Carrasco, K. | Search bioRxiv

bioRxiv2020

DAF-18 is required for the age-dependent increase in DAF-16 activity in Caenorhabditis elegans

The insulin/insulin-like growth factor signaling (IIS) pathway modulates growth, survival, and lifespan by regulating FOXO transcription factors. In Caenorhabditis elegans, IIS maintains DAF-16/FOXO in an inactive state unless animals are challenged by environmental stress. Recent evidence suggests that DAF-16 becomes activated as part of normal aging in C. elegans, yet the regulatory module responsible for this phenomenon is largely undefined. Embedded within IIS is phospholipid signaling in which PIP3 produced by the PI3 kinase AGE-1 is an upstream event in DAF-16 inhibition. Countering AGE-1 is DAF-18, an ortholog of human PTEN phosphatase that dephosphorylates PIP3. Although it is required for normal lifespan in C. elegans, functional characterization of DAF-18 has primarily focused on its roles during development in the germline and neurons. In this study we asked whether DAF-18 plays a role in the age-dependent activation of DAF-16, and specifically in DAF-16-mediated immunity. Our data show that DAF-18 is expressed in multiple tissues during adulthood. We found that DAF-18 contributes to host defense in adult animals by functioning in the neurons and intestine, likely working through DAF-16 which acts in those same tissues to confer immunity. Supporting this possibility, DAF-18 was required for increased DAF-16 transcriptional activity during aging. Post-translational modifications including ubiquitination and sumoylation appear to be required for the function of DAF-18 during aging in C. elegans, indicating that strategies to modulate PTEN activity are evolutionarily conserved. Our results establish an important role for DAF-18 later in life and imply that it is a critical component of a neuroendocrine signaling circuit that governs the dynamic activity of DAF-16.

genetics↗

bioRxiv2020

In silico molecular target prediction unveils mebendazole as a potent MAPK14 inhibitor

The concept of polypharmacology involves the interaction of drug molecules with multiple molecular targets. It provides a unique opportunity for the repurposing of already-approved drugs to target key factors involved in human diseases. Herein, we used an in silico target prediction algorithm to investigate the mechanism of action of mebendazole, an anti-helminthic drug, currently repurposed in the treatment of brain tumors. First, we confirmed that mebendazole decreased the viability of glioblastoma cells in vitro. Our in silico approach unveiled 21 putative molecular targets for mebendazole, including 12 proteins significantly up-regulated at the gene level in glioblastoma as compared to normal brain tissue. Validation experiments were performed on three major kinases involved in cancer biology: ABL1, MAPK1/ERK2 and MAPK14/p38α. Mebendazole could inhibit the activity of these kinases in vitro in a dose-dependent manner, with a high potency against MAPK14. Its direct binding to MAPK14 was further validated in vitro and inhibition of MAPK14 kinase activity was confirmed in live glioblastoma cells. Consistent with biophysical data, molecular modeling suggested that mebendazole was able to bind to the catalytic site of MAPK14. Finally, gene silencing demonstrated that MAPK14 is involved in glioblastoma tumor spheroid growth and response to mebendazole treatment. This study thus highlighted the role of MAPK14 in the anticancer mechanism of action of mebendazole and provides further rationale for the pharmacological targeting of MAPK14 in brain tumors. It also opens new avenues for the development of novel MAPK14/p38α inhibitors to treat human diseases.Significance Statement This study provides a framework to investigate drug polypharmacology by rapidly identifying novel molecular targets of already-approved drugs. It unveils a new mechanism involved in the anticancer activity of anti-helminthic drug, mebendazole, which is currently being repurposed for the treatment of brain tumors. By helping to decipher the mechanism(s) of action of repurposed drugs in their new indications, this approach could contribute to the development of safer and more effective therapeutic strategies in oncology and beyond.Competing Interest StatementThe authors have declared no competing interest.View Full Text

pharmacology and toxicology↗