Cysteine String Protein Promotes Proteasomal Degradation of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) by Increasing Its Interaction with the C Terminus of Hsp70-interacting Protein and Promoting CFTR Ubiquitylation

Abstract

Cysteine string protein (Csp) is a J-domain-containing protein whose overexpression blocks the exit of cystic fibrosis transmembrane conductance regulator (CFTR) from the endoplasmic reticulum (ER). Another method of blocking ER exit, the overexpression of Sar1-GTP, however, yielded twice as much immature CFTR compared with Csp overexpression. This finding suggested that Csp not only inhibits CFTR ER exit but also facilitates the degradation of immature CFTR. This was confirmed by treatment with a proteasome inhibitor, which returned the level of immature CFTR to that found in cells expressing Sar1-GTP only. CspH43Q, which does not interact with Hsc70/Hsp70 efficiently, did not promote CFTR degradation, suggesting that the pro-degradative effect of Csp requires Hsc70/Hsp70 binding/activation. In agreement with this, Csp overexpression increased the amount of Hsc70/Hsp70 co-immunoprecipitated with CFTR, whereas overexpression of CspH43Q did not. The Hsc70/Hsp70 binding partner C terminus of Hsp70-interacting protein (CHIP) can target CFTR for proteasome-mediated degradation. Csp overexpression also increased the amount of CHIP co-immunoprecipitated with CFTR. In addition, CHIP interacted directly with Csp, which was confirmed by in vitro binding experiments. Csp overexpression also increased CFTR ubiquitylation and reduced the half-life of immature CFTR. These findings indicate that Csp not only regulates the exit of CFTR from the ER, but that this action is accompanied by Hsc70/Hsp70 and CHIP-mediated CFTR degradation. Cysteine string protein (Csp) is a J-domain-containing protein whose overexpression blocks the exit of cystic fibrosis transmembrane conductance regulator (CFTR) from the endoplasmic reticulum (ER). Another method of blocking ER exit, the overexpression of Sar1-GTP, however, yielded twice as much immature CFTR compared with Csp overexpression. This finding suggested that Csp not only inhibits CFTR ER exit but also facilitates the degradation of immature CFTR. This was confirmed by treatment with a proteasome inhibitor, which returned the level of immature CFTR to that found in cells expressing Sar1-GTP only. CspH43Q, which does not interact with Hsc70/Hsp70 efficiently, did not promote CFTR degradation, suggesting that the pro-degradative effect of Csp requires Hsc70/Hsp70 binding/activation. In agreement with this, Csp overexpression increased the amount of Hsc70/Hsp70 co-immunoprecipitated with CFTR, whereas overexpression of CspH43Q did not. The Hsc70/Hsp70 binding partner C terminus of Hsp70-interacting protein (CHIP) can target CFTR for proteasome-mediated degradation. Csp overexpression also increased the amount of CHIP co-immunoprecipitated with CFTR. In addition, CHIP interacted directly with Csp, which was confirmed by in vitro binding experiments. Csp overexpression also increased CFTR ubiquitylation and reduced the half-life of immature CFTR. These findings indicate that Csp not only regulates the exit of CFTR from the ER, but that this action is accompanied by Hsc70/Hsp70 and CHIP-mediated CFTR degradation. Cysteine string protein (Csp, DnaJC5) 2The abbreviations used are: Csp, cysteine string protein; BHK, baby hamster kidney; CFTR, cystic fibrosis transmembrane conductance regulator; CHIP, C terminus of Hsp70-interacting protein; CHO, Chinese hamster ovary; ER, endoplasmic reticulum; ERAD, ER-associated degradation; GFP, green fluorescent protein; GST, glutathione S-transferase; Hsc70, 70-kDa heat shock cognate protein; Hsp70, 70-kDa heat shock protein; SNARE, soluble N-ethylmaleimide-sensitive factor attachment protein receptor; NMD1, nucleotide binding domain 1; WT, wild type; E3, ubiquitin-protein isopeptide ligase; shRNA, short hairpin RNA. is a member of the DnaJ/Hsp40 protein chaperone family (1Qiu X.B. Shao Y.M. Miao S. Wang L. Cell. Mol. Life Sci. 2006; 63: 2560-2570Crossref PubMed Scopus (600) Google Scholar, 2Chamberlain L.H. Burgoyne R.D. J. Neurochem. 