Doug Cyr - Academia.edu (original) (raw)

Papers by Doug Cyr

Trends in Biochemical Sciences, 2002

Molecular chaperones act with folding co-chaperones to suppress protein aggregation and refold st... more Molecular chaperones act with folding co-chaperones to suppress protein aggregation and refold stress damaged proteins. However, it is not clear how slowly folding or misfolded polypeptides are targeted for proteasomal degradation. Generally, selection of proteins for degradation is mediated by E3 ubiquitin ligases of the mechanistically distinct HECT and RING domain sub-types. Recent studies suggest that the U-box protein family represents a third class of E3 enzymes. CHIP, a U-box-containing protein, is a degradatory co-chaperone of heat-shock protein 70 (Hsp70) and Hsp90 that facilitates the polyubiquitination of chaperone substrates. These data indicate a model for protein quality control in which the interaction of Hsp70 and Hsp90 with co-chaperones that have either folding or degradatory activity helps to determine the fate of non-native cellular proteins.

Molecular Biology of the Cell, 1993

Science, 1994

The entry of segments of preproteins of defined lengths into the matrix space of mitochondria was... more The entry of segments of preproteins of defined lengths into the matrix space of mitochondria was studied. The mitochondrial chaperone Hsp70 (mtHsp70) interacted with proteins emerging from the protein import channel and stabilized translocation intermediates across the membranes in an adenosine triphosphate-dependent fashion. The chaperone bound to the presequence and mature parts of preproteins. In the absence of mtHsp70 binding,

Cell, 2006

Cystic fibrosis arises from the misfolding and premature degradation of CFTRΔF508, a Cl − ion cha... more Cystic fibrosis arises from the misfolding and premature degradation of CFTRΔF508, a Cl − ion channel with a single amino acid deletion. Yet, the quality-control machinery that selects CFTRΔF508 for degradation and the mechanism for its misfolding are not well defined. We identified ...

Journal of Biological …, 2001

Proper folding of proteins (either newly synthesized or damaged in response to a stressful event)... more Proper folding of proteins (either newly synthesized or damaged in response to a stressful event) occurs in a highly regulated fashion. Cytosolic chaperones such as Hsc/Hsp70 are assisted by cofactors that modulate the folding machinery in a positive or negative manner. CHIP (carboxyl terminus of Hsc70-interacting protein) is such a cofactor that interacts with Hsc70 and, in general, attenuates its most well characterized functions. In addition, CHIP accelerates ubiquitin-dependent degradation of chaperone substrates. Using an in vitro ubiquitylation assay with recombinant proteins, we demonstrate that CHIP possesses intrinsic E3 ubiquitin ligase activity and promotes ubiquitylation. This activity is dependent on the carboxyl-terminal U-box. CHIP interacts functionally and physically with the stress-responsive ubiquitinconjugating enzyme family UBCH5. Surprisingly, a major target of the ubiquitin ligase activity of CHIP is Hsc70 itself. CHIP ubiquitylates Hsc70, primarily with short, noncanonical multiubiquitin chains but has no appreciable effect on steady-state levels or half-life of this protein. This effect may have heretofore unanticipated consequences with regard to the chaperoning activities of Hsc70 or its ability to deliver substrates to the proteasome. These studies demonstrate that CHIP is a bona fide ubiquitin ligase and indicate that U-box-containing proteins may comprise a new family of E3s.

Nature cell …, 2001

The folding of both wild-type and mutant forms of the cystic-fibrosis transmembrane-conductance r... more The folding of both wild-type and mutant forms of the cystic-fibrosis transmembrane-conductance regulator (CFTR), a plasma-membrane chloride-ion channel, is inef-ficient14. Most nascent CFTR is retained in the endoplas-mic reticulum and degraded by the ubiquitin ...

Trends in Biochemical Sciences, 1994

Whatever the scenario, tize importance of poly-ADP-ribosylation reactions in vivo in PARP-delicie... more Whatever the scenario, tize importance of poly-ADP-ribosylation reactions in vivo in PARP-delicient mice and/or in murine cell lines generated by targeted gene inactivation will soon be elucidated.

Nature

Exposure of cells to various stresses often leads to the induction of a group of proteins called ... more Exposure of cells to various stresses often leads to the induction of a group of proteins called heat shock proteins (HSPs, molecular chaperones) 1, 2 . Hsp70 is one of the most highly inducible molecular chaperones, but its expression must be maintained at low levels under ...

The EMBO …, 2003

Induction of molecular chaperones is the characteristic protective response to environmental stre... more Induction of molecular chaperones is the characteristic protective response to environmental stress, and is regulated by a transcriptional program that depends on heat shock factor 1 (HSF1), which is normally under negative regulatory control by molecular chaperones ...

EMBO reports, 2001

Molecular chaperones are known to facilitate cellular protein folding. They bind non-native prote... more Molecular chaperones are known to facilitate cellular protein folding. They bind non-native proteins and orchestrate the folding process in conjunction with regulatory cofactors that modulate the affinity of the chaperone for its substrate. However, not every attempt to fold a protein is successful and chaperones can direct misfolded proteins to the cellular degradation machinery for destruction. Protein quality control thus appears to involve close cooperation between molecular chaperones and energy-dependent proteases. Molecular mechanisms underlying this interplay have been largely enigmatic so far. Here we present a novel concept for the regulation of the eukaryotic Hsp70 and Hsp90 chaperone systems during protein folding and protein degradation.

EMBO reports, 2004

DnaJ is a molecular chaperone and the prototypical member of the J-protein family. J proteins are... more DnaJ is a molecular chaperone and the prototypical member of the J-protein family. J proteins are defined by the presence of a J domain that can regulate the activity of 70-kDa heat-shock proteins. Sequence analysis on the genome of Saccharomyces cerevisiae has revealed ...

The EMBO Journal, Mar 15, 1999

The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride ion channel construc... more The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride ion channel constructed from two membrane-spanning domains (MSDs), two nucleotide-binding domains (NBD) and a regulatory (R) domain. The NBDs and R-domain are cytosolic and how they are assembled with the MSDs to achieve the native CFTR structure is not clear. Human DnaJ 2 (Hdj-2) is a co-chaperone of heat shock cognate 70 (Hsc70) which is localized to the cytosolic face of the ER. Whether Hdj-2 directs Hsc70 to facilitate the assembly of cytosolic regions on CFTR was investigated. We report that immature ER forms of CFTR and ΔF508 CFTR can be isolated in complexes with Hdj-2 and Hsc70. The ΔF508 mutation is localized in NBD1 and causes the CFTR to misfold. Levels of complex formation between ΔF508 CFTR and Hdj-2/Hsp70 were~2-fold higher than those with CFTR. The earliest stage at which Hdj-2/Hsc70 could bind CFTR translation intermediates coincided with the expression of NBD1 in the cytosol. Interestingly, complex formation between Hdj-2 and nascent CFTR was greatly reduced after expression of the R-domain. In experiments with purified components, Hdj-2 and Hsc70 acted synergistically to suppress NBD1 aggregation. Collectively, these data suggest that Hdj-2 and Hsc70 facilitate early steps in CFTR assembly. A putative step in the CFTR folding pathway catalyzed by Hdj-2/Hsc70 is the formation of an intramolecular NBD1-R-domain complex. Whether this step is defective in the biogenesis of ΔF508 CFTR will be discussed.