Global mapping of VEGF-A driven changes in the RNA bound phospho-proteome reveals a molecular switch to coordinate angiogenesis in endothelial cells

R. Wardman (Mannheim)¹, L. Ignucz (Mannheim)², A. Tikhonova (Mannheim)², K. Bennewitz (Mannheim)³, S. Joshi (Mannheim)³, J. Schwartz (Heidelberg)⁴, F. Stein (Heidelberg)⁵, G. Dobreva (Mannheim)⁶, J. Kroll (Mannheim)³, A. Hammes (Berlin)⁷, J. Heineke (Mannheim)^2
1ECAS (European Center for Angioscience), Mannheim Faculty of Medicine, Heidelberg University Department of Cardiovascular Physiology Mannheim, Deutschland; ²Medizinische Fakultät Mannheim der Universität Heidelberg Kardiovaskuläre Physiologie Mannheim, Deutschland; ³Universitätsmedizin Mannheim der Universität Heidelberg CBTM-Sektion Vaskuläre Biologie u. Tumorangiogenese Mannheim, Deutschland; ⁴EMBL Proteomics Core Heidelberg, Deutschland; ⁵European Molecular Biology Laboratory Proteomics core facility Heidelberg, Deutschland; ⁶Medizinische Fakultät Mannheim der Universität Heidelberg Anatomie und Entwicklungsbiologie Mannheim, Deutschland; ⁷Max-Delbrück-Centrum für Molekulare Medizin Berlin, Deutschland

RNA binding proteins (RBPs) are crucial drivers of cellular responses at the post-transcriptional level. RNA-protein interactions are highly dynamic, and as such provide a key response to changes in cellular conditions, differentially sculpting the cellular proteome to various signalling cues. Post-translational modifications are a primary mechanism by which differential changes in RNA-protein interactions are regulated. Therefore, we used phospho-proteomics to identify global changes in phosphorylation in the mRNA bound proteome of mouse cardiac endothelial cells in response to acute and prolonged VEGF-A stimulation to investigate how angiogenesis is coordinated post-transcriptionally. This revealed that VEGF-A results in highly dynamic changes in RBP phosphorylation. Of the differentially phosphorylated RNA binding proteins, we identified that phosphorylation of serine 199 within mRNA bound Phf6 (PHD finger protein 6) was consistently increased following VEGF-A stimulation. Further investigation revealed that Phf6 phosphorylation at this specific site (S199) was sufficient to promote a pro-angiogenic phenotype. We found that Phf6 S199 phosphorylation induces a change in Phf6 conformation to promote the interaction with distinct angiogenesis related RNAs. This specific change in RNA binding facilitates the differential expression of ECM related RNAs, mainly by changing their decay rate. Together, we found that Phf6 phosphorylation at S199, downstream of VEGF-A, acts as a molecular switch to coordinate the differential expression of extracellular matrix related RNAs to drive angiogenesis.