Subcellular Localization of Peptidylarginine Deiminase 2 and Citrullinated Proteins in Brains of Scrapie-Infected Mice

Ilsong Institute of Life Science, Hallym University, Anyang, Republic of Korea.
Journal of Neuropathology and Experimental Neurology (Impact Factor: 3.8). 02/2011; 70(2):116-24. DOI: 10.1097/NEN.0b013e318207559e
Source: PubMed


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.

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    • "Citrullination is carried out by a family of calcium-dependent enzymes , peptidylarginine deiminases (PADs) that have different tissue distributions, often overlapping, and are believed to have distinct substrate specificity [12] [13] [14] [15] [16] [17]. PAD activity has been reported in the cytoplasm , including mitochondrial and microsomal fractions, as well as in the nucleus [18]. Among the known PAD substrates are cytoskeletal proteins and histones [19] [20]. "
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