Overexpression of (β)-actin is known to alter cell morphology, though its effect on cell motility has not been documented previously. Here we show that overexpressing (β)-actin in myoblasts has striking effects on motility, increasing cell speed to almost double that of control cells. This occurs by increasing the areas of protrusion and retraction and is accompanied by raised levels of (β)-actin in the newly protruded regions. These regions of the cell margin, however, show decreased levels of polymerised actin, indicating that protrusion can outpace the rate of actin polymerisation in these cells. Moreover, the expression of (β)*-actin (a G244D mutant, which shows defective polymerisation in vitro) is equally effective at increasing speed and protrusion. Concomitant changes in actin binding proteins show no evidence of a consistent mechanism for increasing the rate of actin polymerisation in these actin overexpressing cells. The increase in motility is confined to poorly spread cells in both cases and the excess motility can be abolished by blocking myosin function with butanedione monoxime (BDM). Our observations on normal myoblasts are consistent with the view that they protrude by the assembly and cross linking of actin filaments. In contrast, the additional motility shown by cells overexpressing (β)-actin appears not to result from an increase in the rate of actin polymerisation but to depend on myosin function. This suggests that the additional protrusion arises from a different mechanism. We discuss the possibility that it is related to retraction-induced protrusion in fibroblasts. In this phenomenon, a wave of increased protrusion follows a sudden collapse in cell spreading. This view could explain why it is only the additional motility that depends on spreading, and has implications for understanding the differences in locomotion that distinguish tissue cells from highly invasive cell types such as leucocytes and malignant cells.
Call for papers: Cell and Tissue Polarity
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We are welcoming submissions for our next special issue, which will focus on ‘Cell and tissue polarity’ and will be guest edited by David Bryant. Submission deadline: 15 July.
The Forest of Biologists
We are excited to announce the launch of The Forest of Biologists, a new biodiversity initiative created with support from the Woodland Trust, aiming to counteract nature loss and safeguard some of the most critically endangered ecosystems for future generations. For every Research Article and Review/Commentary article that is published in JEB (and our sister journals Development, Journal of Cell Science, Disease Models & Mechanisms and Biology Open), a native tree is planted in a forest in the UK.
Propose a new Workshop for 2025
Do you have an idea for a Workshop? We are now accepting proposals for our 2025 Biologists Workshops programme. As the scientific organiser, your involvement will be focused on the science. We'll take care of all the logistics. In 2025 we'll continue our efforts to diversify our Workshop programme and will be reserving one of our Workshops for an application from a Global South (GS) country to host an event overseas.
Editorial: Publishing where it matters
Cell Scientists to Watch
As a community-focused journal, Journal of Cell Science is keen to support the next generation of cell biologists. Check out Cell Scientists to Watch, our interview series featuring talented researchers who have recently set up their own labs.
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