Acting like Actin: The Dynamics of the Nematode Major Sperm Protein (Msp) Cytoskeleton Indicate a Push-Pull Mechanism for Amoeboid Cell Motility

The crawling movement of eukaryotic cells requires establishment of cell polarity, extension of the leading edge, attachment to the substratum, and retraction of the cell body. Each of these events depends on the dynamics of the actin cytoskeleton that are orchestrated by a host of signaling molecules and actin-binding proteins. Indeed, amoeboid cell motility involves so many biochemical components and requires such precise coordination that it can be difficult to formulate models to account completely for the integration of protrusion, adhesion, and retraction at the molecular level. However, the amoeboid sperm of nematodes are a simpler, more specialized system in which the role usually played by actin has been taken over by the 14-kD major sperm protein (MSP). This model system has given insights into the general mechanism of how cells crawl, and has indicated that, at least in...