SENDAI-VIRAL HN AND F-GLYCOPROTEINS AS PROBES OF PLASMA-MEMBRANE PROTEIN CATABOLISM IN HTC CELLS - STUDIES WITH FUSOGENIC RECONSTITUTED SENDAI-VIRAL ENVELOPES

Reconstituted Sendai-virus envelopes (RSVE) were produced by the method of Vainstein, Hershkovitz, Israel and Loyter [(1984) Biochim. Biophys. Acta 773, 181-188]. RSVE are fusogenic unilamellar vesicles containing two transmembrane glycoproteins: the HN (hemagglutinin-neuraminidase) protein and the F (fusion) factor. The fate of the viral proteins after fusion-mediated transplantation of RSVE into hepatoma (HTC) cell plasma membranes was studied to probe plasma-membrane protein degradation. Both protein species are degraded at similar, relatively slow, rates (t1/2 = 67 h) in HTC cells fused with RSVE in suspension. Even slower degradation rates for HN and F proteins (t1/2 = 93 h) were measured when RSVE were fused with HTC cells in monolayer. Lysosomal degradation of the transplanted viral proteins is strongly implicated by the finding that degradation of HN and F proteins is sensitive to inhibition by 10 mM-NH4Cl (81%) and by 50 .mu.g of leupeptin/ml (70%).