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A monomeric myosin first spotted in electron micrographs almost 30 years ago has finally been united with a proposed function. Tyska and Mooseker (page 395) report that myosin-1A associates with and anchors a raft component in apical membranes.
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Myosin-1A was previously thought to shuttle Golgi-derived cargos to the plasma membrane (after most of the distance had been covered using microtubule-based motors). But the in vitro evidence for this came from undifferentiated cells, and in mature, polarized colon epithelial cells, Tyska and Mooseker see no evidence of shuttling by myosin-1A. What they did spot was cofractionation and cross-linking of myosin-1A with the transmembrane disaccharidase sucrase-isomaltase (SI). This raft protein is lost from the apical surface when a fragment of either myosin-1A or SI interferes with the link between the two full-length proteins.
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. Q& K `: {. w- F5 Z0 ]Thus, myosin-1A may serve as an anchor, with the clustering of SI in rafts helping to secure the link even if an individual myosin-1A lets go. The link appears to be specific as other raft proteins〞which probably come and go between different rafts〞are not affected by the dominant-negative constructs. Tyska is now determining whether the myosin-1A–SI link is regulated by signaling proteins or bacterial toxins.(Expression of a dominant-negative myosin) |
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发表于 2009-3-6 08:16
发表于 2024-4-24 12:09
