title: Proline- and arginine-rich peptides constitute a novel class of allosteric inhibitors of proteasome activity.
abstract: Substrate-specific inhibition of the proteasome has been unachievable despite great interest in proteasome inhibitors as drugs. Recent studies demonstrated that PR39, a natural proline- and arginine-rich antibacterial peptide, stimulates angiogenesis and inhibits inflammatory responses by specifically blocking degradation of IkappaBalpha and HIF-1alpha by the proteasome. However, molecular events involved in the PR39-proteasome interaction have not been elucidated. Here we show that PR39 is a noncompetitive and reversible inhibitor of the proteasome function. This effect is achieved by a unique allosteric mechanism allowing for specific inhibition of degradation of selected proteins without affecting total proteasome-dependent proteolysis. Atomic force microscopy (AFM) studies demonstrate that 20S and 26S proteasomes treated with PR39 or its derivatives exhibit serious perturbations in their structure and their normal allosteric movements. These effects are universal for proteasomes from yeast to human. The shortest functional sequence derived from PR39 still showing the allosteric inhibitory effect consists of eleven NH(2)-terminal residues containing essential three NH(2)-terminal arginines. The noncompetitive and reversible in vitro action of PR39 and its truncated derivatives is matched by the ability of the peptides to induce angiogenesis in vivo. We postulate that PR39 changes conformational dynamics of the proteasomes by interactions with the noncatalytic subunit alpha7 in a way that prevents the enzyme from cleaving the substrates of unique structural constraints.
authors.affiliation: Institute of Biotechnology, University of Texas Health Science Center at San Antonio, 15355 Lambda Drive, San Antonio, Texas 78245, USA. gaczynska@uthscsa.edu
authors.forename: Maria
authors.initials: M
authors.lastname: Gaczynska
authors.forename: Pawel A
authors.initials: PA
authors.lastname: Osmulski
authors.forename: Youhe
authors.initials: Y
authors.lastname: Gao
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Post
authors.forename: Michael
authors.initials: M
authors.lastname: Simons
mesh_terms: D000495:Allosteric Site; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000494:pharmacology*; D001120:Arginine / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D003094:Collagen / Q000494:pharmacology; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004338:Drug Combinations; D006801:Humans; D006863:Hydrogen-Ion Concentration; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020672:I-kappa B Proteins / Q000378:metabolism; D007700:Kinetics; D007797:Laminin / Q000494:pharmacology; D051379:Mice; D018625:Microscopy, Atomic Force; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D010447:Peptide Hydrolases / Q000378:metabolism; D010455:Peptides / Q000737:chemistry*; D011392:Proline / Q000737:chemistry*; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011509:Proteoglycans / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D012568:Schizosaccharomyces / Q000378:metabolism; D013822:Thermoplasma / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D023181:Antimicrobial Cationic Peptides; D004338:Drug Combinations; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020672:I-kappa B Proteins; D007797:Laminin; D009097:Multienzyme Complexes; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D010455:Peptides; D011509:Proteoglycans; D014157:Transcription Factors; C059485:matrigel; C072212:PR 39; D000072000:NF-KappaB Inhibitor alpha; D003094:Collagen; D001120:Arginine; D011392:Proline; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease