Stabilization of Phosphatidylinositol 4-Kinase Type IIβ by Interaction with Hsp90
2011; Elsevier BV; Volume: 286; Issue: 14 Linguagem: Inglês
10.1074/jbc.m110.178616
ISSN1083-351X
AutoresGwanghyun Jung, Barbara Baryłko, Dongmei Lu, Hongjun Shu, Helen L. Yin, Joseph Albanesi,
Tópico(s)Insect and Pesticide Research
ResumoMammalian 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. 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. IntroductionPhosphoinositides are essential regulators of fundamental cellular processes, including signal transduction, membrane traffic, cytoskeletal dynamics, and ion transport (reviewed in Refs. 1Krauss M. Haucke V. EMBO Rep. 2007; 8: 241-246Crossref PubMed Scopus (105) Google Scholar, 2Roth M.G. Physiol. Rev. 2004; 84: 699-730Crossref PubMed Scopus (239) Google Scholar, 3Toker A. Cell. Mol. Life. Sci. 2002; 59: 761-779Crossref PubMed Scopus (178) Google Scholar, 4Janmey P.A. Lindberg U. Nat. Rev. Mol. Cell. Biol. 2004; 5: 658-666Crossref PubMed Scopus (184) Google Scholar, 5Gamper N. Shapiro M.S. Nat. Rev. Neurosci. 2007; 8: 921-934Crossref PubMed Scopus (196) Google Scholar, 6Haucke V. Di Paolo G. Curr. Opin. Cell. Biol. 2007; 19: 426-435Crossref PubMed Scopus (79) Google Scholar). Phosphatidylinositol 4-kinases (PI4Ks) initiate the canonical phosphoinositide biosynthetic pathway by phosphorylating the D-4 hydroxyl of the inositol head group of PtdIns. The product of this reaction, PtdIns 4-phosphate (PtdIns4P), 2The abbreviations used are: PtdIns, phosphatidylinositol; PtdIns4P, PtdIns 4-phosphate; GA, geldanamycin; PI4K, phosphatidylinositol 4-kinase. serves not only as a major precursor in the synthesis of more highly phosphorylated phosphoinositides, including PtdIns 4,5-bisphosphate and PtdIns 3,4,5-trisphosphate, but also has itself been shown to be a regulator of membrane trafficking (7De Matteis M. Godi A. Corda D. Curr. Opin. Cell. Biol. 2002; 14: 434-447Crossref PubMed Scopus (81) Google Scholar, 8De Matteis M.A. Godi A. Nat. Cell. Biol. 2004; 6: 487-492Crossref PubMed Scopus (279) Google Scholar). Two types of PI4K (PI4KII and PI4KIII) have been identified in eukaryotes. The type III kinases, which are expressed from yeast to mammals, are further subdivided into α (∼230 kDa) and β (∼100 kDa) isoforms. Although mammals also express two type II kinases (α and β, both ∼55 kDa), Saccharomyces cerevisiae have only one PI4KII ortholog, known as Lsb6p (9Heilmeyer Jr., L.M. Vereb Jr., G. Vereb G. Kakuk A. Szivák I. IUBMB Life. 2003; 55: 59-65Crossref PubMed Scopus (53) Google Scholar, 10Balla A. Balla T. Trends Cell. Biol. 2006; 16: 351-361Abstract Full Text Full Text PDF PubMed Scopus (275) Google Scholar).PI4KIIα and β have conserved catalytic domains but diverse N-terminal regions extending approximately from residues 1 to 90. Unlike PI4KIIIs, which are almost entirely cytosolic, PI4KIIs can associate integrally with membranes by virtue of palmitoylation of multiple cysteines within their catalytic domains (11Barylko B. Gerber S.H. Binns D.D. Grichine N. Khvotchev M. Südhof T.C. Albanesi J.P. J. Biol. Chem. 2001; 276: 7705-7708Abstract Full Text Full Text PDF PubMed Scopus (142) Google Scholar, 12Barylko B. Mao Y.S. Wlodarski P. Jung G. Binns D.D. Sun H.Q. Yin H.L. Albanesi J.P. J. Biol. Chem. 2009; 284: 9994-10003Abstract Full Text Full Text PDF PubMed Scopus (56) Google Scholar). The palmitoylation motif, CCPCC, is present in both PI4KIIα and