TARGETING OF ACETYLCHOLINE-RECEPTOR AND 43 KDA RAPSYN TO THE POSTSYNAPTIC MEMBRANE IN TORPEDO-MARMORATA ELECTROCYTE

In this study we have investigated the intracellular routing of two ma jor components of the postsynaptic membrane in Torpedo electrocytes, t he nicotinic acetylcholine receptor and the extrinsic 43 kDa protein r apsyn, and of a protein from the non-innervated membrane, the Na+,K+ A TPase. We isolated subpopulations of post-Golgi vesicles (PGVs) enrich ed either in AChR or in Na+,K+ ATPase. Rapsyn was associated to AChR-c ontaining PGVs suggesting that both AChR and rapsyn are targeted to in tracellular organelles in the secretory pathway before delivery to the postsynaptic membrane. In vitro assays further show that rapsyn-conta ining PVGs do bind more efficiently to microtubules compared to Na+,K ATPase-enriched PVGs. These data provide evidence in favor of the con tribution of the secretory pathway to the delivery of synaptic compone nts. ((C)Elsevier: Paris).