Imaging real-time aggregation of amyloid beta protein (1-42) by atomic force microscopy.
Amyloid beta protein (AbetaP) is the major fibrillar constituent of senile plaques. However, no causative role for AbetaP-fibers in Alzheimer's disease (AD) pathology is established. Globular AbetaPs are continuously released during normal cellular metabolism at pico- to nano-molar concentration. We used atomic force microscopy (AFM) to examine aggregation of freshly prepared AbetaP(1-42) and to examine the role of AbetaP concentration, imaging medium (air, water, or PBS) and agonists/antagonists on AbetaP-fibrillogenesis. At even very high and non-physiological AbetaP concentrations, 24-48 h of real-time AFM imaging (a) in water show only multiple layers of globular aggregates and no fibrils and (b) in PBS show mainly the globular structures and some short fibrils. On-line addition of Zn, an agonist for AbetaP-fibrillogenesis, induced a slow but non-fibrillar aggregation of globular AbetaPs. EDTA, a chelator of Zn and calcium (a modulator of AbetaP-mediated toxicity) induced a reversible change in the Zn-mediated aggregation. These results strongly suggest that no AbetaP-fibers are formed for the physiologically relevant concentration and thus the plaque-associated fibers may not account for the AD pathophysiology.
Neuroscience Research Institute, University of California, Santa Barbara, CA 93016, USA.
Ashok
A
Parbhu
Hai
H
Lin
Julian
J
Thimm
Ratneshwar
R
Lal
D000388:Air; D016229:Amyloid beta-Peptides / Q000378:metabolism* / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism; D004492:Edetic Acid / Q000378:metabolism / Q000494:pharmacology; D018625:Microscopy, Atomic Force; D009454:Neurofibrils / Q000378:metabolism / Q000648:ultrastructure; D010446:Peptide Fragments / Q000378:metabolism* / Q000648:ultrastructure; D011487:Protein Conformation; D012965:Sodium Chloride; D013997:Time Factors; D014867:Water; D015032:Zinc / Q000378:metabolism / Q000494:pharmacology
D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; D014867:Water; D012965:Sodium Chloride; D004492:Edetic Acid; D015032:Zinc; D002118:Calcium