Microtubule Movie 2
Vesicles Display Bidirectional Motility along Microtubules
Video shows how microtubules can transport vesicles outward and inward from the cell nucleus.
Microtubules generally organised (+) ends to periphery and (-) end to microtubule organising centre (MTOC) lying beside the nucleus.
Kinesin (+) end–directed motor anterograde transport moves mitochondria (carried by KIF1B), lysosomes, and an assortment of membrane vesicles to the endoplasmic reticulum (ER) or cell periphery.
Dynein (−) end–directed motor retrograde transport moves elements of the ER, late endosomes, and lysosomes to the cell centre.
GFP-Rab9 shows a perinuclear distribution near the microtubule organizing center. GFP-Rab9-bearing organelles and vesicles display bidirectional motility along microtubules.
BS-C-1 cells 20 h after transfection with GFP-Rab9 were observed at 37°C. Speed is 5 times actual.
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Visualization of Rab9-mediated vesicle transport from endosomes to the trans-Golgi in living cells. Barbero P, Bittova L, Pfeffer SR. J Cell Biol. 2002 Feb 4;156(3):511-8. Epub 2002 Feb 4. PMID: 11827983
Mannose 6-phosphate receptors (MPRs) are transported from endosomes to the trans-Golgi via a transport process that requires the Rab9 GTPase and the cargo adaptor TIP47. We have generated green fluorescent protein variants of Rab9 and determined their localization in cultured cells. Rab9 is localized primarily in late endosomes and is readily distinguished from the trans-Golgi marker galactosyltransferase. Coexpression of fluorescent Rab9 and Rab7 revealed that these two late endosome Rabs occupy distinct domains within late endosome membranes. Cation-independent mannose 6-phosphate receptors are enriched in the Rab9 domain relative to the Rab7 domain. TIP47 is likely to be present in this domain because it colocalizes with the receptors in fixed cells, and a TIP47 mutant disrupted endosome morphology and sequestered MPRs intracellularly. Rab9 is present on endosomes that display bidirectional microtubule-dependent motility. Rab9-positive transport vesicles fuse with the trans-Golgi network as followed by video microscopy of live cells. These data provide the first indication that Rab9-mediated endosome to trans-Golgi transport can use a vesicle (rather than a tubular) intermediate. Our data suggest that Rab9 remains vesicle associated until docking with the Golgi complex and is rapidly removed concomitant with or just after membrane fusion.
Supplement to Fig. 7.
Video 2 (2.6 MB) http://jcb.rupress.org/cgi/content/full/jcb.200109030/DC1/2
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Dr Mark Hill 2015, UNSW Cell Biology - UNSW CRICOS Provider Code No. 00098G