Axonal elongation triggered by stimulus-induced local translation of a polarity complex protein

Department of Pharmacology, Weill Medical College, Cornell University, NY 10065, USA.
Nature Cell Biology (Impact Factor: 19.68). 09/2009; 11(8):1024-30. DOI: 10.1038/ncb1916
Source: PubMed


During development, axon growth rates are precisely regulated to provide temporal control over pathfinding. The precise temporal regulation of axonal growth is a key step in the formation of functional synapses and the proper patterning of the nervous system. The rate of axonal elongation is increased by factors such as netrin-1 and nerve growth factor (NGF), which stimulate axon outgrowth using incompletely defined pathways. To clarify the mechanism of netrin-1- and NGF-stimulated axon growth, we explored the role of local protein translation. We found that intra-axonal protein translation is required for stimulated, but not basal, axon outgrowth. To identify the mechanism of translation-dependent outgrowth, we examined the PAR complex, a cytoskeleton regulator. We found that the PAR complex, like local translation, is required for stimulated, but not basal, outgrowth. Par3 mRNA is localized to developing axons, and NGF and netrin-1 trigger its local translation. Selective ablation of Par3 mRNA from axons abolishes the outgrowth-promoting effect of NGF. These results identify a new role for local translation and the PAR complex in axonal outgrowth.

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Available from: Ulrich Hengst
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    • "It remains unclear how NGF influences this process. Prior work has implicated direct regulation of microtubule dynamics, actin dynamics, and local protein synthesis (Gehler et al., 2004; Goold and Gordon-Weeks, 2003; Hengst et al., 2009; Tanaka and Kirschner, 1991; Zhou et al., 2004). Does one effect or another have a predominant role? "
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    • "Traditionally, silicon and glass were major materials for microfabrication; however, polydimethylsiloxane polymer-based microfluidic devices are the most widely used due to their advantages in biocompatibility, low cost, optical transparency, practical scalability, gas permeability and easy fabrication. In the field of neuroscience, microfluidic devices have been increasingly used to achieve spatial-temporal control of cellular microenvironments such as those of the axon and soma (for review see (Millet and Gillette, 2012; Harink et al., 2013; Park et al., 2013)) to investigate axon elongation, local signaling events (Hengst et al., 2009; Taylor et al., 2009) as well as interactions with other cells such as oligodendroglia (Park et al., 2012), astrocytes (Li et al., 2012) and microglia (Hosmane et al., 2012). We recently presented a microchip system that is capable of isolating CNS axons from neuronal cell bodies for quick and easy quantitative axonal growth analysis (Park et al., 2014) (Figure 1C, E, F). "

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    • "For the second assay, explants or dissociated DRG neurons were transfected with GFP-L1 (gift of Dr. Galli, Paris, France) via the Sindbis-IRES system10, 14, 31, 56. A modified Sindbis viral vector with reduced neuronal cytotoxicity due to the P76S point mutation in the nsP2 protein and containing an encephalomyocarditis virus internal ribosome entry site (IRES) was used together with the helper plasmid DH-BB (S. "
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    ABSTRACT: The surface of developing axons expands in a process mediated by the exocyst complex. The spatio-temporal regulation of the exocyst is only partially understood. Here we report that stimulated membrane enlargement in dorsal root ganglion (DRG) axons is triggered by intra-axonal synthesis of TC10, a small GTPase required for exocyst function. Induced membrane expansion and axon outgrowth are inhibited after axon-specific knockdown of TC10 mRNA. To determine the relationship of intra-axonal TC10 synthesis with the previously described stimulus-induced translation of the cytoskeletal regulator Par3, we investigate the signalling pathways controlling their local translation in response to NGF. Phosphoinositide 3-kinase (PI3K)-dependent activation of the Rheb-mTOR pathway triggers the simultaneous local synthesis of TC10 and Par3. These results reveal the importance of local translation in the control of membrane dynamics and demonstrate that localized, mTOR-dependent protein synthesis triggers the simultaneous activation of parallel pathways.
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