Domain analysis of α-actinin reveals new aspects of its association with F-actin during cytokinesis

Calcium sensitivity of α-actinin is required for equatorial actin assembly during cytokinesis

“…Upon completion of cytokinesis, EFM-GFP was localized at sites of cell-cell contact. This phenotype is similar to that of wild-type α-actinin 5,8 ( Fig. 2A, α-actinin-GFP).…”

“…Our recent study has revealed that the equatorial localization of α-actinin is dependent solely on its F-actin binding and cross-linking activities. 8 It is therefore plausible that specific alterations in the affinity of α-actinin for F-actin may facilitate its delivery to and accumulation at the equator before furrow ingression and/or its subsequent dissipation from the equator during furrow ingression. However, this requires us to identify the possible modifications to α-actinin that would alter its affinity for F-actin.…”

An Equatorial Contractile Mechanism Drives Cell Elongation but not Cell Division

“…α-actininROD lacks the ability to bind actin, but has been shown to form heterodimers with endogenous α-actinin. The mutant is dominant-negative and causes the displacement of endogenous α-actinin and cytokinesis defects [65]. Expressed under the brachyury promoter, the mutant does not affect the cell division of notochord precursors and notochord convergent extension (Figure S9D).…”

“…α-actinin is crucial for the regulation of furrow progression during cytokinesis [31]. Due to its ability to cross-link actin filaments and to bind membrane proteins [30],[69], it is also involved in the positioning of the ring during cytokinesis in fission yeast [63], and expression of α-actininROD in mammalian cells causes a displacement of the actin ring and accelerated cytokinesis [65]. Similarly, in notochord cells expressing the α-actininROD mutant, equatorial localization of the contractile ring is disturbed, and the circumferential actin filaments roam over the entire basal surface (Movie S8).…”

Proper positioning of the cleavage furrow requires α-actinin to regulate the specification of different populations of microtubules

“…Several studies have revealed that centralspindlin accumulates at the tips of microtubules at the cortex of the midzone (D'Avino et al, 2006;Nishimura and Yonemura, 2006;Hu et al, 2008). After anaphase onset, aactinin accumulates at the equator in an actin-dependent manner (Low et al, 2010). a-actinin is highly dynamic at the equatorial region compared to the polar regions (Mukhina et al, 2007).…”