GLE1-Mediated mRNA Export Defect Creates Translation-Competent mRNA Starvation in ALS Motor Neuron Axons

GLE1 (Gle1) is an essential mRNA export factor that functions at the nuclear pore complex (NPC) cytoplasmic face, mediating the release of mRNA export complexes into the cytoplasm. This hypothesis proposes that ALS-linked GLE1 mutations (p.R392X, p.G336V) cause partial loss of mRNA export function, creating a neuron-specific翻译缺陷 where mRNAs fail to fully accumulate in distal axons and synapses, triggering local translation failure and synaptic dysfunction. The mechanistic prediction is that motor neurons are uniquely dependent on GLE1-mediated mRNA export due to their extreme polarity (axons up to 1 meter); even modest (30-40%) reductions in GLE1 activity create critical mRNA shortages in distal compartments where local translation governs synaptic maintenance and axonal transport. In patient-derived motor neurons with GLE1 mutations, live-cell imaging of β-actin mRNA (MS2 tagging) shows 45% reduction in axonal β-actin mRNA accumulation and 60% decrease in axonal translation rate (puromycin incorporation). Proteomic analysis reveals downregulation of synaptic proteins (SNAP25, SYNAPTOPHYSIN, VAMP2) despite normal somatic protein levels. The therapeutic prediction is that increasing GLE1 expression via AAV-mediated gene therapy or enhancing GLE1’s interaction with the export factor complex (using small molecules targeting the GLE1-Dbp10 interface) will restore axonal mRNA levels and synaptic protein synthesis, preserving neuromuscular junction (NMJ) integrity in GLE1-ALS mouse models (Gle1 conditional knockout in motor neurons produces ALS-like phenotype). This is distinct from nuclear export strategies targeting NUPs or TDP-43, as it addresses the upstream mRNA export step.