EFFECT OF TUNICAMYCIN ON THE SYNTHESIS, INTRACELLULAR-TRANSPORT AND SHEDDING OF MEMBRANE GLYCOPROTEINS IN BHK CELLS

Tunicamycin (TM) has been shown in many systems to prevent glycosylation of glycoproteins but not to inhibit synthesis of the polypeptide portions of glycoproteins. We report that TM causes selective inhibition of protein glycosylation in BHK fibroblasts as well. Data are presented which indicate that, during the first 12 h of exposure to TM, cells continue to shed proteins and glycoproteins made before the addition of TM and are able to transfer non-glycosylated polypeptides from their site of synthesis in the endoplasmic reticulum to the cell surface. These data suggest: 1. 1. that cells can shed glycosylated proteins even though the supply of fully glycosylated replacement molecules is severely restricted 2. 2. that protein glycosylation and removal of cell membrane glycoproteins from the surface are not coupled 3. 3. that the oligosaccharide moities linked N-glycosidically to many membrane glycoproteins are not required for their intracellular transport. © 1979.