The yeast mitogen-activated protein kinase Slt2 is involved in the cellular response to genotoxic stress

The chimaeric protein Bcr/Abl, the hallmark of chronic myeloid leukaemia, has been connected with several signalling pathways, such as those involving protein kinase B/Akt, JNK (c-Jun N-terminal kinase) or ERKs (extracellular-signal-regulated kinases) 1 and 2. However, no data about the p38 MAPK (mitogen-activated protein kinase) have been reported. Here, we present evidence showing that Bcr/Abl is able to modulate this signalling pathway. Transient transfection experiments indicated that overexpression of Bcr/Abl in 293T cells is able to activate p38 MAPK or induce p73 stabilization, suggesting that c-Abl and Bcr/Abl share some biological substrates. Interestingly, the control exerted by Bcr/Abl on the p38 MAPK pathway was not only mediated by the tyrosine kinase activity of Bcr/Abl, as the use of STI571 demonstrated. In fact, Bcr alone was able to induce p38 MAPK activation specifically through MKK3 (MAP kinase kinase 3). Supporting these observations, chronic myeloid leukaemia-derived K562 cells or BaF 3 cells stably transfected with Bcr/Abl showed higher levels of phosphorylated p38 MAPK compared with Bcr/Abl-negative cells. While Bcr/Abl-negative cells activated p38 MAPK in response to Ara-C (1-β-D-arabinofuranosylcytosine), Bcr/Abl-positive cells were unable to activate p38 MAPK, suggesting that the p38 MAPK pathway is not sensitive to Abl-dependent stimuli in Bcr/Abl-positive cells. Our results demonstrate that the involvement of Bcr/Abl in the p38 MAPK pathway is a key mechanism for explaining resistance to Ara-C, and could provide a clue for new therapeutic approaches based on the use of specific Abl inhibitors.

Download Full-text

Cyclic AMP Selectively Uncouples Mitogen-Activated Protein Kinase Cascades from Activating Signals

Molecular and Cellular Biology ◽

10.1128/mcb.26.8.3039-3047.2006 ◽

2006 ◽

Vol 26 (8) ◽

pp. 3039-3047 ◽

Cited By ~ 27

Author(s):

Gray W. Pearson ◽

Svetlana Earnest ◽

Melanie H. Cobb

Keyword(s):

Growth Factors ◽

Growth Factor ◽

Protein Kinase ◽

Cyclic Amp ◽

Map Kinase ◽

Signaling Pathways ◽

Cellular Response ◽

Mitogen Activated Protein Kinase ◽

Extracellular Signal ◽

Mitogen Activated Protein

ABSTRACT Cells integrate signals to select the appropriate response from an array of possible outcomes. Signal integration causes the reorganization of signaling pathways by undescribed events. To analyze the molecular changes in signaling pathways that elicit different responses, we focused on the interaction between cyclic AMP (cAMP) and growth factors. We show that the activation of extracellular signal-regulated kinase 5 (ERK5), but not ERK1/2, by growth factors is disrupted by cAMP through cAMP-dependent protein kinase (PKA). Activation of MEKK2, a mitogen-activated protein (MAP) kinase kinase kinase upstream of ERK5 that is required for growth factor activation of ERK5, is also disrupted by PKA. Transcription of c-Jun is induced by ERK5, and like ERK5, c-Jun induction is also blocked by cAMP. Transcription from the serum response element, like activation of ERK1/2, is not blocked by cAMP. Collectively, these results support a model in which cAMP shapes the growth factor-induced cellular response through PKA-dependent uncoupling of selected MAP kinase cascades from activating signals.

Download Full-text

Role for Lyn Tyrosine Kinase as a Regulator of Stress-Activated Protein Kinase Activity in Response to DNA Damage

Molecular and Cellular Biology ◽

10.1128/mcb.20.15.5370-5380.2000 ◽

2000 ◽

Vol 20 (15) ◽

pp. 5370-5380 ◽

Cited By ~ 47

Author(s):

Kiyotsugu Yoshida ◽

Ralph Weichselbaum ◽

Surender Kharbanda ◽

Donald Kufe

Keyword(s):

Dna Damage ◽

Protein Kinase ◽

Tyrosine Kinase ◽

Cellular Response ◽

Protein Tyrosine Kinase ◽

Genotoxic Stress ◽

Dominant Negative ◽

Mitogen Activated Protein Kinase ◽

Protein Kinase Activity ◽

Genotoxic Agents

ABSTRACT The cellular response to DNA damage includes activation of the nuclear Lyn protein tyrosine kinase. Using cells deficient in Lyn expression, the present studies demonstrate that Lyn is required in part for induction of the stress-activated protein kinase (SAPK) in the response to 1-β-d-arabinofuranosylcytosine (ara-C) and other genotoxic agents. By contrast, exposure of Lyn-deficient cells to ara-C, ionizing radiation, or cisplatin had no effect on activation of extracellular signal-regulated protein kinase or p38 mitogen-activated protein kinase. Similar findings were obtained in cells stably expressing a kinase-inactive, dominant-negative Lyn(K-R) mutant. Coexpression studies demonstrate that Lyn, but not Lyn(K-R), induces SAPK activity. In addition, the results demonstrate that Lyn activates SAPK by an MKK7-dependent, SEK1-independent mechanism. As MEKK1 functions upstream to MKK7 and SAPK, the finding that a dominant-negative MEKK1(K-M) mutant blocks Lyn-induced SAPK activity supports involvement of the MEKK1→MKK7 pathway. The results also demonstrate that inhibition of Lyn-induced SAPK activity abrogates the apoptotic response of cells to genotoxic stress. These findings indicate that activation of SAPK by DNA damage is mediated in part by Lyn and that the Lyn→MEKK1→MKK7→SAPK pathway is functional in the induction of apoptosis by genotoxic agents.

Download Full-text