RESUMEN
Mixed lineage kinases (MLKs) are members of the mitogen-activated protein kinase kinase kinase (MAP3K) family and are reported to activate MAP kinase pathways. There have been at least 9 members of the MLK family identified to date, although the physiological functions of all the family members are yet unknown. However, MLKs in general have been implicated in neurodegenerative diseases, including Parkinson and Alzheimer diseases. Recent reports suggest that some of the MLK members could play a role in cancer via modulating cell migration, invasion, cell cycle, and apoptosis. This review article will first describe the biology of MLK members and then discuss the current progress that relates to their functions in cancer.
RESUMEN
Nuclear protein peptidyl-prolyl isomerase Pin1-mediated prolyl isomerization is an essential and novel regulatory mechanism for protein phosphorylation. Therefore, tight regulation of Pin1 localization and catalytic activity is crucial for its normal nuclear functions. Pin1 is commonly dysregulated during oncogenesis and likely contributes to these pathologies; however, the mechanism(s) by which Pin1 catalytic activity and nuclear localization are increased is unknown. Here we demonstrate that mixed-lineage kinase 3 (MLK3), a MAP3K family member, phosphorylates Pin1 on a Ser138 site to increase its catalytic activity and nuclear translocation. This phosphorylation event drives the cell cycle and promotes cyclin D1 stability and centrosome amplification. Notably, Pin1 pSer138 is significantly up-regulated in breast tumors and is localized in the nucleus. These findings collectively suggest that the MLK3-Pin1 signaling cascade plays a critical role in regulating the cell cycle, centrosome numbers, and oncogenesis.
Asunto(s)
Transporte Activo de Núcleo Celular/fisiología , Neoplasias de la Mama/metabolismo , Centrosoma/metabolismo , Quinasas Quinasa Quinasa PAM/metabolismo , Isomerasa de Peptidilprolil/metabolismo , Transducción de Señal/fisiología , Neoplasias de la Mama/genética , Catálisis , Ciclo Celular/fisiología , Núcleo Celular/metabolismo , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , Ciclina D1/metabolismo , Femenino , Proteínas Fluorescentes Verdes/genética , Células HEK293 , Células HeLa , Humanos , Quinasas Quinasa Quinasa PAM/genética , Peptidilprolil Isomerasa de Interacción con NIMA , Isomerasa de Peptidilprolil/genética , Fosforilación/fisiología , Serina/metabolismo , Proteina Quinasa Quinasa Quinasa 11 Activada por MitógenoRESUMEN
Exposure to environmental neurotoxic metals, pesticides and other chemicals is increasingly recognized as a key risk factor in the pathogenesis of chronic neurodegenerative disorders such as Parkinson's and Alzheimer's diseases. Oxidative stress and apoptosis have been actively investigated as neurotoxic mechanisms over the past two decades, resulting in a greater understanding of neurotoxic processes. Nevertheless, emerging evidence indicates that epigenetic changes, protein aggregation and autophagy are important cellular and molecular correlates of neurodegenerative diseases resulting from chronic neurotoxic chemical exposure. During the Joint Conference of the 13th International Neurotoxicology Association and the 11th International Symposium on Neurobehavioral Methods and Effects in Occupational and Environmental Health, the recent progress made toward understanding epigenetic mechanisms, protein aggregation, autophagy, and deregulated kinase activation following neurotoxic chemical exposure and the relevance to neurodegenerative conditions were one of the themes of the symposium. Dr. Anumantha G. Kanthasamy described the role of acetylation of histones and non-histone proteins in neurotoxicant-induced neurodegenerative processes in the nigral dopaminergic neuronal system. Dr. Arthi Kanthasamy illustrated the role of autophagy as a key determinant in cell death events during neurotoxic insults. Dr. Ajay Rana provided evidence for posttranslational modification of α-synuclein protein by the Mixed Linage Kinase (MLK) group of kinases to initiate protein aggregation in cell culture and animal models of Parkinson's disease. These presentations outlined emerging cutting edge mechanisms that might set the stage for future mechanistic investigations into new frontiers of molecular neurotoxicology. This report summarizes the views of symposium participants, with emphasis on future directions for study of environmentally and occupationally linked chronic neurodegenerative diseases.
