Study on the Molecular Mechanisms of IGF-1-induced Turning Response at Developing Motoneuron

碩士 === 國立中山大學 === 生物科學系研究所 === 104 === The path-finding of developing neurons subject to the guidance of both attractive and repulsive cues emerge in the way to their target. The discoveries of IGF-1 (insulin-like growth factor-1) expression in the developing skeletal muscle increase with the format...

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Bibliographic Details
Main Authors: Kun-lin Yang, 楊昆霖
Other Authors: Jau-Cheng Liou
Format: Others
Language:zh-TW
Published: 2016
Online Access:http://ndltd.ncl.edu.tw/handle/95004687317253976121
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Summary:碩士 === 國立中山大學 === 生物科學系研究所 === 104 === The path-finding of developing neurons subject to the guidance of both attractive and repulsive cues emerge in the way to their target. The discoveries of IGF-1 (insulin-like growth factor-1) expression in the developing skeletal muscle increase with the formation of differentiated skeletal muscle fibers and decrease to very low adult levels during the process of synapse elimination. Although evidence suggests that insulin-like growth factor plays an important role in the development and growth of the neuromuscular synapse, the effect of IGF-1 in the guidance on the growth cone of a motoneuron remains unknown. Here we focus on the possibility and underlying molecular mechanisms of IGF-1 in the guidance of a developing neuron by using 4 to 10 hours (embryonic development) and 1-day-old (mature stage) primary cultured motoneurons of Xenopus laevis. The growth rate of developing axons was increased and the growth cones were significantly attracted toward to the direction of IGF-1 application. Pretreatment of tyrosine kinase inhibitor genistein effectively occluded growth turning response induced by IGF-1. The IGF-1-induced guidance effect was abolished when calcium was eliminated from the culture medium or bath application with the pharmacological calcium channel inhibitor cadmium, indicating that calcium influxes through voltage-activated calcium channels is required. IP3 receptor Xec hampered the IGF-1-induced turning. Treating cells with PI-3 kinase inhibitor wortmannin and with phospholipase Cγ (PLCγ) inhibitor U73122 abolished IGF-1-induced axonal attraction. Moreover, IGF-1-induced turning response is significantly occluded by store depletion-activated calcium channel (TRPC) inhibitors either SKF96369 or Gadolinium, suggesting the involvement of internal calcium store. Overall, results from our studies demonstrate IGF-1 has an attractive effect on axonal guidance and this is done via PLCγ, PI3 kinase and TRPC signaling cascades.