chaowen bai, n/a: No financial relationships to disclose
Aims: The treatment of spinal cord injury (SCI) remains a hard issue due to its unclarified molecular mechanism. Growth factors play important roles in the regeneration of SCI. It was found that CN2097 significantly upregulated the BDNF signaling pathway and improved neural function after SCI. CN2097 has a low affinity with PSD95, and we modified the interbinding domain to obtain a new polypeptide Syn3.
Method: Cerebrospinal fluid specimens were collected from some patients with traumatic spinal cord injury and non-spinal cord injury admitted to the Second Hospital of Soochow University, and a mouse T10 spinal cord contusion model was prepared. WB, IF, Co-IP and RT-PCR were used to detect the expression of Gαi1/3, PSD95 in the injured spinal cord and Gαi1/3-PSD95 coupling. Mouse primary spinal cord neurons and SH-SY5Y cells were cultured in vitro and various methods were used to interfere with intracellular Gai1/3 expression and treated with SYN3. BDNF-TrkB signaling levels were detected using Western blotting, and the number of neurons and axon length were also observed. In the mouse SCI model, the motor function of mice was evaluated by BMS score at 1, 3 and 6 weeks after injury. The number of neurons in the injured area and the activation level of microglia cells were observed by immunofluorescence staining at 6 weeks after injury. Spinal cord tissue homogenates were collected from mice at 6 weeks of injury, and the phosphorylation levels of the relevant proteins in the BDNF-TrkB downstream signal transduction pathway were detected by Western blotting. Result: Our preliminary data found that Gαi1/3 were highly expressed in SCI, promoted neuronal regeneration and motional recovery, and activated growth factor downstream signals mediated by receptor tyrosine kinase (RTKs). Meanwhile, Gαi1/3 were the crucial signal on mediating RTKs as they could block RTKs downstream activation including Akt-mTOR and MAPK-Erk signaling. In primary neurons, Syn3-prone BDNF induced TrkB-PSD95 interactions, downstream signaling, and also increased neuronal axon growth. In a mouse SCI model, intraperitoneal injection of Syn3 improved motor function after injury; Syn3 activated the BDNF-TrkB downstream signaling pathway PI3K-Akt and promoted neuronal axon growth after SCI.
Conclusion: Gαi1/3 was highly expressed in SCI tissues and cerebrospinal fluid. As a key protein, Gαi1/3 mediates signal transduction of downstream Akt-mTOR and Erk-MAPK of BDNF-TrkB. Gαi1/3 regulates BDNF to promote the growth of spinal cord neuron axon. Syn3 combines with PSD95 to enhance Gαi1/3 signaling and promote spinal cord injury repair.
