The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
James T. Stull - One of the best experts on this subject based on the ideXlab platform.
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Role of Myosin Light Chain phosphatase in cardiac physiology and pathophysiology.
Journal of Molecular and Cellular Cardiology, 2016Co-Authors: Audrey N. Chang, Kristine E. Kamm, James T. StullAbstract:Abstract Maintenance of contractile performance of the heart is achieved in part by the constitutive 40% phosphorylation of Myosin regulatory Light Chain (RLC) in sarcomeres. The importance of this extent of RLC phosphorylation for optimal cardiac performance becomes apparent when various mouse models and resultant phenotypes are compared. The absence or attenuation of RLC phosphorylation results in poor performance leading to heart failure, whereas increased RLC phosphorylation is associated with cardiac protection from stresses. Although information is limited, RLC phosphorylation appears compromised in human heart failure which is consistent with data from mouse studies. The extent of cardiac RLC phosphorylation is determined by the balanced activities of cardiac Myosin Light Chain kinases and phosphatases, the regulatory mechanisms of which are now emerging. This review thusly focuses on kinases that may participate in phosphorylating RLC to make the substrate for cardiac Myosin Light Chain phosphatases, in addition to providing perspectives on the family of Myosin Light Chain phosphatases and involved signaling mechanisms. Because biochemical and physiological information about cardiac Myosin Light Chain phosphatase is sparse, such studies represent an emerging area of investigation in health and disease.
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signaling through Myosin Light Chain kinase in smooth muscles
Journal of Biological Chemistry, 2013Co-Authors: Jian Huang, Kristine E. Kamm, Weiqi He, James T. StullAbstract:Abstract Ca2+/calmodulin-dependent Myosin Light Chain kinase (MLCK) phosphorylates smooth muscle Myosin regulatory Light Chain (RLC) to initiate contraction. We used a tamoxifen-activated, smooth muscle-specific inactivation of MLCK expression in adult mice to determine whether MLCK was differentially limiting in distinct smooth muscles. A 50% decrease in MLCK in urinary bladder smooth muscle had no effect on RLC phosphorylation or on contractile responses, whereas an 80% decrease resulted in only a 20% decrease in RLC phosphorylation and contractile responses to the muscarinic agonist carbachol. Phosphorylation of the Myosin Light Chain phosphatase regulatory subunit MYPT1 at Thr-696 and Thr-853 and the inhibitor protein CPI-17 were also stimulated with carbachol. These results are consistent with the previous findings that activation of a small fraction of MLCK by limiting amounts of free Ca2+/calmodulin combined with Myosin Light Chain phosphatase inhibition is sufficient for robust RLC phosphorylation and contractile responses in bladder smooth muscle. In contrast, a 50% decrease in MLCK in aortic smooth muscle resulted in 40% inhibition of RLC phosphorylation and aorta contractile responses, whereas a 90% decrease profoundly inhibited both responses. Thus, MLCK content is limiting for contraction in aortic smooth muscle. Phosphorylation of CPI-17 and MYPT1 at Thr-696 and Thr-853 were also stimulated with phenylephrine but significantly less than in bladder tissue. These results indicate differential contributions of MLCK to signaling. Limiting MLCK activity combined with modest Ca2+ sensitization responses provide insights into how haploinsufficiency of MLCK may result in contractile dysfunction in vivo, leading to dissections of human thoracic aorta.
