Regulatory role of the second gelsolin-like domain of Caenorhabditis elegans gelsolin-like protein 1 (GSNL-1) in its calcium-dependent conformation and actin-regulatory activities

• Type of Material: Article
• Authors: Zhongmei Liu, Emory University; Shoichiro Ono, Emory University
• Language: English
• Date: 2013-04
• Publisher: Wiley: 12 months
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2013 Wiley Periodicals, Inc.
• Final Published Version (URL): http://onlinelibrary.wiley.com/doi/10.1002/cm.21103/abstract
• Title of Journal or Parent Work: Cytoskeleton
• ISSN: 1949-3584
• Volume: 70
• Issue: 4
• Grant/Funding Information: This work was supported by a grant from the National Institute of Health (R01 AR48615) to S. O.
• Keywords: capping; mutagenesis; severing; Actin dynamics; calcium sensitivity
• Research Categories: Biology, Cell; Health Sciences, Pathology

Abstract

Caenorhabditis elegans gelsolin-like protein-1 (GSNL-1) is an unconventional member of the gelsolin family of actin-regulatory proteins. Unlike typical gelsolin-related proteins with three or six G domains, GSNL-1 has four gelsolin-like (G) domains (G1–G4) and exhibits calcium-dependent actin filament severing and capping activities. The first G domain (G1) of GSNL-1 is necessary for its actin-regulatory activities. However, how other domains in GSNL-1 participate in regulation of its functions is not understood. Here, we report biochemical evidence that the second G domain (G2) of GSNL-1 has a regulatory role in its calcium-dependent conformation and actin-regulatory activities. Comparison of the sequences of gelsolin-related proteins from various species indicates that sequences of G2 are highly conserved. Among the conserved residues in G2, we focused on D162 of GSNL-1, since equivalent residues in gelsolin and severin are part of the calcium-binding sites and is a pathogenic mutation site in human gelsolin causing familial amyloidosis, Finnish-type. The D162N mutation does not alter the inactive and fully calcium-activated states of GSNL-1 for actin filament severing (at 20 nM GSNL-1) and capping activities (at 50 nM GSNL-1). However, under these conditions, the mutant shows reduced calcium sensitivity for activation. By contrast, the D162N mutation strongly enhances susceptibility of GSNL-1 to chymotrypsin digestion only at high calcium concentrations but not at low calcium concentrations. The mutation also reduces affinity of GSNL-1 with actin monomers. These results suggest that G2 of GSNL-1 functions as a regulatory domain for its calcium-dependent actin-regulatory activities by mediating conformational changes of the GSNL-1 molecule.