Oncogenic H-Ras G12V and its variants have been shown to inhibit muscle differentiation. However, the role of proto-oncogenic Ras （c-Ras） in muscle differentiation remains unclear. The active GTP-bound form of Ras h...Oncogenic H-Ras G12V and its variants have been shown to inhibit muscle differentiation. However, the role of proto-oncogenic Ras （c-Ras） in muscle differentiation remains unclear. The active GTP-bound form of Ras has been known to associate with diverse effectors including Raf, phosphatidylinositol 3-kinase （PI3K）, RaI-GDS, and other molecules to transmit downstream signals. We hypothesize that c-Ras may stimulate muscle differentiation by selectively activating PI3K, an important mediator for muscle differentiation. In our experiments, inhibition of c-Ras by farnesyltransferase inhibitors and a dominant negative form of H-Ras （Ras S17N） suppressed muscle differentiation. Consistently, individual knockdown of H-Ras, K-Ras, and N-Ras by siRNAs all blocked muscle differentiation. Interestingly, we found that c-Ras preferentially interacts with PI3K rather than its major binding partner c-Raf, during myogenic differentiation, with total c-Ras activity remaining unchanged. PI3K and its downstream myogenic pathway, the Nox2/NF-kB/inducible nitric oxide synthase （iNOS） pathway, were found to be suppressed by inhibition of c-Ras activity during differentiation. Furthermore, expression of a constitutively active form of PI3K completely rescued the differentiation block and reactivated the Nox2/NF-kB/iNOS pathway in c-Ras-inhibited cells. On the ba- sis of our results, we conclude that contrary to oncogenic Ras, proto-oncogenic H-Ras, K-Ras, and N-Ras are directly involved in the promotion of muscle differentiation via PI3K and its downstream signaling pathways. In addition, PI3K pathway activation is associated with a concurrent suppression of the otherwise predominantly activated Raf/ Mek/Erk pathway.展开更多
Objective: To study the relationship between the expression of muscarinic receptor subtype M3R and the decomposition of phosphatidylinositol (PI). Methods: The [3H]-IP contents were detected with [3H] incorporation in...Objective: To study the relationship between the expression of muscarinic receptor subtype M3R and the decomposition of phosphatidylinositol (PI). Methods: The [3H]-IP contents were detected with [3H] incorporation in human cultured detrusor muscle cells after being stimulated by carbachol, atropine, methoctramine, and 4-DAMP, respectively. Results: The [3H]-IP contents were increased with the elevation of carbachol concentration. Both atropine and 4-DAMP significantly inhibited the effect of carbachol on PI decomposition (P<0.01), but methoctramine did not. No significant difference was seen in the effect of atropine and 4-DAMP on PI decomposition. Conclusion: M3R is closely related to the decomposition of PI, the second messenger molecule IP3.展开更多
Intramuscular fat （IMF） content in chickens significantly contributes to meat quality. The main objective of this study was to assess the expression of calcineudn （CAN） and Ca^2＋/calmodutin-dependent protein kina...Intramuscular fat （IMF） content in chickens significantly contributes to meat quality. The main objective of this study was to assess the expression of calcineudn （CAN） and Ca^2＋/calmodutin-dependent protein kinase （CAME） in lipogene- sis in chicken muscle. The chickens were slaughtered and sampled at the ages of 4, 8, and 16 weeks, respectively. IMF content and the expression of CaN subunits and CaMK isoforms were measured in thigh muscle tissue. The results showed that the IMF contents were higher in chickens at the age of 16 weeks compared with those in chickens at the ages of 4 and 8 weeks （P〈0.05）. The expression levels of fatty acid synthase （FAS） and fatty acid translocase CD36 （FAT/CD36） mRNA in 16-week-old chickens were all significantly up-regulated compared with those in 4-week-old chickens （P〈0.05）. The mRNA levels of CaNB and CaMK IV in 16-week-old chickens were significantly lower than those in 4-week-old chickens （P〈0.05）. But the CaMK II mRNA levels in 16-week-old chickens were significantly higher than those in 4-week-old chickens （P〈0.05）. To investigate the roles of CaMK and CaN in adipogenesis, SV cells were incubated in standard adipogenesis medium for 24 h and treated with specific inhibitor of CaMK and CaN. The ex- pressions of CCAAT/enhancer binding protein β（C/EBPJ3）, sterol regulatory element- binding protein 1 （SREBP1） and peroxisome proliferation-activated receptor ）, （PPARy） were dramatically enhanced by CsA and CaN inhibitor （P〈0.05）. KN93, a CaMK Ⅱ inhibitor, dramatically repressed the expression of those lipogenic genes （P〈0.05）. All the results above indicated that CaN and CaMK had different effects on adipogenesis in the muscle of chickens.展开更多
