Tyrosine kinase Pyk2 mediates G-protein-coupled receptor regulation of the Ewing sarcoma RNA-binding protein EWS

Abstract

Ewing family tumors result from the effects of chromosomal translocations that fuse the Ewing sarcoma (EWS) gene to various genes encoding transcription factors [1]. The resulting chimeric EWS fusion proteins are transcriptional activators with transforming potential that have received much study [2]. By contrast, the cellular function of somatic EWS remains obscure. EWS belongs to a family of RNA-binding proteins thought to play role in RNA synthesis or processing [3,4]. Here, we show that EWS interacts with Pyk2, a protein tyrosine kinase implicated in a variety of signal transduction processes [5–7][8]. G-protein-coupled receptor signaling and other stimuli of Pyk2 kinase activity significantly block the interaction between EWS and Pyk2. Furthermore, as assessed by sucrose gradient centrifugation, EWS partitions with dense ribosome-containing fractions in a manner that is enhanced by signaling from the G-protein-coupled m1 muscarinic acetylcholine receptor (mAChR). We conclude that extranuclear EWS is a previously unrecognized target of G-protein-coupled receptor regulation.