[CITATION][C] Are stress fibres contractile?

K Burridge - Nature, 1981 - nature.com
Nature, 1981nature.com
INTEREST in stress fibres arises in part because their organization resembles the structure
of striated muscle myofibrils. Not only do they contain many of the same proteins (for
example, actin, myosin, a--actinin and tropomyosin) but many of these are arranged in an
alternating periodic pattern similar to that seen in sarcomeres. The similarity to muscle
structure has suggested that they may have a similar function and be involved in nonmuscle
cell movement. Here, however, is a paradox. Stress fibres are not required for cell movement …
INTEREST in stress fibres arises in part because their organization resembles the structure of striated muscle myofibrils. Not only do they contain many of the same proteins (for example, actin, myosin, a--actinin and tropomyosin) but many of these are arranged in an alternating periodic pattern similar to that seen in sarcomeres. The similarity to muscle structure has suggested that they may have a similar function and be involved in nonmuscle cell movement. Here, however, is a paradox. Stress fibres are not required for cell movement or migration, and rapidly moving cells such as macrophages or amoebae lack them. Couchman and Rees1 have shown that fibroblasts migrating from primary tissue explants generally lack stress fibres in the first few days when they are migrating rapidly. With time the migration of the cells slows down and stress fibres become more prominent. The correlation of lack of movement with the presence of stress fibres has been best documented by Herman, Crisona and Pollard2• Fibroblasts migrating randomly in culture were filmed, then fixed and prepared for immunofluorescence with antibodies against actin, and examined for the presence or absence of stress fibres. Cells or regions of cells moving most actively appeared to contain no stress fibres while regions of cells with prominent stress fibres moved very little. Because of the similarity of stress fibres to myofibrils, several groups have looked for contractility. Isenberg and co-workers1 demonstrated that stress fibres which have been microdissected from living cells with lasers will contract in the presence ofMg2+ _ ATP. An elegant approach was used by Kreis and Birchmeier4 who microinjected fluorescently labelled a--actinin into living cells so that it would be incorporated into the stress fibres. Contraction was then induced in permeabilized cell models with Mg2+-ATP. During such contractions, shortening of the non-fluorescent space between the fluorescent regions of a--actinin was observed, consistent with a sliding filament mechanism like that found _in muscle. Contraction was not, however, observed in live cells as they first had to be permeabilized. Clearly these structures are potentially contractile, but what is their function in intact cells? It would be helpful to know under what physiological circumstances stress fibres are found in the body but, unfortunately, rather little information is available. Stress fibres have been described in aortic
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