A glycolipid anchoring domain containing phosphatidylinositol may be involved in the attachment of acetylcholinesterase to frog muscle basal lamina sheaths

Abstract

In frog muscle, acetylcholinesterase (AChE) is concentrated in motor endplate rich regions (MEP-r) and is present as globular and asymmetric molecular forms. The synaptic basal lamina sheaths (BLs) contain both forms and most of the AChE motor endplate activity. Here, we report that control MEP-r and in vivo BLs preparations incubated with phosphatidylinositol-specific phospholipase C (PIPLC) release an important proportion of their total AChE. PIPLC specifically releases most of the 6 S detergent-sensitive dimeric form in a dose dependent manner from both MEP-r regions and BLs preparations. Asymmetric forms associated with MEP-r regions of muscle are also susceptible to the action of PIPLC and are partially released. These observations demonstrate that: (1) a covalent association between a glycolipid and catalytic or structural AChE polypeptidic chains exists not only for dimeric AChE but also for some variants of the asymmetric species of AChE; and (2) such glycolipid anchored species are associated not only with the plasma membrane but also with the extracellular muscle basal lamina.