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The Drosophila Short stop (Shot/Kakapo) gene encodes several protein isoforms, some of which may link integrins to microtubules. In analyzing the Shot locus, R?per and Brown (page 1305) found something odd: a previously unnoticed exon encoding a series of plakin repeats. The only known function of plakin repeats though is to interact with cytoplasmic intermediate filaments, which flies lack.
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Based on a biochemical analysis, the plakin repeats are incorporated into a gigantic isoform of Shot that is the third-largest protein discovered in flies. This isoform includes an actin-binding domain, the plakin repeats, a microtubule-binding domain, and spectrin repeats, and is found in adherens junctions, a localization that seems to be determined by a portion of the plakin domain. Reducing the quantity of the largest Shot isoform in early embryos weakens epithelial intercellular contacts, so it is essential for maintaining epithelial integrity.
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5 s2 [. z6 h+ M0 u) J0 ]* vThe authors propose that the giant Shot isoform helps link the adherens junction to an associated belt of actin filaments and microtubules. This novel intermediate filament-independent activity of plakin repeats may be a conserved function of the domain, or it could be a distinct adaptation in insects, where a lack of intermediate filaments left the plakin domain free to evolve a new function.(Plakin repeats (green) take Shot to adhe) |
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发表于 2009-3-6 00:58
发表于 2015-5-22 15:52
