Unknown,Transcriptomics,Genomics,Proteomics

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The TAB1-p38α complex aggravates myocardial injury and can be targeted by small molecules

ABSTRACT: There is considerable evidence that inhibition of p38α mitogen-activated protein kinase diminishes cardiac damage during myocardial ischemia. During myocardial ischemia p38α interacts with TAB1, a scaffold protein, which promotes p38α autoactivation; active p38α (pp38α) then trans-phosphorylates TAB1. Previously, we solved the X-ray structure of the p38α-TAB1(384-412) complex. Here we further characterize the interaction by resolving the structure of the pp38α-TAB1(1-438) complex in the active state. Based on this information we created a global knock-in mouse with substitution of four residues on TAB1 (V390A, Y392A, V408G, M409A) we show are required for docking onto p38α. Whereas ablating p38α or TAB1 results in early embryonal lethality, the TAB1 KI mice are viable, develop normally and have no appreciable alteration in their lymphocyte repertoire or myocardial transcriptional profile. Nonetheless, following in vivo regional myocardial ischemia, infarction volume is significantly reduced and the trans- phosphorylation of TAB1 is disabled. Unexpectedly, the activation of myocardial p38α during ischemia is only mildly attenuated in TAB1 KI hearts, an effect most likely due to the removal of the steric hindrance to MAP2K3 binding. We conclude that it is the phosphorylation of TAB1 by pp38α during ischemia that is associated with cardiac damage. The data reveal that it is possible to selectively inhibit signalling downstream of p38α to attenuate ischemic injury. Our findings validate the p38α-TAB1 complex as a therapeutic target that may circumvent the toxicity associated with ATP-competitive inhibitors of p38α.

INSTRUMENT(S): Illumina HiSeq 2500

ORGANISM(S): Mus musculus

SUBMITTER: Gian De Nicola

PROVIDER: E-MTAB-6460 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Background: Clear cell renal cell carcinoma (ccRCC) is the most common kidney cancer in the adult population. Late diagnosis, resistance to therapeutics and recurrence of metastatic lesions account for the highest mortality rate among kidney cancer patients. Identifying novel biomarkers for early cancer detection and elucidating the mechanisms underlying ccRCC growth and progression will provide clues to treat this aggressive malignant tumor. Method: Expression studies of RING ligase praja2 and tyrosine kinase receptors (RTKs) in renal cell carcinoma was evaluated by immunoblot and immunohistochemistry. Gene transcription profiling in RCC cells was evaluated by RNA sequencing and Ingenuity Pathway Analysis. Imunofluorescence assays were used to evaluate the intracellular distribution and clearance of membrane receptors in cells devoid of praja2. Ubiquitin modifications and protein-protein interaction networks were monitored by IP, western blot, mass spectrometry and proteomic analysis. Experiments in vitro and in vivo were performed to define the role of praja2 in RTKs turnover, metabolism, renal cell carcinoma growth and metastatic diffusion. Results: We report here that the ubiquitin ligase praja2 controls endocytosis and the signal strength of different types of receptors (EGFR, VEGFR, TfR). Praja2 forms a complex with- and ubiquitinates the adaptor protein AP2m required for the activity of ATPase and acidification of endosomes and lysosomes necessary for receptor endocytosis and clearance. Downregulation of praja2 blocks the endocytosis of several membrane receptors, including EGFR, VEGFR and TfR and amplifies mitogenic and proliferative signaling as shown in the clear cell renal cell carcinoma (ccRCC). Restoring praja2 expression in RCC cells reduces EGFR levels, rewires cancer cell metabolism and inhibits growth and metastatic diffusion. In vivo, praja2 knockout mice show upregulation of tyrosine kinase receptors (RTKs) and pronounced histopathological renal alterations. Conclusion: Our findings identify praja2 as an important regulator of tyrosine kinase receptor(s) turnover and can be considered a bona fide oncosuppressor because it finely regulates signaling of several types of receptors and its loss supports kidney cancer growth and diffusion.

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The TAB1-p38α complex aggravates myocardial injury and can be targeted by small molecules

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