Biology subjects

Raghu, P.

Publications and source records attributed to Raghu, P..

2 recordsLinked to original sources

bioRxiv2018

Insulin sensitivity and PIP3 turnover in Drosophila are regulated by phosphatidylinositol 5 phosphate 4-kinase.

Phosphatidylinositol-3,4,5-trisphosphate (PIP3) generation at the plasma membrane is a key event during activation of receptor tyrosine kinases such as the insulin receptor and is critical for normal growth and metabolism. The lipid kinases and phosphatases regulating PIP3 levels are described but mechanisms controlling their activity remain unclear. We report that in Drosophila, phosphatidylinositol 5 phosphate 4-kinase (PIP4K) function at the plasma membrane is required for normal PIP3 levels during insulin receptor activation. Depletion of PIP4K increases PIP3 levels and augments sensitivity to insulin through enhanced Class I phosphoinositide 3-kinase (PI3K) activity. Animals lacking PIP4K show enhanced insulin signalling dependent phenotypes in vivo and are resistant to the metabolic consequences of a high-sugar diet, highlighting the importance of PIP4K in normal metabolism and development. Thus, PIP4KS are key regulators of receptor tyrosine kinase signalling with implications for growth factor dependent processes including tumour growth, T-cell activation and metabolism.

cell biology↗

bioRxiv2017

Evidence of sinks and sources in the PLC activated PIP2 cycle

In many eukaryotic signalling cascades, receptor mediated phospholipase C (PLC) activity triggers phosphatidylinositol 4,5 bisphosphate (PIP2) hydrolysis leading to information transfer in cells. Coupled with PLC activation is a sequence of reactions spread across multiple compartments by which PIP2 is resynthesized, a process essential to maintain PIP2 levels and support sustained PLC signalling. The biochemical strategies to co-ordinate these reactions and support PIP2 levels have remained poorly understood. In particular, the question of whether the PIP2 cycle is a closed cycle with no net addition or loss of metabolites has not been addressed. Using mathematical modelling approaches, we find that a closed PIP2 cycle cannot explain experimentally observed changes in the metabolic intermediates when changing enzyme activities in the PIP2 cycle. Thus, we propose that the PIP2 cycle likely includes at least one metabolic source and one sink whose net activity results in the experimentally observed regulation of this key signalling pathway.

biophysics↗