Actin Networking Collapse Under STAT5A Deficiency Drives Mitochondrial Dysfunction and Autocrine IFN-beta Production

Coordination between actin cytoskeleton networking and mitochondrial organization and health underpins cellular homeostasis. Here, we found STAT5A to be a pivotal transcription factor that sustains the expression of key actin regulators, including ACTN1. STAT5A, but not STAT5B deficiency dismantles F-actin architecture leading to amorphous cell shape, reduced cellular motility, and corrals mitochondria around the nucleus. This actin networking disruption impairs mitochondrial DRP1 recruitment and dynamic equilibrium, leading to ROS-associated DNA damage and cGAS-STING mediated type I IFN production. Consequently, this establishes a chronically IFN-stimulated state in neighboring cells. Conversely, overexpression of STAT5A increases actin cytoskeleton networking and promotes faster cell motility. Moreover, ectopic expression of ACTN1 in the background of STAT5A-knockout cells is sufficient to restore the actin cytoskeleton organization and mitochondrial network morphology, eliminating DNA damage and IFN-signaling. Giving the importance of actin in cellular homeostasis, our findings place actin abundance, as regulated by the STAT5A-ACTN1 axis as essential for linking cytoskeletal integrity with mitochondrial health, restraining aberrant innate immune activation. Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=172 SRC="FIGDIR/small/656095v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@1cee57aorg.highwire.dtl.DTLVardef@3be0cdorg.highwire.dtl.DTLVardef@123ed52org.highwire.dtl.DTLVardef@1b1bfcc_HPS_FORMAT_FIGEXP M_FIG C_FIG Key pointsSTAT5A deficiency disrupts cytoskeletal integrity via ACTN1 loss. The disrupted actin-cytoskeleton impairs mitochondria organization, causing ROS production and DNA damage. STAT5A knockout activates cGAS-STING signaling and IFN-{beta} production. Restoring ACTN1 rescues cytoskeleton, mitochondrial function, and immune balance.