Putative Coiled-Coil Domain-Dependent Autoinhibition and Alternative Splicing Determine SHTN1’s Actin-Binding Activity

• Published in: Journal of molecular biology Vol. 432; no. 14; pp. 4154 - 4166
• Main Authors: Ergin, Volkan, Zheng, Sika
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 26.06.2020
• Subjects: actin; Actin Cytoskeleton - genetics; actin-binding proteins; Actins - genetics; alternative splicing; Alternative Splicing - genetics; Amino Acid Sequence - genetics; Animals; autoinhibition; Cytoskeletal Proteins - genetics; Drosophila melanogaster - genetics; Humans; Microfilament Proteins - genetics; microfilaments; morphogenesis; nuclear localization signals; Protein Binding - genetics; Protein Domains - genetics; Sequence Homology, Amino Acid; shootin1; WH2 domain; WH2; alternative splicing; CCD; FAB; actin-binding proteins; shootin1; WH2 domain; SHTN1L; autoinhibition; ABP; PRR; SHTN1S; NLS
• ISSN: 0022-2836; 1089-8638; 1089-8638
• DOI: 10.1016/j.jmb.2020.04.025

The actin cytoskeleton plays a pivotal role in cell development, morphogenesis, and other cellular functions. Precise control of actin dynamics requires actin-binding proteins. Here, we characterize multifarious regulation of SHTN1 (shootin1) and show that, unlike known actin-binding proteins, SHTN1’s actin binding activity is intrinsically inhibited by a putative coiled-coil domain (CCD) and the autoinhibition is overcome by alternative splicing regulation. We found SHTN1 contains a noncanonical WH2 domain and an upstream proline-rich region (PRR) that by themselves are sufficient for actin interaction. Alternative splicing of Shtn1 at the C terminus and downstream of the WH2-PRR domain produces a long (SHTN1L or shootin1b) and a short (SHTN1S or shootin1a) isoform, which both contain the described PRR and WH2 domains. However, SHTN1S does not interact with actin due to inhibition mediated by an N-terminal CCD. A SHTN1L-specific C-terminal motif counters the intramolecular inhibition and allows SHNT1L to bind actin. A nuclear localization signal is embedded between PRR and WH2 and is subject to similar autoinhibition. SHTN1 would be the first WH2-containing molecule that adopts CCD-dependent autoinhibition and alternative splicing-dependent actin interaction. [Display omitted] •SHTN1 has a noncanonical WH2 domain for actin binding.•The SHTN1 short isoform exhibits no actin-binding activity.•A putative coiled-coil domain autoinhibits actin-binding activity of SHTN1 isoforms.•SHTN1 uses alternative splicing instead of a third protein to relieve autoinhibition.