Laminin inhibition of ?-amyloid protein (A?) fibrillogenesis and identification of an A? binding site localized to the globular domain repeats on the laminin a chain

Abstract

β‐Amyloid protein (Aβ) is a major component of neuritic plaques and cerebrovascular amyloid deposits in the brains of patients with Alzheimer's disease (AD). Inhibitors of Aβ fibrillogenesis are currently sought as potential future therapeutics for AD and related disorders. In the present study, the basement membrane protein laminin was found to bind Aβ 1–40 with a single dissociation constant, Kd = 2.7 × 10–9 M, and serve as a potent inhibitor of Aβ fibril formation. 25 μM of Aβ 1–40 was incubated at 37°C for 1 week in the presence of 100 nM of laminin or other basement membrane components, including perlecan, type IV collagen, and fibronectin to determine their effects on Aβ fibril formation as evaluated by thioflavin T fluorometry. Of all the basement membrane components tested, laminin demonstrated the greatest inhibitory effect on Aβ‐amyloid fibril formation, causing a ninefold inhibition at 1 and 3 days and a 21‐fold inhibition at 1 week. The inhibitory effects of laminin on Aβ fibrillogenesis occurred in a dose‐dependent manner and were still effective at lower concentrations. The inhibitory effects of laminin on Aβ 1–40 fibril formation was confirmed by negative stain electron microscopy, whereby laminin caused an almost complete inhibition of Aβ fibril formation and assembly by 3 days, resulting in the appearance of primarily amorphous nonfibrillar material. Laminin also caused partial disassembly of preformed Aβ‐amyloid fibrils following 4 days of coincubation. Laminin was not effective as an inhibitor of islet amyloid polypeptide fibril formation, suggesting that laminin's amyloid inhibitory effects were Aβ‐specific. To identify a potential Aβ‐binding site(s) on laminin, laminin was first digested with V8, trypsin, or elastase. An Aβ‐binding elastase digestion product of ∼120–130 kDa was found. In addition, a ∼55 kDa fragment derived from V8 and elastase‐digested laminin interacted with biotinylated Aβ 1–40. Amino acid sequencing of the ∼55 kDa fragment identified a conformationally dependent Aβ‐binding site within laminin localized to the globular repeats on the laminin A chain. These studies demonstrate that laminin not only binds Aβ with relatively high affinity but is a potent inhibitor of Aβ‐amyloid fibril formation. In addition, further identification of an Aβ‐binding domain within the globular repeats on the laminin A chain may lead to the design of new therapeutics for the inhibition of Aβ fibrillogenesis. J. Neurosci. Res. 62:451–462, 2000. © 2000 Wiley‐Liss, Inc.

CD14 Protein Acts as an Adaptor Molecule for the Immune Recognition of Salmonella Curli Fibers

“…Furthermore, both human and bacterial amyloids show similar functional features. For instance, both ␤-amyloid 1-42, the amyloid found in the plaques of Alzheimer's disease patients, and curli fibers, produced by enteric bacteria, bind to fibronectin (20 -22) and laminin (23) and trigger fibrinogen and plasminogen activation (24,25).…”

Centella asiatica extract selectively decreases amyloid β levels in hippocampus of Alzheimer's disease animal model

“…Centella asiatica has also shown to regulate dermal fibroblast associated genes that contribute to wound healing, including genes involved in extracellular matrix synthesis (Shukla et al, 1999;Maquart et al, 1999;Widgerow et al, 2000;Cataldi et al, 2001;Coldren et al, 2003;Lu et al, 2004). Deposition of fibrillar amyloid β can be promoted by the extracellular matrix molecule, perlecan or fibril formation inhibited by another extracellular matrix molecule, laminin (Holcomb et al, 2000;Castillo et al, 2000). Altered production of extracellular matrix molecules involved in wound healing has been reported following a 24 h treatment of fibroblasts with asiaticoside extracted from Centella (Lu et al, 2004).…”

Patented biological approaches for the therapeutic modulation of the 37 kDa/67 kDa laminin receptor

“…Studies have demonstrated that an interaction between laminin and Ab promotes neurite outgrowth [79]. Further investigations have revealed that the A chain of the laminin protein exhibits an Ab binding site and the association of laminin and Ab proteins through this site inhibits fibrillogenisis: a process required for the formation of amyloid plaques [80,81]. Moreover, the addition of laminin results in the dissolution of preformed amyloid plaques.…”