The development of amyloidotic diseases is believed to be determined in large part by the structure and metabolism of the amyloid subunit protein. The amino-terminal region of serum amyloid A (SAA), the subunit precursor protein in reactive amyloidosis, appears to confer fibrillogenic potential. Here we present data consistent with the hypothesis that amyloid A fibrillogenesis is favored when proteolysis of the amino-terminal region of SAA is impaired. Murine tissue extracts were found to contain pepstatin- inhibitable protease activity that cleaved mouse SAA2 between Glu8 and Ala9. Tissues obtained from mice that had been treated with pepstatin for 3 days lacked this activity. To investigate a possible relationship between inhibition of aspartic proteases and amyloidogenesis, mice were treated with pepstatin while concurrently undergoing a standard amyloid induction protocol (repeated casein injections). Pepstatin-treated mice showed amyloid deposition significantly sooner than the control group, which had received only casein. During the preamyloidotic phase, pepstatin-treated mice had higher concentrations of SAA in serum and spleen than control mice. In addition, clearance of injected 125I-labeled SAA from plasma was significantly delayed. Based on these findings, it is reasonable to postulate that inhibition of aspartic protease activity can lead to an accumulation of amino-terminally intact SAA molecules and thereby accelerate amyloid fibril formation.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Immunology|
|State||Published - Jul 15 1996|
ASJC Scopus subject areas
- Immunology and Allergy