β. However, whereas >90% of PI4KIIα is palmitoylated and exists in cells as an active, integrally membrane-bound species, PI4KIIβ is divided almost evenly between cytosolic and membrane-bound pools (13Wei Y.J. Sun H.Q. Yamamoto M. Wlodarski P. Kunii K. Martinez M. Barylko B. Albanesi J.P. Yin H.L. J. Biol. Chem. 2002; 277: 46586-46593Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar, 14Jung G. Wang J. Wlodarski P. Barylko B. Binns D.D. Shu H. Yin H.L. Albanesi J.P. Biochem. J. 2008; 409: 501-509Crossref PubMed Scopus (31) Google Scholar). Moreover, almost half of membrane-bound PI4KIIβ is only peripherally associated with membranes, extractable by sodium carbonate at pH 11 in the absence of detergent. Therefore, it appears that only ∼25–30% of PI4KIIβ is normally palmitoylated in cells. Because palmitoylation is essential for catalytic activity (14Jung G. Wang J. Wlodarski P. Barylko B. Binns D.D. Shu H. Yin H.L. Albanesi J.P. Biochem. J. 2008; 409: 501-509Crossref PubMed Scopus (31) Google Scholar), 70–75% of this isoform may be inactive under resting conditions. Although a small portion (∼7%) of PI4KIIβ is recruited to membranes in response to growth factor receptor activation (13Wei Y.J. Sun H.Q. Yamamoto M. Wlodarski P. Kunii K. Martinez M. Barylko B. Albanesi J.P. Yin H.L. J. Biol. Chem. 2002; 277: 46586-46593Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar), conditions have not yet been found that result in a major redistribution of the kinase from cytosol to membranes. We reported that the different membrane binding properties and palmitoylation states of PI4KIIα and β are not due to their highly diverse N-terminal regions but instead to relatively slight differences in their C-terminal 160 residues (14Jung G. Wang J. Wlodarski P. Barylko B. Binns D.D. Shu H. Yin H.L. Albanesi J.P. Biochem. J. 2008; 409: 501-509Crossref PubMed Scopus (31) Google Scholar).PI4KIIα has been implicated in generating PtdIns4P pools that regulate membrane trafficking from the trans-Golgi network (15Wang Y.J. Wang J. Sun H.Q. Martinez M. Sun Y.X. Macia E. Kirchhausen T. Albanesi J.P. Roth M.G. Yin H.L. Cell. 2003; 114: 299-310Abstract Full Text Full Text PDF PubMed Scopus (424) Google Scholar, 16Pizarro-Cerdá J. Payrastre B. Wang Y.J. Veiga E. Yin H.L. Cossart P. Cell. Microbiol. 2007; 9: 2381-2390Crossref PubMed Scopus (64) Google Scholar, 17Minogue S. Waugh M.G. De Matteis M.A. Stephens D.J. Berditchevski F. Hsuan J.J. J. Cell. Sci. 2006; 119: 571-581Crossref PubMed Scopus (106) Google Scholar) and in late stages of endocytosis (17Minogue S. Waugh M.G. De Matteis M.A. Stephens D.J. Berditchevski F. Hsuan J.J. J. Cell. Sci. 2006; 119: 571-581Crossref PubMed Scopus (106) Google Scholar). Although no specific function has been ascribed to PI4KIIβ, its partial redistribution to the plasma membrane in response to growth factor receptor activation (13Wei Y.J. Sun H.Q. Yamamoto M. Wlodarski P. Kunii K. Martinez M. Barylko B. Albanesi J.P. Yin H.L. J. Biol. Chem. 2002; 277: 46586-46593Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar) and tyrosine phosphorylation in response to activation of the T-cell receptor (18Fernandis A.Z. Subrahmanyam G. Mol. Immunol. 