p38 gamma regulates interaction of nuclear PSF and RNA with the tumour-suppressor hDlg in response to osmotic shock

Activation of p38 gamma modulates the integrity of the complex formed by the human discs large protein (hDlg) with cytoskeletal proteins, which is important for cell adaptation to changes in environmental osmolarity. Here we report that, in response to hyperosmotic stress, p38 gamma also regulates formation of complexes between hDlg and the nuclear protein polypyrimidine tract-binding protein-associated-splicing factor (PSF). Following osmotic shock, p38 gamma in the cell nucleus increases its association with nuclear hDlg, thereby causing dissociation of hDlg-PSF complexes. Moreover, hDlg and PSF bind different RNAs; in response to osmotic shock, p38 gamma causes hDlg-PSF and hDlg-RNA dissociation independently of its kinase activity. These findings identify a novel nuclear complex and suggest a previously unreported function of p38 gamma, which is independent of its catalytic activity and could affect mRNA processing and/or gene transcription to aid cell adaptation to osmolarity changes in the environment.