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Arp2/3 for axon turning

Arp2/3 (green) lies in the center of growth cones. Lanier/Elsevier

Axons miss turning signals if they do not have the Arp2/3 complex to slow them down, according to Geraldine Strasser, Lorene Lanier (University of Minnesota, Minneapolis, MN), and colleagues.

Arp2/3 forms short, branched actin filaments in lamellipodia to drive movement in fibroblasts. Axons, however, do not need Arp2/3 activity for forward momentum, as the authors show that axons are longer if Arp2/3 is inhibited. But these axons did not change direction in response to guidance cues. They passed straight over inhibitory signals rather than turning away.

Longer axons usually have very stable microtubules, but the long Arp2/3-less axons had overly dynamic microtubules. Their instability may impair the coordination of actin and microtubule networks that is needed for growth cone turning. "The microtubules are out of control," says Lanier. "Like on a highway, if you go too fast, you might see the exit, which is the turning cue, but you might not respond in time."

Arp2/3 was found at the center of growth cones rather than the periphery, where it lies in fibroblasts. A highly branched central actin network might be a physical barrier to microtubules, thus slowing their growth just enough for a timely response to actin changes.

Reference:

Strasser, G., et al. 2004. Neuron. 43:81–94.[CrossRef][Medline]

Nicole LeBrasseur

lebrasn{at}rockefeller.edu

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This Article Full Text (PDF, 2428K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by LeBrasseur, N. Search for Related Content PubMed Articles by LeBrasseur, N. Social Bookmarking                            What's this?