2000; 37: 273-280Crossref PubMed Scopus (12) Google Scholar) suggest that it may have a role in cellular signaling. To understand how extracellular stimuli recruit PI4KIIβ to membranes, where it can be palmitoylated and activated, we sought to understand the basis for its distribution between membranes and cytosol. To this end, we attempted to identify binding partners that (a) selectively bind to PI4KIIβ over PI4KIIα and (b) could sequester PI4KIIβ to the cytosol. The data presented below demonstrate that the molecular chaperone Hsp90 fulfills these criteria. They further demonstrate that the interaction with Hsp90 is required to stabilize the cytosolic pool of PI4KIIβ and that the PI4KIIβ-Hsp90 interaction is disrupted by growth factor receptor activation, resulting in a partial redistribution of the kinase to membranes.DISCUSSIONOf the four mammalian PtdIns 4-kinase isoforms, PI4KIIβ is by far the least understood in terms of function or regulation. Unlike the other three isoforms, PI4KIIβ is almost evenly distributed between membranes and cytosol. The two type III kinases are almost entirely cytosolic (10Balla A. Balla T. Trends Cell. Biol. 2006; 16: 351-361Abstract Full Text Full Text PDF PubMed Scopus (275) Google Scholar), and the other type II isoform, PI4KIIα, is almost entirely membrane-bound (11Barylko B. Gerber S.H. Binns D.D. Grichine N. Khvotchev M. Südhof T.C. Albanesi J.P. J. Biol. Chem. 2001; 276: 7705-7708Abstract Full Text Full Text PDF PubMed Scopus (142) Google Scholar). Because cytosolic PI4KIIβ is catalytically inactive, its redistribution to membranes is likely to represent a major mechanism of regulation. Indeed, a portion of PI4KIIβ is recruited to membranes in response to stimuli, such as growth factor receptor activation (13Wei Y.J. Sun H.Q. Yamamoto M. Wlodarski P. Kunii K. Martinez M. Barylko B. Albanesi J.P. Yin H.L. J. Biol. Chem. 2002; 277: 46586-46593Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar). In an effort to explain the subcellular distribution of PI4KIIβ, we sought to identify binding partners that could either recruit the kinase to membranes or sequester it in the cytosol. Our results revealed that the molecular chaperone Hsp90 binds preferentially to cytosolic (and weakly membrane-bound) PI4KIIβ, inhibits its association with membranes, and protects it from proteolytic degradation. Moreover, the interaction between PI4KIIβ and Hsp90 was weakened upon treatment of cells with EGF or PDGF, suggesting that Hsp90 is a key regulator of stimulus-dependent PtdIns4P production. Based on our data, we propose a model for the life cycle of PI4KIIβ shown in Fig. 10. According to this model, cytosolic PI4KIIβ associates with Hsp90 for stabilization. An extracellular signal disrupts the interaction, allowing the free kinase to translocate to the membrane, where it may undergo palmitoylation and activation. Short exposure to GA may mimic the effect of growth factors. In contrast to PI4KIIβ, we suggest that PI4KIIα rapidly associates with Golgi membranes after its synthesis on cytosolic ribosomes and then is stably palmitoylated and, hence, constitutively active.Hsp90 is essential for the maturation, stability, and translocation of a defined set of so-called "client" proteins (reviewed in Refs. 26Young J.C. Agashe V.R. Siegers K. Hartl F.U. Nat. Rev. Mol. Cell. Biol. 2004; 5: 781-791Crossref PubMed Scopus (930) Google Scholar, 31Pratt W.B. Toft D.O. Exp. Biol. Med. 2003; 228: 111-133Crossref PubMed Scopus (1249) Google Scholar, 39Mayer M.P. Bukau B. Curr. Biol. 1999; 9: R322-R325Abstract Full Text Full Text PDF PubMed Scopus (136) Google Scholar, and 40Caplan A.J. Mandal A.K. Theodoraki