The Spontaneously Diabetic Torii (SDT) rat is a nonobese type 2 diabetic model, showing the overt hyperglycemia after about 16 weeks of age. In this study, we investigated the protein tyrosine phosphatase (PTPase) act...The Spontaneously Diabetic Torii (SDT) rat is a nonobese type 2 diabetic model, showing the overt hyperglycemia after about 16 weeks of age. In this study, we investigated the protein tyrosine phosphatase (PTPase) activities in insulin-sensitive tissues in SDT rats. PTPase activities in the liver, muscle, and fat were examined at 8 weeks (pre-diabetes), 16 weeks (onset-diabetes), and 24 weeks (diabetes). SDT rats showed glucose intolerance at 8 weeks and hyperglycemia after 16 weeks. The PTPase activities in fat increased at 8 weeks and the increase was sustained to 24 weeks. In the liver, PTPase activities increased only at 24 weeks. On the other hand, the PTPase activities in muscle did not change. The increase of PTPase activity in fat might be related to progression of glucose intolerance and diabetes in SDT rats.展开更多
Water deficit-induced ABA accumulation is an ideal model or 搒timulus-response?system to investigate cellular stress signaling in plant cells, using such a model the cellular stress signaling triggered by water defici...Water deficit-induced ABA accumulation is an ideal model or 搒timulus-response?system to investigate cellular stress signaling in plant cells, using such a model the cellular stress signaling triggered by water deficit was inves-tigated in Maize L. coleoptile. Water deficit-induced ABA accumulation was sensitively blocked by NaVO3, a potent inhibitor both to plasma membrane H+-ATPase (PM-H+- ATPase) and protein tyrosine phosphatase (PTPase). How-ever, while PM- H+-ATPase activity was unaffected under water deficit and PM- H+-ATPase activator did not induce an ABA accumulation instead of water deficit, water deficit induced an increase in the protein phosphatase activity, and furthermore, ABA accumulation was inhibited by PAO, a specific inhibitor of PTPase. These results indicate that pro-tein phosphtases may be involved in the cellular signaling in response to water deficit. Further studies identified at least four species of protein phosphtase as assayed by using pNPP as substrate, among which one component was especially sensitive to NaVO3. The NaVO3-sensitive enzyme was puri-fied and finally showed a protein band about 66 kD on SDS/PAGE. The purified enzyme showed a great activity to some specific PTPase substrates at pH 6.0. In addition to NaVO3, the enzyme was also sensitive to some other PTPase inhibitors such as Zn2+ and MO33+, but not to Ca2+ and Mg2+, indicating that it might be a protein tyrosine phosphatase. Interestingly, the purified enzyme could be deactivated by some reducing agent DTT, which was previously proved to be an inhibitor of water deficit-induced ABA accumulation. This result further proved that PTPase might be involved in the cellular signaling of ABA accumulation in response to water deficit.展开更多
文摘The Spontaneously Diabetic Torii (SDT) rat is a nonobese type 2 diabetic model, showing the overt hyperglycemia after about 16 weeks of age. In this study, we investigated the protein tyrosine phosphatase (PTPase) activities in insulin-sensitive tissues in SDT rats. PTPase activities in the liver, muscle, and fat were examined at 8 weeks (pre-diabetes), 16 weeks (onset-diabetes), and 24 weeks (diabetes). SDT rats showed glucose intolerance at 8 weeks and hyperglycemia after 16 weeks. The PTPase activities in fat increased at 8 weeks and the increase was sustained to 24 weeks. In the liver, PTPase activities increased only at 24 weeks. On the other hand, the PTPase activities in muscle did not change. The increase of PTPase activity in fat might be related to progression of glucose intolerance and diabetes in SDT rats.
基金the National Natural Science Foundation of China (Grant Nos.30070071& 30270135)and the National Key Basic Research Project (Grant No. G1999011700)
文摘Water deficit-induced ABA accumulation is an ideal model or 搒timulus-response?system to investigate cellular stress signaling in plant cells, using such a model the cellular stress signaling triggered by water deficit was inves-tigated in Maize L. coleoptile. Water deficit-induced ABA accumulation was sensitively blocked by NaVO3, a potent inhibitor both to plasma membrane H+-ATPase (PM-H+- ATPase) and protein tyrosine phosphatase (PTPase). How-ever, while PM- H+-ATPase activity was unaffected under water deficit and PM- H+-ATPase activator did not induce an ABA accumulation instead of water deficit, water deficit induced an increase in the protein phosphatase activity, and furthermore, ABA accumulation was inhibited by PAO, a specific inhibitor of PTPase. These results indicate that pro-tein phosphtases may be involved in the cellular signaling in response to water deficit. Further studies identified at least four species of protein phosphtase as assayed by using pNPP as substrate, among which one component was especially sensitive to NaVO3. The NaVO3-sensitive enzyme was puri-fied and finally showed a protein band about 66 kD on SDS/PAGE. The purified enzyme showed a great activity to some specific PTPase substrates at pH 6.0. In addition to NaVO3, the enzyme was also sensitive to some other PTPase inhibitors such as Zn2+ and MO33+, but not to Ca2+ and Mg2+, indicating that it might be a protein tyrosine phosphatase. Interestingly, the purified enzyme could be deactivated by some reducing agent DTT, which was previously proved to be an inhibitor of water deficit-induced ABA accumulation. This result further proved that PTPase might be involved in the cellular signaling of ABA accumulation in response to water deficit.
