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_5 label "Selventa" provenance.
_4 value "Recently, a third isoform (gelsolin-3) has been described [9]. Gelsolin-3 is cytoplasmic and is characterized by 11 additional residues at the N-terminus. Gelsolin-3 is expressed in oligodendrocytes and mainly in the brain, lungs and testis [9], but its specific function is still unknown. Gelsolin contains six gelsolin-like (G) domains and was first described as a protein able to bind and sever actin filaments, and to control polymerization of barbed ends. Furthermore, this protein also initiates formation of actin filaments by binding two monomeric actin molecules. Gelsolin activity is regulated by Ca2+, intracellular pH, phosphoinositides and tyrosine phosphorylation. Crystallographic studies of gelsolin complexed with its substrate have been recently performed [10-14]. Results have been reviewed in [15] and will not be discussed here. The other gelsolin superfamily members; villin, advillin, supervillin and flightless, have additional domains beyond the sixfold repeat. Villin has been demonstrated to participate in cytoskeleton remodeling in response to various stimuli in the intestine [16]. Flightless is the only member of gelsolin superfamily that has been shown to be essential for mouse development [17]. Among all of the proteins forming the gelsolin superfamily, adseverin (also named scinderin) is the one that shares the highest degree of homology with gelsolin. Indeed, adseverin shares 60% amino acid homology with gelsolin [18], and displays Ca2+-regulated actin filament severing activity. As compared to gelsolin, adseverin has a more restricted expression. Adseverin was first discovered in platelets, megakaryocytes and chromaffin cells [19]. This protein is present in all secretory cells and is involved in actin cytoskeleton remodeling occurring during exocytosis [19-22]. With flightless [23] and supervillin [24, 25], capG (also named gCap39, Mbh1 or macrophage capping protein) is the only other protein of gelsolin family sharing a nuclear localization [26, 27]. CapG only contains three G domains and can bind and cap actin filaments but cannot sever them [28]. CapG has been demonstrated to play an important role as a mediator of endothelial cell response to mechanical forces [29]. Actin filament remodeling In the absence of Ca2+, gelsolin exists in a globular conformation. Crystal structure analysis has revealed the existence of a C-terminal tail ('latch helix') which is in close contact with the actin binding region of G2 domain. The importance of this latch helix in Ca2+ regulation of gelsolin-actin interactions was first revealed by the demonstration that a lack of 20 residues in the C-terminus tail abrogates the Ca2+ regulation of actin binding [30, 31]. The latch hypothesis suggests that Ca2+ binding to G6 domain induces a first conformational change in the gelsolin structure, releasing tail latch inhibition of G2 binding to actin. G2 binding to actin directs the G1 domain to its actin binding site. In the absence of Ca2+, G4 and G6 domains are close together. Ca2+ opens this structure, and the G6 domain forms new contacts with the G5 domain, releasing the G4 domain, which now can form a Ca2+ binding domain coordinated by actin and G4 itself. The actin binding sites at the N- and C-terminal parts bind to two adjacent actin filaments. Slowly, gelsolin severs the two actin filaments, remaining bound to the newly formed actin + end (barbed end) of one of the two shorter filaments (fig. 1B)." provenance.
_4 wasQuotedFrom 15526166 provenance.
assertion hadPrimarySource 15526166 provenance.
large_corpus.bel title "BEL Framework Large Corpus Document" provenance.
large_corpus.bel description "Approximately 61,000 statements." provenance.
assertion wasDerivedFrom large_corpus.bel provenance.
assertion wasDerivedFrom _4 provenance.
large_corpus.bel authoredBy _5 provenance.
large_corpus.bel version "1.4" provenance.