Collapsin Response Mediator Protein 4a (CRMP4a) Is Upregulated in Motoneurons of Mutant SOD1 Mice and Can Trigger Motoneuron Axonal Degeneration and Cell Death

Abstract

Embryonic motoneurons from mutant SOD1 (mSOD1) mouse models of amyotrophic lateral sclerosis (ALS), but not wild-type motoneurons, can be triggered to die by exposure to nitric oxide (NO), leading to activation of a motoneuron-specific signaling pathway downstream of the death receptor Fas/CD95. To identify effectors of mSOD1-dependent cell death, we performed a proteomic analysis. Treatment of cultured mSOD1 motoneurons with NO led to a 2.5-fold increase in levels of collapsin response mediator protein 4a (CRMP4a). In vivo, the percentage of mSOD1 lumbar motoneurons expressing CRMP4 in mSOD1 mice increased progressively from presymptomatic to early-onset stages, reaching a maximum of 25%. Forced adeno-associated virus (AAV)-mediated expression of CRMP4a in wild-type motoneurons in vitro triggered a process of axonal degeneration and cell death affecting 60% of motoneurons, whereas silencing of CRMP4a in mSOD1 motoneurons protected them from NO-induced death. In vivo, AAV-mediated overexpression of CRMP4a but not CRMP2 led to the death of 30% of the lumbar motoneurons and an 18% increase in denervation of neuromuscular junctions in the gastrocnemius muscle. Our data identify CRMP4a as a potential early effector in the neurodegenerative process in ALS.

Reduced Calreticulin Levels Link Endoplasmic Reticulum Stress and Fas-Triggered Cell Death in Motoneurons Vulnerable to ALS

“…In an earlier study (Duplan et al, 2010) we used 2D gel electrophoresis and peptide sequencing to identify proteins whose levels change when primary cultures of SOD1 G85R motoneurons are exposed for 24 h to the NO donor DETANONOate, which is known to activate the Fas pathway in motoneurons and to kill half of them after 48 h. One such protein (reported in supplemental Table 1 available at www.jneurosci.org as supplemental material) in (Duplan et al, 2010) but not further studied in that paper, was CRT. Spot volumes for CRT expressed as a percentage of the signal for untreated WT cultures did not differ significantly between untreated WT (100 Ϯ 18; mean Ϯ SD, n ϭ 4) and untreated SOD1 G85R neurons (95 Ϯ 18).…”

“…We recently used an unbiased proteomic approach to identify molecular changes that occur selectively in mSOD1 motoneurons in response to activation of the Fas/NO pathway, and therefore might explain the exacerbated sensitivity of ALS model motoneurons to Fas/NO-triggered cell death (Duplan et al, 2010). One of the very few changes detected was a twofold reduction in the levels of calreticulin (CRT).…”

IFNγ triggers a LIGHT-dependent selective death of motoneurons contributing to the non-cell-autonomous effects of mutant SOD1

“…Light À/À and SOD1 G93A mice were genotyped as previously described. 27,49 Light À/À males were crossed with SOD1 G93A females to obtain SOD1 G93A /Light þ /À mice. SOD1 G93A /Light þ /À male mice were then backcrossed with Light þ /À female mice.…”

Phosphorylation of kinesin light chain 1 at serine 460 modulates binding and trafficking of calsyntenin-1

“…DNA sequences were verified by sequencing. EGFP-calsyntenin-1 (Konecna et al, 2006), Myc-HAP1A and EGFP-Myc-HAP1A (Prigge and Schmidt, 2007), EGFP-Kidins220/ARMS (Bracale et al, 2007), and Myc-tagged CRMP2 (Duplan et al, 2010) were as described previously. Verified non-targeting control siRNA and human-specific KLC1 siRNA (5Ј-AAAGAGCCCUCGAGAUCUA-3Ј) were purchased from Dharmacon.…”