Ca2+ and calmodulin regulate the binding of filamin A to actin filaments.
Filamin A (FLNa) cross-links actin filaments (F-actin) into three-dimensional gels in cells, attaches F-actin to membrane proteins, and is a scaffold that collects numerous and diverse proteins. We report that Ca(2+)-calmodulin binds the actin-binding domain (ABD) of FLNa and dissociates FLNa from F-actin, thereby dissolving FLNa.F-actin gels. The FLNa ABD has two calponin homology domains (CH1 and CH2) separated by a linker. Recombinant CH1 but neither FLNa nor its ABD binds Ca(2+)-calmodulin in the absence of F-actin. Extending recombinant CH1 to include the negatively charged region linker domain makes it, like full-length FLNa, unable to bind Ca(2+)-calmodulin. Ca(2+)-calmodulin does, however, dissociate the FLNa ABD from F-actin provided that the CH2 domain is present. These findings identify the first evidence for direct regulation of FLNa, implicating a mechanism whereby Ca(2+)-calmodulin selectively targets the FLNa.F-actin complex.
Nakamura
Fumihiko
F
Hematology Division, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115, USA.
Hartwig
John H
JH
Stossel
Thomas P
TP
Szymanski
Pawel T
PT
D000199:Actins / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry; D002147:Calmodulin / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003285:Contractile Proteins / Q000737:chemistry*; D030562:Databases, Protein; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D064448:Filamins; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D008840:Microfilament Proteins / Q000737:chemistry*; D008954:Models, Biological; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D000096985:Calponins
D000199:Actins; D002118:Calcium; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D003285:Contractile Proteins; D004533:Egtazic Acid; D064448:Filamins; D005982:Glutathione Transferase; D008840:Microfilament Proteins; D011994:Recombinant Proteins; D000096985:Calponins