Fig. 4.

Procollagen trafficking through the cell. a and Movie 1 Golgi (red) refill by fluorescent GFP-proα2(I) (green) in a Col1a2^GFP-A cell after photobleaching of GFP-proα2(I) in the Golgi area (dashed oval in the middle panel). Scale bars = 10 µm. b Kinetics of GFP-proα2(I) fluorescence recovery after photobleaching averaged over 5 different cells (1 = full recovery). c Relative kinetics of procollagen secretion per cell (1 = maximum average secretion). Each experiment was done in triplicate with one or two Col1a2^GFP clones and MC3T3 control at the same time. Since all experiments produced consistent results, the values were averaged over all cultures: Col1a2^GFP- A (N = 9), E (N = 6), F (N = 3), and MC3T3 (N = 12). d and Movie 2 Time-lapse images of rapidly moving transport vesicles delivering GFP-proα2(I) from the ER to Golgi (box 1) and from Golgi to the plasma membrane (box 2) of a Col1a2^GFP-A cell. In a and d, cis-Golgi cisternae (red) were marked by transfecting the cells with cis-Golgi marker mCherry-GM130 in the presence of Asc2P. Scale bars = 10 µm (whole cell) and = 1 µm (zoomed regions). In b and c, error bars show SEM