An image-based RNAi screen identifies the EGF.R signaling pathway as a regulator of Imp/ IGF2BP RNP granules

J Cell Sci. 2024 Dec 1;137(23):jcs262119. doi: 10.1242/jcs.262119

An image-based RNAi screen identifies the EGF.R signaling pathway as a regulator of Imp/ IGF2BP RNP granules

Fabienne De Graeve¹, Eric Debreuve², Kavya Vinayan Pushpalata¹, Xuchun Zhang³, Somia Rahmoun³, Djampa Kozlowski¹, Nicholas Cedilnik¹, Jeshlee Vijayakumar¹, Paul Cassini¹, Sebastien Schaub^1,4, Xavier Descombes³, Florence Besse¹

Affiliations
¹Université Côte D’Azur, CNRS, Inserm, Institut de Biologie Valrose, Nice, France.
²Université Côte D’Azur, CNRS, INRIA, I3S, Sophia Antipolis, France.
³Université Côte D’Azur, INRIA, CNRS, I3S, Sophia Antipolis, France.
⁴Université Sorbonne, CNRS, LBDV, Villefranche-sur-mer, France.

Abstract

Biomolecular condensates have recently retained much attention since they provide a fundamental mechanism of cellular organization. Among those, cytoplasmic RNP granules selectively and reversibly concentrate RNA molecules and regulatory proteins, thus contributing to the spatio-temporal regulation of associated RNAs. Extensive in vitro work has unraveled the molecular and chemical bases of RNP granule assembly. The signaling pathways controlling this process in a cellular context are however still largely unknown. Here, we aimed at identifying regulators of cytoplasmic RNP granules characterized by the presence of the evolutionarily conserved IGF2BP/Imp/ZBP1 RNA binding protein. We performed a high-content image-based RNAi screen targeting all Drosophila genes encoding RNA binding proteins, phosphatases and kinases. This led to the identification of dozens of genes regulating the number of Imp+ RNP granules in S2R+ cells, among which components of the MAPK pathway. Combining functional approaches, phospho-mapping and generation of phospho-variants, we further showed that the EGF.R signaling inhibits Imp+ RNP granule assembly through activation of MAPK/Rolled and Imp S15 phosphosite. This work illustrates how signaling pathways can regulate cellular condensate assembly by post-translational modifications of specific components.

DOI: 10.1242/jcs.262119