title: Deletions within its subcellular targeting domain enhance the axon protective capacity of Nmnat2 in vivo.
abstract: The NAD-synthesising enzyme Nmnat2 is a critical survival factor for axons in vitro and in vivo. We recently reported that loss of axonal transport vesicle association through mutations in its isoform-specific targeting and interaction domain (ISTID) reduces Nmnat2 ubiquitination, prolongs its half-life and boosts its axon protective capacity in primary culture neurons. Here, we report evidence for a role of ISTID sequences in tuning Nmnat2 localisation, stability and protective capacity in vivo. Deletion of central ISTID sequences abolishes vesicle association and increases protein stability of fluorescently tagged, transgenic Nmnat2 in mouse peripheral axons in vivo. Overexpression of fluorescently tagged Nmnat2 significantly delays Wallerian degeneration in these mice. Furthermore, while mammalian Nmnat2 is unable to protect transected Drosophila olfactory receptor neuron axons in vivo, mutant Nmnat2s lacking ISTID regions substantially delay Wallerian degeneration. Together, our results establish Nmnat2 localisation and turnover as a valuable target for modulating axon degeneration in vivo.
authors.affiliation: Babraham Institute, Babraham Research Campus, Cambridge, United Kingdom.
authors.forename: Stefan
authors.initials: S
authors.lastname: Milde
authors.forename: A Nicole
authors.initials: AN
authors.lastname: Fox
authors.forename: Marc R
authors.initials: MR
authors.lastname: Freeman
authors.forename: Michael P
authors.initials: MP
authors.lastname: Coleman
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000473:pathology*; D002478:Cells, Cultured; D017353:Gene Deletion; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009612:Nicotinamide-Nucleotide Adenylyltransferase / Q000235:genetics* / Q000378:metabolism; D013329:Structure-Activity Relationship; D013347:Subcellular Fractions / Q000378:metabolism* / Q000648:ultrastructure; D014855:Wallerian Degeneration / Q000473:pathology* / Q000503:physiopathology* / Q000517:prevention & control
chemical_list: D009612:Nicotinamide-Nucleotide Adenylyltransferase; C579543:Nmnat2 protein, mouse