It is believed that amyloid-βpeptide（Aβ）plays a central role in the pathogenesis of Alzheimer’s disease（AD）.Thus,the process of amyloid precursor protein（APP）cleavage is a key event and has raised much attent...It is believed that amyloid-βpeptide（Aβ）plays a central role in the pathogenesis of Alzheimer’s disease（AD）.Thus,the process of amyloid precursor protein（APP）cleavage is a key event and has raised much attention in the field of AD research.It is proposed that APP,β-andγ-secretases are all located on the lipid raft,and the meeting of them is an indispensable step for Aβgeneration.Endocytosis can lead to clustering of APP,β-andγ-secretases from separate smaller lipid rafts into a larger one.On the other hand,for myristoylated alanine-rich C kinase substrate（MARCKS）,phosphorylation by protein kinase C（PKC）or interaction with Ca2＋can lead to its release from membrane into cytoplasm.This process induces the release of actins and phosphatidylinositol 4,5-bisphosphate（PIP2）,which are important factors for endocytosis.Thus,the present review proposes that MARCKS may be implicated in Aβgeneration,by modulating free PIP 2 level and actin movement,causing endocytosis.展开更多
OBJECTIVE: To study the changes in activity of phosphatidylinositol 4 kinase (PI 4 kinase), phosphatidylinositol 4 phosphate 5 kinase (PIP 5 kinase) and protein kinase C (PKC) during myocardial ischemia and elucidate ...OBJECTIVE: To study the changes in activity of phosphatidylinositol 4 kinase (PI 4 kinase), phosphatidylinositol 4 phosphate 5 kinase (PIP 5 kinase) and protein kinase C (PKC) during myocardial ischemia and elucidate the relationship between phosphatidylinositol signal pathways and prolonged myocardial ischemia. METHODS: In vivo an ischemic rat model was used. Activity of PI 4 kinase, PIP 5 kinase and PKC were measured at different times in postischemic heart cells using isotope analysis. RESULTS: The activity of PI kinase, PIP kinase and PKC in the myocardium increased to peak at 1 hour postischemia, with activities 6.1, 3.0 and 4.0 fold over control levels, respectively. Their activities declined to normal levels with time. CONCLUSION: The phosphatidylinositol signal pathway is involved in prolonged myocardial ischemia, but its mechanism needs further study.展开更多
文摘Oncogenic H-Ras G12V and its variants have been shown to inhibit muscle differentiation. However, the role of proto-oncogenic Ras （c-Ras） in muscle differentiation remains unclear. The active GTP-bound form of Ras has been known to associate with diverse effectors including Raf, phosphatidylinositol 3-kinase （PI3K）, RaI-GDS, and other molecules to transmit downstream signals. We hypothesize that c-Ras may stimulate muscle differentiation by selectively activating PI3K, an important mediator for muscle differentiation. In our experiments, inhibition of c-Ras by farnesyltransferase inhibitors and a dominant negative form of H-Ras （Ras S17N） suppressed muscle differentiation. Consistently, individual knockdown of H-Ras, K-Ras, and N-Ras by siRNAs all blocked muscle differentiation. Interestingly, we found that c-Ras preferentially interacts with PI3K rather than its major binding partner c-Raf, during myogenic differentiation, with total c-Ras activity remaining unchanged. PI3K and its downstream myogenic pathway, the Nox2/NF-kB/inducible nitric oxide synthase （iNOS） pathway, were found to be suppressed by inhibition of c-Ras activity during differentiation. Furthermore, expression of a constitutively active form of PI3K completely rescued the differentiation block and reactivated the Nox2/NF-kB/iNOS pathway in c-Ras-inhibited cells. On the ba- sis of our results, we conclude that contrary to oncogenic Ras, proto-oncogenic H-Ras, K-Ras, and N-Ras are directly involved in the promotion of muscle differentiation via PI3K and its downstream signaling pathways. In addition, PI3K pathway activation is associated with a concurrent suppression of the otherwise predominantly activated Raf/ Mek/Erk pathway.
