THE TGN38 GLYCOPROTEIN CONTAINS 2 NONOVERLAPPING SIGNALS THAT MEDIATELOCALIZATION TO THE TRANS-GOLGI NETWORK

The membrane-spanning and cytoplasmic domains of CD4 and CD8 were repl aced by those of TGN38. After transient expression in HeLa cells, the location of the hybrid proteins was determined using immunofluorescenc e and quantitative immuno-electron microscopy, FACS analysis and metab olic labeling. The membrane-spanning domain was found to contain a sig nal that localized hybrid proteins to the TGN. This was in addition to the signal previously identified in the cytoplasmic domain (Bos, K., C. Wraight, and K. Stanley. 1993. EMBO (Eur. Mol. Biol. Organ) J. 12:2 219-2228. Humphrey, J. S., P. J. Peters, L. C. Yuan, and J. S. Bonifac ino. 1993. J. Cell Biol. 120:1123-1135. Wong, S. H., and W. Hong. 1993 . J. Biol. Chem. 268:22853-22862). The different properties of these t wo signals suggest that each operates by a different mechanism.