Navakkode, S. | bioRxiv Science

bioRxiv2020

LOCAL REGULATION AND FUNCTION OF IMPORTIN-β1 DURING TRANSCRIPTION-DEPENDENT PLASTICITY

Activity-dependent transcription is critical for the encoding of long-term memories. Regulated nuclear entry of soluble proteins is one method to relay synaptic signals to the nucleus to couple neuronal excitation with transcription. To date, the role of importin-{beta}1 in nuclear shuttling of proteins during activity-dependent transcription has always been inferred but not directly investigated. In this study, we demonstrate activity-dependent nuclear accumulation of importin-{beta}1 from the soma and the synapto-dendritic compartments. Importantly, inhibition of importin-{beta}1 mediated nuclear import during synaptic stimulation impairs long-term plasticity. We show evidence that importin-{beta}1 mRNA-ribosome complex is distributed throughout the synapto-dendritic compartment and synaptic stimulation induces importin-{beta}1 local protein synthesis. Finally, we identified candidate proteins that associate with importin-{beta}1 at the synapse and characterize NDRG1 as an importin-{beta}1 interactor that undergoes activity-dependent translocation into the nucleus. Collectively, our results highlight the crucial role of importin-{beta}1 in the nuclear import of soluble proteins during long-term plasticity.

neuroscience↗

bioRxiv2020

mTOR S-nitrosylation inhibits autophagy and lysosomal proteolysis

Mammalian Target of Rapamycin (mTOR) is a master regulator of autophagy and lysosomes, and its downstream kinase-dependent pathways have been extensively characterized. Here, we report an unexpected kinase-independent regulation of autophagy and lysosomes by S-nitrosylation at Cys423 position of mTOR that resulted in suppression of VPS34 and PIKfyve-dependent phosphoinositide synthesis. Physiologically, S-nitrosylation of mTOR reduced basal lysosomal proteolysis via nitric oxide synthase (NOS)-mediated synthesis of NO from lysosomal arginine precursor, a marker of cellular nutrition status. Significantly, we found increased lysosomal NOS-mTOR complexes in APP-PS1 Alzheimers disease (AD) murine model, and increased mTOR S-nitrosylation in AD patient-derived fibroblasts. Lastly, we demonstrated that pharmacological inhibition of NOS or overexpression of mTORCys423Ala mutant reversed lysosomal and autophagic dysfunction in AD patient-derived fibroblasts, suggesting novel therapeutic strategies for autophagosome-lysosomal activation.

cell biology↗