The propeptide of preprosomatostatin mediates intracellular transport and secretion of alpha-globin from mammalian cells

Psi-2 cells were transfected with pLJSIG-GLO and pLJPRO-GLO DNAs and grown in the presence of G418; subsequent virus production and target cell (GH3) infection were exactly as previously described (41) . 10 G418 resistant clonal lines expressing SIG-GLO (GH3SIG-GLO) and PRO-GLO (GH3PRO-GLO) were generated and one clonal line expressing each chimera was selected for analysis. GH3SIG-GLO.9 and GH3PRO-GLO.9 cells were pulse-labeled for 15 min with PsSlmethionine and chased in complete media for times up to 2 h. The cells and medium were treated with anti-human hemoglobin antiserum and the immune corn- plexes resolved by SDS-PAGE (Fig. 2) . During the 15-min pulse of GH3SIG-GLO cells, a major globin-immunoreactive polypeptide having the same electrophoretic mobility as ot-globin was evident (Fig. 2, lane 11, bottom arrow) . After 30 min of chase, this polypepfide had completely disappeared from the cell lysate (Fig. 2, lane 12) but no globin-related material was recovered in the medium (Fig. 2, lanes 14-16) .