The BAR domain of the Arf GTPase-activating protein ASAP1 directly binds actin filaments

• Published in: The Journal of biological chemistry Vol. 295; no. 32; pp. 11303 - 11315
• Main Authors: Chen, Pei-Wen, Billington, Neil, Maron, Ben Y., Sload, Jeffrey A., Chinthalapudi, Krishna, Heissler, Sarah M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 07.08.2020; American Society for Biochemistry and Molecular Biology
• Subjects: actin; Actin Cytoskeleton - metabolism; actin-binding protein; Adaptor Proteins, Signal Transducing - metabolism; Animals; Arf GAP with SH3 domain ankyrin repeat and PH domain 1 (ASAP1); circular dorsal ruffles; cytoskeleton; enzyme mechanism; Enzymology; focal adhesion; invadopodia; mechanosensing; membrane dynamics; Mice; N-BAR domain; NIH 3T3 Cells; Protein Binding; protein complex; protein–protein interaction; Signal Transduction; focal adhesion; mechanosensing; cytoskeleton; protein–protein interaction; protein complex; N-BAR domain; circular dorsal ruffles; membrane dynamics; actin-binding protein; Arf GAP with SH3 domain ankyrin repeat and PH domain 1 (ASAP1); actin; invadopodia; enzyme mechanism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.RA119.009903

The Arf GTPase-activating protein (Arf GAP) with SH3 domain, ankyrin repeat and PH domain 1 (ASAP1) establishes a connection between the cell membrane and the cortical actin cytoskeleton. The formation, maintenance, and turnover of actin filaments and bundles in the actin cortex are important for cell adhesion, invasion, and migration. Here, using actin cosedimentation, polymerization, and depolymerization assays, along with total internal reflection fluorescence (TIRF), confocal, and EM analyses, we show that the N-terminal N-BAR domain of ASAP1 directly binds to F-actin. We found that ASAP1 homodimerization aligns F-actin in predominantly unipolar bundles and stabilizes them against depolymerization. Furthermore, the ASAP1 N-BAR domain moderately reduced the spontaneous polymerization of G-actin. The overexpression of the ASAP1 BAR–PH tandem domain in fibroblasts induced the formation of actin-filled projections more effectively than did full-length ASAP1. An ASAP1 construct that lacked the N-BAR domain failed to induce cellular projections. Our results suggest that ASAP1 regulates the dynamics and the formation of higher-order actin structures, possibly through direct binding to F-actin via its N-BAR domain. We propose that ASAP1 is a hub protein for dynamic protein–protein interactions in mechanosensitive structures, such as focal adhesions, invadopodia, and podosomes, that are directly implicated in oncogenic events. The effect of ASAP1 on actin dynamics puts a spotlight on its function as a central signaling molecule that regulates the dynamics of the actin cytoskeleton by transmitting signals from the plasma membrane.