LIMK2 is a crucial regulator and effector of Aurora-A-kinase-mediated malignancy

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We uncovered a crucial role for the Aurora kinase A (AURKA)-Twist1 axis in promoting epithelial-to-mesenchymal transition (EMT) and chemoresistance in pancreatic cancer. Twist1 is the first EMT-specific target of AURKA that was identified using an innovative screen. AURKA phosphorylates Twist1 at three sites, which results in its multifaceted regulation -AURKA inhibits its ubiquitylation, increases its transcriptional activity and favors its homodimerization. Twist1 reciprocates and prevents AURKA degradation, thereby triggering a feedback loop. Ablation of either AURKA or Twist1 completely inhibits EMT, highlighting both proteins as central players in EMT progression. Phosphorylation-dead Twist1 serves as a dominant-negative and fully reverses the EMT phenotype induced by Twist1, underscoring the crucial role of AURKA-mediated phosphorylation in mediating Twist1-induced malignancy. Likewise, Twist1-overexpressing BxPC3 cells formed large tumors in vivo, whereas expression of phosphorylation-dead Twist1 fully abrogated this effect. Furthermore, immunohistochemical analysis of pancreatic cancer specimens revealed a 3-fold higher level of Twist1 compared to that seen in healthy normal tissues. This is the first study that links Twist1 in a feedback loop with its activating kinase, which indicates that concurrent inhibition of AURKA and Twist1 will be synergistic in inhibiting pancreatic tumorigenesis and metastasis.

“…Importantly, MLN8237 treatment also reduced AURKA levels as reported previously ( Fig. 2C,F ;Johnson et al, 2012).…”

Section: Aurka Associates With Twist1 and Regulates Its Subcellular Lsupporting

confidence: 88%

Section: Aurka Inhibits Twist1 Degradationmentioning

confidence: 95%

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The Aurora-A–Twist1 axis promotes highly aggressive phenotypes in pancreatic carcinoma

Wang

Nikhil

Viccaro

et al. 2017

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“…A kinase of interest is engineered (analog-sensitive kinase), which in the presence of a radioactive orthogonal ATP analog (e.g. N6-phenethyl ATP) specifically transfers the radioactive tag to its substrates (Shah et al, 1997;Shah and Shokat, 2002;Shah and Shokat, 2003;Shah and Vincent, 2005;Kim and Shah, 2007;Sun et al, 2008a;Sun et al, 2008b;Chang et al, 2011;Johnson et al, 2011, Johnson et al, 2012. The engineered pocket is generated by replacing a conserved bulky residue (gatekeeper residue) with glycine in the active site of the kinase.…”

Section: Resultsmentioning

confidence: 99%

Deregulated Cdk5 Triggers Aberrant Activation of Cell Cycle Kinases and Phosphatases Inducing Neuronal Death

Chang

Vincent

Shah

2012

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SummaryAberrant activation of cell cycle proteins is believed to play a critical role in Alzheimer's disease (AD) pathogenesis; although, the molecular mechanisms leading to their activation in diseased neurons remain elusive. The goal of this study was to investigate the mechanistic link between Cdk5 deregulation and cell cycle re-activation in b-amyloid 1-42 (Ab )-induced neurotoxicity. Using a chemical genetic approach, we identified Cdc25A, Cdc25B and Cdc25C as direct Cdk5 substrates in mouse brain lysates. We show that deregulated Cdk5 directly phosphorylates Cdc25A, Cdc25B and Cdc25C at multiple sites, which not only increases their phosphatase activities but also facilitates their release from 14-3-3 inhibitory binding. -treated primary cortical neurons, emphasizing a major role of Cdk5 in the activation of Cdc25 isoforms and Cdks in AD pathogenesis. These results were further confirmed in human AD clinical samples, which had higher Cdc25A, Cdc25B and Cdc25C activities that were coincident with increased Cdk5 activity, as compared to age-matched controls. Inhibition of Cdk5 confers the highest neuroprotection against Ab 1-42 toxicity, whereas inhibition of Cdc25 isoforms was partially neuroprotective, further emphasizing a decisive role of Cdk5 deregulation in cell-cycle-driven AD neuronal death.

“…The complementary substituent on ATP is created by attaching bulky groups at the N-6 position of ATP. These ATP analogs are not accepted by wild-type kinases due to steric effects, permitting unbiased identification of direct substrates of the engineered kinase in a global environment (Shah and Vincent, 2005;Kim and Shah, 2007;Johnson et al, 2011;Johnson et al, 2012). Importantly, the sensitized allele created by this mutation has identical substrate specificity to the wild-type kinase.…”

Section: Foxo3a Is a Direct Substrate Of Cdk5mentioning

confidence: 99%

Cdk5–Foxo3 axis: initially neuroprotective, eventually neurodegenerative in Alzheimer's disease models

Shi

Viccaro

Lee

et al. 2016

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Deregulated Cdk5 causes neurotoxic amyloid beta peptide (Aβ) processing and cell death, two hallmarks of Alzheimer's disease, through the Foxo3 transcriptional factor in hippocampal cells, primary neurons and an Alzheimer's disease mouse model. Using an innovative chemical genetic screen, we identified Foxo3 as a direct substrate of Cdk5 in brain lysates. Cdk5 directly phosphorylates Foxo3, which increased its levels and nuclear translocation. Nuclear Foxo3 initially rescued cells from ensuing oxidative stress by upregulating MnSOD (also known as SOD2). However, following prolonged exposure, Foxo3 upregulated Bim (also known as BCL2L11) and FasL (also known as FASLG) causing cell death. Active Foxo3 also increased Aβ(1-42) levels in a phosphorylationdependent manner. These events were completely inhibited either by expressing phosphorylation-resistant Foxo3 or by depleting Cdk5 or Foxo3, highlighting a key role for Cdk5 in regulating Foxo3. These results were confirmed in an Alzheimer's disease mouse model, which exhibited increased levels and nuclear localization of Foxo3 in hippocampal neurons, which preceded neurodegeneration and Aβ plaque formation, indicating this phenomenon is an early event in Alzheimer's disease pathogenesis. Collectively, these results show that Cdk5-mediated phospho-regulation of Foxo3 can activate several genes that promote neuronal death and aberrant Aβ processing, thereby contributing to the progression of neurodegenerative pathologies.