Alfred Goldberg

..During protein breakdown, this peptide-induced channel opening may function to facilitate the release of products from the proteasome...

..Thus, degradation of most 9-17 residue proteasome products is initiated by endoproteolytic cleavages, primarily by TOP, and the resulting 6-9 residue fragments are further digested to amino acids by aminopeptidases...

..This capacity of PGC-1alpha and PGC-1beta to inhibit FoxO3 and NFkappaB actions and proteolysis helps explain how exercise prevents muscle atrophy...

..The development of proteasome inhibitors illustrates the unpredictability, frustrations, and potential rewards of drug development but also emphasizes the dependence of medical advances on basic biological research...

..A full understanding of the pathogenesis of the protein-folding diseases will require greater knowledge of how misfolded proteins are recognized and selectively degraded...

..Inhibitors of its proteolytic activity are widely used as research tools and have proven effective in cancer therapy...

..If cells express large amounts of TOP, class I presentation decreases, and if TOP is inhibited, presentation increases. Thus, peptide degradation in the cytosol appears to limit the efficiency of antigen presentation...

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..Thus, substrate binding activates ATP hydrolysis, which promotes three processes: substrate unfolding, gate opening in the 20S, and protein translocation...

..Presumably, this change in peptides produced accounts for the capacity of PA28 to enhance antigen presentation...

..Unfolded or loosely folded polypeptides can inhibit this tighter binding. This commitment step precedes substrate deubiquitination and allows for selection of ubiquitinated proteins capable of being unfolded and efficiently degraded...

..Thus, many cytosolic proteins proceed through a prolonged "fragile period" during which they are sensitive to degradation induced by superoxide radicals or increased temperatures...

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..Thus, BRUCE normally inhibits apoptosis, and Nrdp1 can be important in the initiation of apoptosis by catalyzing ubiquitination and degradation of BRUCE...

..Thus, occupancy of the caspase-like sites stimulates the trypsin-like activity of proteasomes, but substrates of the caspase-like sites inhibit the chymotrypsin-like activity by binding to a distinct noncatalytic site...

..Our results demonstrate that c-IAP1 exerts its oncogenic functions by promoting the degradation of an important negative regulator in the Myc pathway...

..This tendency of S5a to associate with the growing Ub chain can explain how S5a, unlike typical substrates, which are recognized by certain E3s through specific motifs, is ubiquitinated by all E3s tested and is rapidly degraded in vivo...

..Thus, different types of muscle atrophy share a common transcriptional program that is activated in many systemic diseases...

..This activation enhances the selectivity of the 26S proteasome for ubiquitinated proteins and links their deubiquitination to their degradation...

..Occasional failure of these long undegradable sequences to exit may interfere with proteasome function and help explain why longer polyQ expansions promote early disease onset...

..These results suggest that the ability of BRUCE to antagonize both the precursor and mature forms of Smac and caspase-9 is an important mechanism for the prevention of apoptosis under normal conditions...

..Using the protease protection maps, we modeled the conformational changes associated with ATP binding and hydrolysis in PAN based on the x-ray structures of the homologous AAA ATPase, HslU...

..These data indicate that Nrdp1 is a RING finger-type of ubiquitin ligase, which promotes degradation of ErbB3 by proteasomes and, thus, may be an important factor influencing cell growth...

..Because these proteins stabilize the thick filament, their selective ubiquitylation may facilitate thick filament disassembly. However, the thin filament components decreased by a mechanism not requiring MuRF1...

..Its "molecular ruler" mechanism involves binding the hydrophobic C terminus of the substrate 9-16 residues away from the active site...

..Thus, the C termini of the proteasomal ATPases function like a "key in a lock" to induce gate opening and allow substrate entry...

..Thus, S5a (and presumably certain other UIM proteins) function with certain E3/E2 pairs to ensure synthesis of efficiently degraded non-forked Ub conjugates...

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..ATP therefore serves multiple functions in proteolysis and the only step that absolutely requires ATP hydrolysis is the unfolding of globular proteins. The 26S proteasome appears to function by similar mechanisms...

