Coordinated activation of the nuclear ubiquitin ligase Cul3-SPOP by the generation of phosphatidylinositol 5-phosphate.
Phosphoinositide signaling pathways regulate numerous processes in eukaryotic cells, including migration, proliferation, and survival. The regulatory lipid phosphatidylinositol 4,5-bisphosphate is synthesized by two distinct classes of phosphatidylinositol phosphate kinases (PIPKs), the type I and II PIPKs. Although numerous physiological functions have been identified for type I PIPKs, little is known ... about the functions and regulation of type II PIPK. Using a yeast two-hybrid screen, we identified an interaction between the type IIbeta PIPK isoform (PIPKIIbeta) and SPOP (speckle-type POZ domain protein), a nuclear speckle-associated protein that recruits substrates to Cul3-based ubiquitin ligases. PIPKIIbeta and SPOP interact and co-localize at nuclear speckles in mammalian cells, and SPOP mediates the ubiquitylation of PIPKIIbeta by Cul3-based ubiquitin ligases. Additionally, stimulation of the p38 MAPK pathway enhances the ubiquitin ligase activity of Cul3-SPOP toward multiple substrate proteins. Finally, a kinase-dead PIPKIIbeta mutant enhanced ubiquitylation of Cul3-SPOP substrates. The kinase-dead PIPKIIbeta mutant increases the cellular content of its substrate lipid phosphatidylinositol 5-phosphate (PI5P), suggesting that PI5P may stimulate Cul3-SPOP activity through a p38-dependent signaling pathway. Expression of phosphatidylinositol-4,5-bisphosphate 4-phosphatases that generate PI5P dramatically stimulated Cul3-SPOP activity and was blocked by the p38 inhibitor SB203580. Taken together, these data define a novel mechanism whereby the phosphoinositide PI5P leads to stimulation of Cul3-SPOP ubiquitin ligase activity and also implicate PIPKIIbeta as a key regulator of this signaling pathway through its association with the Cul3-SPOP complex.
Mesh Terms:
Active Transport, Cell Nucleus, Cell Cycle Proteins, Cell Line, Cullin Proteins, Enzyme Activation, Humans, Imidazoles, MAP Kinase Kinase 6, Nuclear Proteins, Phosphatidylinositol Phosphates, Phosphotransferases (Alcohol Group Acceptor), Protein Binding, Protein Kinase Inhibitors, Pyridines, Repressor Proteins, Sensitivity and Specificity, Signal Transduction, Substrate Specificity, Ubiquitination, p38 Mitogen-Activated Protein Kinases
Active Transport, Cell Nucleus, Cell Cycle Proteins, Cell Line, Cullin Proteins, Enzyme Activation, Humans, Imidazoles, MAP Kinase Kinase 6, Nuclear Proteins, Phosphatidylinositol Phosphates, Phosphotransferases (Alcohol Group Acceptor), Protein Binding, Protein Kinase Inhibitors, Pyridines, Repressor Proteins, Sensitivity and Specificity, Signal Transduction, Substrate Specificity, Ubiquitination, p38 Mitogen-Activated Protein Kinases
J. Biol. Chem.
Date: Mar. 28, 2008
PubMed ID: 18218622
View in: Pubmed Google Scholar
Download Curated Data For This Publication
76632
Switch View:
- Interactions 4
- PTM Genes 4