title: Nuclear localization of phosphatidylinositol 4-kinase beta.
abstract: Whereas most phosphatidylinositol 4-kinase (PtdIns 4-kinase) activity is localized in the cytoplasm, PtdIns 4-kinase activity has also been detected in membrane-depleted nuclei of rat liver and mouse NIH 3T3 cells. Here we have characterized the PtdIns 4-kinase that is present in nuclei from NIH 3T3 cells. Both type II and type III PtdIns 4-kinase activity were observed in the detergent-insoluble fraction of NIH 3T3 cells. Dissection of this fraction into cytoplasmic actin filaments and nuclear lamina-pore complexes revealed that the actin filament fraction contains solely type II PtdIns 4-kinase, whereas lamina-pore complexes contain type III PtdIns 4-kinase activity. Using specific antibodies, the nuclear PtdIns 4-kinase was identified as PtdIns 4-kinase beta. Inhibition of nuclear export by leptomycin B resulted in an accumulation of PtdIns 4-kinase beta in the nucleus. These data demonstrate that PtdIns 4-kinase beta is present in the nuclei of NIH 3T3 fibroblasts, suggesting a specific function for this kinase in nuclear processes.
authors.affiliation: Molecular Cell Biology, Institute of Biomembranes, Universiteit Utrecht, The Netherlands.
authors.forename: Petra
authors.initials: P
authors.lastname: de Graaf
authors.forename: Elsa E
authors.initials: EE
authors.lastname: Klapisz
authors.forename: Thomas K F
authors.initials: TK
authors.lastname: Schulz
authors.forename: Alfons F M
authors.initials: AF
authors.lastname: Cremers
authors.forename: Arie J
authors.initials: AJ
authors.lastname: Verkleij
authors.forename: Paul M P
authors.initials: PM
authors.lastname: van Bergen en Henegouwen
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase / Q000235:genetics / Q000378:metabolism*; D016475:3T3 Cells; D000199:Actins / Q000378:metabolism*; D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000241:Adenosine / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D019556:COS Cells; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000201:enzymology*; D002867:Chromones / Q000494:pharmacology; D003902:Detergents / Q000737:chemistry / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051381:Rats; D000077191:Wortmannin
chemical_list: D000199:Actins; D000730:Androstadienes; D002867:Chromones; D003902:Detergents; D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D009025:Morpholines; D009687:Nuclear Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019870:1-Phosphatidylinositol 4-Kinase; D000241:Adenosine; D000077191:Wortmannin; C038753:leptomycin B