Organization of oligodendroglial membrane sheets: II. Galactocerebroside:antibody interactions signal changes in cytoskeleton and myelin basic protein.

Antibodies to galactocerebroside (GalC) cause patching of this surface glycolipid over internal domains of myelin basic protein (MBP), which are demarcated by a network of microtubules. The patching occurs whether or not second antibody is present, but the process is accelerated by the presence of second antibody. GalC patching results in disruption of microtubules in the lacy networks in oligodendroglial membrane sheets and in the eventual fusion of MBP domains, similar to the effects of colchicine (Dyer and Benjamins, 1989). Antibodies to GalC also disrupt F-actin in the lacy networks. Since colchicine does not alter the distribution of F-actin, anti-GalC is causing F-actin redistribution by a mechanism other than microtubule depolymerization. Extended exposure to anti-GalC results in coalescence of surface GalC patches concomitant with fusion of internal MBP domains. When anti-GalC is applied to induce GalC patching in cells previously treated with cytoskeletal inhibitors, patching is altered. After colchicine treatment, GalC surface staining is granular; i.e., patching is totally disorganized. Following cytochalasin B treatment, most membrane sheets display a few very large patches rather than the normal multiple, small patches. These GalC surface patterns are similar to the MBP distributions following the respective drug treatments (Dyer and Benjamins, 1989). Thus, the pattern of GalC distribution in the presence of antibody always reflects the organization of the underlying MBP domains; in turn, the organization of the MBP domains is determined by the lacy networks of microtubules in the oligodendroglial membrane sheets.