Asunto(s)
Exposición a Riesgos Ambientales/efectos adversos , Contaminantes Ambientales/efectos adversos , Epigénesis Genética/efectos de los fármacos , Sistema Nervioso/efectos de los fármacos , Enfermedades Neurodegenerativas/inducido químicamente , Transducción de Señal/efectos de los fármacos , Animales , Modelos Animales de Enfermedad , Neuronas Dopaminérgicas/efectos de los fármacos , Neuronas Dopaminérgicas/metabolismo , Neuronas Dopaminérgicas/patología , Regulación de la Expresión Génica/efectos de los fármacos , Interacción Gen-Ambiente , Predisposición Genética a la Enfermedad , Humanos , Degeneración Nerviosa , Sistema Nervioso/metabolismo , Sistema Nervioso/patología , Enfermedades Neurodegenerativas/genética , Enfermedades Neurodegenerativas/metabolismo , Enfermedades Neurodegenerativas/patología , Trastornos Parkinsonianos/inducido químicamente , Trastornos Parkinsonianos/genética , Trastornos Parkinsonianos/metabolismo , Trastornos Parkinsonianos/patología , Complejo de la Endopetidasa Proteasomal/metabolismo , Proteínas Quinasas/metabolismo , Medición de Riesgo , Factores de Riesgo , alfa-Sinucleína/metabolismoRESUMEN
Expression of ß-catenin is strictly regulated in normal cells via the glycogen synthase kinase 3ß (GSK3ß)- adenomatous polyposis coli-axin-mediated degradation pathway. Mechanisms leading to inactivation of this pathway (example: activation of Wnt/ß-catenin signaling or mutations of members of the degradation complex) can result in ß-catenin stabilization and activation of ß-catenin/T-cell factor (TCF) signaling. ß-Catenin-mediated cellular events are diverse and complex. A better understanding of the cellular signaling networks that control ß-catenin pathway is important for designing effective therapeutic strategies targeting this axis. To gain more insight, we focused on determining any possible cross-talk between ß-catenin and mixed lineage kinase 3 (MLK3), a MAPK kinase kinase member. Our studies indicated that MLK3 can induce ß-catenin expression via post-translational stabilization in various cancer cells, including prostate cancer. This function of MLK3 was dependent on its kinase activity. MLK3 can interact with ß-catenin and phosphorylate it in vitro. Overexpression of GSK3ß-WT or the S9A mutant was unable to antagonize MLK3-induced stabilization, suggesting this to be independent of GSK3ß pathway. Surprisingly, despite stabilizing ß-catenin, MLK3 inhibited TCF transcriptional activity in the presence of both WT and S37A ß-catenin. These resulted in reduced expression of ß-catenin/TCF downstream targets Survivin and myc. Immunoprecipitation studies indicated that MLK3 did not decrease ß-catenin/TCF interaction but promoted interaction between ß-catenin and KLF4, a known repressor of ß-catenin/TCF transcriptional activity. In addition, co-expression of MLK3 and ß-catenin resulted in significant G(2)/M arrest. These studies provide a novel insight toward the regulation of ß-catenin pathway, which can be targeted to control cancer cell proliferation, particularly those with aberrant activation of ß-catenin signaling.
Asunto(s)
Quinasas Quinasa Quinasa PAM/metabolismo , Proteínas de Neoplasias/metabolismo , Neoplasias/metabolismo , Transducción de Señal , beta Catenina/metabolismo , Sustitución de Aminoácidos , Puntos de Control del Ciclo Celular/genética , División Celular/genética , Fase G2/genética , Regulación Neoplásica de la Expresión Génica/genética , Glucógeno Sintasa Quinasa 3/genética , Glucógeno Sintasa Quinasa 3/metabolismo , Glucógeno Sintasa Quinasa 3 beta , Células HEK293 , Células HeLa , Humanos , Proteínas Inhibidoras de la Apoptosis/genética , Proteínas Inhibidoras de la Apoptosis/metabolismo , Factor 4 Similar a Kruppel , Factores de Transcripción de Tipo Kruppel/genética , Factores de Transcripción de Tipo Kruppel/metabolismo , Quinasas Quinasa Quinasa PAM/genética , Mutación Missense , Proteínas de Neoplasias/genética , Neoplasias/genética , Fosforilación , Survivin , Factores de Transcripción TCF/genética , Factores de Transcripción TCF/metabolismo , beta Catenina/genética , Proteina Quinasa Quinasa Quinasa 11 Activada por MitógenoRESUMEN
Little knowledge exists about the mechanisms by which estrogen can impede chemotherapy-induced cell death of breast cancer cells. 17beta-Estradiol (E(2)) hinders cytotoxic drug-induced cell death in estrogen receptor-positive (ER(+)) breast cancer cells. We noted that the activity of the proapoptotic mixed lineage kinase 3 (MLK3) kinase was relatively higher in estrogen receptor-negative (ER(-)) breast tumors, suggesting that E(2) might inhibit MLK3 activity. The kinase activities of MLK3 and its downstream target, c-Jun NH(2)-terminal kinase, were rapidly inhibited by E(2) in ER(+) but not in ER(-) cells. Specific knockdown of AKT1/2 prevented MLK3 inhibition by E(2), indicating that AKT mediated this event. Furthermore, MLK3 inhibition by E(2) involved phosphorylation of MLK3 Ser(674) by AKT, attenuating the proapoptotic function of MLK3. We found that a pan-MLK inhibitor (CEP-11004) limited Taxol-induced cell death and that E(2) accentuated this limitation. Taken together, our findings indicate that E(2) inhibits the proapoptotic function of MLK3 as a mechanism to limit cytotoxic drug-induced death of ER(+) breast cancer cells.