2000; 74: 1781-1789Crossref PubMed Scopus (119) Google Scholar). Csp contains a short N-terminal sequence, followed by the J-domain, a linker region, and the central cysteine-rich region, which gives these proteins their name. The cysteine residues in this region are post-translationally modified by the palmitate groups that serve for the membrane attachment of Csp (3Gundersen C.B. Mastrogiacomo A. Faull K. Umbach J.A. J. Biol. Chem. 1994; 269: 19197-19199Abstract Full Text PDF PubMed Google Scholar). This structure is followed by a C-terminal domain, which is the most variable region among the three Csp paralogs in the human genome. Csp was originally discovered as an abundant protein in presynaptic junctions of Drosophila neurons (4Zinsmaier K.E. Hofbauer A. Heimbeck G. Pflugfelder G.O. Buchner S. Buchner E. J. Neurogenet. 1990; 7: 15-29Crossref PubMed Scopus (185) Google Scholar). Csps are expressed at high levels in neurons and in cell types involved in regulated exocytosis (5Mastrogiacomo A. Parsons S.M. Zampighi G.A. Jenden D.J. Umbach J.A. Gundersen C.B. Science. 1994; 263: 981-982Crossref PubMed Scopus (156) Google Scholar, 6Takamori S. Holt M. Stenius K. Lemke E.A. Gronborg M. Riedel D. Urlaub H. Schenck S. Brugger B. Ringler P. Muller S.A. Rammner B. Grater F. Hub J.S. De Groot B.L. Mieskes G. Moriyama Y. Klingauf J. Grubmuller H. Heuser J. Wieland F. Jahn R. Cell. 2006; 127: 831-846Abstract Full Text Full Text PDF PubMed Scopus (1693) Google Scholar, 7Chamberlain L.H. Henry J. Burgoyne R.D. J. Biol. Chem. 1996; 271: 19514-19517Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar), where they have been shown to govern exocytic secretory functions. For example, depolarization-induced synaptic vesicle exocytosis is impaired in neurons from Csp-deficient Drosophila (8Ranjan R. Bronk P. Zinsmaier K.E. J. Neurosci. 1998; 18: 956-964Crossref PubMed Google Scholar), and Csp overexpression produced decreases in stimulated insulin release from β-cells and stimulated catecholamine release from chromaffin cells (9Zhang H. Kelley W.L. Chamberlain L.H. Burgoyne R.D. Lang J. J. Cell Sci. 1999; 112: 1345-1351Crossref PubMed Google Scholar, 10Brown H. Larsson O. Branstrom R. Yang S.-N. Leibiger B. Leibiger I. Fried G. Moede T. Deeney J.T. Brown G.R. Jacobsson G. Rhodes C.J. Braun J.E.A. Scheller R.H. Corkey B.E. Berggren P.-O. Meister B. EMBO J. 1998; 17: 5048-5058Crossref PubMed Scopus (79) Google Scholar, 11Graham M.E. Burgoyne R.D. J. Neurosci. 2000; 20: 1281-1289Crossref PubMed Google Scholar). Deletion of the Csp gene proved to be lethal both in Drosophila and in mice causing a progressive, fatal sensorimotor disorder characterized by developing neurodegenerative changes (12Fernandez-Chacon R. Wolfel M. Nishimune H. Tabares L. Schmitz F. Castellano-Munoz M. Rosenmund C. Montesinos M.L. Sanes J.R. Schneggenburger R. Sudhof T.C. Neuron. 2004; 42: 237-251Abstract Full Text Full Text PDF PubMed Scopus (223) Google Scholar, 13Zinsmaier K.E. Eberle K.K. Buchner E. Walter N. Benzer S. Science. 1994; 263: 977-980Crossref PubMed Scopus (318) Google Scholar). As for other the is for the of Csp to Hsc70/Hsp70 and L.H. Burgoyne R.D. J. PubMed Scopus Google Scholar). to other chaperone Csp can be found in protein in the and the of these Csp been to from membrane to protein and with the proteins and membrane protein Csp been to be a regulator of R. Bronk P. Zinsmaier K.E. J. Neurosci. 1999; PubMed Google Scholar, C. S. B. L. M. M. De M. M. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar), a by with a protein A. J. PubMed Scopus Google Scholar). As of a chaperone with Hsp70, and nucleotide inhibitor, Csp release by the of from presynaptic T. T. J. H. EMBO J. PubMed Scopus Google Scholar). Csp a with Hsc70/Hsp70 and This is synaptic and can to the that Csp with the of proteins at the S. P. R. Sudhof T.C. J. B. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar). This protein also with In this Csp as a factor for which to of and to of M. B. S. Braun J.E.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, Braun J.E.A. Neuron. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). a for Csp at endoplasmic reticulum in the of the cystic fibrosis transmembrane conductance regulator The overexpression of Csp the of CFTR H. F. Lang J. Burgoyne R.D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, H. F. M. J. Biol. Chem. