Subcellular localization of peptidylarginine deiminase 2 and citrullinated proteins in brains of scrapie-infected mice: nuclear localization of PAD2 and membrane fraction-enriched citrullinated proteins.
ABSTRACT Peptidylarginine deiminase (PAD) and citrullinated proteins have emerged as key molecules in various human diseases, but detailed subcellular localizations of PAD2 and citrullinated proteins are poorly mapped in brain under normal and pathologic conditions. We performed subcellular fractionation and electron microscopic analysis using brains of normal and scrapie-infected mice. Peptidylarginine deiminase 2 was abundantly present in cytosol and weakly in microsomal and mitochondrial fractions and expression in these fractions was higher in brains of scrapie-infected mice. Despite relatively low PAD2 expression, in microsomal and mitochondrial fractions, citrullinated proteins were present at high levels in these fractions in scrapie-infected brains. Surprisingly, increased PAD2 expression and accumulated citrullinated proteins were also found in nuclear fractions in scrapie-infected brains. By electron microscopy, PAD2 and citrullinated proteins in scrapie-infected brains were widely distributed in most cellular compartments including mitochondria, endoplasmic reticulum, glial filaments, nuclei, and Golgi apparatus in astrocytes and hippocampal neurons. Taken together, we report for the first time the nuclear localization of PAD2 and the detailed subcellular localization of PAD2 and of citrullinated proteins in scrapie-infected brains. Our findings suggest that different subcellular compartmentalization of PAD2 and citrullinated proteins may have different physiological roles in normal and neurodegenerative conditions.
- SourceAvailable from: Cameron A. Ackerley[show abstract] [hide abstract]
ABSTRACT: The etiology of multiple sclerosis (MS) is considered to involve genetic, environmental, infective, and immunological factors which affect the integrity of a normally assembled myelin sheath, either directly or indirectly resulting in demyelination. In a correlative study involving protein chemical, mass spectrometric, and electron microscopic techniques we have determined that myelin obtained from victims of MS is arrested at the level of the first growth spurt (within the first 6 yr of life) and is therefore developmentally immature. The data supporting this conclusion include (a) the pattern of microheterogeneity of myelin basic protein (MBP); (b) the NH2-terminal acylation of the least cationic component of MBP ("C-8"); (c) the phase transition temperature (Tc) of myelin isolated from victims of MS correlated with the increased proportion of the least cationic component of MBP; and (d) immunogold electron microscopy using an antibody specific for "C-8" showed that the distribution of gold particles in a 2-yr-old infant was similar to the distribution found in a victim of MS. We postulate that this developmentally immature myelin is more susceptible to degradation by one or a combination of factors mentioned above, providing the initial antigenic material to the immune system.Journal of Clinical Investigation 08/1994; 94(1):146-54. · 12.81 Impact Factor