M.A. Trends Cell. Biol. 2007; 17: 87-92Abstract Full Text Full Text PDF PubMed Scopus (151) Google Scholar). Currently there are more than 100 known Hsp90 clients, and many of those, including steroid hormone receptors, transcription factors, and protein kinases, participate in signal transduction pathways. To our knowledge, this is the first example of a lipid kinase as an Hsp90 client, although PI3K activity is indirectly regulated by Hsp90 (36Fujita N. Sato S. Ishida A. Tsuruo T. J. Biol. Chem. 2002; 277: 10346-10353Abstract Full Text Full Text PDF PubMed Scopus (185) Google Scholar). The chaperone function of Hsp90 is ATP-driven and involves the coordinated assistance of a variety of co-chaperones, as well as of Hsp70 (26Young J.C. Agashe V.R. Siegers K. Hartl F.U. Nat. Rev. Mol. Cell. Biol. 2004; 5: 781-791Crossref PubMed Scopus (930) Google Scholar, 27Terasawa K. Minami M. Minami Y. J. Biochem. 2005; 137: 443-447Crossref PubMed Scopus (129) Google Scholar). Specific inhibitors of the Hsp90 ATPase reaction, such as GA, have been used to disrupt interactions between Hsp90 and its client proteins in cells and to establish the functional significance of these interactions (24Whitesell L. Mimnaugh E.G. De Costa B. Myers C.E. Neckers L.M. Proc. Natl. Acad. Sci. U.S.A. 1994; 91: 8324-8328Crossref PubMed Scopus (1317) Google Scholar). As shown in this study for PI4KIIβ, GA treatment has often resulted in enhanced proteolytic degradation and reduction in cellular levels of Hsp90 clients (reviewed in Ref. 41Whitesell L. Lindquist S.L. Nat. Rev. Cancer. 2005; 5: 761-772Crossref PubMed Scopus (1925) Google Scholar).Based on our observations, we hypothesize that growth factor-dependent stimulation of PI4KIIβ is tightly and obligatorily linked to its release from Hsp90. There are other examples in the literature of Hsp90 serving as an inhibitor of kinase activity. For example, protein kinase R is activated by dsRNA, which triggers its dissociation from Hsp90 (42Donzé O. Abbas-Terki T. Picard D. EMBO J. 2001; 20: 3771-3780Crossref PubMed Scopus (95) Google Scholar). Also, Src is transiently activated upon its release from Hsp90 (43Koga F. Xu W. Karpova T.S. McNally J.G. Baron R. Neckers L. Proc. Natl. Acad. Sci. U.S.A. 2006; 103: 11318-11322Crossref PubMed Scopus (102) Google Scholar). Thus, it appears that in some cases, interaction with Hsp90 can be inhibitory in the short term, although protective in the long term. At present, we have no information regarding the downstream signaling event(s) that might trigger growth factor-dependent dissociation of PI4KIIβ from Hsp90. The most obvious possibility, stimulus-dependent phosphorylation of PI4KIIβ, has not yet been examined, although it is interesting that this modification occurs only in the membrane-associated species (14Jung G. Wang J. Wlodarski P. Barylko B. Binns D.D. Shu H. Yin H.L. Albanesi J.P. Biochem. J. 2008; 409: 501-509Crossref PubMed Scopus (31) Google Scholar). Moreover, because there is evidence that Hsp90 kinase interactions can be disrupted by phosphorylation (44Tucker D.E. Gijón M.A. Spencer D.M. Qiu Z.H. Gelb M.H. Leslie C.C. J. Leukocyte Biol. 2008; 84: 798-806Crossref PubMed Scopus (8) Google Scholar), this direction will be pursued in future studies. IntroductionPhosphoinositides are essential regulators of fundamental cellular processes, including signal transduction, membrane traffic, cytoskeletal dynamics, and ion transport (reviewed in Refs. 1Krauss M. Haucke V. EMBO Rep. 2007; 8: 241-246Crossref PubMed Scopus (105) Google Scholar, 2Roth M.G. Physiol. Rev. 2004; 84: 699-730Crossref PubMed Scopus (239) Google Scholar, 3Toker A. Cell. Mol. Life. Sci. 2002; 59: 761-779Crossref PubMed Scopus (178) Google Scholar, 4Janmey P.A. Lindberg U. Nat. Rev. Mol. Cell. Biol. 2004; 5: 658-666Crossref PubMed Scopus (184) Google Scholar, 5Gamper N. Shapiro M.S. Nat. Rev. Neurosci. 