..These studies indicate that decreased IGF-1-PI3K-Akt signaling activates autophagy not only through mTOR but also more slowly by a transcription-dependent mechanism involving FoxO3...

..Like other proteins involved in antigen presentation, ERAP1 is induced by interferon-gamma. When overexpressed in vivo, we found that ERAP1 stimulates the processing and presentation of an antigenic precursor in the ER...

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..Recent studies have shed light on the pathway for ordered assembly of the base of the 19S regulatory particle of the 26S proteasome by identifying new precursor complexes and four dedicated chaperones involved in its assembly...

..These findings on muscle provide the first evidence for coordinate regulation of proteasomal and lysosomal systems, although in neuronal and hepatic cells, FoxO3 stimulates the autophagic process selectively...

..Thus, forkhead factor(s) play a critical role in the development of muscle atrophy, and inhibition of Foxo factors is an attractive approach to combat muscle wasting...

..Thus, below 10 degrees C, yeast show an adaptive response that sustains viability at low or freezing temperatures, which are commonly encountered in natural environments and laboratory refrigerators...

..Thus, in cardiomyocytes, as in skeletal muscle, FOXO3a activates an atrogene transcriptional program, which retards or prevents hypertrophy and is down-regulated by multiple physiological and pathological stimuli of myocyte growth...

..Thus an important component of growth stimulation by IGF-I, through the PI3K-Akt pathway, is its ability to rapidly suppress transcription of the atrophy-related E3 atrogin-1 and other atrogenes and degradation of myofibrillar proteins...

..Thus, the extent of antigen presentation depends on the balance between several proteolytic processes that may generate or destroy epitopes...

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..A novel assay of proteasome activity in crude cell extracts that allows rapid evaluation of the state of the proteasomes in cells treated with inhibitors is also described...

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..TOP therefore plays an important role in vivo in degrading peptides released by proteasomes and is a significant factor limiting the extent of antigen presentation...

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..Moreover, these findings reveal that three sequential proteolytic steps (by proteasomes, TPPII, and then ER aminopepsidase 1) are required for the generation of a subset of epitopes...

..Thus in human 26S proteasomes, hRpn13 appears to be important for the binding of UCH37 to the 19S complex and for efficient proteolysis...

..This mechanism differs from that of PA26/28, which lacks the HbYX motif and does not cause alpha subunit rotation. These findings demonstrated how the ATPases' C termini function to facilitate substrate entry...

..However, after interferon-gamma treatment, which causes proteasomes to produce more NH2-extended antigenic precursors, ERAP1 increased the supply of peptides for MHC class I antigen presentation...

..Thus, UbcH2 up-regulation is a novel response to TNF-alpha/NF-kappaB signaling in skeletal muscle that appears to be essential for the increased ubiquitin conjugation induced by this cytokine...

..In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to verify an autophagic response...

..These findings point to FoxO3 and Bnip3 as potential therapeutic targets in muscle wasting disorders and other degenerative and neoplastic diseases in which autophagy is involved...

..We also hope to learn more about this trimming process and about the competing pathway by which most proteasome products are digested to amino acids. ..

..Specific Aim D will define the chaperone like function of the PAN and HslU ATPases which support protein breakdown by proteasome homologs in archeabacteria and E. coli. ..

..We hope to learn how this disaccharide protects cell proteins against cold-induced denaturation, whether trehalose influences protein degradation, and whether higher eukaryotes show similar adaptations to near-freezing temperatures. ..

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..g. cancer, sepsis, renal failure) and aging. ..

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..We also hope to elucidate the roles of ATP in their function and to learn whether these enzymes utilize similar mechanisms as the bacterial ATP-hydrolyzing proteases...

..Finally, the project will explore the processive mechanism of the model ATP-dependent protease, La (lon), which catalyzes the rapid degradation of abnormal proteins in E. coli and mitochondria. ..

..We recently found that trehalose is also required for efficient protein degradation, even in normal cells. The mechanisms of this unexpected new protective function of trehalose will be investigated. ..