title: P75 and phosphorylated c-Jun are differentially regulated in spinal motoneurons following axotomy in rats.
abstract: The neurotrophin receptor (p75) activates the c-Jun N-terminal kinase (JNK) pathway. Activation of JNK and its substrate c-Jun can cause apoptosis. Here we evaluate the role of p75 in spinal motoneurons by comparing immunoreactivity for p75 and phosphorylated c-Jun (p-c-Jun), the production of JNK activation in axotomized motoneurons in postnatal day (PN)1, PN7, PN14 and adult rats. Intensive p-c-Jun was induced in axotomized motoneurons in PN1 and PN7. In PN14, p-c-Jun expression was sharply reduced after the same injury. The decreased expression of p-c-Jun at this age coincided with a developmental switch of re-expression of p75 in axotomized cells. In adult animals, no p-c-Jun but intensive p75 was detected in axotomized motoneurons. These results indicate differential expression or turnover of phosphorylation of c-Jun and p75 in immature versus mature spinal motoneurons in response to axonal injury. The non-co-occurrence of p75 and p-c-Jun in injured motoneurons indicated that p75 may not activate JNK pathway, suggesting that the p75 may not be involved in cell death in axotomized motoneurons.
authors.affiliation: School of Chinese Medicine, Faculty of Science, the Chinese University of Hong Kong, Shatin, N.T, Hong Kong Special Administrative Region, China.
authors.forename: Qiuju
authors.initials: Q
authors.lastname: Yuan
authors.affiliation: Department of Anatomy, Li Ka Shing Faculty of Medicine, the University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China.
authors.forename: Huanxing
authors.initials: H
authors.lastname: Su
authors.affiliation: Department of Anatomy, Li Ka Shing Faculty of Medicine, the University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China ; Joint Laboratory for Brain Function and Health (BFAH), Jinan University and the University of Hong Kong, Guangzhou, China.
authors.forename: Wutian
authors.initials: W
authors.lastname: Wu
authors.affiliation: School of Chinese Medicine, Faculty of Science, the Chinese University of Hong Kong, Shatin, N.T, Hong Kong Special Administrative Region, China.
authors.forename: Zhi-Xiu
authors.initials: ZX
authors.lastname: Lin
keywords: adult; apoptosis; axonal regeneration; axotomy; c-Jun N-terminal kinase; motoneuron; neonatal; nerve growth factor receptor; spinal cord; transcription factor