UC San Diego

Amyloid β (Aβ) oligomers are the predominant toxic species in the pathology of Alzheimer's disease. The prevailing mechanism for toxicity by Aβ oligomers includes ionic homeostasis destabilization in neuronal cells by forming ion channels. These channel structures have been previously studied in model lipid bilayers. In order to gain further insight into the interaction of Aβ oligomers with natural membrane compositions, we have examined the structures and conductivities of Aβ oligomers in a membrane composed of brain total lipid extract (BTLE). We utilized two complementary techniques: atomic force microscopy (AFM) and black lipid membrane (BLM) electrical recording. Our results indicate that Aβ_1-42 forms ion channel structures in BTLE membranes, accompanied by a heterogeneous population of ionic current fluctuations. Notably, the observed current events generated by Aβ_1-42 peptides in BTLE membranes possess different characteristics compared to current events generated by the presence of Aβ_1-42 in model membranes comprising a 1:1 mixture of DOPS and POPE lipids. Oligomers of the truncated Aβ fragment Aβ_17-42 (p3) exhibited similar ion conductivity behavior as Aβ_1-42 in BTLE membranes. However, the observed macroscopic ion flux across the BTLE membranes induced by Aβ_1-42 pores was larger than for p3 pores. Our analysis of structure and conductance of oligomeric Aβ pores in a natural lipid membrane closely mimics the in vivo cellular environment suggesting that Aβ pores could potentially accelerate the loss of ionic homeostasis and cellular abnormalities. Hence, these pore structures may serve as a target for drug development and therapeutic strategies for AD treatment.