Temporal-spatial expression of presenilin 1 and the production of amyloid-β after acute spinal cord injury in adult rat

Regulated intramembrane proteolysis (RIP) is one of the signaling pathways mediating information transfer from the extracellular to the intracellular domain. gamma-Secretase is an aspartyl protease of the RIP that cleaves the intramembrane region of type I integral membrane proteins, such as amyloid precursor protein (APP). Presenilin 1 (PS1) is the catalytic subunit of gamma-secretase and PSI mutations cause Alzheimer's disease, spastic paraplegia and spinal cord atrophy. The biological function of PSI in the spinal cord has not been fully elucidated. Thus, to clarify the involvement of RIP in spinal cord injury, we examined the expression of PS1, APP and amyloid-beta protein (A beta) following rat spinal cord hemisection. Western blot analysis showed that PSI, APP and A beta levels increased I day after spinal cord hemisection. Immunohistochemistry showed an increased number of PS1 immunopositive cells about 1 mm from the lesion site. PS1,APP and A beta double staining with cell-type specific markers showed colocalization of PS1 with axons in the white matter of the lesioned side. These findings suggest that RIP signaling occurs following rat spinal cord injury. In the future, the control of RIP may offer a new strategy for the treatment of spinal cord injury. (C) 2009 Elsevier Ltd. All rights reserved.