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Recombinant endostatin forms amyloid fibrils that bind and are cytotoxic to murine neuroblastoma cells in vitro
Author(s) -
Kranenburg Onno,
Kroon-Batenburg Loes M.J,
Reijerkerk Arie,
Wu Ya-Ping,
Voest Emile E,
Gebbink Martijn F.B.G
Publication year - 2003
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(03)00218-7
Subject(s) - endostatin , chemistry , fibrillogenesis , in vitro , biochemistry , angiogenesis , fibril , amyloid (mycology) , viability assay , recombinant dna , microbiology and biotechnology , cancer research , biology , inorganic chemistry , gene
Endostatin is a fragment of collagen XVIII that acts as an endogenous inhibitor of tumor angiogenesis and tumor growth. Anti‐tumor effects have been described using both soluble and insoluble recombinant endostatin. However, differences in endostatin structure are likely to cause differences in bioactivity. In the present study we have investigated the structure and cellular effects of insoluble endostatin. We found that insoluble endostatin shows all the hallmarks of amyloid aggregates. Firstly, it binds Congo red and shows the characteristic apple‐green birefringe when examined under polarized light. Secondly, electron microscopy shows that endostatin forms short unbranched fibrils. Thirdly, X‐ray analysis shows the abundant presence of cross‐β sheets, the tertiary structure that underlies fibrillogenesis. None of these properties was observed when examining soluble endostatin. Soluble endostatin can be triggered to form cross‐β sheets following denaturation, indicating that endostatin is a protein fragment with an inherent propensity to form amyloid deposits. Like β‐amyloid, found in the brains of patients with Alzheimer's disease, amyloid endostatin binds to and is toxic to neuronal cells, whereas soluble endostatin has no effect on cell viability. Our results demonstrate a previously unrecognized functional difference between soluble and insoluble endostatin, only the latter acting as a cytotoxic amyloid substance.