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Myosin Light Chain kinase and the role of Myosin Light Chain phosphorylation in skeletal muscle
Archives of Biochemistry and Biophysics, 2011Co-Authors: James T. Stull, Kristine E. Kamm, Rene VandenboomAbstract:Abstract Skeletal muscle Myosin Light Chain kinase (skMLCK) is a dedicated Ca 2+ /calmodulin-dependent serine–threonine protein kinase that phosphorylates the regulatory Light Chain (RLC) of sarcomeric Myosin. It is expressed from the MYLK2 gene specifically in skeletal muscle fibers with most abundance in fast contracting muscles. Biochemically, activation occurs with Ca 2+ binding to calmodulin forming a (Ca 2+ ) 4 •calmodulin complex sufficient for activation with a diffusion limited, stoichiometric binding and displacement of a regulatory segment from skMLCK catalytic core. The N-terminal sequence of RLC then extends through the exposed catalytic cleft for Ser15 phosphorylation. Removal of Ca 2+ results in the slow dissociation of calmodulin and inactivation of skMLCK. Combined biochemical properties provide unique features for the physiological responsiveness of RLC phosphorylation, including (1) rapid activation of MLCK by Ca 2+ /calmodulin, (2) limiting kinase activity so phosphorylation is slower than contraction, (3) slow MLCK inactivation after relaxation and (4) much greater kinase activity relative to Myosin Light Chain phosphatase (MLCP). SkMLCK phosphorylation of Myosin RLC modulates mechanical aspects of vertebrate skeletal muscle function. In permeabilized skeletal muscle fibers, phosphorylation-mediated alterations in Myosin structure increase the rate of force-generation by Myosin cross bridges to increase Ca 2+ -sensitivity of the contractile apparatus. Stimulation-induced increases in RLC phosphorylation in intact muscle produces isometric and concentric force potentiation to enhance dynamic aspects of muscle work and power in unfatigued or fatigued muscle. Moreover, RLC phosphorylation-mediated enhancements may interact with neural strategies for human skeletal muscle activation to ameliorate either central or peripheral aspects of fatigue.
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real time evaluation of Myosin Light Chain kinase activation in smooth muscle tissues from a transgenic calmodulin biosensor mouse
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Kristine E. Kamm, Jian Huang, Eiji Isotani, Yusuke Mizuno, Anthony Persechini, Ramaz Geguchadze, James T. StullAbstract:Ca2+/calmodulin (CaM)-dependent phosphorylation of Myosin regulatory Light Chain (RLC) by Myosin Light Chain kinase (MLCK) initiates smooth muscle contraction and regulates actoMyosin-based cytoskeletal functions in nonmuscle cells. The net extent of RLC phosphorylation is controlled by MLCK activity relative to Myosin Light Chain phosphatase activity. We have constructed a CaM-sensor MLCK where Ca2+-dependent CaM binding increases the catalytic activity of the kinase domain, whereas coincident binding to the biosensor domain decreases fluorescence resonance energy transfer between two fluorescent proteins. We have created transgenic mice expressing this construct specifically in smooth muscle cells to perform real-time evaluations of the relationship between smooth muscle contractility and MLCK activation in intact tissues and organs. Measurements in intact bladder smooth muscle demonstrate that MLCK activation increases rapidly during KCl-induced contractions but is not maximal, consistent with a limiting amount of cellular CaM. Carbachol treatment produces the same amount of force development and RLC phosphorylation, with much smaller increases in [Ca2+]i and MLCK activation. A Rho kinase inhibitor suppresses RLC phosphorylation and force but not MLCK activation in carbachol-treated tissues. These observations are consistent with a model in which the magnitude of an agonist-mediated smooth muscle contraction depends on a rapid but limited Ca2+/CaM-dependent activation of MLCK and Rho kinase-mediated inhibition of Myosin Light Chain phosphatase activity. These studies demonstrate the feasibility of producing transgenic biosensor mice for investigations of signaling processes in intact systems.
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Properties of filament-bound Myosin Light Chain kinase.
Journal of Biological Chemistry, 1999Co-Authors: Katherine Luby-phelps, James T. StullAbstract:Abstract Myosin Light Chain kinase binds to actin-containing filaments from cells with a greater affinity than to F-actin. However, it is not known if this binding in cells is regulated by Ca2+/calmodulin as it is with F-actin. Therefore, the binding properties of the kinase to stress fibers were examined in smooth muscle-derived A7r5 cells. Full-length Myosin Light Chain kinase or a truncation mutant lacking residues 2–142 was expressed as chimeras containing green fluorescent protein at the C terminus. In intact cells, the full-length kinase bound to stress fibers, whereas the truncated kinase showed diffuse fluorescence in the cytoplasm. After permeabilization with saponin, the fluorescence from the truncated kinase disappeared, whereas the fluorescence of the full-length kinase was retained on stress fibers. Measurements of fluorescence intensities and fluorescence recovery after photobleaching of the full-length Myosin Light Chain kinase in saponin-permeable cells showed that Ca2+/calmodulin did not dissociate the kinase from these filaments. However, the filament-bound kinase was sufficient for Ca2+-dependent phosphorylation of Myosin regulatory Light Chain and contraction of stress fibers. Thus, dissociation of Myosin Light Chain kinase from actin-containing thin filaments is not necessary for phosphorylation of Myosin Light Chain in thick filaments. We note that the distance between the N terminus and the catalytic core of the kinase is sufficient to span the distance between thin and thick filaments.
