The Dictyostelium Type V Myosin MyoJ Is Responsible For The Cortical Association And Motility of Contractile Vacuole Membranes. (PDF Link)                                                  
Jung G, Titus MA, Hammer JA 3rd. (2009). J Cell Biol. 186:555-70. 

Abstract:
The contractile vacuole (CV) complex in Dictyostelium is a tubulovesicular osmoregulatory organelle that exhibits extensive motility along the actin-rich cortex, providing a useful model for investigating myosin-dependent membrane transport. Here, we show that the type V myosin myoJ localizes to CV membranes and is required for efficient osmoregulation, the normal accumulation of CV membranes in the cortex, and the conversion of collapsed bladder membranes into outwardly radiating cortical CV tubules. Complementation of myoJ-null cells with a version of myoJ containing a shorter lever arm causes these radiating tubules to move at a slower speed, confirming myoJ's role in translocating CV membranes along the cortex. MyoJ-null cells also exhibit a dramatic concentration of CV membranes around the microtubule-organizing center. Consistently, we demonstrate that CV membranes also move bi-directionally on microtubules between the cortex and the centrosome. Therefore, myoJ cooperates with plus and minus end-directed microtubule motors to drive the normal distribution and dynamics of the CV complex in Dictyostelium.

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Figure 5 from paper:  The central aggregate of CV membranes in myoJ-null cells is focused at the MTOC. Shown are a WT cell (A–C) and a myoJ-null cell (D–F) that were expressing GFP-dajumin (B and E) and that were agar overlaid and stained for -tubulin (A and D). (C and F) Corresponding overlaid image. Also shown are two myoJ-null cells (G) that were expressing GFP-dajumin (H) and that were stained for -tubulin (I). J shows the overlaid image. The cell in the middle of the image has two closely spaced centrosomes. Bars: (C and E) 3 μm; (J) 5 μm. 


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