1. Membrane and organelle dynamics.
Membrane and organelle dynamics. (A) Motors are coupled to almost all cellular membranes to drive membrane traffic between organelles as well as to shape and position organelles within the cytosol. These pathways are discussed in more detail in the text and here we simply illustrate some key example motors that are known to be involved in each step. LE, late endosome. (B) An example of the dynamic nature of organelles. Stable expression of GFP-tagged sorting nexin 1 (SNX1) in HeLa cells labelling early endosomes. Large numbers of puncta (arrows) are distributed throughout the cytoplasm [see twofold enlargements in (b1), and along with some tubular structures (b2)]. (C) Live-cell imaging reveals the dynamics of puncta structures. The data set has been colour coded according to time (the colour scale shown in the top right-hand corner). White indicates structures that do not move during the time sequence; coloured tracks indicate moving objects. Clearly visible within this processed image is the long-range translocation of endosomes in both directions. Note the colour change from red to yellow to green and so on over time (c1), which is presumably directed by opposing motors. Net movement is consistently centripetal, as becomes clear from the enlargement in (c2) where structures are consistently coloured in the sequence red–yellow–blue–pink, which indicates net movement over time in the same direction (small arrows). Scale bars: 10 µm.
David J. Stephens J Cell Sci 2012;125:
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