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Published on: November 5, 2014
Peptidylarginine deiminase: a candidate factor in demyelinating disease
M A Moscarello1, L Pritzker, F G Mastronardi
1Department of Structural Biology & Biochemistry, The Hospital for Sick Children, Toronto, Ontario, Canada. mam@sickkids.ca
Abstract:
In earlier studies we demonstrated that an increase in the relative amounts of citrullinated myelin basic protein (MBP) was found in multiple sclerosis (Moscarello et al. 1994). To determine the temporal relationship between the citrullinated MBP and peptidylarginine deiminase (PAD), the enzyme responsible for deiminating arginyl residues in proteins, we studied enzyme activity, enzyme protein, PAD mRNA in a spontaneously demyelinating transgenic mouse model and we correlated the amount of PAD with citrullinated MBP. Both PAD protein as measured in an immunoslot blot method and PAD RNA were elevated. In fractionation studies we showed that the increase in PAD enzyme was due to an increase in the PAD found in membrane fractions and not the soluble PAD (PADII). From our data we concluded that up-regulation of myelin-associated PAD was responsible for the increase in citrullinated MBP in our transgenic mice prior to onset of clinical or pathological signs of demyelination. We postulate that a similar mechanism may be responsible for the increase in citrullinated MBP in multiple sclerosis.
Insights
Elevated peptidylarginine deiminase (PAD) in myelin membranes precedes demyelination in a mouse model. This suggests PAD
Area of Science:
- Neuroscience
- Biochemistry
- Immunology
Background:
- Increased citrullinated myelin basic protein (MBP) is observed in multiple sclerosis (MS).
- Peptidylarginine deiminase (PAD) enzymes catalyze protein citrullination.
- The temporal relationship between PAD and citrullinated MBP in demyelination is unclear.
Purpose of the Study:
- To investigate the temporal relationship between PAD and citrullinated MBP.
- To identify the role of PAD in a mouse model of spontaneous demyelination.
Main Methods:
- Studied enzyme activity, protein, and mRNA levels of PAD.
- Utilized a spontaneously demyelinating transgenic mouse model.
- Fractionation studies to localize PAD activity.
Main Results:
- Both PAD protein and mRNA were elevated in the mouse model.
- Increased PAD was localized to membrane fractions, not soluble fractions.
- Elevated PAD correlated with increased citrullinated MBP prior to demyelination.
Conclusions:
- Up-regulation of myelin-associated PAD causes increased citrullinated MBP.
- This occurs before clinical or pathological signs of demyelination.
- A similar mechanism may contribute to citrullinated MBP increase in multiple sclerosis.