Jerrold R Turner - One of the best experts on this subject based on the ideXlab platform.
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Myosin Light Chain kinase pulling the strings of epithelial tight junction function
Annals of the New York Academy of Sciences, 2012Co-Authors: Kevin E Cunningham, Jerrold R TurnerAbstract:Dynamic regulation of paracellular permeability is essential for physiological epithelial function, while dysregulated permeability is common in disease. The recent elucidation of the molecular composition of the epithelial tight junction complex has been accompanied by characterization of diverse intracellular mediators of paracellular permeabiltiy. Myosin Light Chain kinase, which induces contraction of the perijunctional actoMyosin ring through Myosin II regulatory Light Chain phosphorylation, has emerged as a key regulator of tight junction permeability. Examination of the regulation and role of MLCK in tight junction dysfunction has helped to define pathological processes, characterize the role of barrier loss in disease pathogenesis, and may provide future therapeutic targets to treat intestinal disease.
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Myosin Light Chain phosphorylation regulates barrier function by remodeling tight junction structure
Journal of Cell Science, 2006Co-Authors: Le Shen, Eric D Black, Edwina D Witkowski, Wayne I Lencer, Vince Guerriero, Eveline E Schneeberger, Jerrold R TurnerAbstract:Epithelial tight junctions form a barrier against passive paracellular flux. This barrier is regulated by complex physiologic and pathophysiologic signals that acutely fine-tune tight junction permeability. Although actoMyosin contraction and Myosin Light Chain phosphorylation are clearly involved in some forms of tight junction regulation, the contributions of other signaling events and the role of Myosin Light Chain phosphorylation in this response are poorly understood. Here we ask if activation of Myosin Light Chain kinase alone is sufficient to induce downstream tight junction regulation. We use a confluent polarized intestinal epithelial cell model system in which constitutively active Myosin Light Chain kinase, tMLCK, is expressed using an inducible promoter. tMLCK expression increases Myosin Light Chain phosphorylation, reorganizes perijunctional F-actin, and increases tight junction permeability. TJ proteins ZO-1 and occludin are markedly redistributed, morphologically and biochemically, but effects on claudin-1 and claudin-2 are limited. tMLCK inhibition prevents changes in barrier function and tight junction organization induced by tMLCK expression, suggesting that these events both require Myosin Light Chain phosphorylation. We conclude that Myosin Light Chain phosphorylation alone is sufficient to induce tight junction regulation and provide new insights into the molecular mechanisms that mediate this regulation.
Kristine E. Kamm - One of the best experts on this subject based on the ideXlab platform.
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Role of Myosin Light Chain phosphatase in cardiac physiology and pathophysiology.
Journal of Molecular and Cellular Cardiology, 2016Co-Authors: Audrey N. Chang, Kristine E. Kamm, James T. StullAbstract:Abstract Maintenance of contractile performance of the heart is achieved in part by the constitutive 40% phosphorylation of Myosin regulatory Light Chain (RLC) in sarcomeres. The importance of this extent of RLC phosphorylation for optimal cardiac performance becomes apparent when various mouse models and resultant phenotypes are compared. The absence or attenuation of RLC phosphorylation results in poor performance leading to heart failure, whereas increased RLC phosphorylation is associated with cardiac protection from stresses. Although information is limited, RLC phosphorylation appears compromised in human heart failure which is consistent with data from mouse studies. The extent of cardiac RLC phosphorylation is determined by the balanced activities of cardiac Myosin Light Chain kinases and phosphatases, the regulatory mechanisms of which are now emerging. This review thusly focuses on kinases that may participate in phosphorylating RLC to make the substrate for cardiac Myosin Light Chain phosphatases, in addition to providing perspectives on the family of Myosin Light Chain phosphatases and involved signaling mechanisms. Because biochemical and physiological information about cardiac Myosin Light Chain phosphatase is sparse, such studies represent an emerging area of investigation in health and disease.
