Actin-depolymerizing factor homology domain: a conserved fold performing diverse roles in cytoskeletal dynamics

Actin filaments are essential for cellular movement and shape changes. Their dynamics are tightly controlled by actin-binding proteins. While much is known about actin's role in processes like migration and division, the precise mechanisms of regulatory proteins remain unclear. The ADF-H domain is a conserved structural motif found in several actin-related proteins. Despite shared structural features, these proteins perform distinct functions. Some promote filament disassembly, others inhibit assembly, and some regulate filament branching. The lack of complete functional understanding for all ADF-H domain proteins creates a gap in the field. Researchers have yet to fully map how these proteins interact with actin and other complexes. This uncertainty motivates further investigation into their biochemical roles and regulation.

This review article aims to clarify the biochemical functions and cellular roles of ADF-H domain proteins. It focuses on five distinct classes of these proteins and their interactions with actin structures. The goal is to synthesize current knowledge about how each group contributes to cytoskeletal dynamics. The study also seeks to identify gaps in understanding, particularly for proteins like coactosin. By comparing the known functions of ADF-H proteins, the authors hope to highlight differences in their mechanisms. The review also emphasizes the need for more detailed studies on less-characterized proteins. Understanding these roles could lead to better insights into actin-dependent cellular processes. The paper serves as a resource for researchers studying cytoskeletal regulation.

The authors use a review approach to compile and analyze existing literature on ADF-H domain proteins. They categorize the proteins into five groups based on structural and functional similarities. For each group, they summarize known biochemical activities and cellular roles. The review includes comparisons of how each protein interacts with actin or the Arp2/3 complex. The authors also highlight areas where functional data is incomplete or conflicting. They reference prior studies to establish a baseline of known mechanisms. The synthesis is based on published findings rather than new experiments. The approach allows for a comprehensive overview of current understanding.

ADF-H domain proteins are grouped into five classes with distinct functions. ADF/cofilin accelerates disassembly of older actin filaments. Twinfilin inhibits filament assembly by binding monomers and barbed ends. GMF regulates the Arp2/3 complex without directly interacting with actin. Abp1 and drebrin are multidomain proteins that influence actin-dependent processes. Coactosin’s role remains unclear despite structural similarity to other ADF-H proteins. The review highlights differences in how each group regulates actin dynamics. Some proteins promote disassembly, while others inhibit assembly or modulate branching. These findings suggest that ADF-H domain proteins are functionally diverse despite shared structural features.

The authors synthesize evidence to show that ADF-H domain proteins perform diverse roles in actin regulation. Despite structural homology, each group has unique biochemical functions. ADF/cofilin and twinfilin regulate filament turnover, while GMF acts on the Arp2/3 complex. Abp1 and drebrin have broader regulatory roles. Coactosin remains poorly characterized. The review emphasizes the need for further studies to clarify the full range of ADF-H protein functions. It also highlights the importance of understanding how these proteins interact with actin and other complexes. The authors suggest that future work should focus on less-studied proteins like coactosin. The synthesis provides a framework for interpreting how ADF-H domains contribute to cytoskeletal dynamics.