title: Stabilization of phosphatidylinositol 4-kinase type IIbeta by interaction with Hsp90.
abstract: Mammalian cells express two isoforms of type II phosphatidylinositol 4-kinase: PI4KIIα and PI4KIIβ. PI4KIIα exists almost exclusively as a constitutively active integral membrane protein because of its palmitoylation (Barylko, B., Gerber, S. H., Binns, D. D., Grichine, N., Khvotchev, M., Südhof, T. C., and Albanesi, J. P. (2001) J. Biol. Chem. 276, 7705-7708). In contrast, PI4KIIβ is distributed almost evenly between membranes and cytosol. Whereas the palmitoylated membrane-bound pool is catalytically active, the cytosolic kinase is inactive (Wei, Y. J., Sun, H. Q., Yamamoto, M., Wlodarski, P., Kunii, K., Martinez, M., Barylko, B., Albanesi, J. P., and Yin, H. L. (2002) J. Biol. Chem. 277, 46586-46593; Jung, G., Wang, J., Wlodarski, P., Barylko, B., Binns, D. D., Shu, H., Yin, H. L., and Albanesi, J. P. (2008) Biochem. J. 409, 501-509). In this study, we identify the molecular chaperone Hsp90 as a binding partner of PI4KIIβ, but not of PI4KIIα. Geldanamycin (GA), a specific Hsp90 inhibitor, disrupts the Hsp90-PI4KIIβ interaction and destabilizes PI4KIIβ, reducing its half-life by 40% and increasing its susceptibility to ubiquitylation and proteasomal degradation. Cytosolic PI4KIIβ is much more sensitive to GA treatment than is the integrally membrane-associated species. Exposure to GA induces a partial redistribution of PI4KIIβ from the cytosol to membranes and, with brief GA treatments, a corresponding increase in cellular phosphatidylinositol 4-kinase activity. Stimuli such as PDGF receptor activation that also induce recruitment of the kinase to membranes disrupt the Hsp90-PI4KIIβ interaction to a similar extent as GA treatment. These results support a model wherein Hsp90 interacts predominantly with the cytosolic, inactive pool of PI4KIIβ, shielding it from proteolytic degradation but also sequestering it to the cytosol until an extracellular stimulus triggers its translocation to the Golgi or plasma membrane and subsequent activation.
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75239, USA.
authors.forename: Gwanghyun
authors.initials: G
authors.lastname: Jung
authors.forename: Barbara
authors.initials: B
authors.lastname: Barylko
authors.forename: Dongmei
authors.initials: D
authors.lastname: Lu
authors.forename: Hongjun
authors.initials: H
authors.lastname: Shu
authors.forename: Helen
authors.initials: H
authors.lastname: Yin
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Albanesi
mesh_terms: D000818:Animals; D016227:Benzoquinones / Q000494:pharmacology; D019556:COS Cells; D002522:Chlorocebus aethiops; D003513:Cycloheximide / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D057809:HEK293 Cells; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D013058:Mass Spectrometry; D008856:Microscopy, Fluorescence; D015778:Minor Histocompatibility Antigens; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D055550:Protein Stability / Q000187:drug effects; D051381:Rats
chemical_list: D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D015778:Minor Histocompatibility Antigens; D003513:Cycloheximide; D017853:Phosphotransferases (Alcohol Group Acceptor); C402182:phosphatidylinositol phosphate 4-kinase; C001277:geldanamycin