AIM: To study preliminarily the properties of myosin light chain kinase (MLCK) in rabbit liver. METHODS: The expression of MLCK was detected by reverse transcription-polymerase chain reaction(RT-PCR); the MLCK was obt...AIM: To study preliminarily the properties of myosin light chain kinase (MLCK) in rabbit liver. METHODS: The expression of MLCK was detected by reverse transcription-polymerase chain reaction(RT-PCR); the MLCK was obtained from rabbit liver, and its activity was analyzed by gamma-(32)P incorporation technique to detect the phosphorylation of myosin light chain. RESULTS: MLCK was expressed in rabbit liver, and the activity of the enzyme was similar to rabbit smooth muscle MLCK, and calmodulin-dependent. When the concentration was 0.65 mg x L(-1), the activity was at the highest level. CONCLUSION: MLCK expressed in rabbit liver may catalyze the phosphorylation of myosin light chain, which may play important roles in the regulation of hepatic cell functions.展开更多
Objective To investigate role and mechanism of phosphate myosin light chain ( pMLC) in rat kidney of chronic allograft nephropathy ( CAN) model. Methods Left donor kidneys from Fisher ( F344) rats were ortho-topically...Objective To investigate role and mechanism of phosphate myosin light chain ( pMLC) in rat kidney of chronic allograft nephropathy ( CAN) model. Methods Left donor kidneys from Fisher ( F344) rats were ortho-topically transplanted into Lewis recipients,Meanwhile, F344 rats and LEW rats with resection of right展开更多
Background:Dysuria is one of the main symptoms of genitourinary syndrome of menopause,which causes serious disruption to the normal life of peri-menopausal women.Studies have shown that it is related to decrease of de...Background:Dysuria is one of the main symptoms of genitourinary syndrome of menopause,which causes serious disruption to the normal life of peri-menopausal women.Studies have shown that it is related to decrease of detrusor contractile function,but the exact mechanism is still poorly understood.Previous results have suggested that the sphingosine-1-phosphate(S1P)pathway can regulate detrusor contraction,and this pathway is affected by estrogen in various tissues.However,how estrogen affects this pathway in the detrusor has not been investigated.In this study,we detected changes of the S1P/RhoA/Rho associated kinases(ROCK)/myosin light chain(MLC)pathway in the detrusor of ovariectomized rats in order to explore the underlying mechanism of dysuria during peri-menopause.Methods::Thirty-six female Sprague-Dawley rats were randomly divided into SHAM(sham operation),OVX(ovariectomy),and E groups(ovariectomy+estrogen),with 12 rats in each group.We obtained bladder detrusor tissues from each group and examined the mRNA and protein levels of the major components of the S1P/RhoA/ROCK/MLC pathway using quantitative real-time polymerase chain reaction and Western blotting,respectively.We also quantified the content of S1P in the detrusor using an enzyme linked immunosorbent assay.Finally,we compared results between the groups with one-way analysis of variance.Results::The components of the S1P pathway and the RhoA/ROCK/MLC pathway of the OVX group were significantly decreased,as compared with SHAM group.The percent decreases of the components in the S1P pathway were as follows:sphingosine kinase 1(mRNA:39%,protein:45%)(both P<0.05),S1P(21.73±1.09 nmol/g vs.18.86±0.69 nmol/g)(P<0.05),and S1P receptor 2/3(S1PR2/3)(mRNA:25%,27%,respectively)(P<0.05).However,the protein expression levels of S1PR2/3 and the protein and mRNA levels of SphK2 and S1PR1 did not show significant differences between groups(P>0.05).The percent decreases of the components in the RhoA/ROCK/MLC pathway were as follows:ROCK2(protein:41%,mRNA:36%)(both P<0.05),p-MYPT1(protein:54%)(P<0.05),and p-MLC20(protein:47%)(P<0.05),but there were no significant differences in the mRNA and protein levels of RhoA,ROCK1,MYPT1,and MLC20(all P>0.05).In addition,all of the above-mentioned decreases could be reversed after estrogen supplementation(E group vs.SHAM group)(all P>0.05).Conclusion::In this study,we confirmed that ovariectomy is closely associated with the down-regulation of the S1P/RhoA/ROCK/MLC pathway in the rat detrusor,which may be one mechanism of dysuria caused by decreased contractile function of the female detrusor during peri-menopause.展开更多
