Abstract
Sprouty proteins act ubiquitously as signaling integrators and inhibitors of receptor tyrosine kinase (RTK) activated pathways. Among the four Sprouty isoforms, Sprouty2 is a key regulator of growth factor signaling in several neurological disorders. High protein levels correlate with reduced survival of glioma patients. We recently demonstrated that abrogating its function inhibits tumor growth by overstimulation of ERK and induction of DNA replication stress. The important role of Sprouty2 in the proliferation of malignant glioma cells prompted us to investigate its subcellular localization applying super-resolution fluorescence and immunoelectron microscopy. We found that cytoplasmic Sprouty2 is not homogenously distributed but localized to small spots (<100 nm) partly attached to vimentin filaments and co-localized with activated ERK. The protein is associated with early, late and recycling endosomes in response to but also independently of growth factor stimulation. The subcellular localization of Sprouty2 in all areas exhibiting strong RTK activities may reflect a protective response of glioma cells to limit excessive ERK activation and to prevent cellular senescence and apoptosis.
Highlights
The strength and duration of receptor tyrosine kinase (RTK) activated signaling pathways are tightly regulated by positive and negative regulators
We investigated the subcellular localization of Sprouty2 in three human glioma cell lines by means of confocal laser scanning, super-resolution stimulated emission depletion (STED), immunoelectron microscopy and immunoprecipitation
We provide evidence that overexpressed Sprouty2 is targeted to all three major endosomal compartments in growth factor-stimulated and in non-stimulated cells
Summary
The strength and duration of receptor tyrosine kinase (RTK) activated signaling pathways are tightly regulated by positive and negative regulators. We investigated the subcellular localization of Sprouty2 in three human glioma cell lines by means of confocal laser scanning, super-resolution stimulated emission depletion (STED), immunoelectron microscopy and immunoprecipitation. No quantitative co-localization analysis was performed for EGF (glioma cells exhibited highly variable uptake of EGF probably due to different EGFR levels), for vimentin or pERK (both often revealed close association but not true co-localization in high-resolution images).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