2007; 8: 921-934Crossref PubMed Scopus (196) Google Scholar, 6Haucke V. Di Paolo G. Curr. Opin. Cell. Biol. 2007; 19: 426-435Crossref PubMed Scopus (79) Google Scholar). Phosphatidylinositol 4-kinases (PI4Ks) initiate the canonical phosphoinositide biosynthetic pathway by phosphorylating the D-4 hydroxyl of the inositol head group of PtdIns. The product of this reaction, PtdIns 4-phosphate (PtdIns4P), 2The abbreviations used are: PtdIns, phosphatidylinositol; PtdIns4P, PtdIns 4-phosphate; GA, geldanamycin; PI4K, phosphatidylinositol 4-kinase. serves not only as a major precursor in the synthesis of more highly phosphorylated phosphoinositides, including PtdIns 4,5-bisphosphate and PtdIns 3,4,5-trisphosphate, but also has itself been shown to be a regulator of membrane trafficking (7De Matteis M. Godi A. Corda D. Curr. Opin. Cell. Biol. 2002; 14: 434-447Crossref PubMed Scopus (81) Google Scholar, 8De Matteis M.A. Godi A. Nat. Cell. Biol. 2004; 6: 487-492Crossref PubMed Scopus (279) Google Scholar). Two types of PI4K (PI4KII and PI4KIII) have been identified in eukaryotes. The type III kinases, which are expressed from yeast to mammals, are further subdivided into α (∼230 kDa) and β (∼100 kDa) isoforms. Although mammals also express two type II kinases (α and β, both ∼55 kDa), Saccharomyces cerevisiae have only one PI4KII ortholog, known as Lsb6p (9Heilmeyer Jr., L.M. Vereb Jr., G. Vereb G. Kakuk A. Szivák I. IUBMB Life. 2003; 55: 59-65Crossref PubMed Scopus (53) Google Scholar, 10Balla A. Balla T. Trends Cell. Biol. 2006; 16: 351-361Abstract Full Text Full Text PDF PubMed Scopus (275) Google Scholar).PI4KIIα and β have conserved catalytic domains but diverse N-terminal regions extending approximately from residues 1 to 90. Unlike PI4KIIIs, which are almost entirely cytosolic, PI4KIIs can associate integrally with membranes by virtue of palmitoylation of multiple cysteines within their catalytic domains (11Barylko B. Gerber S.H. Binns D.D. Grichine N. Khvotchev M. Südhof T.C. Albanesi J.P. J. Biol. Chem. 2001; 276: 7705-7708Abstract Full Text Full Text PDF PubMed Scopus (142) Google Scholar, 12Barylko B. Mao Y.S. Wlodarski P. Jung G. Binns D.D. Sun H.Q. Yin H.L. Albanesi J.P. J. Biol. Chem. 2009; 284: 9994-10003Abstract Full Text Full Text PDF PubMed Scopus (56) Google Scholar). The palmitoylation motif, CCPCC, is present in both PI4KIIα and β. However, whereas >90% of PI4KIIα is palmitoylated and exists in cells as an active, integrally membrane-bound species, PI4KIIβ is divided almost evenly between cytosolic and membrane-bound pools (13Wei Y.J. Sun H.Q. Yamamoto M. Wlodarski P. Kunii K. Martinez M. Barylko B. Albanesi J.P. Yin H.L. J. Biol. Chem. 2002; 277: 46586-46593Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar, 14Jung G. Wang J. Wlodarski P. Barylko B. Binns D.D. Shu H. Yin H.L. Albanesi J.P. Biochem. J. 2008; 409: 501-509Crossref PubMed Scopus (31) Google Scholar). Moreover, almost half of membrane-bound PI4KIIβ is only peripherally