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Elevated protein carbonylation, and misfolding in sciatic nerve from db/db and Sod1(-/-) mice: plausible link between oxidative stress and demyelination.

Hamilton RT, Bhattacharya A, Walsh ME, Shi Y, Wei R, Zhang Y, Rodriguez KA, Buffenstein R, Chaudhuri AR, Van Remmen H - PLoS ONE (2013)

Bottom Line: Since peripheral myelin protein 22 (PMP22) is a key component of myelin sheath and has been found mutated and aggregated in several peripheral neuropathies, we predicted that an increase in carbonylation and aggregation of PMP22 may be associated with demyelination in dbdb mice.Indeed, PMP22 was found to be carbonylated and aggregated in sciatic nerves of dbdb mice.Sequence-driven hydropathy plot analysis and in vitro oxidation-induced aggregation of purified PMP22 protein supported the premise for oxidation-dependent aggregation of PMP22 in dbdb mice.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, USA.

ABSTRACT
Diabetic peripheral polyneuropathy is associated with decrements in motor/sensory neuron myelination, nerve conduction and muscle function; however, the mechanisms of reduced myelination in diabetes are poorly understood. Chronic elevation of oxidative stress may be one of the potential determinants for demyelination as lipids and proteins are important structural constituents of myelin and highly susceptible to oxidation. The goal of the current study was to determine whether there is a link between protein oxidation/misfolding and demyelination. We chose two distinct models to test our hypothesis: 1) the leptin receptor deficient mouse (dbdb) model of diabetic polyneuropathy and 2) superoxide dismutase 1 knockout (Sod1(-/-) ) mouse model of in vivo oxidative stress. Both experimental models displayed a significant decrement in nerve conduction, increase in tail distal motor latency as well as reduced myelin thickness and fiber/axon diameter. Further biochemical studies demonstrated that oxidative stress is likely to be a potential key player in the demyelination process as both models exhibited significant elevation in protein carbonylation and alterations in protein conformation. Since peripheral myelin protein 22 (PMP22) is a key component of myelin sheath and has been found mutated and aggregated in several peripheral neuropathies, we predicted that an increase in carbonylation and aggregation of PMP22 may be associated with demyelination in dbdb mice. Indeed, PMP22 was found to be carbonylated and aggregated in sciatic nerves of dbdb mice. Sequence-driven hydropathy plot analysis and in vitro oxidation-induced aggregation of purified PMP22 protein supported the premise for oxidation-dependent aggregation of PMP22 in dbdb mice. Collectively, these data strongly suggest for the first time that oxidation-mediated protein misfolding and aggregation of key myelin proteins may be linked to demyelination and reduced nerve conduction in peripheral neuropathies.

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Increase in hydrophobic domain of protein exposure in dbdb and Sod1−/− mice.Total BisANS labeling of sciatic nerve homogenates for (A) dbdb and (B) Sod1−/− mice are presented. Results are expressed as mean ± SEM (n = 6; *p<0.05 by two-tailed t-test).
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pone-0065725-g004: Increase in hydrophobic domain of protein exposure in dbdb and Sod1−/− mice.Total BisANS labeling of sciatic nerve homogenates for (A) dbdb and (B) Sod1−/− mice are presented. Results are expressed as mean ± SEM (n = 6; *p<0.05 by two-tailed t-test).

Mentions: Since both cytosolic and detergent-soluble fractions exhibited elevation in protein carbonylation, we next asked whether the global state of protein conformation is affected in these experimental models by measuring protein hydrophobicity using a BisANS photolabeling approach. There was a 1.8±0.1 (p<0.001) fold increase in global exposure of hydrophobic pockets in sciatic nerves of dbdb mice (Figure 4A) and a 1.26±0.03 fold increase (p<0.05, Figure 4B) in Sod1−/− mice.


Elevated protein carbonylation, and misfolding in sciatic nerve from db/db and Sod1(-/-) mice: plausible link between oxidative stress and demyelination.

Hamilton RT, Bhattacharya A, Walsh ME, Shi Y, Wei R, Zhang Y, Rodriguez KA, Buffenstein R, Chaudhuri AR, Van Remmen H - PLoS ONE (2013)

Increase in hydrophobic domain of protein exposure in dbdb and Sod1−/− mice.Total BisANS labeling of sciatic nerve homogenates for (A) dbdb and (B) Sod1−/− mice are presented. Results are expressed as mean ± SEM (n = 6; *p<0.05 by two-tailed t-test).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3672154&req=5

pone-0065725-g004: Increase in hydrophobic domain of protein exposure in dbdb and Sod1−/− mice.Total BisANS labeling of sciatic nerve homogenates for (A) dbdb and (B) Sod1−/− mice are presented. Results are expressed as mean ± SEM (n = 6; *p<0.05 by two-tailed t-test).
Mentions: Since both cytosolic and detergent-soluble fractions exhibited elevation in protein carbonylation, we next asked whether the global state of protein conformation is affected in these experimental models by measuring protein hydrophobicity using a BisANS photolabeling approach. There was a 1.8±0.1 (p<0.001) fold increase in global exposure of hydrophobic pockets in sciatic nerves of dbdb mice (Figure 4A) and a 1.26±0.03 fold increase (p<0.05, Figure 4B) in Sod1−/− mice.

Bottom Line: Since peripheral myelin protein 22 (PMP22) is a key component of myelin sheath and has been found mutated and aggregated in several peripheral neuropathies, we predicted that an increase in carbonylation and aggregation of PMP22 may be associated with demyelination in dbdb mice.Indeed, PMP22 was found to be carbonylated and aggregated in sciatic nerves of dbdb mice.Sequence-driven hydropathy plot analysis and in vitro oxidation-induced aggregation of purified PMP22 protein supported the premise for oxidation-dependent aggregation of PMP22 in dbdb mice.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, USA.

ABSTRACT
Diabetic peripheral polyneuropathy is associated with decrements in motor/sensory neuron myelination, nerve conduction and muscle function; however, the mechanisms of reduced myelination in diabetes are poorly understood. Chronic elevation of oxidative stress may be one of the potential determinants for demyelination as lipids and proteins are important structural constituents of myelin and highly susceptible to oxidation. The goal of the current study was to determine whether there is a link between protein oxidation/misfolding and demyelination. We chose two distinct models to test our hypothesis: 1) the leptin receptor deficient mouse (dbdb) model of diabetic polyneuropathy and 2) superoxide dismutase 1 knockout (Sod1(-/-) ) mouse model of in vivo oxidative stress. Both experimental models displayed a significant decrement in nerve conduction, increase in tail distal motor latency as well as reduced myelin thickness and fiber/axon diameter. Further biochemical studies demonstrated that oxidative stress is likely to be a potential key player in the demyelination process as both models exhibited significant elevation in protein carbonylation and alterations in protein conformation. Since peripheral myelin protein 22 (PMP22) is a key component of myelin sheath and has been found mutated and aggregated in several peripheral neuropathies, we predicted that an increase in carbonylation and aggregation of PMP22 may be associated with demyelination in dbdb mice. Indeed, PMP22 was found to be carbonylated and aggregated in sciatic nerves of dbdb mice. Sequence-driven hydropathy plot analysis and in vitro oxidation-induced aggregation of purified PMP22 protein supported the premise for oxidation-dependent aggregation of PMP22 in dbdb mice. Collectively, these data strongly suggest for the first time that oxidation-mediated protein misfolding and aggregation of key myelin proteins may be linked to demyelination and reduced nerve conduction in peripheral neuropathies.

Show MeSH
Related in: MedlinePlus