ELAVL Proteins, miRNA Fate, and Extracellular RNA Communication in Brain Aging and Neurodegeneration.

Brain aging is accompanied by changes in RNA homeostasis, intercellular communication, and stress responses that increase vulnerability to neurodegenerative diseases. The neuronal protein HuD (ELAVL4) and the broadly expressed HuR (ELAVL1) regulate RNA stability, translation, localization, and selected microRNA (miRNA) activities. Recent studies further show that HuD can promote export of let-7a and miR-125b during differentiation of PC12 cells, whereas HuR can bind selected miRNAs and engage endosomal export or intracellular buffering mechanisms in other cellular contexts. These observations support an emerging ELAVL-miRNA-extracellular vesicle (EV) framework. They do not yet establish an integrated HuD/HuR-dependent neuron-glia pathway in aging human brain or Alzheimer's disease (AD). We therefore distinguish direct, model-specific findings from hypotheses that age-, amyloid-, or inflammation-associated changes in ELAVL abundance, localization, or RNA binding could redistribute miRNAs between intracellular pools and EVs. Testing this framework in primary human neural cells, induced pluripotent stem cell-derived systems, organoids, and in vivo models may identify context-specific mechanisms and therapeutic opportunities.