Cell Biology

Capping the Barb

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Science  17 Dec 2004:
Vol. 306, Issue 5704, pp. 2003
DOI: 10.1126/science.306.5704.2003b

The propulsive force in cell motility is provided by the regulated growth of actin filaments. Actin filaments have a polarized structure with so-called pointed and barbed ends. It is the barbed end that is the site at which new actin subunits are added when actin filaments are forming in the cell, and this growth is regulated by proteins, exemplified by the protein gelsolin, that “cap” the barbed end. Disanza et al. now identify a new class of barbed end-capping proteins—in particular a protein termed Eps8, previously identified as a receptor tyrosine kinase substrate. Eps8 accumulates at sites where actin is showing dynamic growth. Reduction of the levels of Eps8 impairs actin-based motility. Eps8 contains an effector domain that caps actin and a domain that autoinhibits this activity. The autoinhibition is relieved by interaction with another regulatory protein: Abi1. Croce et al. examined nematode worms that had been engineered to lack Eps8. Eps8 was found to be essential for embryonic development. Two isoforms of Eps8 were found, one of which, Eps8A, was specifically required for the apical morphogenesis of intestinal cells. The barbed end-capping ability provided by the C-terminal domain of the protein was important in promoting morphogenesis. — SMH

Nature Cell Biol. 6, 1180; 1173 (2004).

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