RESUMO
Dynamic positioning of endothelial tip and stalk cells, via the interplay between VEGFR2 and NOTCH signaling, is essential for angiogenesis. VEGFR2 activates PI3K, which phosphorylates PI(4,5)P2 to PI(3,4,5)P3, activating AKT; however, PI3K/AKT does not direct tip cell specification. We report that PI(4,5)P2 hydrolysis by the phosphoinositide-5-phosphatase, INPP5K, contributes to angiogenesis. INPP5K ablation disrupted tip cell specification and impaired embryonic angiogenesis associated with enhanced DLL4/NOTCH signaling. INPP5K degraded a pool of PI(4,5)P2 generated by PIP5K1C phosphorylation of PI(4)P in endothelial cells. INPP5K ablation increased PI(4,5)P2, thereby releasing ß-catenin from the plasma membrane, and concurrently increased PI(3,4,5)P3-dependent AKT activation, conditions that licensed DLL4/NOTCH transcription. Suppression of PI(4,5)P2 in INPP5K-siRNA cells by PIP5K1C-siRNA, restored ß-catenin membrane localization and normalized AKT signaling. Pharmacological NOTCH or AKT inhibition in vivo or genetic ß-catenin attenuation rescued angiogenesis defects in INPP5K-null mice. Therefore, PI(4,5)P2 is critical for ß-catenin/DLL4/NOTCH signaling, which governs tip cell specification during angiogenesis.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal , beta Catenina , Animais , Camundongos , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , beta Catenina/genética , beta Catenina/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Células Endoteliais/metabolismo , Proteínas de Ligação ao Cálcio/genética , Proteínas de Ligação ao Cálcio/metabolismo , Neovascularização Fisiológica/genética , Proteínas de Membrana/metabolismo , RNA Interferente Pequeno/metabolismo , Receptores Notch/genética , Receptores Notch/metabolismoRESUMO
Phosphoinositide signaling regulates numerous downstream effectors that mediate cellular processes which influence cell cycle progression, migration, proliferation, growth, survival, metabolism and vesicular trafficking. A prominent role for phosphoinositide 3-kinase, which generates phosphatidylinositol 3,4,5-trisphosphate, a phospholipid that activates a plethora of effectors including AKT and FOXO during embryonic and postnatal angiogenesis, has been described. In addition, phosphatidylinositol 3-phosphate signaling is required for endosomal trafficking, which contributes to vascular remodeling. This review will examine the role phosphoinositide signaling plays in the endothelium and its contribution to sprouting angiogenesis.
Assuntos
Neovascularização Fisiológica/fisiologia , Fosfatidilinositol 3-Quinases/metabolismo , Fosfatos de Fosfatidilinositol/metabolismo , Transdução de Sinais/fisiologia , Animais , Fatores de Transcrição Forkhead/metabolismo , Humanos , Proteínas Proto-Oncogênicas c-akt/metabolismoRESUMO
Alternative splicing is a key process of multi-exonic gene expression during pre-mRNA maturation. In this process, particular exons of a gene will be included within or excluded from the final matured mRNA, and the resulting transcripts generate diverse protein isoforms. Recent evidence demonstrates that approximately 95% of human genes with multiple exons undergo alternative splicing during pre-mRNA maturation. Thus, alternative splicing plays a critical role in physiological processes and cell development programs, and.dysregulation of alternative splicing is highly associated with human diseases, such as cancer, diabetes and neurodegenerative diseases. In this review, we discuss the regulation of alternative splicing, examine the relationship between alternative splicing and human diseases, and describe several approaches that modify alternative splicing, which could aid in human disease diagnosis and therapy.