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signaling through Myosin Light Chain kinase in smooth muscles
Journal of Biological Chemistry, 2013Co-Authors: Jian Huang, Kristine E. Kamm, Weiqi He, James T. StullAbstract:Abstract Ca2+/calmodulin-dependent Myosin Light Chain kinase (MLCK) phosphorylates smooth muscle Myosin regulatory Light Chain (RLC) to initiate contraction. We used a tamoxifen-activated, smooth muscle-specific inactivation of MLCK expression in adult mice to determine whether MLCK was differentially limiting in distinct smooth muscles. A 50% decrease in MLCK in urinary bladder smooth muscle had no effect on RLC phosphorylation or on contractile responses, whereas an 80% decrease resulted in only a 20% decrease in RLC phosphorylation and contractile responses to the muscarinic agonist carbachol. Phosphorylation of the Myosin Light Chain phosphatase regulatory subunit MYPT1 at Thr-696 and Thr-853 and the inhibitor protein CPI-17 were also stimulated with carbachol. These results are consistent with the previous findings that activation of a small fraction of MLCK by limiting amounts of free Ca2+/calmodulin combined with Myosin Light Chain phosphatase inhibition is sufficient for robust RLC phosphorylation and contractile responses in bladder smooth muscle. In contrast, a 50% decrease in MLCK in aortic smooth muscle resulted in 40% inhibition of RLC phosphorylation and aorta contractile responses, whereas a 90% decrease profoundly inhibited both responses. Thus, MLCK content is limiting for contraction in aortic smooth muscle. Phosphorylation of CPI-17 and MYPT1 at Thr-696 and Thr-853 were also stimulated with phenylephrine but significantly less than in bladder tissue. These results indicate differential contributions of MLCK to signaling. Limiting MLCK activity combined with modest Ca2+ sensitization responses provide insights into how haploinsufficiency of MLCK may result in contractile dysfunction in vivo, leading to dissections of human thoracic aorta.
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Myosin Light Chain kinase and the role of Myosin Light Chain phosphorylation in skeletal muscle
Archives of Biochemistry and Biophysics, 2011Co-Authors: James T. Stull, Kristine E. Kamm, Rene VandenboomAbstract:Abstract Skeletal muscle Myosin Light Chain kinase (skMLCK) is a dedicated Ca 2+ /calmodulin-dependent serine–threonine protein kinase that phosphorylates the regulatory Light Chain (RLC) of sarcomeric Myosin. It is expressed from the MYLK2 gene specifically in skeletal muscle fibers with most abundance in fast contracting muscles. Biochemically, activation occurs with Ca 2+ binding to calmodulin forming a (Ca 2+ ) 4 •calmodulin complex sufficient for activation with a diffusion limited, stoichiometric binding and displacement of a regulatory segment from skMLCK catalytic core. The N-terminal sequence of RLC then extends through the exposed catalytic cleft for Ser15 phosphorylation. Removal of Ca 2+ results in the slow dissociation of calmodulin and inactivation of skMLCK. Combined biochemical properties provide unique features for the physiological responsiveness of RLC phosphorylation, including (1) rapid activation of MLCK by Ca 2+ /calmodulin, (2) limiting kinase activity so phosphorylation is slower than contraction, (3) slow MLCK inactivation after relaxation and (4) much greater kinase activity relative to Myosin Light Chain phosphatase (MLCP). SkMLCK phosphorylation of Myosin RLC modulates mechanical aspects of vertebrate skeletal muscle function. In permeabilized skeletal muscle fibers, phosphorylation-mediated alterations in Myosin structure increase the rate of force-generation by Myosin cross bridges to increase Ca 2+ -sensitivity of the contractile apparatus. Stimulation-induced increases in RLC phosphorylation in intact muscle produces isometric and concentric force potentiation to enhance dynamic aspects of muscle work and power in unfatigued or fatigued muscle. Moreover, RLC phosphorylation-mediated enhancements may interact with neural strategies for human skeletal muscle activation to ameliorate either central or peripheral aspects of fatigue.
