Proximal giant neurofilamentous axonopathy in mice genetically engineered to resist calpain and caspase cleavage of α-II spectrin.
We use 1,2-diacetylbenzene (1,2-DAB) to probe molecular mechanisms of proximal giant neurofilamentous axonopathy (PGNA), a pathological hallmark of amyotrophic lateral sclerosis. The spinal cord proteome of rodents displaying 1,2-DAB PGNA suggests a reduction in the abundance of α-II spectrin (Spna2), a key protein in the maintenance of axonal integrity. Protein immunoblotting indicates that this reduction is due to Spna2 degradation. We investigated the importance of such degradation in 1,2-DAB PGNA. Spna2 mutant mice lacking a calpain- and/or caspase-sensitive domain (CSD), thus hypothetically resistant to 1,2-DAB, and wild-type littermates, were treated with 1,2-DAB, 35 mg/kg/day, or saline control, for 3 weeks. 1,2-DAB induced motor weakness and PGNA, irrespective of the genotype. Spna2-calpain breakdown products were not detected in mutant mice, which displayed a normal structure of the nervous system under saline treatment. Intriguingly, treatment with 1,2-DAB reduced the abundance of the caspase-specific 120-kDa Spna2 breakdown products. Our findings indicate that degradation of Spna2 by calpain- and/or caspase is not central to the pathogenesis of 1,2-DAB axonopathy. In addition, the Spna2-CSD seems to be not required for the maintenance of the cytoskeleton integrity. Our conceptual framework offers opportunities to study the role of calpain-caspase cross talk, including that of the protease degradomics, in models of axonal degeneration.
Center for Research on Occupational and Environmental Toxicology, Oregon Health & Science University (OHSU), Portland, OR 97239, USA.
R
R
Kassa
V
V
Monterroso
J
J
Wentzell
A L
AL
Ramos
E
E
Couchi
M C
MC
Lecomte
M
M
Iordanov
D
D
Kretzschmar
G
G
Nicolas
D
D
Tshala-Katumbay
D000690:Amyotrophic Lateral Sclerosis / Q000139:chemically induced / Q000201:enzymology / Q000235:genetics; D000818:Animals; D002154:Calpain / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D020169:Caspases / Q000235:genetics* / Q000378:metabolism; D004195:Disease Models, Animal; D005818:Genetic Engineering / Q000379:methods*; D056768:Giant Axonal Neuropathy / Q000139:chemically induced / Q000201:enzymology / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D013049:Spectrin / Q000235:genetics / Q000378:metabolism*
D002154:Calpain; D002352:Carrier Proteins; D020169:Caspases; D008840:Microfilament Proteins; D013049:Spectrin