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar), a in CFTR and an in immature CFTR, which was to the The of CFTR of a of Csp that Hsc70/Hsp70 CFTR the of Csp increased of CFTR. these findings that Csp regulates CFTR to In the for of in proteasome-mediated CFTR degradation. of Csp increased the of CFTR with and with the CHIP terminus of Hsp70-interacting and in vitro binding a Csp and The overexpression of Csp also increased the ubiquitylation of CFTR, in agreement with to CFTR levels and increased with Csp, and CHIP a in which Csp the of a that facilitates the degradation of CFTR as blocks CFTR exit from the and from from from was from for from and and the was from from was from and other from The and Csp with the and the as (9Zhang H. Kelley W.L. Chamberlain L.H. Burgoyne R.D. Lang J. J. Cell Sci. 1999; 112: 1345-1351Crossref PubMed Google Scholar). For of proteins in the Sar1-GTP and in a from I. The CHIP was by the CHIP and by to the nucleotide binding domain of CFTR was from the C terminus of CFTR was from from the C-terminal of the domain of was from the The to human by was from the the of the of and by the of and in M. J. S. C. J. Cell Biol. 1998; PubMed Scopus Google Scholar). The from both and and was from was from was from and was from Cell and and cells in modified with and cells with CFTR K. T. M. 1996; Google Scholar, A. Brown A. S. J. B. R. M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google in with and of and cells by the of a of cells used for was as by of a For of cells in of a and of of the The amount of used for CFTR, for Csp, and for Sar1-GTP was used to twice the with modified and in of modified the and by in the for followed by short of with a For cells the in Cell of by at for at and protein the from Cell co-immunoprecipitated directly by and in the to a membrane Life the membrane was in blocking modified and and in blocking with the from at to in the the protein with and at the and by of protein with and in the for the with and the was from the by and at for in the of CFTR, at for by and as In of GST, and proteins in cells was with at for proteins from cell to the modified and in in CHIP protein was by in the of of protein was with of glutathione in of at for proteins by of and the with of CHIP in a for an at three with in and the proteins by and proteins by the with In the shown in only of protein was the at and CHIP was by with and cells and as the with for of cells to the The the cells and in and modified for and with the Life for at was was both the and the in and from by of was to of protein for and the with of protein for The three with proteins from the by of and at for and and the by the the cells to from a in and from a in the cells at and the cell by Csp with the nucleotide of and was the and The of was the and nucleotide of and was the and The of was the and cells in of and with of of of the The cells the the with of CFTR and as in of S. of are expressed as with with a Csp the of CFTR that overexpression of Csp produced a in CFTR and an in immature CFTR, which in the endoplasmic reticulum H. F. Lang J. Burgoyne R.D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, H. F. M. J. Biol. Chem. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar). Csp was CFTR in their from the endoplasmic reticulum to the CFTR in the ER, overexpression of Sar1-GTP a of as an of blocking CFTR exit from the is for of the to the ER membrane and to Sar1-GTP and blocks ER by with the and of C. S. S. and M. J. Cell Biol. Scholar). As overexpression of Sar1-GTP CFTR as by the of CFTR J. Y. B. S. J.R. J. Cell Biol. 2004; PubMed Scopus Google Scholar). overexpression of with Sar1-GTP the level of immature CFTR to of that with Sar1-GTP and that the effect of Csp blocking the of CFTR to the with finding that of Csp produced in CFTR levels H. F. Lang J. Burgoyne R.D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), the of to the that Csp the degradation of CFTR. Csp is CFTR in a of is to the and as a of attachment to the ER membrane and to Sar1-GTP, also blocks CFTR J. Y. B. S. J.R. J. Cell Biol. 2004; PubMed Scopus Google Scholar), but the of C. S. S. and M. J. Cell Biol. Scholar). with Csp reduced the level of immature CFTR that with that