Long myosin light chain kinase (L-MLCK) contains five DFRXXL motifs with ability to bind F-actin. Binding stoichiometry data indicated that each DFRXXL motif might bind each G-actin, but its biological significance re...Long myosin light chain kinase (L-MLCK) contains five DFRXXL motifs with ability to bind F-actin. Binding stoichiometry data indicated that each DFRXXL motif might bind each G-actin, but its biological significance remained unknown. We hypothesized that L-MLCK might act as an F-actin bundle peptides by its multiple binding sites of 5DFRXXL motifs to actin. In order to characterize F-actin-bundle formation properties of 5DFRXXL region of long myosin light chain kinase, we expressed and purified 5DFRXXL peptides tagged with HA in vitro. The properties of 5DFRXXL peptides binding to myofilaments or F-actin were analyzed by binding stoichiometries assays. The results indicated that 5DFRXXL peptides bound to myofilaments or F-actin with high affinity. KD values of 5DFRXXL binding to myofilaments and F-actin were 0.45 and 0.41 μmol/L, re- spectively. Cross-linking assay demonstrated that 5DFRXXL peptides could bundle F-actin efficiently. Typical F-actin bundles were observed morphologically through determina- tion of confocal and electron microscopy after adding 5DFRXXL peptides. After transfection of pEGFP-5DFRXXL plasmid into eukaryocyte, spike structure was observed around cell membrane edge. We guess that such structure formation may be attributable to F-actin over-bundle forma- tion caused by 5DFRXXL peptides. Therefore, we suppose that L-MLCK may be a new bundling protein and somehow play a certain role in organization of cell skeleton besides mediating cell contraction by it kinase activity.展开更多
In the course of analysis of single fibers randomly excided from the fast and slow muscles of the rat for myosin light chain patterns, we have found that the light chains of all fibers taken from extensor digitorum lo...In the course of analysis of single fibers randomly excided from the fast and slow muscles of the rat for myosin light chain patterns, we have found that the light chains of all fibers taken from extensor digitorum longus (EDL) show the same as but different from those of fibers taken from soleus (Sol) in pattern. This characteristic differentiation of展开更多
The aim of this short review is to describe the role of myosin isoforms during the adaptation of skeletal muscle to prolonged physical activity (for example endurance exercise) and to show the coordination between cha...The aim of this short review is to describe the role of myosin isoforms during the adaptation of skeletal muscle to prolonged physical activity (for example endurance exercise) and to show the coordination between changes in muscle oxidative capacity and myofibrillar apparatus in slow-twitch and fast-twitch muscles. Adaptational changes in myosin isoforms during long lasting muscle activity (decrease of MyHC IIb isoforms relative content and increase of that MyHC IIa and decrease of MyLC 1 fast isoforms in fast-twitch muscles) are in good coordination with changes of muscle oxidative capacity. These changes show that during regular endurance exercise fast-twitch muscle fibers (type IIA) are also recruited and create the potential source of increase in endurance capacity during the process of adaptation to the prolonged physical activity.展开更多
Inhibition of protein tyrosine phosphatase by orthovanadate induces vasoconstriction, which is mediated by the Rho kinase-dependent inactivation of myosin light chain phosphatase (MLCP) via signaling downstream of Src...Inhibition of protein tyrosine phosphatase by orthovanadate induces vasoconstriction, which is mediated by the Rho kinase-dependent inactivation of myosin light chain phosphatase (MLCP) via signaling downstream of Src-induced activation of the epidermal growth factor (EGF) receptor. The present study investigated the potential role of EGF in orthovanadate (OVA)-dependent vaso-constriction. OVA-induced aortic contraction significantly increased in the presence of EGF, and was abolished by inhibitors of Rho kinase (Y27632), extracellular signal-regulated kinase 1 and 2 (Erk1/2) (FR180204), Erk1/2 kinase (PD98059), EGF receptor (AG1478), and Src (PP2). Treatment of the rat endothelium-denuded thoracic aorta with either EGF or OVA augmented the phosphorylation of myosin phosphatase target subunit 1 (MYPT1) at Thr-853 and of the EGF receptor at Tyr-1173. The phosphorylation of MYPT1 was further increased by co-stimulation with EGF and OVA. EGF receptor phosphorylation at Tyr-845 was also increased by EGF or OVA;this effect was augmented by co-stimulation with EGF and OVA, and was abolished by Src inhibition. In addition, Erk1/2 was phosphorylated by EGF or by co-treatment with EGF and OVA;this was abolished by an EGF receptor inhibitor, but not by Src inhibition. These results suggested that OVA-induced EGF-related contraction was mediated by the Rho kinase-dependent inactivation of MLCP via two different signaling cascades: Src-dependent phosphorylation of the EGF receptor at Tyr-845 and EGF-dependent phosphorylation of Erk1/2.展开更多
