Structural Basis for Vertebrate Filamin Dimerization

Abstract

Filamins are essential in cell motility and many developmental processes. They are large actin cross linking proteins that contain actin binding domains in their N termini and a long rod region constructed from 24 tandem Ig domains. Dimerization is crucial for the actin crosslinking function of filamins and requires the most C-terminal Ig domain. We describe here the crystal structure of this 24th Ig domain (Ig24) of human filamin C and show how it mediates dimerization. The dimer interface is novel and quite different to that seen in the Dictyostelium discoideum filamin analog. The sequence signature of the dimerization interface suggests that the C-terminal domains of all vertebrate filamins share the same dimerization mechanism. Furthermore, we show that point mutations in the dimerization interface disrupt the dimer and that the dissociation constant for recombinant Ig24 is in the micromolar range.

Postmortem protein degradation is a key contributor to fresh pork loin tenderness

“…Filamin interacts with F-actin and functions to aid in the stabilization of the muscle cytoskeleton and helps with transmitting chemical signals at the Z-line (Wang and Singer, 1977;Clark et al, 2002). The dimerization of filamin is essential for the interaction of filamin with F-actin (Pudas et al, 2005). Extreme proteolytic differences in the degradation of filamin were observed between classification groups where low star probe samples had significantly less intact filamin.…”

“…These results demonstrate that the removal of the 109 AA from the carboxy-terminal end in degraded filamin could be the first cleavage of intact filamin observed in postmortem muscle. The carboxy-terminal end of filamin is responsible for dimerization and interaction with other cellular components such as β integrins, androgen receptors, and portions of potassium channels (Stossel et al, 2001;Feng and Walsh, 2004;Pudas et al, 2005;Nakamura et al, 2011). Therefore, the loss of this carboxy-terminal end causes the loss of ability for this protein to form dimers and impairs anchoring to the Z-line and could impair the structural integrity of the internal architecture of the muscle cell.…”

Organ-wide profiling in mouse reveals high editing levels of Filamin B mRNA in the musculoskeletal system

“…FLNA and FLNB are built up of an N-terminal actin-binding domain which is followed by 24 immunoglobulin (Ig)-like repeats, interrupted by two hinge regions. Homo- and heterodimerization of FLNA and FLNB occur via their carboxyl-terminal Ig-like repeat [14]. A recent study showed that FLNA and FLNB expression is reciprocally regulated with opposing effects on actin dynamics and cell spreading [15].…”

A novel interaction between FlnA and Syk regulates platelet ITAM-mediated receptor signaling and function

“…The most abundant isoform of the family, FlnA, is encoded by the X chromosome in humans and mice (Feng and Walsh, 2004;Robertson, 2005). FlnA is composed of an N-terminal actin-binding domain followed by 24 Ig repeats, the C-terminal of which mediates their dimerization (Pudas et al, 2005). Human melanoma cells that lack FlnA have poor motility and continuous membrane blebbing (Cunningham et al, 1992;Flanagan et al, 2001).…”