the action of Csp CFTR degradation does not that CFTR be in This was by a in the of of the of the and with CFTR Csp was the was not that the overexpression of of Sar1-GTP, produced CFTR levels to with the overexpression of Sar1-GTP to immature CFTR in the ER, was that the of CFTR to can in cells J. Y. B. S. J.R. J. Cell Biol. 2004; PubMed Scopus Google Scholar). The that in CFTR levels indicate that CFTR in is from to in as overexpression of Csp the effect CFTR of be that Csp can the effect of Sar1-GTP that Csp CFTR is in C. S. S. and M. J. Cell Biol. also The in immature CFTR to Hsc70/Hsp70 CspH43Q a in that been shown to be for of the domain of the proteins interact L.H. Burgoyne R.D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). In to overexpression of CspH43Q with Sar1-GTP increased the level of immature CFTR to of that in cells Sar1-GTP only This is with findings H. F. Lang J. Burgoyne R.D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), that Csp a chaperone that does not the of the of CFTR and the of CFTR of also the level of CFTR in cells expressing CFTR as compared with overexpression of CspH43Q that this action of Csp is not the effect of the level of CFTR was not the effect of CspH43Q CFTR level Sar1-GTP was also not. The amount of from to an of Sar1-GTP Sar1-GTP was most of CFTR to the which is not by the CspH43Q the blocking of ER exit was not for the of CFTR level by Csp, in the Csp was not expressed in with Sar1-GTP to of the For however, a in which CFTR was with Sar1-GTP, to serve as Csp the of Hsc70/Hsp70 and CHIP with of the Csp a in to the degradation of CFTR Hsc70/Hsp70 as an of CFTR degradation. the binding of Hsc70/Hsp70 to B. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar), and Csp both Hsc70/Hsp70 and CFTR H. F. Lang J. Burgoyne R.D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), that overexpression of Csp is to the amount of Hsc70/Hsp70 to CFTR. This was of and are to in the degradation of CFTR Y. S. J.A. Sci. S. A. PubMed Scopus Google Scholar, Y. G. M.L. S. Mol. Biol. Cell. PubMed Scopus Google Scholar). overexpression of increased the amount of Hsc70/Hsp70 that co-immunoprecipitated with CFTR as compared with the overexpression of Sar1-GTP CspH43Q and of increased the amount of Hsc70/Hsp70 with CFTR by as compared with overexpression of Sar1-GTP whereas overexpression of CspH43Q did not have a In the of J-domain-containing proteins is for both binding and J. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google Scholar). Csp a in their are in the of and in binding to L.H. Burgoyne R.D. J. PubMed Scopus Google Scholar, H. F. M. J. Biol. Chem. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar, L.H. Burgoyne R.D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). was not that also found that the amount of Hsc70/Hsp70 with CspH43Q was only of that with and These findings in the of the in vitro the indicate that overexpression of the degradation of CFTR a that whereas CspH43Q does not the Hsc70/Hsp70 The C terminus of (CHIP) is a that been shown to target immature CFTR for degradation C. Cell Biol. PubMed Scopus Google Scholar). This effect is with and for of The increased of Hsc70/Hsp70 with CFTR was also accompanied by an in the amount of CHIP with CFTR of the that CHIP co-immunoprecipitated with CFTR was as compared with Sar1-GTP of CspH43Q, however, to the amount of CHIP with CFTR. Csp CHIP of Csp, Hsc70, and protein been in which three S. P. R. Sudhof T.C. J. B. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar). both Csp and CHIP interact with was a Csp and that both and CspH43Q co-immunoprecipitated CHIP however, a of the of CHIP and Hsc70/Hsp70 in with and CspH43Q and co-immunoprecipitated of CHIP, Hsc70/Hsp70 co-immunoprecipitated with CspH43Q as compared with in agreement with in and B. This suggested that Hsc70/Hsp70 not be to serve as a Csp and be a the The of CHIP with Csp was in CHIP protein co-immunoprecipitated the Csp protein in cells for binding Csp and CHIP, CHIP, and CspH43Q and to glutathione of CHIP whereas the did not CHIP The of the CHIP protein was also confirmed by in an Csp CFTR protein and the characterized binding Csp and the CHIP suggested that Csp proteasome-mediated degradation of CFTR by ubiquitylation