Axonal protein synthesis is rapidly regulated by extrinsic cues during neural wiring but the full landscape of proteomic changes and their translational control mechanisms remain unknown. The ability to investigate the nascent proteome on subcellular compartments has been hampered by the low sensitivity of existing methodology on quantity-limited samples combined with the difficulty of obtaining sufficient amounts of pure material. By combining pulsed Stable Isotope Labelling by Amino acids in Cell culture (pSILAC) with Single-Pot Solid-Phase-enhanced Sample Preparation (SP3), I have established an approach to characterize the nascent proteome from quantity-limited somaless retinal axons (~2μg) on an unparalleled rapid time-scale (5 min). The results show that a surprisingly large number of proteins (>350) is translated constitutively in axons, many of which are linked to neurological disease. Axons stimulated by different cues (Netrin-1, BDNF, Sema3A) each show a signature set of up/down newly synthesised protein (NSP) changes (>100) within 5 min. Remarkably, conversion of Netrin-1-induced responses from repulsion to attraction triggers opposite translational regulation for 73% of a common subset corresponding to >100 NSPs. Further, I show that pharmacological increase in cAMP, known to induce chemoattractive response, also leads to rapid and wide-scale remodelling of the nascent axonal proteome (~100 NSP changes). I find that the cAMP-elicited NSP changes underlie the attractive turning but are distinct from those induced by the physiological chemoattractant Netrin-1, suggesting that the same type of chemotropic response can be mediated by different protein synthesis-dependent mechanisms. Finally, I show that Sema3A, but not Slit1, triggers a physiological and non-canonical PERK-eIF2α-eIF2B signalling pathway required in neural wiring to elicit the rapid (< 15 min) local translation control of a specific subset of NSPs. Collectively my findings lead to the general conclusion that guidance molecules rapidly induce cue-specific remodelling of the nascent axonal proteome via distinct regulatory mechanisms.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:744814 |
| Date | January 2018 |
| Creators | Cagnetta, Roberta |
| Contributors | Holt, Christine |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.repository.cam.ac.uk/handle/1810/275601 |
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