associated with membranes, extractable by sodium carbonate at pH 11 in the absence of detergent. Therefore, it appears that only ∼25–30% of PI4KIIβ is normally palmitoylated in cells. Because palmitoylation is essential for catalytic activity (14Jung G. Wang J. Wlodarski P. Barylko B. Binns D.D. Shu H. Yin H.L. Albanesi J.P. Biochem. J. 2008; 409: 501-509Crossref PubMed Scopus (31) Google Scholar), 70–75% of this isoform may be inactive under resting conditions. Although a small portion (∼7%) of PI4KIIβ is recruited to membranes in response to growth factor receptor activation (13Wei Y.J. Sun H.Q. Yamamoto M. Wlodarski P. Kunii K. Martinez M. Barylko B. Albanesi J.P. Yin H.L. J. Biol. Chem. 2002; 277: 46586-46593Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar), conditions have not yet been found that result in a major redistribution of the kinase from cytosol to membranes. We reported that the different membrane binding properties and palmitoylation states of PI4KIIα and β are not due to their highly diverse N-terminal regions but instead to relatively slight differences in their C-terminal 160 residues (14Jung G. Wang J. Wlodarski P. Barylko B. Binns D.D. Shu H. Yin H.L. Albanesi J.P. Biochem. J. 2008; 409: 501-509Crossref PubMed Scopus (31) Google Scholar).PI4KIIα has been implicated in generating PtdIns4P pools that regulate membrane trafficking from the trans-Golgi network (15Wang Y.J. Wang J. Sun H.Q. Martinez M. Sun Y.X. Macia E. Kirchhausen T. Albanesi J.P. Roth M.G. Yin H.L. Cell. 2003; 114: 299-310Abstract Full Text Full Text PDF PubMed Scopus (424) Google Scholar, 16Pizarro-Cerdá J. Payrastre B. Wang Y.J. Veiga E. Yin H.L. Cossart P. Cell. Microbiol. 2007; 9: 2381-2390Crossref PubMed Scopus (64) Google Scholar, 17Minogue S. Waugh M.G. De Matteis M.A. Stephens D.J. Berditchevski F. Hsuan J.J. J. Cell. Sci. 2006; 119: 571-581Crossref PubMed Scopus (106) Google Scholar) and in late stages of endocytosis (17Minogue S. Waugh M.G. De Matteis M.A. Stephens D.J. Berditchevski F. Hsuan J.J. J. Cell. Sci. 2006; 119: 571-581Crossref PubMed Scopus (106) Google Scholar). Although no specific function has been ascribed to PI4KIIβ, its partial redistribution to the plasma membrane in response to growth factor receptor activation (13Wei Y.J. Sun H.Q. Yamamoto M. Wlodarski P. Kunii K. Martinez M. Barylko B. Albanesi J.P. Yin H.L. J. Biol. Chem. 2002; 277: 46586-46593Abstract Full Text Full Text PDF PubMed Scopus (105) Google Scholar) and tyrosine phosphorylation in response to activation of the T-cell receptor (18Fernandis A.Z. Subrahmanyam G. Mol. Immunol. 2000; 37: 273-280Crossref PubMed Scopus (12) Google Scholar) suggest that it may have a role in cellular signaling. To understand how extracellular stimuli recruit PI4KIIβ to membranes, where it can be palmitoylated and activated, we sought to understand the basis for its distribution between membranes and cytosol. To this end, we attempted to identify binding partners that (a) selectively bind to PI4KIIβ over PI4KIIα and (b) could sequester PI4KIIβ to the cytosol. The data presented below demonstrate that the molecular chaperone Hsp90 fulfills these criteria. They further demonstrate that the interaction with Hsp90 is required to stabilize the cytosolic pool of PI4KIIβ and that the PI4KIIβ-Hsp90 interaction is disrupted by growth factor receptor activation, resulting in a partial redistribution of the kinase to membranes.
Referência(s)