Structural basis of filamin A functions.
Filamin A (FLNa) can effect orthogonal branching of F-actin and bind many cellular constituents. FLNa dimeric subunits have N-terminal spectrin family F-actin binding domains (ABDs) and an elongated flexible segment of 24 immunoglobulin (Ig) repeats. We generated a library of FLNa fragments to examine their F-actin binding to define the structural properties of FLNa that enable its various functions. We find that Ig repeats 9-15 contain an F-actin-binding domain necessary for high avidity F-actin binding. Ig repeats 16-24, where most FLNa-binding partners interact, do not bind F-actin, and thus F-actin does not compete with Ig repeat 23 ligand, FilGAP. Ig repeats 16-24 have a compact structure that suggests their unfolding may accommodate pre-stress-mediated stiffening of F-actin networks, partner binding, mechanosensing, and mechanoprotection properties of FLNa. Our results also establish the orientation of FLNa dimers in F-actin branching. Dimerization, mediated by FLNa Ig repeat 24, accounts for rigid high-angle FLNa/F-actin branching resistant to bending by thermal forces, and high avidity F-actin binding and cross-linking.
Translational Medicine Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA. fnakamura@rics.bwh.harvard.edu
Fumihiko
F
Nakamura
Teresia M
TM
Osborn
Christopher A
CA
Hartemink
John H
JH
Hartwig
Thomas P
TP
Stossel
D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D001665:Binding Sites; D045744:Cell Line, Tumor; D003285:Contractile Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000648:ultrastructure; D019281:Dimerization; D064448:Filamins; D020690:GTPase-Activating Proteins / Q000378:metabolism; D006801:Humans; D008840:Microfilament Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D050505:Mutant Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship
C497033:ARHGAP24 protein, human; D000199:Actins; D003285:Contractile Proteins; D003432:Cross-Linking Reagents; D064448:Filamins; D020690:GTPase-Activating Proteins; D008840:Microfilament Proteins; D050505:Mutant Proteins; D010446:Peptide Fragments; D021122:Protein Subunits; D011994:Recombinant Proteins