Sreenivas BK, A. | bioRxiv Science

bioRxiv2026

α-Synuclein Triggers Intercellular Nanotubes Formation to Prevent Apoptosis in Astroglia by Promoting Stemness

Astrocytes play a significant role in neuroprotection by internalizing neurodegenerative aggregates and facilitating their degradation. Recent studies indicate that -Synuclein (-SYN) protofibrils promote the transfer of pathogenic aggregates and dysfunctional mitochondria between astroglia via tunneling nanotubes (TNTs), which enhances cell survival and resistance to apoptosis. However, the underlying mechanism of TNT-driven apoptosis resistance remains unclear. We find that -SYN protofibrils induce aberrant mitochondria with decreased membrane potential ({Psi}m) and promote dynamic actin remodeling by relocating phosphorylated focal adhesion kinase (pFAK) to the nucleus, which triggers TNT formation in human astrocytoma cell lines and primary murine astrocytes. The important novel finding of this study is that pFAK in the nucleus co-localizes with Nanog, a crucial transcription factor for preserving stemness, and the interaction between pFAK and Nanog is critical for promoting p53 degradation via Mdm2-mediated ubiquitination and upregulating autophagy, thereby supporting the survival of astroglia exposed to toxic -SYN protofibrils. ROCK inhibitor y-27632 also drives TNT-formation via pFAK translocation to the nucleus, colocalizes with Nanog, and enhances stemness-related gene expression. Inhibiting TNT with the actin depolymerizing agent cytochalasin-D prevents pFAK co-localization with Nanog in the nucleus and fails to protect cells from -SYN-induced apoptosis. Nanog knockdown does not degrade p53 and hinders cell rescue from apoptosis. Furthermore, these transient TNTs transfer mitochondria to adjacent cells, potentially helping maintain metabolic stability. This study reveals that the TNT formation pathway promotes pFAK-Nanog interaction in the nucleus, leading to p53 degradation, which protects astroglia against -SYN proteotoxicity and prevents apoptosis. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=194 SRC="FIGDIR/small/727344v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@18d8675org.highwire.dtl.DTLVardef@76a383org.highwire.dtl.DTLVardef@e92202org.highwire.dtl.DTLVardef@1b7ee4b_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2026

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

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. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=163 SRC="FIGDIR/small/711517v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@192307dorg.highwire.dtl.DTLVardef@ad8b75org.highwire.dtl.DTLVardef@19ece78org.highwire.dtl.DTLVardef@1056395_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