Nonspecific Interaction of Prefibrillar Amyloid Aggregates with Glutamatergic Receptors Results in Ca2+ Increase in Primary Neuronal Cells

Abstract

It is widely reported that the Ca 2؉ increase following nonspecific cell membrane permeabilization is among the earliest biochemical modifications in cells exposed to toxic amyloid aggregates. However, more recently receptors with Ca 2؉ channel activity such as ␣-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), N-methyl D-aspartate (NMDA), ryanodine, and inositol 1,4,5-trisphosphate receptors have been proposed as mediators of the Ca 2؉ increase in neuronal cells challenged with ␤-amyloid peptides. We previously showed that prefibrillar aggregates of proteins not associated with amyloid diseases are toxic to exposed cells similarly to comparable aggregates of disease-associated proteins. In particular, prefibrillar aggregates of the prokaryotic HypF-N were shown to be toxic to different cultured cell lines by eliciting Ca 2؉ and reactive oxygen species increases. This study was aimed at assessing whether NMDA and AMPA receptor activations could be considered a generic feature of cell interaction with amyloid aggregates rather than a specific effect of some aggregated protein. Therefore, we investigated whether NMDA and AMPA receptors were involved in the Ca 2؉ increase following exposure of rat cerebellar granule cells to HypF-N prefibrillar aggregates. We found that the intracellular Ca 2؉ increase was associated with the early activation of NMDA and AMPA receptors, although some nonspecific membrane permeabilization was also observed at longer times of exposure. This result matched a significant co-localization of the aggregates with both receptors on the plasma membrane. Our data support the possibility that glutamatergic channels are generic sites of interaction with the cell membrane of prefibrillar aggregates of different peptides and proteins as well as the key structures responsible for the resulting early membrane permeabilization to Ca 2؉ .

Interaction of toxic and non-toxic HypF-N oligomers with lipid bilayers investigated at high resolution with atomic force microscopy

“…However, the possibility that intracellular calcium overload can in part be due to the interaction of oligomers with endogenous calcium-permeable channels or membrane receptors cannot be ruled out. In this context, several cell surface proteins have been considered as possible candidate receptors of Aβ oligomers, including APP [54], tumor-necrosis factor receptor-1 (TNFR1) [55], the receptor for advanced glycation end products (RAGE) [56], the non-infectious form of the prion protein (PrPc) [57], voltage-gated calcium channels [58] or ligand-gated calcium channels such as the glutamate N-methyl D-aspartate (NMDA) receptors and the α-amino-3-hydroxy-5-methyl- 4-isoxazolepropionic acid (AMPA) receptor [59, 60]. …”

Cholesterol in Alzheimers Disease: Unresolved Questions

“…At later times, the oligomer-receptor complexes could hinder NMDA receptor-mediated Ca 2+ influx into active dendritic spines inducing spine loss and receptor internalization by endocytosis, thus reverting the initial activation effects [175,176]. Very recently a similar behaviour has been reported for amyloid aggregates of a protein not associated with amyloid diseases suggesting that NMDA and AMPA receptors can be generic interaction sites for amyloids [177]. Membrane cholesterol can modulate aggregate- Fig.…”

Effect of molecular chaperones on aberrant protein oligomers in vitro: super-versus sub-stoichiometric chaperone concentrations

“…First, it forms fibrils that are morphologically, tinctorially and structurally similar to those found in amyloid deposition diseases (Chiti et al, 2001;Relini et al, 2004). Second, HypF-N forms pre-fibrillar oligomers that are toxic to cells in culture and in animal models (Bucciantini et al, 2002;Bucciantini et al, 2004;Cecchi et al, 2005;Baglioni et al, 2006;Pellistri et al, 2008). Furthermore, HypF-N pre-fibrillar oligomers have similar pathogenic effects as A oligomers on cells at the biochemical, molecular, electrophysiological and animal level Tatini et al, 2013).…”