of CFTR. the overexpression of Csp CFTR found that overexpression of increased CFTR ubiquitylation twice as much was to CFTR in cells that as compared with cells Sar1-GTP This level of CFTR ubiquitylation was also that CspH43Q was for the increased of CFTR be to an in the of to CFTR to of CFTR. the level of CFTR to Sar1-GTP, is that the degradation of that Csp the of to CFTR. The effect of Csp CFTR ubiquitylation is not to of also increased ubiquitylation of CFTR as compared with overexpression of CspH43Q in cells Csp CFTR level by the degradation of CFTR by the the proteasome the effect of cells with an of the at for at an in CFTR level that was at of did not in a of cells with returned CFTR levels to of that in cells that the of the proteasome is for Csp to the level of CFTR. Csp CFTR are with the that Csp the degradation of CFTR by ubiquitylation by the of CFTR with CHIP, with Csp as a CFTR and is the in levels of CFTR be in a half-life of CFTR is as to overexpression of Sar1-GTP cells with CFTR that of Sar1-GTP The cells with and for to both the of and the of CFTR to C CFTR. This treatment was the exit of CFTR from the ER CspH43Q is of the of Sar1-GTP, and CspH43Q overexpression. In agreement with the that CFTR from the cells at a much was as compared with overexpression of Sar1-GTP at of only of the amount of in the cells was whereas was CspH43Q, Sar1-GTP was and is of that CFTR from the cells at a CspH43Q was overexpression Sar1-GTP does not have a effect of CFTR in in cells J. Y. B. S. J.R. J. Cell Biol. 2004; PubMed Scopus Google Scholar). cells with for the of CFTR that of CFTR and CFTR and The the cells with and cysteine for and CFTR from the cell of the that with CFTR reduced the amount of CFTR at the of the by as compared with cells expressing CFTR only and of CspH43Q with CFTR effect the amount of CFTR at the of the that the produced by was not to reduced of the CFTR This was by the that in the of the was in the amount of CFTR at the of the from cells as compared with cells expressing CFTR CFTR CspH43Q these that an of CFTR in the ER is not for the action of Csp CFTR. of the of the proteasome to of proteins and treatment with is used to of proteins that as a much as a the can that the ubiquitylation of CFTR CFTR cells with of CFTR that of CFTR and CFTR and CspH43Q, and the cells for in the of and CFTR from the cell used for cell and to to that the that is from CFTR and not from other proteins with CFTR. the high from cells for in the in the of high in cells that in cells a in CFTR CFTR the of C CFTR. a in the amount of CFTR the of only a in the amount of CFTR a that degradation by the be the Csp CFTR that overexpression of to ubiquitylation and degradation of CFTR. to Csp a in CFTR is not expressed Csp also CFTR degradation, a in Csp levels in CFTR Csp The target only from the three Csp in and in however, the expressed in human L.H. Burgoyne R.D. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google the other Csp paralogs and are at in mice (12Fernandez-Chacon R. Wolfel M. Nishimune H. Tabares L. Schmitz F. Castellano-Munoz M. Rosenmund C. Montesinos M.L. Sanes J.R. Schneggenburger R. Sudhof T.C. Neuron. 2004; 42: 237-251Abstract Full Text Full Text PDF PubMed Scopus (223) Google Scholar). of cells with Csp Csp a in Csp level with a in the level of CFTR Csp levels reduced by as compared with cells with the In agreement with in cells H. F. Lang J. Burgoyne R.D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), the in Csp a to in CFTR levels that Csp degradation of CFTR not only is but at as In this for a of Csp and in proteasome-mediated protein degradation in the Csp CFTR degradation of CFTR exit from the ER is by the action of Sar1-GTP, Csp The pro-degradative effect of Csp requires with Csp also the of CFTR with Hsc70/Hsp70 and with the Csp overexpression a in CFTR an for the of Csp to immature CFTR levels proteasome-mediated degradation. that Csp CFTR degradation that expressed Csp also CFTR degradation, Csp to an in CFTR Csp in where protein that in These the of that synaptic exocytic as as the of and protein that to synaptic vesicle This and from indicate that Csp also in the ER, where the of CFTR. Csp can both as a chaperone of CFTR and as an of CFTR from ER to of these of Csp immature CFTR the of Csp CFTR degradation compared the level of immature CFTR Csp overexpression with that exit of CFTR from the ER was by with the of the overexpression of the that overexpression of Csp does not an in that the of an protein is not for CFTR degradation. The of ER exit and pro-degradative action the that Csp a as a regulator of the of CFTR. This is by Csp which produced a in CFTR of that Csp directly to the and the terminus of CFTR H. F. M. J. Biol. Chem. