LPPR1/LPPR5蛋白复合体通过mTOR-rpS6通路促进小鼠脊髓损伤后轴突再生的作用研究

LPPR1和LPPR5是脑特异磷脂磷酸水解酶相关蛋白家族成员，分别被报道可促进丝状伪足和神经突起生长，LPPR1还可促进脊髓损伤轴突再生，但其机制仍不明确。我们前期发现LPPR1可与LPPR5形成蛋白复合体；与mTOR存在相互作用；若二者共表达可使轴突再生关键信号通路mTOR下游rpS6磷酸化增加；还发现LPPR1可克服轴突生长抑制分子CSPGs的作用，促进神经元突起生长。由此我们提出假设：LPPR1/LPPR5功能性蛋白复合体可通过激活mTOR-rpS6信号通路促进脊髓损伤后轴突再生和环路重塑。本项目拟在原代皮层神经元和小鼠脊髓损伤模型中，采用过表达并结合信号通路阻断等策略，从组织学、电生理、行为学、分子机制等层面获得LPPR1/5复合体激活mTOR通路，促进脊髓损伤轴突再生、神经环路重塑和功能恢复的直接证据，为确立LPPR作为脊髓损伤修复新靶点提供科学依据。

LPPR1 and LPPR5 belong to a family of brain-specific lipid phosphate phosphatase related proteins, both of which can induce filopodia formation and promote neurite outgrowth. LPPR1 has also recently been reported to be able to promote axonal regeneration after spinal cord injury. However, the underlying mechanisms of action remain largely unknown. Previously, using co-immunoprecipitation coupled to mass spectrometry to identify the potential binding partners of LPPR1 in Neuro2A cells, we identified the interaction of LPPR1 with its family members including LPPR5, we also found association between mTOR and LPPR1. Moreover, co-expressing LPPR1 and LPPR5 resulted in an increase in the phosphorylation of mTOR downstream target ribosomal protein S6 (rpS6). Overexpressing LPPR1 also overcomes the inhibitory effect of CSPGs, a class of axon growth inhibitors. Based on these findings, we hypothesize that LPPR1 forms functional complex with LPPR5, which may overcome the CSPG inhibition and promote axonal regeneration through activating mTOR-rpS6 pathway. In this proposal, we aimed to test this hypothesis both in primary cortical neuron cultures and in a mouse dorsal spinal cord hemisection model. This work would provide new insight into the role of LPPR1/LPPR5 complex in axonal regeneration, which may serve as a novel target for the treatment of spinal cord injury.