Asunto(s)
Apoptosis/efectos de los fármacos , Neoplasias de la Mama/patología , Carcinoma/patología , Estradiol/farmacología , Receptor alfa de Estrógeno/genética , Quinasas Quinasa Quinasa PAM/antagonistas & inhibidores , Animales , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/genética , Carcinoma/tratamiento farmacológico , Carcinoma/genética , Línea Celular Tumoral , Células Cultivadas , Regulación hacia Abajo/efectos de los fármacos , Resistencia a Antineoplásicos/efectos de los fármacos , Resistencia a Antineoplásicos/genética , Activación Enzimática/efectos de los fármacos , Receptor alfa de Estrógeno/metabolismo , Receptor alfa de Estrógeno/fisiología , Femenino , Humanos , Proteínas Quinasas JNK Activadas por Mitógenos/antagonistas & inhibidores , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , Quinasas Quinasa Quinasa PAM/metabolismo , Quinasas Quinasa Quinasa PAM/fisiología , Ratones , Modelos Biológicos , Proteínas Proto-Oncogénicas c-akt/metabolismo , Receptores de Progesterona/genética , Receptores de Progesterona/metabolismo , Proteina Quinasa Quinasa Quinasa 11 Activada por MitógenoRESUMEN
Gastrin is a gastrointestinal peptide hormone, secreted by the gastric G cells and can exist as a fully processed amidated form (G17) or as unprocessed forms. All forms of gastrin possess trophic properties towards the gastrointestinal mucosa. An understanding of the signaling pathways involved is important to design therapeutic approaches to target gastrin-mediated cellular events. The studies described here were designed to identify the signaling pathways by which amidated gastrin (G17) mediates cancer cell migration. These studies indicated a time- and dose-dependent increase in gastric cancer cell migration after G17 stimulation, involving cholecystokinin 2 receptor. G17-induced migration was preceded by activation of MAPK pathways and was antagonized after pretreatment with SP600125, a pharmacological inhibitor of c-Jun-NH(2)-terminal kinase (JNK) pathway. Knockdown of endogenous JNK1 expression via small interference RNA (JNK1-siRNA) inhibited G17-induced phosphorylation of c-Jun and migration, and overexpression of wild-type JNK1 or constitutive active JNK1 promoted G17-induced migration. Studies designed to identify the MAPK kinase kinase member mediating JNK activation indicated the involvement of mixed lineage kinase-3 (MLK3), which was transiently activated upon G17 treatment. Inhibition of MLK3 pathway via a pan-MLK inhibitor or knockdown of MLK3 expression by MLK3-siRNA antagonized G17-induced migration. Incubation with G17 also resulted in an induction of matrix metalloproteinase 7 promoter activity, which is known to mediate migration and invasion pathways in cancer cells. Modulation of MLK3, JNK1, and c-Jun pathways modulated G17-induced matrix metalloproteinase 7 promoter activation. These studies indicate that the MLK3/JNK1 axis mediates G17-induced gastric cancer cell migration, which can be targeted for designing novel therapeutic strategies for treating gastric malignancies.
Asunto(s)
Movimiento Celular/efectos de los fármacos , Gastrinas/farmacología , Quinasas Quinasa Quinasa PAM/metabolismo , Neoplasias Gástricas/metabolismo , Neoplasias Gástricas/patología , Antracenos/farmacología , Western Blotting , Línea Celular Tumoral , Movimiento Celular/genética , Activación Enzimática/efectos de los fármacos , Humanos , Proteínas Quinasas JNK Activadas por Mitógenos/antagonistas & inhibidores , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , Quinasas Quinasa Quinasa PAM/genética , Metaloproteinasa 7 de la Matriz/genética , Proteína Quinasa 8 Activada por Mitógenos/metabolismo , Fosforilación/efectos de los fármacos , ARN Interferente Pequeño , Proteina Quinasa Quinasa Quinasa 11 Activada por MitógenoRESUMEN
Mixed lineage kinase 3 (MLK3) is a mitogen-activated protein kinase kinase kinase that is activated by tumor necrosis factor-alpha (TNF-alpha) and specifically activates c-Jun N-terminal kinase (JNK) on TNF-alpha stimulation. The mechanism by which TNF-alpha activates MLK3 is still not known. TNF receptor-associated factors (TRAFs) are adapter molecules that are recruited to cytoplasmic end of TNF receptor and mediate the downstream signaling, including activation of JNK. Here, we report that MLK3 associates with TRAF2, TRAF5 and TRAF6; however only TRAF2 can significantly induce the kinase activity of MLK3. The interaction domain of TRAF2 maps to the TRAF domain and for MLK3 to its C-terminal half (amino acids 511-847). Endogenous TRAF2 and MLK3 associate with each other in response to TNF-alpha treatment in a time-dependent manner. The association between MLK3 and TRAF2 mediates MLK3 activation and competition with the TRAF2 deletion mutant that binds to MLK3 attenuates MLK3 kinase activity in a dose-dependent manner, on TNF-alpha treatment. Furthermore the downstream target of MLK3, JNK was activated by TNF-alpha in a TRAF2-dependent manner. Hence, our data show that the direct interaction between TRAF2 and MLK3 is required for TNF-alpha-induced activation of MLK3 and its downstream target, JNK.