Stress induces cytoprotective TDP-43 nuclear bodies through lncRNA NEAT1-promoted phase separation

Abstract

Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=121 SRC="FIGDIR/small/802058v2_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@1963bb9org.highwire.dtl.DTLVardef@2b00eforg.highwire.dtl.DTLVardef@14a7a2forg.highwire.dtl.DTLVardef@9ba973_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights(Up to four bullet points. The length of each highlight cannot exceed 85 characters, including spaces) O_LIStress induces phase-separated TDP-43 NBs to alleviate cytotoxicity C_LIO_LIThe two RRMs interact with different RNAs and act distinctly in the assembly of TDP-43 NBs C_LIO_LILncRNA NEAT1 promotes TDP-43 LLPS and is upregulated in stressed neurons C_LIO_LIThe ALS-causing D169G mutation is NB-defective and forms pTDP-43 cytoplasmic foci C_LI SummaryDespite the prominent role of TDP-43 in neurodegeneration, its physiological and pathological functions are not fully understood. Here, we report an unexpected function of TDP-43 in the formation of dynamic, reversible, liquid droplet-like nuclear bodies (NBs) in response to stress. Formation of NBs alleviates TDP-43-mediated cytotoxicity in mammalian cells and fly neurons. Super-resolution microscopy reveals a "core-shell" organization of TDP-43 NBs, antagonistically maintained by the two RRMs. TDP-43 NBs are partially colocalized with nuclear paraspeckles, whose scaffolding lncRNA NEAT1 is dramatically upregulated in stressed neurons. Moreover, increase of NEAT1 promotes TDP-43 liquid-liquid phase separation (LLPS) in vitro. Finally, we uncover that the ALS-associated mutation D169G impairs the NEAT1-mediated TDP-43 LLPS and NB assembly, causing excessive cytoplasmic translocation of TDP-43 to form stress granules that become phosphorylated TDP-43 cytoplasmic foci upon prolonged stress. Together, our findings suggest a stress-mitigating role and mechanism of TDP-43 NBs, whose dysfunction may be involved in ALS pathogenesis.