DEFECTIVE MATURATION OF A VIRAL GLYCOPROTEIN AND PARTIAL LOSS OF THE GOLGI STACK STRUCTURE DURING IN-VITRO MYOGENESIS

In the present study, the functional and structural reorganization of the Golgi compartment shortly after the fusion of rat L6 myoblasts int o multinucleated muscle cells was examined. When we followed the matur ation and the transport of a bulk flow marker protein, the vesicular s tomatitis virus G glycoprotein, in the fused cells, we found that only about half of the newly synthesized G protein acquired endo H resista nce within the Golgi prior to its transport to the cell surface. The o ther half of the G protein remained endo H-sensitive and was retarded intracellularly. Our immunofluorescence and cell fractionation data in dicated that this maturation defect did not result from the inefficien t transport of the G protein into the Golgi, but rather from the funct ional impairment of the Gels compartment in the fused cells. In accord ance with this view, electron microscopy revealed that the majority of the Golgi-derived elements in the fused cells were structurally abnor mal and consisted of large tubulovesicular ''Golgi clusters.'' Our res ults support the view that reorganization of the Golgi complex during myogenesis involves at least a partial loss of both Golgi structure an d function. (C) 1995 Academic Press, Inc.