Figure 8.

TGN–to–cell surface transport of VSV G tsO45 protein is inhibited by overexpression of either GDI isoform. GDI-1 and GDI-2 tagged with a VSV G epitope were coexpressed with the temperature-sensitive VSV G tsO45 protein in BHK cells. This enabled the simultaneous monitoring of both overexpressed proteins. Transfected cells were maintained and metabolically labeled (10 min, 5 h after transfection) at nonpermissive temperature (39°C). Cell surface transport of VSV G tsO45 protein was induced by transfer to permissive temperature (31°C) for various chase times (0–120 min). (A) The cell surface delivery of the VSV G protein as a function of time was monitored by surface biotinylation as described in MATERIALS AND METHODS. Representative data from one of three independent experiments is shown. (B) TGN–to–cell surface transport of VSV G tsO45 proteins was monitored by transferring transfected cells from 39 to 20°C for 1 h to accumulate VSV G in the TGN and subsequently transferring them to 31°C for 1 h. Cell surface delivery was quantified by biotinylation as described in MATERIALS AND METHODS. Each column represents the mean ± SEM of triplicate samples from one of two independent experiments.