title: Phosphorylation of SRSF1 by SRPK1 regulates alternative splicing of tumor-related Rac1b in colorectal cells.
abstract: The premessenger RNA of the majority of human genes can generate various transcripts through alternative splicing, and different tissues or disease states show specific patterns of splicing variants. These patterns depend on the relative concentrations of the splicing factors present in the cell nucleus, either as a consequence of their expression levels or of post-translational modifications, such as protein phosphorylation, which are determined by signal transduction pathways. Here, we analyzed the contribution of protein kinases to the regulation of alternative splicing variant Rac1b that is overexpressed in certain tumor types. In colorectal cells, we found that depletion of AKT2, AKT3, GSK3β, and SRPK1 significantly decreased endogenous Rac1b levels. Although knockdown of AKT2 and AKT3 affected only Rac1b protein levels suggesting a post-splicing effect, the depletion of GSK3β or SRPK1 decreased Rac1b alternative splicing, an effect mediated through changes in splicing factor SRSF1. In particular, the knockdown of SRPK1 or inhibition of its catalytic activity reduced phosphorylation and subsequent translocation of SRSF1 to the nucleus, limiting its availability to promote the inclusion of alternative exon 3b into the Rac1 pre-mRNA. Altogether, the data identify SRSF1 as a prime regulator of Rac1b expression in colorectal cells and provide further mechanistic insight into how the regulation of alternative splicing events by protein kinases can contribute to sustain tumor cell survival.
authors.forename: Vânia
authors.initials: V
authors.lastname: Gonçalves
authors.forename: Andreia F A
authors.initials: AF
authors.lastname: Henriques
authors.forename: Andreia
authors.initials: A
authors.lastname: Henriques
authors.forename: Joana F S
authors.initials: JF
authors.lastname: Pereira
authors.forename: Joana
authors.initials: J
authors.lastname: Pereira
authors.forename: Ana
authors.initials: A
authors.lastname: Neves Costa
authors.forename: Mary Pat
authors.initials: MP
authors.lastname: Moyer
authors.forename: Luís Ferreira
authors.initials: LF
authors.lastname: Moita
authors.forename: Margarida
authors.initials: M
authors.lastname: Gama-Carvalho
authors.forename: Paulo
authors.initials: P
authors.lastname: Matos
authors.forename: Peter
authors.initials: P
authors.lastname: Jordan
mesh_terms: D017398:Alternative Splicing / Q000235:genetics*; D015153:Blotting, Western; D002467:Cell Nucleus / Q000235:genetics; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism; D005091:Exons / Q000235:genetics; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D008856:Microscopy, Fluorescence; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000068103:Serine-Arginine Splicing Factors; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D020830:rac1 GTP-Binding Protein / Q000235:genetics* / Q000378:metabolism
chemical_list: D009687:Nuclear Proteins; C107953:RAC1 protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors; C087728:SRPK1 protein, human; C494921:AKT2 protein, human; C491754:AKT3 protein, human; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; D020830:rac1 GTP-Binding Protein
keywords: SRPK1; SRSF1; alternative splicing; colorectal cancer; signal transduction pathways