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Enhanced expression of 14-3-3 family members in injured motoneurons
K Namikawa1, Q Su, S Kiryu-Seo
1Department of Anatomy, Asahikawa Medical College, Nishikagura 4-5-3-11, Asahikawa 078-8510, Japan.
Abstract:
An increase in 14-3-3 mRNA expression after hypoglossal nerve injury was demonstrated by RNA finger printing using the arbitrary primed polymerase chain reaction (RAP-PCR). RAP-PCR was carried out to compare differences in mRNA expression between axotomized (6 h after the transection) and normal hypoglossal nuclei in mice. The expression of several gene fragments was increased after nerve injury; one fragment was identified as 14-3-3 which is an activator of Raf-1. Since a family of 14-3-3 genes are identified in the rat, we examined the expression of five members of the rat 14-3-3 family after injury (beta, gamma, zeta, eta and theta). Among these family members, a substantial up-regulation in mRNA expression was observed for the zeta and θ forms. Subsequent emulsion autoradiography of hybridization tissue sections revealed an increase in zeta and theta mRNA in injured motoneurons. Since 14-3-3 has the ability to dimerize and activate Raf-1, the up-regulation of 14-3-3 expression would be expected to facilitate the Ras-Erk signal pathway by Raf-1 activation. Our previous results have demonstrated that Shc, Erk1 and Mek1 mRNAs are up-regulated during nerve regeneration, whereas PKA which inhibits the Ras-Erk pathway via Raf-1 was down-regulated. Taken together, the present results suggest that enhancement in expression of molecules involved in the Ras-Erk signaling is required for peripheral nerve regeneration.
Insights
Increased expression of 14-3-3 zeta and theta mRNA in injured hypoglossal neurons suggests a role in peripheral nerve regeneration via the Ras-Erk pathway.
Area of Science:
- Neuroscience
- Molecular Biology
- Regenerative Medicine
Background:
- Peripheral nerve injury triggers complex cellular responses.
- The Ras-Erk signaling pathway is implicated in nerve regeneration.
- 14-3-3 proteins are known activators of Raf-1, a key component of this pathway.
Purpose of the Study:
- To investigate the expression of 14-3-3 mRNA following hypoglossal nerve injury.
- To identify specific 14-3-3 family members involved in the injury response.
- To explore the role of 14-3-3 in the Ras-Erk signaling pathway during nerve regeneration.
Main Methods:
- RNA fingerprinting using arbitrary primed polymerase chain reaction (RAP-PCR) to compare mRNA expression in axotomized and normal hypoglossal nuclei.
- Examination of five rat 14-3-3 family members (beta, gamma, zeta, eta, theta) post-injury.
- Emulsion autoradiography of tissue sections to localize mRNA expression in injured motoneurons.
Main Results:
- RAP-PCR revealed increased expression of several gene fragments, including 14-3-3, after hypoglossal nerve injury.
- Significant up-regulation of 14-3-3 zeta and theta mRNA was observed in injured rat hypoglossal nuclei.
- Localization studies confirmed increased zeta and theta mRNA expression within injured motoneurons.
Conclusions:
- The up-regulation of 14-3-3 zeta and theta mRNA in injured motoneurons suggests their involvement in the nerve injury response.
- Enhanced 14-3-3 expression likely facilitates the Ras-Erk signaling pathway through Raf-1 activation.
- These findings support the hypothesis that increased expression of Ras-Erk pathway molecules is crucial for peripheral nerve regeneration.