Mechanical Strain in Actin Networks Regulates FilGAP and Integrin Binding to Filamin A

Translational Medicine Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Nature (Impact Factor: 41.46). 09/2011; 478(7368):260-3. DOI: 10.1038/nature10430
Source: PubMed


Mechanical stresses elicit cellular reactions mediated by chemical signals. Defective responses to forces underlie human medical disorders such as cardiac failure and pulmonary injury. The actin cytoskeleton's connectivity enables it to transmit forces rapidly over large distances, implicating it in these physiological and pathological responses. Despite detailed knowledge of the cytoskeletal structure, the specific molecular switches that convert mechanical stimuli into chemical signals have remained elusive. Here we identify the actin-binding protein filamin A (FLNA) as a central mechanotransduction element of the cytoskeleton. We reconstituted a minimal system consisting of actin filaments, FLNA and two FLNA-binding partners: the cytoplasmic tail of β-integrin, and FilGAP. Integrins form an essential mechanical linkage between extracellular and intracellular environments, with β-integrin tails connecting to the actin cytoskeleton by binding directly to filamin. FilGAP is an FLNA-binding GTPase-activating protein specific for RAC, which in vivo regulates cell spreading and bleb formation. Using fluorescence loss after photoconversion, a novel, high-speed alternative to fluorescence recovery after photobleaching, we demonstrate that both externally imposed bulk shear and myosin-II-driven forces differentially regulate the binding of these partners to FLNA. Consistent with structural predictions, strain increases β-integrin binding to FLNA, whereas it causes FilGAP to dissociate from FLNA, providing a direct and specific molecular basis for cellular mechanotransduction. These results identify a molecular mechanotransduction element within the actin cytoskeleton, revealing that mechanical strain of key proteins regulates the binding of signalling molecules.

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    • "Recent literature emphasizes the microscopic, bottomup , granular approach in the context of specific molecules, their roles and their interdependencies [1] [2] [3]. This can range from identifying mechanically sensitive actin-linkers [4], to characterizing signaling pathways, [5] to finding downstream effectors of mechanotransduction such as YAP/TAZ [6]. The older literature, by contrast, emphasizes the macroscopic, coarse-grained, topdown approach in the context of mechanical forces, fields, and integrative physiological function. "
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    • "ightly associated and are turned over together by this exercise - stimulated pathway . Therefore exercise - stimulated autophagy might lead to a further increase in the exchange rate of aciculin to ensure stable protein amounts in Z - disc and to prevent damage during exercise . In this context , filamins have been shown to act as mechanosensors ( Ehrlicher et al . , 2011 ; Pentikäinen and Ylänne , 2009 ; Rognoni et al . , 2012 ; Ulbricht et al . , 2013 ) , and FLNc probably plays such a role in the Z - disc , at the sarcolemma and in cell – cell and cell – matrix contacts ( Ulbricht et al . , 2013 ) . FLNc – aciculin binding might be modulated by structural alterations in FLNc , suggesting that aciculin"
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