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. Author manuscript; available in PMC: 2010 Dec 1.
Published in final edited form as: Traffic. 2009 Sep 22;10(12):1773–1784. doi: 10.1111/j.1600-0854.2009.00992.x

Figure 9. A model for the role of myosin II and VwkA in protecting amoeba from flooding.

Figure 9

A. In this model, water influx leads to contractile vacuole growth, accompanied by recruitment of VwkA to the CV membrane (steps 1 & 2). Myosin II in the cortical cytoskeleton helps create cortical tension that has a positive role in CV fusion/expulsion, but by analogy to myosin II roles in adrenal chromaffin cells (35), myosin II may also have barrier roles, inhibiting CV fusion with the plasma membrane. VwkA is proposed to act on myosin II, either directly or indirectly, to disassemble/dissolve this cortical barrier, allowing CV-plasma membrane fusion and emptying to occur (step 3). B. We propose that in vwkA null cells there is a defect in CV/plasma membrane fusion due to failure of the cortical cytoskeletal barrier of the cell to disassemble. C. Impaired CV fusion/expulsion in myosin II nulls cells is proposed to be a consequence of reduced cytosolic pressure in the absence of normal cortical contractility.