Agnete Louise Bjerregaard Madsen - University of Sydney, Australia

PhD student Agnete Madsen has received an exchange travel grant of 75.000 DKK for a research visit at the laboratory of Professor David James, University of Sydney, Australia. The James laboratory has been a frontrunner within molecular cell biology for the past two decades.

A major part of her PhD project is to elucidate novel mechanisms of crosstalk between AMPK and mTORC1. To accomplish this goal, she has stimulated wildtype mouse EDL muscles with a combination of the AMPK activator (AICAR) and passive stretch. This setup is highly suitable for investigating the crosstalk between mTORC1 and AMPK, since both signaling pathways are potently activated. By performing quantitative phosphoproteomic analyses using multiplexed isobaric labeling and phosphopeptide enrichment coupled to tandem mass spectrometry, it is possible to study each of the phosphorylation patterns of the three different conditions.

The laboratory of Prof. David James in Sydney analyzed the samples, and a total of 14,268 phosphosites were identified, whereof 1,968 were found significantly regulated by AICAR, stretch, or combined AICAR and stretch. Many of these were not previously annotated in the Phosphosite.org database. Interestingly, the regulation of the various affected phosphosites is highly differential, some are stretch responsive, others respond to AICAR, while a third category is phosphorylated by one and antagonized by the other, and finally, a fourth group of substrates are synergistically regulated by AICAR and stretch. Currently, Agnete Madsen is working on validating the phosphoproteome by immunoblotting and characterizing novel targets.