Proteasome Biology Is Compromised in White Matter After Asphyxic Cardiac Arrest in Neonatal Piglets.

Background Neurological deficits in hypoxic-ischemic encephalopathy, even with therapeutic hypothermia, are partially attributed to white matter injury. We theorized that proteasome insufficiency contributes to white matter injury. Methods and Results Neonatal piglets received hypoxia-ischemia ( HI ) or sham procedure with normothermia, hypothermia, or hypothermia+rewarming. Some received a proteasome activator drug (oleuropein) or white matter-targeted, virus-mediated proteasome knockdown. We measured myelin oligodendrocyte glycoprotein, proteasome subunit 20S (P20S), proteasome activity, and carbonylated and ubiquitinated protein levels in white matter and cerebral cortex. HI reduced myelin oligodendrocyte glycoprotein levels regardless of temperature, and myelin oligodendrocyte glycoprotein loss was associated with increased ubiquitinated and carbonylated protein levels. Ubiquitinated and carbonyl-damaged proteins increased in white matter 29 hours after HI during hypothermia to exceed levels at 6 to 20 hours. In cortex, ubiquitinated proteins decreased. Ubiquitinated and carbonylated protein accumulation coincided with lower P20S levels in white matter; P20S levels also decreased in cerebral cortex. However, proteasome activity in white matter lagged behind that in cortex 29 hours after HI during hypothermia. Systemic oleuropein enhanced white matter P20S and protected the myelin, whereas proteasome knockdown exacerbated myelin oligodendrocyte glycoprotein loss and ubiquitinated protein accumulation after HI . At the cellular level, temperature and HI interactively affected macroglial P20S enrichment in subcortical white matter. Rewarming alone increased macroglial P20S immunoreactivity, but this increase was blocked by HI . Conclusions Oxidized and ubiquitinated proteins accumulate with HI -induced white matter injury. Proteasome insufficiency may drive this injury. Hypothermia did not prevent myelin damage, protect the proteasome, or preserve oxidized and ubiquitinated protein clearance after HI .

The myelin oligodendrocyte glycoprotein directly binds nerve growth factor to modulate central axon circuitry.

Myelin oligodendrocyte glycoprotein (MOG) is a central nervous system myelin-specific molecule expressed on the outer lamellae of myelin. To date, the exact function of MOG has remained unknown, with MOG knockout mice displaying normal myelin ultrastructure and no apparent specific phenotype. In this paper, we identify nerve growth factor (NGF) as a binding partner for MOG and demonstrate that this interaction is capable of sequestering NGF from TrkA-expressing neurons to modulate axon growth and survival. Deletion of MOG results in aberrant sprouting of nociceptive neurons in the spinal cord. Binding of NGF to MOG may offer widespread implications into mechanisms that underlie pain pathways.

Novel pathogenic epitopes of myelin oligodendrocyte glycoprotein induce experimental autoimmune encephalomyelitis in C57BL/6 mice.

Myelin oligodendrocyte glycoprotein (MOG), a minor protein of the central nervous system myelin, is recognized as a potential target in multiple sclerosis and neuromyelitis optica. The extracellular domain of MOG is commonly used in a wide range of mouse strains and other animals to induce experimental autoimmune encephalomyelitis (EAE), an autoimmune animal model of multiple sclerosis, because it is a target for antibody-mediated attack. Previous studies, using selected peptides, have indicated that MOG(35-55) peptide is an encephalitogenic epitope in C57BL/6 (H-2(b)) mice. A more systematic analysis of both T-cell and B-cell responses following immunization of C57BL/6 mice with either recombinant extracellular mouse MOG protein (1-116) or with overlapping peptides spanning the whole sequence of MOG, before assessment of responses to 15 mer and 23 mer peptides was undertaken. The studies identified T-cell responses within the MOG(35-55) (extracellular domain) but also two new immunogenic and encephalitogenic T-cell epitopes within residues MOG(113-127), MOG(120-134) (localized in the transmembrane region) and MOG(183-197) (in the second hydrophobic MOG domain). In addition, residue MOG(113-127) was found to be a B-cell epitope, suggesting that this may be a useful adjunct for the induction of EAE as well as for immunological studies in C57BL/6 mice, which are increasingly being used to study immune function through the use of transgenic and gene knockout technology.