SHANK3 regulates nuclear hnRNP K and oxidative stress-associated DNA damage signaling in neurons.

SHANK3 is a major postsynaptic scaffold protein that plays essential roles in synaptic organization and excitatory neurotransmission. Beyond its established synaptic functions, SHANK3 has been shown to translocate from excitatory synapses to the nucleus following synaptic stimulation. Here, we demonstrate that nuclear SHANK3 localization changes during the differentiation of human induced pluripotent stem cell-derived neurons, with transient enrichment at the neural rosette stage. To identify potential nuclear interaction partners, we analyzed SHANK3-associated protein complexes in HEK293T cells and selected hnRNP K, a multifunctional regulator of developmental and stress-responsive signaling pathways, as a biologically motivated follow-up candidate. Biochemical and immunocytochemical analyses further confirmed the presence of a nuclear SHANK3-hnRNP K complex in hippocampal neurons and demonstrated that SHANK3 protein levels influence the nuclear abundance of hnRNP K. To assess the functional relevance of this interaction, we examined oxidative stress-induced DNA damage-associated responses under conditions of SHANK3 deficiency. SHANK3 depletion resulted in increased accumulation of phosphorylated histone H2AX (γH2AX) following H₂O₂ treatment, indicating enhanced DNA damage. At the same time, stress-induced phosphorylation of hnRNP K and nuclear p53 levels were reduced, accompanied by increased overall Bax abundance in SHANK3-deficient neurons and an altered cleaved caspase-3 response to oxidative stress. These findings indicate impaired activation of hnRNP K-p53-associated stress-response pathways. Together, our results identify a previously unrecognized nuclear function of SHANK3 and suggest that SHANK3 contributes to hnRNP K-dependent signaling pathways involved in the cellular response to oxidative stress.