β‐amyloid peptide binding protein does not couple to G protein in a heterologous Xenopus expression system

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Abstract
Alzheimer's disease is a neurodegenerative disorder related to the formation of protein aggregates. β‐Amyloid protein (Aβ), generated by enzymatic cleavage of amyloid precursor protein (APP), can cause such aggregation, and these aggregates may cause neuronal cell death by inducing apoptosis. However, Aβ‐induced intracellular signaling pathways involved in the neuronal death are not well understood. Recently it was shown that Aβ aggregates induce neuronal cell death via β‐amyloid peptide‐binding protein (BBP), a receptor for Aβ in BBP‐transfected cells, which is known to be sensitive to pertussis toxin, a Gαi/o family inhibitor. However, the actual coupling of BBP to the pertussis‐sensitive G protein was not demonstrated. In this study, we performed electrophysiological recordings using the two‐electrode voltage‐clamp technique to test whether human or Drosophila BBPs, singly or in combination with APP, are coupled to a specific type of G protein. Our results suggest that BBP is not directly coupled to Gαi/o, Gαs, or Gαq proteins and that BBP may need a component other than APP to exert its toxic effect in concert with Aβ.