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real time evaluation of Myosin Light Chain kinase activation in smooth muscle tissues from a transgenic calmodulin biosensor mouse
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Kristine E. Kamm, Jian Huang, Eiji Isotani, Yusuke Mizuno, Anthony Persechini, Ramaz Geguchadze, James T. StullAbstract:Ca2+/calmodulin (CaM)-dependent phosphorylation of Myosin regulatory Light Chain (RLC) by Myosin Light Chain kinase (MLCK) initiates smooth muscle contraction and regulates actoMyosin-based cytoskeletal functions in nonmuscle cells. The net extent of RLC phosphorylation is controlled by MLCK activity relative to Myosin Light Chain phosphatase activity. We have constructed a CaM-sensor MLCK where Ca2+-dependent CaM binding increases the catalytic activity of the kinase domain, whereas coincident binding to the biosensor domain decreases fluorescence resonance energy transfer between two fluorescent proteins. We have created transgenic mice expressing this construct specifically in smooth muscle cells to perform real-time evaluations of the relationship between smooth muscle contractility and MLCK activation in intact tissues and organs. Measurements in intact bladder smooth muscle demonstrate that MLCK activation increases rapidly during KCl-induced contractions but is not maximal, consistent with a limiting amount of cellular CaM. Carbachol treatment produces the same amount of force development and RLC phosphorylation, with much smaller increases in [Ca2+]i and MLCK activation. A Rho kinase inhibitor suppresses RLC phosphorylation and force but not MLCK activation in carbachol-treated tissues. These observations are consistent with a model in which the magnitude of an agonist-mediated smooth muscle contraction depends on a rapid but limited Ca2+/CaM-dependent activation of MLCK and Rho kinase-mediated inhibition of Myosin Light Chain phosphatase activity. These studies demonstrate the feasibility of producing transgenic biosensor mice for investigations of signaling processes in intact systems.
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Phosphorylation of Myosin Light Chain kinase: a cellular mechanism for Ca2+ desensitization
Molecular and Cellular Biochemistry, 1993Co-Authors: James T. Stull, Malú G. Tansey, Da Chun Tang, R. Ann Word, Kristine E. KammAbstract:Phosphorylation of the regulatory Light Chain of Myosin by the Ca2+/calmodulin-dependent Myosin Light Chain kinase plays an important role in smooth muscle contraction, nonmuscle cell shape changes, platelet contraction, secretion, and other cellular processes. Smooth muscle Myosin Light Chain kinase is also phosphorylated, and recent results from experiments designed to satisfy the criteria of Krebs and Beavo for establishing the physiological significance of enzyme phosphorylation have provided insights into the cellular regulation and function of this phosphorylation in smooth muscle. The multifunctional Ca2+/calmodulin-dependent protein kinase II phosphorylates Myosin Light Chain kinase at a regulatory site near the calmodulin-binding domain. This phosphorylation increases the concentration of Ca2+/calmodulin required for activation and hence increases the Ca2+ concentrations required for Myosin Light Chain kinase activity in cells. However, the concentration of cytosolic Ca2+ required to effect Myosin Light Chain kinase phosphorylation is greater than that required for Myosin Light Chain phosphorylation. Phosphorylation of Myosin Light Chain kinase is only one of a number of mechanisms used by the cell to down regulate the Ca2+ signal in smooth muscle. Since both smooth and nonmuscle cells express the same form of Myosin Light Chain kinase, this phosphorylation may play a regulatory role in cellular processes that are dependent on Myosin Light Chain phosphorylation.
Kozo Kaibuchi - One of the best experts on this subject based on the ideXlab platform.
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thrombin inactivates Myosin Light Chain phosphatase via rho and its target rho kinase in human endothelial cells
Journal of Biological Chemistry, 1998Co-Authors: Markus Essler, Mutsuki Amano, Hansjoachim Kruse, Kozo Kaibuchi, Peter C Weber, Martin AepfelbacherAbstract:Abstract The role of Rho GTPase and its downstream targets Rho kinase and Myosin Light Chain phosphatase in thrombin-induced endothelial cell contraction was investigated. The specific Rho inactivator C3-transferase from Clostridium botulinum as well as microinjection of the isolated Rho-binding domain of Rho kinase or active Myosin Light Chain phosphatase abolished thrombin-stimulated endothelial cell contraction. Conversely, microinjection of constitutively active V14Rho, constitutively active catalytic domain of Rho kinase, or treatment with the phosphatase inhibitor tautomycin caused contraction. These data are consistent with the notion that thrombin activates Rho/Rho kinase to inactivate Myosin Light Chain phosphatase in endothelial cells. In fact, we demonstrate that thrombin transiently inactivated Myosin Light Chain phosphatase, and this correlated with a peak in Myosin Light Chain phosphorylation. C3-transferase abolished the decrease in Myosin Light Chain phosphatase activity as well as the subsequent increase in Myosin Light Chain phosphorylation and cell contraction. These data suggest that thrombin activates the Rho/Rho kinase pathway to inactivate Myosin Light Chain phosphatase as part of a signaling network that controls Myosin Light Chain phosphorylation/contraction in human endothelial cells.
