Discovery and characterization of a mammalian amyloid disaggregation activity

Abstract

The formation of amyloid, a cross-b-sheet fibrillar aggregate, is associated with a variety of aging-associated degenerative diseases. Herein, we report the existence of a mammalian amyloid disaggregase activity that is present in all tissues and cell types tested. Homogenates from mammalian tissues and cell lines are able to disaggregate amyloid fibrils composed of amyloid b (Ab) 1-40 or the 8 kDa plasma gelsolin fragment. The mammalian disaggregase activity is sensitive to proteinase K digestion and can be uncoupled from proteolysis activity using a protease inhibitor cocktail. Amyloid disaggregation and proteolysis activities are remarkably resistant to changes in temperature and pH. Identification and manipulation of the proteins responsible for the amyloid disaggregation/degradation activities offers the possibility of ameliorating aggregation-associated diseases.

Cellular Strategies of Protein Quality Control

“…Chaperones such as ClpB in bacteria and Hsp104 in yeast extract misfolded polypeptides from aggregates by threading them through a central pore lined with aromatic residues (Lum et al 2004;Haslberger et al 2008;Wendler et al 2009). Higher eukaryotes lack a clear Hsp104 homolog, but a "disaggregase" activity has recently been reported (Bieschke et al 2009;Murray et al 2010). The extracted protein can then be transferred to Hsp70 and Hsp40 chaperones for refolding or degradation (Buchberger et al 2010;Lotz et al 2010;Richter et al 2010).…”

Protein folding: The dark side of proteins

“…A third strategy is to boost the activity of these clearance mechanisms -which, according to work by Kelly's lab, includes enzymes that specifically disaggregate amyloids 7 . "There's a group of 500-600 genes that protect us when we're young, even if we've been so unlucky as to inherit, for example, a predisposing Parkinson's or Alzheimer's mutation, " he says.…”

Chaperone-assisted protein aggregate reactivation: Different solutions for the same problem

“…However, different reports pointed out that cell extracts from the worm C. elegans and several mouse tissues possessed disaggregation activity [14,149,150]. Eukaryotes contain a much higher number of HSP genes than prokaryotes, and different combinations of chaperones might perform the reactivation of protein aggregates in the absence of a potent Hsp100 disaggregase.…”

“…The second one, reactivation of protein aggregates, is achieved by the disaggregases Hsp104 (heat shock protein of 104 kDa) in eukaryotes and ClpB (caseinolytic peptidase B) in prokaryotes, which solubilize aggregated proteins in collaboration with the corresponding Hsp70 system in an ATP-dependent manner. A disaggregase activity has also been observed in cell extracts from higher eukaryotes, although these cells lack homologues of ClpB and Hsp104 [14,15]. The finding that expression of Hsp104 increases the disaggregation activity in human cell lines and in the nematode Caenorhabditis elegans indicates that the disaggregation capacity is limited in these organisms [16].…”