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar). also with a chaperone both and CspH43Q the in vitro of the nucleotide binding domain of CFTR with the H. F. M. J. Biol. Chem. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar), and for and S. E. A. EMBO J. 1999; 18: PubMed Scopus Google Scholar). In this that the overexpression of CspH43Q to an in the level of immature CFTR that with this finding as of the chaperone effect of CspH43Q CFTR that the of Csp in immature CFTR, that their immature CFTR level and did not with with the of both Csp H. F. M. J. Biol. Chem. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar). these interact directly with CFTR to in to other chaperone they also promote protein degradation their with CFTR is of the action of was by a of the CFTR levels the ER exit of CFTR was by overexpression of the In that Csp the of CFTR with Hsc70/Hsp70 as as with CHIP, and that Csp with both CHIP and also that Csp can CHIP Hsc70/Hsp70 as a the this CspH43Q, a of Csp that Hsc70/Hsp70 to CHIP, and CHIP and CspH43Q proteins interacted in an in vitro binding This of Csp with CHIP that Csp CFTR to the in a to the pro-degradative of L. A. C. J. Cell Biol. 2004; PubMed Scopus Google Scholar). for pro-degradative action of Csp a the Hsc70/Hsp70 binding and CspH43Q, did not promote CFTR degradation. that CspH43Q to CHIP was that CspH43Q did not the of to promote CFTR CspH43Q produced a in the amount of CHIP with CFTR. The for in CFTR degradation for an of Hsc70/Hsp70 in the and ubiquitylation in for Csp to promote the degradation of CFTR with CHIP, Hsc70/Hsp70 the This is with of CHIP both of which that the of both and was for of CFTR by CHIP in in vitro ubiquitylation L. A. C. J. Cell Biol. 2004; PubMed Scopus Google Scholar, S. Y. M. T. K. EMBO PubMed Scopus Google Scholar). the binding of CHIP to CFTR the of Csp does not in ubiquitylation of CFTR to the of CspH43Q to Hsc70/Hsp70 the In addition, overexpression of CspH43Q decreases the binding of CHIP to CFTR, by CHIP from the of Csp is in the not Csp the which increased ubiquitylation and degradation of CFTR, to the by The of a binding in as degradation and vesicle been for the the and this protein to also membrane of the in with and of the ER and in with S. S. Sci. Full Text Full Text PDF PubMed Scopus Google Scholar, D. M. Mol. Cell. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar, K. G. M. Y. E. I. F. P. H. Cell. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar, Wang Y. G. EMBO J. PubMed Scopus Google Scholar). a of functions. is for Csp a of the pro-degradative effect of CHIP, is not that is of CHIP have been and S. K. Schmitz A. J. Mol. Biol. Cell. 2004; PubMed Scopus Google Scholar, C. S. J. Mol. Biol. Cell. PubMed Scopus Google Scholar). The overexpression of CHIP a in the levels of CFTR. proteins interact with the domain of Hsc70/Hsp70 and with Hsc70/Hsp70 and to Csp, also CHIP whereas does not. As been shown to be for the in vitro ubiquitylation of of CFTR by CHIP L. A. C. J. Cell Biol. 2004; PubMed Scopus Google Scholar). In this be as a regulator of CHIP the overexpression of with CFTR in both immature and CFTR levels CFTR degradation H. F. M. J. Biol. Chem. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar). the chaperone of pro-degradative is J-domain-containing protein that CHIP-mediated ubiquitylation in vitro B. J. J. M.E. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar), and CFTR levels proteasome-mediated degradation. is not however, can interact directly with In the Csp and CHIP, this the for protein degradation by a of a protein with the In this Csp is blocking the of CFTR to the is also the degradation of CFTR a with Hsc70/Hsp70 and and for CHIP are to of for for with and to and B. of for and B. S. the to by R. and with