Hiroko Tanino

Differential subcellular localization of caspase family proteins in the adult rat brain

The distribution of the caspase family (caspase-2, -3, -6, -7, -8, -9, -10) was assessed using immunochemical detection of subcellular fractions of 8-week-old rat brain tissues. The present study demonstrated that the relative protein level of caspase-2, -3, -6, -8 and -10 was highest in the soluble cytosolic fraction, while that for caspase-9 was highest in the nucleus. We also found that caspase-3 and -6 were present at high levels and caspase-2, -8 and -9 at moderate levels in the nerve endings fraction as well as in the soluble cytosolic fraction. These results suggest that rat brain caspases are differentially expressed in the subcellular fractions of the rat brain, and that caspases not only contribute to the regulation of neuronal death, but also to synaptic plasticity.

Alteration of myo-inositol monophosphatase in Alzheimer's disease brains.

myo-Inositol monophosphatase (E.C.3.1.3.25) catalyzes the hydrolysis of myo-inositol 1-phosphate in the presence of Mg2+ at a physiologic pH to form free myo-inositol, maintaining a supply that represents the precursor for inositol phospholipid second messenger signaling systems. In the present study the activity and protein level of myo-inositol monophosphatase were investigated in samples from normal human and Alzheimers disease (AD) postmortem brains. The separation profile on Sephadex G-100 gel filtration chromatography revealed one major form of myo-inositol monophosphatase in crude extracts from both normal human and AD brains. In AD brains myo-inositol monophosphatase activity and its protein level were significantly higher than in control brains. The activity of myo-inositol monophosphatase per enzyme molecule was similar in control and AD brains. These results suggest that myo-inositol monophosphatase is upregulated in AD, probably reflecting compensatory mechanisms concerned with phospholipid metabolism.

Effects of hyperoxia and acrylonitrile on the phospholipase C isozyme protein levels in rat heart and brain.

We previously showed that hyperoxia exerts oxidative stress on the rat cerebral cortex, and the protein levels of phospholipase C (PLC) -beta1 and -delta1, but not PLC-gamma1, were changed. Acrylonitrile (ACN) appears to induce astrocytomas through induction of oxidative stress on the rat brain selectively. This study compared hyperoxia or ACN treatments of rats with respect to lipid peroxidation and PLC levels in the heart and cerebral cortex. Treatment of rats with ACN promoted lipid peroxidation in the heart and cerebral cortex, the percent increase above control being greater in the cortex than heart. Hyperoxia did not cause significant increases in lipid peroxidation in the cerebral cortex or heart. In the ACN-treated cerebral cortex, significant increases in the PLC-beta1 and -delta1 in the cytosol, and PLC-gamma1 in the cytosolic and particulate fractions, and lysate were observed. In the rat heart, in which PLC-beta1 could not be detected, PLC-gamma1 and -delta1 were increased and decreased in the cytosolic and particulate fractions, respectively, by hyperoxia. In addition, the expression level of PLC-gamma1 was decreased in the lysate by the treatment. In the heart treated with ACN, there was no change in the level of PLC-gamma1, while PLC-delta1 was elevated in all fractions. These findings suggested that the expression levels of PLC isozymes are altered by hyperoxia and ACN, but there are apparent differences in these altered levels between the different levels of oxidative stress, and between the organs.

myo-Inositol Monophosphatase in the Brain Has Zinc Ion-Dependent Tyrosine Phosphatase Activity

1. myo-Inositol monophosphatase (E.C. 3.1.3.25) hydrolyzes inositol monophosphate to form free myo-inositol, the precursor for the inositol phospholipid second-messenger signaling systems. The biochemical properties of the enzyme were examined in detail. 2. The enzyme exhibited significant hydrolytic activity only on phosphotyrosine among physiological substrates tested in the presence of Zn2+ ions in an acidic environment. 3. The enzyme was recognized and immunoprecipitated with polyclonal antibodies developed against the Zn2+-dependent tyrosine phosphatase of bovine brain. 4. These results indicate that myo-inositol monophosphatase exhibits Zn2+-dependent tyrosine phosphatase activity in an acidic environment and has immunological identity with a Zn2+-dependent tyrosine phosphatase.