MIP-8, a Morchella importuna-derived peptide, protects against 6-OHDA-induced neurotoxicity via AKT signaling modulation

Natural bioactive peptides from edible and medicinal fungi are emerging as promising candidates for neuroprotection, but the activities and mechanisms of Morchella importuna-derived peptides remain poorly defined. Here, we identified a morel-derived octapeptide, MIP-8, and investigated its protective effects against 6-hydroxydopamine (6-OHDA)-induced neuronal injury. In NGF-differentiated PC12 cells, MIP-8 significantly improved cell viability, reduced intracellular reactive oxygen species and malondialdehyde accumulation, restored superoxide dismutase, catalase, and glutathione peroxidase activities, and attenuated apoptosis, as evidenced by Annexin V-FITC/PI flow cytometry, TUNEL staining, restoration of the Bcl-2/Bax mRNA expression ratio, and reduced caspase-9/-3 activities. Integrated transcriptomic and TMT-based proteomic analyses revealed broad MIP-8-associated molecular remodeling involving metabolic regulation, oxidative stress responses, protein processing/proteostasis, energy metabolism, and cell signaling-related processes. Further proteomic screening identified multiple PI3K-AKT-mTOR-related proteins with altered abundance after MIP-8 treatment, providing a rationale for pathway validation. Western blotting showed that MIP-8 restored the phosphorylation of PI3K, AKT, and mTOR under neurotoxic stress. Molecular docking predicted a favorable interaction between MIP-8 and AKT1, and surface plasmon resonance supported MIP-8 binding to AKT1/protein kinase B alpha in a purified protein system with micromolar affinity. Pharmacological inhibition of AKT with MK-2206 attenuated MIP-8-mediated cytoprotection and suppressed AKT-mTOR pathway reactivation in both PC12 and SH-SY5Y cells. Collectively, these findings identify MIP-8 as a Morchella importuna-derived neuroprotective peptide and suggest that its protective effect is associated, at least partly, with AKT signaling modulation, providing a basis for future pharmacokinetic and in vivo efficacy studies.