In this report, we demonstrate that TRAF2 is critical for LIGHT- and LTβR-mediated activation of both the transcription factor NF-κB and the mitogen-activated protein kinase JNK. In HeLa cells, LIGHT induces NF-κB and JNK activation, which can be blocked by the dominant negative mutant of TRAF2. In these cells, LIGHT causes the recruitment of TRAF2, TRAF3, and IκB kinase into the LTβR complex. Importantly, while both NF-κB and JNK are activated by LIGHT in wild-type mouse embryonic fibroblasts, no activation of either of these two pathways is observed in TRAF2 null fibroblasts. However, LIGHT-induced NF-κB and JNK activation can be restored by ectopic expression of TRAF2 in TRAF2−/− cells. Interestingly, in contrast to TNF signaling, the activation of both NF-κB and JNK by LIGHT was normal in RIP−/− and TRAF5−/− cells. Taken together, our data demonstrate that TRAF2, an important effector molecule of TNF signaling, plays a critical, nonredundant role in LIGHT-LTβR signaling.

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