Biology subjects

Siesser, P. F.

Publications and source records attributed to Siesser, P. F..

2 recordsLinked to original sources

bioRxiv2025

Optogenetic control of PLC-γ1 activity polarizes cell motility

Phospholipase C-{gamma}1 (PLC-{gamma}1) signaling is required for mesenchymal chemotaxis, but is it sufficient to bias motility? PLC-{gamma}1 enzyme activity is basally autoinhibited, and light-controlled membrane recruitment of wild-type PLC-{gamma}1 (OptoPLC-{gamma}1) in Plcg1-null fibroblasts does not trigger lipid hydrolysis, complicating efforts to isolate its contribution. Utilizing cancer-associated mutations to investigate the regulatory logic of PLC-{gamma}1, we demonstrate that a hallmark of enzyme activity, phosphorylated Tyr783 (pTyr783), is not a proxy for activity level, but is rather a marker of dysregulated autoinhibition. Accordingly, OptoPLC-{gamma}1 with a deregulating mutation (P867R, S345F, or D1165H) exhibits elevated phosphorylation, and membrane localization of such is sufficient to activate substrate hydrolysis and concomitant motility responses. In particular, local recruitment of OptoPLC-{gamma}1 S345F polarizes cell motility and migration on demand. This response is spatially dose-sensitive and only partially reduced by blocking canonical PLC-{gamma}1 signaling yet is lipase-dependent. Our findings reframe the interpretation of PLC-{gamma}1 regulation and demonstrate that local activation of PLC-{gamma}1 is sufficient to direct cell motility.

cell biology↗

bioRxiv2019

Gain-of-function genetic screen of the kinome reveals BRSK2 as an inhibitor of the NRF2 transcription factor

NFE2L2/NRF2 is a transcription factor and master regulator of cellular antioxidant response. Aberrantly high NRF2-dependent transcription is recurrent in human cancer, and conversely NRF2 protein levels as well as activity is diminished with age and in neurodegenerative disorders. Though NRF2 activating drugs are clinically beneficial, NRF2 inhibitors do not yet exist. Here we used a gain-of-function genetic screen of the kinome to identify new druggable regulators of NRF2 signaling. We found that the understudied protein kinase Brain Specific Kinase 2 (BRSK2) and the related BRSK1 kinases suppress NRF2-dependent transcription and NRF2 protein levels in an activity-dependent manner. Integrated phosphoproteomics and RNAseq studies revealed that BRSK2 drives AMPK activation and suppresses mTOR signaling. As a result, BRSK2 kinase activation suppressed ribosome-RNA complexes, global protein synthesis, and NRF2 protein levels. Collectively, our data establish the catalytically active BRSK2 kinase as a negative regulator of NRF2 via the AMPK/mTOR signaling. This signaling axis may prove useful for therapeutically targeting NRF2 in human diseases.\n\nSummary StatementBRSK2 suppresses NRF2 signaling by inhibiting protein synthesis through mTOR downregulation.

cell biology↗