基金Supported by the National Natural Science Foundation of China(39870324,YW)Key Innovation Project of Chinese Academy of Science,P.R.China(KSCX 2-2-01,XB Yao)Grant for Excellent Young Teachers of Ministry of Education of China(99044312,YW)
文摘AIM: To study preliminarily the properties of myosin light chain kinase (MLCK) in rabbit liver. METHODS: The expression of MLCK was detected by reverse transcription-polymerase chain reaction(RT-PCR); the MLCK was obtained from rabbit liver, and its activity was analyzed by gamma-(32)P incorporation technique to detect the phosphorylation of myosin light chain. RESULTS: MLCK was expressed in rabbit liver, and the activity of the enzyme was similar to rabbit smooth muscle MLCK, and calmodulin-dependent. When the concentration was 0.65 mg x L(-1), the activity was at the highest level. CONCLUSION: MLCK expressed in rabbit liver may catalyze the phosphorylation of myosin light chain, which may play important roles in the regulation of hepatic cell functions.
文摘Objective To investigate role and mechanism of phosphate myosin light chain ( pMLC) in rat kidney of chronic allograft nephropathy ( CAN) model. Methods Left donor kidneys from Fisher ( F344) rats were ortho-topically transplanted into Lewis recipients,Meanwhile, F344 rats and LEW rats with resection of right
基金This study was supported by a grant of the National Key Research&Development Program of China(No.2018YFC2002202).
文摘Background:Dysuria is one of the main symptoms of genitourinary syndrome of menopause,which causes serious disruption to the normal life of peri-menopausal women.Studies have shown that it is related to decrease of detrusor contractile function,but the exact mechanism is still poorly understood.Previous results have suggested that the sphingosine-1-phosphate(S1P)pathway can regulate detrusor contraction,and this pathway is affected by estrogen in various tissues.However,how estrogen affects this pathway in the detrusor has not been investigated.In this study,we detected changes of the S1P/RhoA/Rho associated kinases(ROCK)/myosin light chain(MLC)pathway in the detrusor of ovariectomized rats in order to explore the underlying mechanism of dysuria during peri-menopause.Methods::Thirty-six female Sprague-Dawley rats were randomly divided into SHAM(sham operation),OVX(ovariectomy),and E groups(ovariectomy+estrogen),with 12 rats in each group.We obtained bladder detrusor tissues from each group and examined the mRNA and protein levels of the major components of the S1P/RhoA/ROCK/MLC pathway using quantitative real-time polymerase chain reaction and Western blotting,respectively.We also quantified the content of S1P in the detrusor using an enzyme linked immunosorbent assay.Finally,we compared results between the groups with one-way analysis of variance.Results::The components of the S1P pathway and the RhoA/ROCK/MLC pathway of the OVX group were significantly decreased,as compared with SHAM group.The percent decreases of the components in the S1P pathway were as follows:sphingosine kinase 1(mRNA:39%,protein:45%)(both P<0.05),S1P(21.73±1.09 nmol/g vs.18.86±0.69 nmol/g)(P<0.05),and S1P receptor 2/3(S1PR2/3)(mRNA:25%,27%,respectively)(P<0.05).However,the protein expression levels of S1PR2/3 and the protein and mRNA levels of SphK2 and S1PR1 did not show significant differences between groups(P>0.05).The percent decreases of the components in the RhoA/ROCK/MLC pathway were as follows:ROCK2(protein:41%,mRNA:36%)(both P<0.05),p-MYPT1(protein:54%)(P<0.05),and p-MLC20(protein:47%)(P<0.05),but there were no significant differences in the mRNA and protein levels of RhoA,ROCK1,MYPT1,and MLC20(all P>0.05).In addition,all of the above-mentioned decreases could be reversed after estrogen supplementation(E group vs.SHAM group)(all P>0.05).Conclusion::In this study,we confirmed that ovariectomy is closely associated with the down-regulation of the S1P/RhoA/ROCK/MLC pathway in the rat detrusor,which may be one mechanism of dysuria caused by decreased contractile function of the female detrusor during peri-menopause.
