Mechanical Signaling Drives Tunneling Nanotubes to Preserve Cytoskeleton Tension and Lamin Integrity Against α-Synuclein-Induced Senescence in Astroglia

Abstract

Astroglia can counteract the harmful effects of -synuclein (-SYN) protofibrils and reverse premature cellular senescence by promoting tunneling nanotubes (TNTs). However, the mechanism behind this recovery is unknown. This study is the first to examine TNT-mediated mechanical stability in senescent astroglial recovery. We demonstrate that disruption of Lamin A/C in -SYN-protofibrils-treated senescent cells reduces actin-cytoskeleton stress, as measured by nucleus flatness index and isometric scale factor from quantitative microscopy. ROCK (Rho-associated kinase) inhibition, which is crucial for reducing actin-cytoskeleton tension, promotes TNTs. Small molecules like Cytochalasin-D, Nocodazole, and Jasplakinolide, which inhibit TNTs by altering actin tension other than ROCK pathway, cannot reverse senescence. RNA-sequence heatmaps reveal changes in senescence-, integrin-, and ROCK-pathway genes; STRING links these to the Hippo pathway. Experimental results show that cytosolic YAP translocation, a key regulator of Hippo pathway, is vital for TNT formation and actin-based stability in U87-MG astrocytoma and primary astrocytes. Interestingly, TNTs form between two cells with different actin tensions: one exhibits low actin tension with Hippo signaling on, while the other has higher actin tension with Hippo signaling off. The most notable observation is the high abundance of YAP inside the TNTs, along with actin. The study shows that TNTs maintain mechanical stability through Lamin A/C integrity and actin tension in -SYN-induced senescent astroglia, thereby protecting the cells, reversing senescence.