Mechanism of lysophosphatidic acid-induced amyloid fibril formation of beta(2)-microglobulin in vitro under physiological conditions.
Biochemistry
; 48(24): 5689-99, 2009 Jun 23.
Article
en En
| MEDLINE
| ID: mdl-19432419
ABSTRACT
Beta(2)-microglobulin- (beta2m-) based fibril deposition is the key symptom in dialysis-related amyloidosis. beta2m readily forms amyloid fibrils in vitro at pH 2.5. However, it is not well understood which factors promote this process in vivo, because beta2m cannot polymerize at neutral pH without additives even at elevated concentration. Here we show that lysophosphatidic acid (LPA), an in vivo occurring lysophospholipid mediator, promotes amyloid formation under physiological conditions through a complex mechanism. In the presence of LPA, at and above its critical micelle concentration, native beta2m became sensitive to limited proteolytic digestion, indicating increased conformational flexibility. Isothermal titration calorimetry indicates that beta2m exhibits high affinity for LPA. Fluorescence and CD spectroscopy, as well as calorimetry, showed that LPA destabilizes the structure of monomeric beta2m inducing a partially unfolded form. This intermediate is capable of fibril extension in a nucleation-dependent manner. Our findings also indicate that the molecular organization of fibrils formed under physiological conditions differs from that of fibrils formed at pH 2.5. Fibrils grown in the presence of LPA depolymerize very slowly in the absence of LPA; moreover, LPA stabilizes the fibrils even below its critical micelle concentration. Neither the amyloidogenic nor the fibril-stabilizing effects of LPA were mimicked by its structural and functional lysophospholipid analogues, showing its selectivity. On the basis of our findings and the observed increase in blood LPA levels in dialysis patients, we suggest that the interaction of LPA with beta2m might contribute to the pathomechanism of dialysis-related amyloidosis.
Texto completo:
1
Base de datos:
MEDLINE
Asunto principal:
Lisofosfolípidos
/
Microglobulina beta-2
/
Amiloide
Tipo de estudio:
Prognostic_studies
Idioma:
En
Revista:
Biochemistry
Año:
2009
Tipo del documento:
Article