Flexible Structure of Peptide-Bound Filamin A Mechanosensor Domain Pair 20-21.

Filamins (FLNs) are large, multidomain actin cross-linking proteins with diverse functions. Besides regulating the actin cytoskeleton, they serve as important links between the extracellular matrix and the cytoskeleton by binding cell surface receptors, functioning as scaffolds for signaling proteins, and binding several other cytoskeletal proteins that regulate cell adhesion dynamics. Structurally, FLNs are formed of an amino terminal actin-binding domain followed by 24 immunoglobulin-like domains (IgFLNs). Recent studies have demonstrated that myosin-mediated contractile forces can reveal hidden protein binding sites in the domain pairs IgFLNa18-19 and 20-21, enabling FLNs to transduce me…

Structural studies on filamin domain interactions

Determination of a conformational change in filamin A with Förster resonance energy transfer

Filamins are large rod-like proteins that cross-link actin filaments into three-dimensional networks. They also bind to a plethora of proteins with distinct functions showing that they have a versatile role in cells. Functional filamins are dimers consisting of an N-terminal actin binding domain followed by 24 immunoglobulin-like domains. The most C-terminal domains mediate the dimerization. Two hinge regions are located between the domains 15 and 16 and 23 and 24, respectively, and produce structural flexibility that is essential for the protein function. The domains 18-19 and 20-21 are folded in a pairwise manner in which the first β strands of the even numbered domains are folded along w…

A novel structural unit in the N-terminal region of filamins.

Immunoglobulin-like (Ig) domains are a widely expanded superfamily that act as interaction motifs or as structural spacers in multidomain proteins. Vertebrate filamins (FLNs), which are multifunctional actin-binding proteins, consist of 24 Ig domains. We have recently discovered that in the C-terminal rod 2 region of FLN, Ig domains interact with each other forming functional domain pairs, where the interaction with signaling and transmembrane proteins is mechanically regulated by weak actomyosin contraction forces. Here, we investigated if there are similar inter-domain interactions around domain 4 in the N-terminal rod 1 region of FLN. Protein crystal structures revealed a new type of dom…

Skeletal Dysplasia Mutations Effect on Human Filamins’ Structure and Mechanosensing

AbstractCells’ ability to sense mechanical cues in their environment is crucial for fundamental cellular processes, leading defects in mechanosensing to be linked to many diseases. The actin cross-linking protein Filamin has an important role in the conversion of mechanical forces into biochemical signals. Here, we reveal how mutations in Filamin genes known to cause Larsen syndrome and Frontometaphyseal dysplasia can affect the structure and therefore function of Filamin domains 16 and 17. Employing X-ray crystallography, the structure of these domains was first solved for the human Filamin B. The interaction seen between domains 16 and 17 is broken by shear force as revealed by steered mo…