文摘Objective: To study the relationship between the expression of muscarinic receptor subtype M3R and the decomposition of phosphatidylinositol (PI). Methods: The [3H]-IP contents were detected with [3H] incorporation in human cultured detrusor muscle cells after being stimulated by carbachol, atropine, methoctramine, and 4-DAMP, respectively. Results: The [3H]-IP contents were increased with the elevation of carbachol concentration. Both atropine and 4-DAMP significantly inhibited the effect of carbachol on PI decomposition (P<0.01), but methoctramine did not. No significant difference was seen in the effect of atropine and 4-DAMP on PI decomposition. Conclusion: M3R is closely related to the decomposition of PI, the second messenger molecule IP3.
基金Supported by Natural Science Foundation of Hubei Province of China(2011CDB012)Project of State Key Laboratory of Animal Nutrition(2004DA125184F1012)
文摘Intramuscular fat （IMF） content in chickens significantly contributes to meat quality. The main objective of this study was to assess the expression of calcineudn （CAN） and Ca^2＋/calmodutin-dependent protein kinase （CAME） in lipogene- sis in chicken muscle. The chickens were slaughtered and sampled at the ages of 4, 8, and 16 weeks, respectively. IMF content and the expression of CaN subunits and CaMK isoforms were measured in thigh muscle tissue. The results showed that the IMF contents were higher in chickens at the age of 16 weeks compared with those in chickens at the ages of 4 and 8 weeks （P〈0.05）. The expression levels of fatty acid synthase （FAS） and fatty acid translocase CD36 （FAT/CD36） mRNA in 16-week-old chickens were all significantly up-regulated compared with those in 4-week-old chickens （P〈0.05）. The mRNA levels of CaNB and CaMK IV in 16-week-old chickens were significantly lower than those in 4-week-old chickens （P〈0.05）. But the CaMK II mRNA levels in 16-week-old chickens were significantly higher than those in 4-week-old chickens （P〈0.05）. To investigate the roles of CaMK and CaN in adipogenesis, SV cells were incubated in standard adipogenesis medium for 24 h and treated with specific inhibitor of CaMK and CaN. The ex- pressions of CCAAT/enhancer binding protein β（C/EBPJ3）, sterol regulatory element- binding protein 1 （SREBP1） and peroxisome proliferation-activated receptor ）, （PPARy） were dramatically enhanced by CsA and CaN inhibitor （P〈0.05）. KN93, a CaMK Ⅱ inhibitor, dramatically repressed the expression of those lipogenic genes （P〈0.05）. All the results above indicated that CaN and CaMK had different effects on adipogenesis in the muscle of chickens.
基金supported by the National Natural Science Foundation of China(No.30701137)
文摘It is believed that amyloid-βpeptide（Aβ）plays a central role in the pathogenesis of Alzheimer’s disease（AD）.Thus,the process of amyloid precursor protein（APP）cleavage is a key event and has raised much attention in the field of AD research.It is proposed that APP,β-andγ-secretases are all located on the lipid raft,and the meeting of them is an indispensable step for Aβgeneration.Endocytosis can lead to clustering of APP,β-andγ-secretases from separate smaller lipid rafts into a larger one.On the other hand,for myristoylated alanine-rich C kinase substrate（MARCKS）,phosphorylation by protein kinase C（PKC）or interaction with Ca2＋can lead to its release from membrane into cytoplasm.This process induces the release of actins and phosphatidylinositol 4,5-bisphosphate（PIP2）,which are important factors for endocytosis.Thus,the present review proposes that MARCKS may be implicated in Aβgeneration,by modulating free PIP 2 level and actin movement,causing endocytosis.
基金the National Great Foundamental Research Proiect (No．G2000057004) the National Nature Science Foundation of China(No．19890308)．
文摘OBJECTIVE: To study the changes in activity of phosphatidylinositol 4 kinase (PI 4 kinase), phosphatidylinositol 4 phosphate 5 kinase (PIP 5 kinase) and protein kinase C (PKC) during myocardial ischemia and elucidate the relationship between phosphatidylinositol signal pathways and prolonged myocardial ischemia. METHODS: In vivo an ischemic rat model was used. Activity of PI 4 kinase, PIP 5 kinase and PKC were measured at different times in postischemic heart cells using isotope analysis. RESULTS: The activity of PI kinase, PIP kinase and PKC in the myocardium increased to peak at 1 hour postischemia, with activities 6.1, 3.0 and 4.0 fold over control levels, respectively. Their activities declined to normal levels with time. CONCLUSION: The phosphatidylinositol signal pathway is involved in prolonged myocardial ischemia, but its mechanism needs further study.
