INVESTIGATION OF COFILIN-ACTIN RODS ON CYTOSKELETAL DYNAMICS AND MITOCHONDRIAL APOPTOSIS

Abstract

The actin-binding protein cofilin plays a central role in regulating cytoskeletal dynamics through the severing and depolymerization of actin filaments. Dysregulation of cofilin activity has been implicated in neurodegenerative diseases, where stable cofilin–actin rods disrupt normal cellular function. Understanding the molecular determinants that regulate cofilin–actin interactions is therefore important for both normal cytoskeletal remodeling and disease-associated rod formation. This study investigates how mutations at residue 119 of cofilin influence actin dynamics and rod formation, with a focus on the gain-of-function mutant S119W. Using live-cell imaging, biochemical assays, and neuronal morphology analysis, the effects of multiple residue 119 substitutions were characterized. Aromatic substitutions at this position enhanced rod formation, while phosphomimetic substitutions abolished this phenotype, highlighting the importance of residue identity at this site. Biochemical assays further supported that S119W exhibits reduced depolymerization activity while permitting continued filament accumulation. Cells containing large numbers of S119W-induced rods also showed increased resistance to apoptosis, suggesting that rod stabilization can influence cellular stress responses. In neurons, S119W expression altered dendritic spine morphology and cofilin mobility. Together, these findings identify residue 119 as an important regulator of cofilin function and provide insight into how altered cofilin–actin interactions may contribute to cytoskeletal dysfunction in disease.