Iatic nerve protein carbonyls in dbdb mice and increase in global exposure of hydrophobic pockets, we next investigated if peripheral myelin proteins undergo carbonylation and aggregation in diabetic neuropathy. We chose PMP22 to test our hypothesis as it is one of the abundant proteins (2? ) in peripheral myelin [11]. Moreover, PMP22 has been found as a key player in multiple Charcot Marie Tooth Disease 1a neuropathies and has been reported to be mutated and aggregated in several neuropathies [32,33,34,35]. We first asked whether the primary sequence of PMP22 can predict and identify any domain that have motif(s) of hydrophobicity as hydrophobic domains in general initiate the aggregation process. We utilized the primary sequence of PMP22 obtained from protein search and online software Kyte-Doolittle Hydropathy plots for this theoretical study. We found that certain regions in PMP22 have motifs of hydrophobicity which can predict its region-specific hydrophobicity (Figure 5A). We next determined if PMP22 is preferentially carbonylated in dbdb mice and found that immunoprecipitated Title Loaded From File cytosolic PMP22 is heavily carbonylated (1.760.3 fold increase over dbm, p,0.05, Figure 5B). Since oxidative modifications often induce protein aggregation, we investigated if oxidized PMP22 can be detected in the detergent-soluble fraction selectively in Dbdb mice and also to determine if PMP22 undergoes Title Loaded From File higher-order aggregation state. We found that the detergent-soluble PMP22 is heavily carbonylated in dbdb mice (1.3160.12 fold increase over dbm, p,0.05, Figure 5C). 18204824 Also, we observed a higher-order aggregation state of PMP22 (1.660.2 fold increasincrease) in Dbdb mice (p,0.05, Figure 5D). Based on these intriguing in vivo observations, we predicted that the oxidative environment is likely to induce aggregation of PMP22 protein which has been found as aggregates in multiple PMP22 aggregation-dependent neuropathies. Therefore, we exposed purified PMP22 to different concentrations of tBHP (which generates hydroxyl radical and forms protein carbonyls) and then followed the structural consequences of PMP22. The results of Figure 6 shows a dose-dependent increase in insoluble to soluble ratio of PMP22, which confirms our in vivo finding that oxidative stress indeed increases the sensitivity of PMP22 to undergo aggregation.Protein carbonylation and misfolding in dbdb and Sod12/2 miceOur findings on impaired nerve conduction and reduced myelin thickness in dbdb and Sod12/2 mice strongly suggest that oxidative stress might be the common contributor for these changes. In fact, other studies have indicated that oxidative stress might be the causative factor for nerve fiber abnormalities in diabetes [4,5]. We have previously shown that oxidative stress has major impact to the structure and function of proteins and enzymes [36]. Therefore, we investigated if protein oxidation and misfolding are selectively elevated in both the experimental models. Protein carbonylation is one of the common oxidative modifications detected and studied in aging [14,37,38,39] and in various pathophysiological conditions including diabetes [40]. In this study, we asked if protein carbonylation has any negative impact to structure of proteins in sciatic nerves of dbdb and Sod12/2 mice. We measured protein carbonylation and exposure 1676428 of hydrophobic domain of sciatic nerve proteins utilizing two distinct fluorescencebased technologies developed by our group [14,41]. We found a significant incr.Iatic nerve protein carbonyls in dbdb mice and increase in global exposure of hydrophobic pockets, we next investigated if peripheral myelin proteins undergo carbonylation and aggregation in diabetic neuropathy. We chose PMP22 to test our hypothesis as it is one of the abundant proteins (2? ) in peripheral myelin [11]. Moreover, PMP22 has been found as a key player in multiple Charcot Marie Tooth Disease 1a neuropathies and has been reported to be mutated and aggregated in several neuropathies [32,33,34,35]. We first asked whether the primary sequence of PMP22 can predict and identify any domain that have motif(s) of hydrophobicity as hydrophobic domains in general initiate the aggregation process. We utilized the primary sequence of PMP22 obtained from protein search and online software Kyte-Doolittle Hydropathy plots for this theoretical study. We found that certain regions in PMP22 have motifs of hydrophobicity which can predict its region-specific hydrophobicity (Figure 5A). We next determined if PMP22 is preferentially carbonylated in dbdb mice and found that immunoprecipitated cytosolic PMP22 is heavily carbonylated (1.760.3 fold increase over dbm, p,0.05, Figure 5B). Since oxidative modifications often induce protein aggregation, we investigated if oxidized PMP22 can be detected in the detergent-soluble fraction selectively in Dbdb mice and also to determine if PMP22 undergoes higher-order aggregation state. We found that the detergent-soluble PMP22 is heavily carbonylated in dbdb mice (1.3160.12 fold increase over dbm, p,0.05, Figure 5C). 18204824 Also, we observed a higher-order aggregation state of PMP22 (1.660.2 fold increasincrease) in Dbdb mice (p,0.05, Figure 5D). Based on these intriguing in vivo observations, we predicted that the oxidative environment is likely to induce aggregation of PMP22 protein which has been found as aggregates in multiple PMP22 aggregation-dependent neuropathies. Therefore, we exposed purified PMP22 to different concentrations of tBHP (which generates hydroxyl radical and forms protein carbonyls) and then followed the structural consequences of PMP22. The results of Figure 6 shows a dose-dependent increase in insoluble to soluble ratio of PMP22, which confirms our in vivo finding that oxidative stress indeed increases the sensitivity of PMP22 to undergo aggregation.Protein carbonylation and misfolding in dbdb and Sod12/2 miceOur findings on impaired nerve conduction and reduced myelin thickness in dbdb and Sod12/2 mice strongly suggest that oxidative stress might be the common contributor for these changes. In fact, other studies have indicated that oxidative stress might be the causative factor for nerve fiber abnormalities in diabetes [4,5]. We have previously shown that oxidative stress has major impact to the structure and function of proteins and enzymes [36]. Therefore, we investigated if protein oxidation and misfolding are selectively elevated in both the experimental models. Protein carbonylation is one of the common oxidative modifications detected and studied in aging [14,37,38,39] and in various pathophysiological conditions including diabetes [40]. In this study, we asked if protein carbonylation has any negative impact to structure of proteins in sciatic nerves of dbdb and Sod12/2 mice. We measured protein carbonylation and exposure 1676428 of hydrophobic domain of sciatic nerve proteins utilizing two distinct fluorescencebased technologies developed by our group [14,41]. We found a significant incr.
