Influence of immobilization stress on the expression and phosphatase activity of protein phosphatase 2A in the rat brain.
BACKGROUND
Protein phosphatase 2A (PP2A) is a major kinase phosphatase that plays an important role in regulating the activities of protein kinase cascades. It has been revealed that stress changes neuronal gene expression by activating these cascades. We examined the expression of the catalytic subunit C and serine and threonine phosphatase activity of PP2A in the rat frontal cortex and hippocampus following various immobilization stress paradigms.


METHODS
Immunoblot and immunohistochemical analyses were performed to examine the expression of PP2A. The level of phosphatase activity of PP2A was determined as the amount of free phosphate generated from a synthetic phosphopeptide.


RESULTS
Immunoblot analysis revealed no significant change in the level of PP2A immunoreactivity in response to either a single or repeated stress. Immunohistochemical analysis revealed that neither a single nor repeated stress changed PP2A immunoreactivity in the hippocampus; however, the levels of serine and threonine phosphatase activity in the frontal cortex and hippocampus were significantly upregulated in response to a single or repeated stress.


CONCLUSIONS
These results demonstrated that both a single and repeated immobilization stress upregulated the activity of PP2A in the rat brain, suggesting that PP2A may be involved, at least in part, in the downregulation of protein kinase activation induced by stress.
Morinobu
Shigeru
S
Department of Psychiatry and Neurosciences, Hiroshima University School of Medicine, Hiroshima, Japan.
Fujimaki
Koichiro
K
Kawano
Ki-ichiro
K
Tanaka
Kazuhide
K
Takahashi
Jun
J
Ohkawa
Masako
M
Yamawaki
Shigeto
S
Kato
Nobumasa
N
D000818:Animals; D020134:Catalytic Domain / Q000502:physiology; D005625:Frontal Lobe / Q000201:enzymology*; D006624:Hippocampus / Q000201:enzymology*; D007103:Immobilization; D015151:Immunoblotting / Q000379:methods; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010768:Phosphoserine / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism; D054648:Protein Phosphatase 2; D051381:Rats; D017207:Rats, Sprague-Dawley; D013312:Stress, Physiological / Q000201:enzymology* / Q000378:metabolism; D013997:Time Factors
D010769:Phosphothreonine; D010768:Phosphoserine; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2