Molecular determinants of the physicochemical properties of a critical prion protein region comprising residues 106-126.
Prion diseases are marked by the cerebral accumulation of conformationally modified forms of the cellular prion protein (PrP(C)), known as PrP(res). The region comprising the residues 106-126 of human PrP seems to have a key role in this conformational conversion, because a synthetic peptide homologous with this sequence (PrP106-126) adopts different secondary structures in different environments. To investigate the molecular determinants of the physicochemical characteristics of PrP106-126, we synthesized a series of analogues including PrP106-126 H(D), PrP106-126 A and PrP106-126 K, with l-His-->d-His, His-->Ala and His-->Lys substitutions respectively at position 111, PrP106-126 NH(2) with amidation of the C-terminus, PrP106-126 V with an Ala-->Val substition at position 117, and PrP106-126 VNH(2) with an Ala-->Val substitution at position 117 and amidation of the C-terminus. The analysis of the secondary structure and aggregation properties of PrP106-126 and its analogues showed the following. (1) His(111) is central to the conformational changes of PrP peptides. (2) Amidation of the C-terminal Gly(126) yields a predominantly random coil structure, abolishes the molecular polymorphism and decreases the propensity of PrP106-126 to generate amyloid fibrils. (3) PrP106-126 V, carrying an Ala-->Val substitution at position 117, does not demonstrate a fibrillogenic ability superior to that of PrP106-126. However, the presence of Val at position 117 increases the aggregation properties of the amidated peptide. (4) Amyloid fibrils are not required for neurotoxicity because the effects of PrP106-126 NH(2) on primary neuronal cultures were similar to those of the wild-type sequence. Conversely, astroglial proliferation is related to the presence of amyloid fibrils, suggesting that astrogliosis in prion encephalopathies without amyloid deposits is a mediated effect rather than a direct effect of disease-specific PrP isoforms.
Salmona
M
M
Istituto di Ricerche Farmacologiche 'Mario Negri', Via Eritrea 62, 20157 Milano, Italy. salmona@irfmn.mnegri.it
Malesani
P
P
De Gioia
L
L
Gorla
S
S
Bruschi
M
M
Molinari
A
A
Della Vedova
F
F
Pedrotti
B
B
Marrari
M A
MA
Awan
T
T
Bugiani
O
O
Forloni
G
G
Tagliavini
F
F
D000577:Amides / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002942:Circular Dichroism; D016098:Gerstmann-Straussler-Scheinker Disease / Q000235:genetics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000187:drug effects; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D058225:Plaque, Amyloid / Q000378:metabolism / Q000648:ultrastructure; D011110:Polymorphism, Genetic; D011328:Prions / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D017433:Protein Structure, Secondary; D051381:Rats; D055672:Static Electricity
D000577:Amides; D010446:Peptide Fragments; D011328:Prions; C082632:prion protein (106-126)