Acetylcholine receptors from Torpedo californica membrane vesicles are metabolized after fusion with cultured mammalian muscle cells

Abstract

Polyethylene glycol was used to fuse Torpedo californica membrane vesicles containing acetylcholine receptors to monolayers of mammalian muscle cells in culture. Ten to 15% of the transferred Torpedo receptors had an outwardly-directed α-bungarotoxin binding site and were degraded by the host cells with an apparent halftime of 30–40 h. The apparent half-time of degradation of host cell AChRs in contrast, was 8–12 h. Treatment of the cells with NaCN or puromycin reduced the rate of degradation of both endogenous and Torpedo acetylcholine receptors. The remaining Torpedo receptors that were associated with the host cells were not accessible to α-bungarotoxin, but were in membrane vesicles that were sloughed off into the medium. These data suggest that a portion of the transferred receptors are integrated into the host cell membranes.