Differential SHIP2 Activation by EGF and Insulin Uncovers Pathway-Specific Control of PI(3,4)P2 Signaling
Amir Damouni
Molecular Medicine Division
Dr. Várnai Péter
EOK.IV.em. OBI Könyvtár
2026-08-25 15:30:00
Cellular and Molecular Physiology
Dr. Hunyady László
Dr. Várnai Péter
Dr. Sarnyai Farkas
Dr. Laczka Csilla
Dr. Csala Miklós
Dr. Liliom Károly
Dr. Lontay Beáta
This study explored the regulation of phosphoinositide signaling with a focus on receptor-specific control of PIP3 and PI(3,4)P2 dynamics in mammalian cells. Using BRET-based biosensors we monitored lipid changes at the plasma membrane in response to distinct stimuli, particularly EGF and insulin. Despite activating overlapping pathways, these ligands produced divergent phosphoinositide profiles, with EGF consistently generating a higher PI(3,4)P2/PIP3 ratio. This difference was shown to be driven largely by the differential regulation of SHIP2 by the two agents. Further analysis revealed that SHIP2 activation is regulated through stimulus-specific tyrosine phosphorylation, which was dependent on PLC-mediated calcium influx and, to a lesser extent, PI3K activity. Inhibition of SHIP2 phosphorylation via PLC blockade significantly reduced PI(3,4)P2 levels, highlighting a functional role for phosphorylation in enhancing the phosphatase activity of SHIP2. In parallel, we optimized lipid biosensors for more selective PIP3 detection. Mutations in GRP1-PH domains that disrupted non-lipid interactions improved specificity but considerably reduced signal strength. This limitation was addressed by developing tandem mutated GRP1-PH constructs, which restored signal amplitude and demonstrated robust responsiveness to EGF stimulation in both BRET and confocal microscopy. These optimized biosensors provide a more reliable tool for monitoring the localization and dynamics of PIP3. Overall, this work provides new mechanistic insights into the regulation of PI(3,4)P2 production, particularly via SHIP2, and delivers improved biosensors for studying PIP3 signaling. These advances contribute to a deeper understanding of how growth factors uniquely shape phosphoinositide signaling landscapes and have potential implications for therapeutic targeting in diseases linked to dysregulated lipid metabolism.
