Arabidopsis Vacuolar H+-ATPase (V-ATPase) B Subunits Are Involved in Actin Cytoskeleton Remodeling via Binding to, Bundling, and Stabilizing F-actin

Abstract

Vacuolar H؉ -ATPase (V-ATPase) is a membrane-bound multisubunit enzyme complex composed of at least 14 different subunits. The complex regulates the physiological processes of a cell by controlling the acidic environment, which is necessary for certain activities and the interaction with the actin cytoskeleton through its B and C subunits in both humans and yeast. Arabidopsis V-ATPase has three B subunits (AtVAB1, AtVAB2, and AtVAB3), which share 97.27% sequence identity and have two potential actin-binding sites, indicating that these AtVABs may have crucial functions in actin cytoskeleton remodeling and plant cell development. However, their biochemical functions are poorly understood. In this study, we demonstrated that AtVABs bind to and co-localize with F-actin, bundle F-actin to form higher order structures, and stabilize actin filaments in vitro. In addition, the AtVABs also show different degrees of activities in capping the barbed ends but no nucleating activities, and these activities were not regulated by calcium. The functional similarity and differences of the AtVABs implied that they may play cooperative and distinct roles in Arabidopsis cells.

Overexpression of the Tomato Pollen Receptor Kinase LePRK1 Rewires Pollen Tube Growth to a Blebbing Mode

“…Because the LePRK1-KPP complex preferentially localized at the tip plasma membrane, and the tip cell wall is less rigid, anchoring actin bundles to the tip provides a possibility for local membrane deformation and, therefore, a way to change the morphology of this tip-growing cell. Actin bundles have been reported to link with vacuoles through vacuolar H + -ATPase subunits (Ma et al, 2012), which might account for vacuole movement toward the tip in blebbing pollen tubes.…”

The vacuolar-type H+-ATPase at a glance – more than a proton pump

“…The V-ATPase has long been known to interact with actin. This association, originally observed in osteoclasts (Lee et al, 1999;Nakamura et al, 1997), involves subunits B and C of the V 1 domain (Chen et al, 2004;Holliday et al, 2000;Ma et al, 2012;Vitavska et al, 2003). The C subunit contains 'head' and 'foot' structural motifs similar to those found in actin-binding proteins, such as gelsolin (Drory et al, 2004).…”

Arabidopsis CROLIN1, a Novel Plant Actin-binding Protein, Functions in Cross-linking and Stabilizing Actin Filaments

“…Indeed, only a small number of actin-bundling proteins have been identified in plants to date. These proteins include the conserved ABP family proteins, such as villin, fimbrin, LIM, and formin (4 -5, 8 -13, 16, 18), plant-specific ABPs, such as SCAB1 (22), and plant ABPs with bundling activities, such as the V-ATPase B subunit and ADF9 (24,25). However, the mechanism of higher order actin bundle formation remains unknown.…”

“…THRUMIN1, which contains a conserved C-terminal glutaredoxin-like domain and a putative cysteine-rich zinc-binding domain, bundles F-actin in vitro (23). V-ATPase B subunits in Arabidopsis show actin binding, bundling, and stabilizing activities in vitro (24), despite an absence of reports on actin-bundling functions for members of this protein family in animals or yeast. Interestingly, Arabidopsis actin depolymerization factor 9 (ADF9) facilitates F-actin bundling in vitro (25), and SB401, a pollen-specific protein from Solanum berthaultii, also exhibits bundling activity (26).…”