Unveiling the role of PSD95 phosphorylation after traumatic brain injury: insights from phosphoproteomic analysis.

BACKGROUND: Traumatic brain injury (TBI) is a global public health problem. Pathophysiology of TBI remains unclear. Thus, methods of TBI treatment are limited. Phosphorylation plays a vital role in many neurological diseases, including TBI. As an emerging technique, phosphoproteomic has been widely applied in many fields. METHODS: Rats were subjected to controlled cortical impact (CCI) or divided to sham group. Protein was extracted from cortex, digested and labeled by iTRAQ. After undergoing mass spectrometry (MS), differential expressed phosphorylated sites (DEPSs) were identified, and proteins of these DEPSs were also listed. PSD95 was chosen as a target protein for further research. ZL006 was used to treat TBI rats. Nissl staining was applied to assess lesion volume, apoptosis was evaluated by TUNEL immunofluorescence staining, and PSD95 phosphorylation was further validated by Western blot. RESULTS: A total of 2753 phosphorylation sites across 1001 proteins were identified. A total of 221 DEPSs were identified. Phosphorylation of PSD95 at serine 417 and 418 were significantly upregulated after TBI. PSD95 had most interactions with other differential expressed phosphorylated proteins (DEPPs). Following ZL006 treatment, brain lesion volume and apoptotic rate were significantly reduced, and phosphorylation of PSD95 at Ser418 was decreased. CONCLUSIONS: After TBI, PSD95 was significantly phosphorylated at Ser417 and Ser418. ZL006 markedly reduced brain lesion volume and apoptotic rate and suppressed the phosphorylation of PSD95 at Ser418.