Amyloid β protein does not interact with tachykinin receptors coupled to inositol phospholipid hydrolysis in human astrocytoma cells

We have tested the interaction between amyloid β protein (AβP) and tachykinin receptors in cultured UC-11MG astrocytoma cells, which express high affinity substance P receptors and respond to substance P with an unusually large stimulation of polyphosphoinositide hydrolysis. Both the full-length AβP (AβP_1-40) and the fragment 25-35 (AβP_25-35) did not affect the stimulation of [³H]inositolmonophosphate (InsP) formation by substance P. AβP_25-35 was also inactive when applied to the cultures 18 or 72 h prior to the assay. In addition, AβP_25-35 did not displace specifically bound [³H]SarMet substance P from its recognition sites in intact UC-11MG cells. These results suggest that, at least in this specific cell type, amyloid peptides do not interact with substance P receptors.