基金supported by the National Natural Science Foundation of China(Grant No.30470852)the National Gongguan Project of China(Grant No.21001BA710B).
文摘Long myosin light chain kinase (L-MLCK) contains five DFRXXL motifs with ability to bind F-actin. Binding stoichiometry data indicated that each DFRXXL motif might bind each G-actin, but its biological significance remained unknown. We hypothesized that L-MLCK might act as an F-actin bundle peptides by its multiple binding sites of 5DFRXXL motifs to actin. In order to characterize F-actin-bundle formation properties of 5DFRXXL region of long myosin light chain kinase, we expressed and purified 5DFRXXL peptides tagged with HA in vitro. The properties of 5DFRXXL peptides binding to myofilaments or F-actin were analyzed by binding stoichiometries assays. The results indicated that 5DFRXXL peptides bound to myofilaments or F-actin with high affinity. KD values of 5DFRXXL binding to myofilaments and F-actin were 0.45 and 0.41 μmol/L, re- spectively. Cross-linking assay demonstrated that 5DFRXXL peptides could bundle F-actin efficiently. Typical F-actin bundles were observed morphologically through determina- tion of confocal and electron microscopy after adding 5DFRXXL peptides. After transfection of pEGFP-5DFRXXL plasmid into eukaryocyte, spike structure was observed around cell membrane edge. We guess that such structure formation may be attributable to F-actin over-bundle forma- tion caused by 5DFRXXL peptides. Therefore, we suppose that L-MLCK may be a new bundling protein and somehow play a certain role in organization of cell skeleton besides mediating cell contraction by it kinase activity.
文摘In the course of analysis of single fibers randomly excided from the fast and slow muscles of the rat for myosin light chain patterns, we have found that the light chains of all fibers taken from extensor digitorum longus (EDL) show the same as but different from those of fibers taken from soleus (Sol) in pattern. This characteristic differentiation of
文摘The aim of this short review is to describe the role of myosin isoforms during the adaptation of skeletal muscle to prolonged physical activity (for example endurance exercise) and to show the coordination between changes in muscle oxidative capacity and myofibrillar apparatus in slow-twitch and fast-twitch muscles. Adaptational changes in myosin isoforms during long lasting muscle activity (decrease of MyHC IIb isoforms relative content and increase of that MyHC IIa and decrease of MyLC 1 fast isoforms in fast-twitch muscles) are in good coordination with changes of muscle oxidative capacity. These changes show that during regular endurance exercise fast-twitch muscle fibers (type IIA) are also recruited and create the potential source of increase in endurance capacity during the process of adaptation to the prolonged physical activity.
文摘Inhibition of protein tyrosine phosphatase by orthovanadate induces vasoconstriction, which is mediated by the Rho kinase-dependent inactivation of myosin light chain phosphatase (MLCP) via signaling downstream of Src-induced activation of the epidermal growth factor (EGF) receptor. The present study investigated the potential role of EGF in orthovanadate (OVA)-dependent vaso-constriction. OVA-induced aortic contraction significantly increased in the presence of EGF, and was abolished by inhibitors of Rho kinase (Y27632), extracellular signal-regulated kinase 1 and 2 (Erk1/2) (FR180204), Erk1/2 kinase (PD98059), EGF receptor (AG1478), and Src (PP2). Treatment of the rat endothelium-denuded thoracic aorta with either EGF or OVA augmented the phosphorylation of myosin phosphatase target subunit 1 (MYPT1) at Thr-853 and of the EGF receptor at Tyr-1173. The phosphorylation of MYPT1 was further increased by co-stimulation with EGF and OVA. EGF receptor phosphorylation at Tyr-845 was also increased by EGF or OVA;this effect was augmented by co-stimulation with EGF and OVA, and was abolished by Src inhibition. In addition, Erk1/2 was phosphorylated by EGF or by co-treatment with EGF and OVA;this was abolished by an EGF receptor inhibitor, but not by Src inhibition. These results suggested that OVA-induced EGF-related contraction was mediated by the Rho kinase-dependent inactivation of MLCP via two different signaling cascades: Src-dependent phosphorylation of the EGF receptor at Tyr-845 and EGF-dependent phosphorylation of Erk1/2.
