Regulation of actin cytoskeleton by Ca²⁺-binding S100 proteins

The actin cytoskeleton is a dynamic network present in all eukaryotic cells. It plays a central role in various cellular processes, including cell shape maintenance, motility, intracellular transport, and cell division. The actin cytoskeleton consists of actin filaments and a diverse array of associated actin-binding proteins (ABPs), which regulate the assembly, organization, and functions of actin filaments. S100 proteins, a family of low-molecular-weight Ca²⁺-binding proteins, have emerged as important regulators of actin filaments. They exert their regulatory functions either directly, through interactions with actin and actin-binding proteins (ABPs), or indirectly, by modulating Ca²⁺ release and thereby influencing actin-dependent contractility. This review article provides a comprehensive overview of current literature on the S100-dependent regulation of actin cytoskeleton dynamics in diverse cellular contexts. Specifically, it highlights the role of S100 proteins in modulating striated muscle contractility, actin-myosin interactions in smooth muscle, mechanotransduction, stress fiber assembly, lamellipodia formation, actin cortex organization, and structural organization of the actin cytoskeleton within synapses.