Medin is the main constituent of aortic medial amyloid that occurs in virtually all individuals older than sixty. It is derived from a proteolytic fragment of lactadherin, a mammary epithelial cell expressed glycoprotein that is secreted as part of the milk fat globule membrane. It was previously demonstrated that an octapeptide fragment of medin (NH2-NFGSVQFV- COOH) forms typical well-ordered amyloid fibrils. To obtain further insights into the molecular determinants that mediate this process by such a short peptide fragment, we examined the amyloidogenic potential of its truncated forms and analogues. Our results clearly indicated that a truncated fragment of medin, the hexapeptide, NFGSVQ can form typical amyloid fibrils. A shorter pentapeptide fragment, NFGSV, self-assembled into a gel structure that exhibited a network of fibrous structures. The amyloid forming NFGSVQ hexapeptide is noticeably similar to the short amyloidogenic peptide fragments of the islet amyloid polypeptide (IAPP), NFGAIL and NFLVH. Moreover, the substitution of the phenylalanine residue with either alanine or isoleucine significantly reduced the amyloidogenic potential of the peptide fragment. Taken together, the results are consistent with the assumed role of stacking interactions in the self-assembly processes that lead to the formation of amyloid fibrils. The results are discussed in the context of models for the mechanism of fibril formation and ways to design inhibitors.
|Number of pages
|Amyloid : the international journal of experimental and clinical investigation : the official journal of the International Society of Amyloidosis
|Published - Jun 2004
Bibliographical noteFunding Information:
We thank Yaacov Delarea for help with electron microscopy experiments, and members of the Gazit laboratory for helpful discussions. This research was supported by a start-up grant from the German-Israel Research Foundation (G.I.F.) to E.G.
- Amyloid formation
- Aortic medial amyloid
- Protein misfolding
- Stacking interactions