Fragiadaki, M. | Search bioRxiv

bioRxiv2018

Curcumin inhibits cystogenesis in autosomal dominant polycystic kidney disease cells via altering JAK2/STAT3 activity.

Dysregulated JAK/STAT signalling is implicated in polycystic kidney disease, which is a common genetic disease leading to renal failure. However, the mechanisms underlying JAK/STAT-mediated cystogenesis arepoorlyunderstood.TheroleofJAK2wasinvestigated immunohistochemically in a murine model of cystic disease (Pkd1nl/nl). In the normal kidney, JAK2 is restricted to tubular epithelial and vascular cells with lesser staining in bowmans capsule and is undetectable in the interstitium. By contrast, in the diseased kidney JAK2 appears stronger in cyst-lining cells when compared to normal tubules and appears mislocalised in the interstitium. Given that JAK2 is a major tyrosine kinase activating JAK/STAT, we considered whether its inhibition can attenuate cystic growth in vitro. To assess this we used curcumin, a natural phytochemical, which significantly reduced JAK2 levels and STAT3 activity. Consistently, reduced JAK2/STAT3 activity was correlated with reduced cystic growth of cystic cells in three-dimensional cyst assays. Taken together, our results suggest that JAK2 is a key signalling molecule that functions to inhibit cystic growth in cystic tubular epithelial cells, thus providing the foundation for its development as a novel therapeutic in polycystic kidney disease.

cell biology↗

bioRxiv2017

A genome-wide RNAi screen identifies MASK as a positive regulator of cytokine receptor stability

In order for cells to sense and thus respond to their environment, they require transmembrane receptors, which bind extracellular ligands and then transduce this signal within the cell. A subset of receptors, with single-pass transmembrane domains are known as cytokine receptors and act via the Janus Kinase and Signal Transducer and Activator of Transcription (JAK/STAT) pathway. These receptors are essential for processes such as haematopoiesis, immune responses and tissue homeostasis. In order to transduce ligand activation, cytokine receptors must dimerise. However, mechanisms regulating their dimerisation are largely unknown. In order to better understand the processes regulating cytokine receptor levels, activity and dimerisation, we used the highly conserved JAK/STAT pathway in Drosophila, which acts via a single receptor, known as Domeless. We have performed a genome-wide RNAi screen in Drosophila cells, identifying MASK as a positive regulator of Domeless dimerisation and protein levels. We show that MASK is able to regulate JAK/STAT signalling both in vitro and in vivo. We go on to show that MASK is able to bind to Domeless via its Ankyrin repeat domains and alters the stability of the receptor. Finally, we extend our observations to the human homologue, ANKHD1, and demonstrate functional conservation, with ANKHD1 able to regulate JAK/STAT signalling and the levels of a subset of pathway receptors in human cells. Taken together, we have identified MASK as a conserved regulator of cytokine receptor levels, which may have implications for human health.

cell biology↗