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rho associated kinase directly induces smooth muscle contraction through Myosin Light Chain phosphorylation
Journal of Biological Chemistry, 1997Co-Authors: Yasuko Kureishi, Mutsuki Amano, Sei Kobayashi, Kazushi Kimura, Hideo Kanaide, Takeshi Nakano, Kozo KaibuchiAbstract:Abstract Small GTPase Rho plays pivotal roles in the Ca2+ sensitization of smooth muscle. However, the GTP-bound active form of Rho failed to exert Ca2+-sensitizing effects in extensively Triton X-100-permeabilized smooth muscle preparations, due to the loss of the important diffusible cofactor (Gong, M. C., Iizuka, K., Nixon, G., Browne, J. P., Hall, A., Eccleston, J. F., Sugai, M., Kobayashi, S., Somlyo, A. V., and Somlyo, A. P. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 1340–1345). Here we demonstrate the contractile effects of Rho-associated kinase (Rho-kinase), recently identified as a putative target of Rho, on the Triton X-100-permeabilized smooth muscle of rabbit portal vein. Introduction of the constitutively active form of Rho-kinase into the cytosol of Triton X-100-permeabilized smooth muscle provoked a contraction and a proportional increase in levels of monophosphorylation of Myosin Light Chain in both the presence and the absence of cytosolic Ca2+. These effects of constitutively active Rho-kinase were wortmannin (a potent Myosin Light Chain kinase inhibitor)-insensitive. Immunoblot analysis revealed that the amount of native Rho-kinase was markedly lower in Triton X-100-permeabilized tissue than in intact tissue. Our results demonstrate that Rho-kinase directly modulates smooth muscle contraction through Myosin Light Chain phosphorylation, independently of the Ca2+-calmodulin-dependent Myosin Light Chain kinase pathway.
Mitsuo Ikebe - One of the best experts on this subject based on the ideXlab platform.
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zipper interacting protein kinase induces ca2 free smooth muscle contraction via Myosin Light Chain phosphorylation
Journal of Biological Chemistry, 2001Co-Authors: Naohisa Niiro, Mitsuo IkebeAbstract:Abstract The inhibition of Myosin phosphatase evokes smooth muscle contraction in the absence of Ca2+, yet the underlying mechanisms are not understood. To this end, we have cloned smooth muscle zipper-interacting protein (ZIP) kinase cDNA. ZIP kinase is present in various smooth muscle tissues including arteries. Triton X-100 skinning did not diminish ZIP kinase content, suggesting that ZIP kinase associates with the filamentous component in smooth muscle. Smooth muscle ZIP kinase phosphorylated smooth muscle Myosin as well as the isolated 20-kDa Myosin Light Chain in a Ca2+/calmodulin-independent manner. ZIP kinase phosphorylated Myosin Light Chain at both Ser19 and Thr18 residues with the same rate constant. The actin-activated ATPase activity of Myosin increased significantly following ZIP kinase-induced phosphorylation. Introduction of ZIP kinase into Triton X-100-permeabilized rabbit mesenteric artery provoked a Ca2+-free contraction. A protein phosphatase inhibitor, microcystin LR, also induced contraction in the absence of Ca2+, which was accompanied by an increase in both mono- and diphosphorylation of Myosin Light Chain. The observed sensitivity of the microcystin-induced contraction to various protein kinase inhibitors was identical to the sensitivity of isolated ZIP kinase to these inhibitors. These results suggest that ZIP kinase is responsible for Ca2+ independent Myosin phosphorylation and contraction in smooth muscle.
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Substrate based inhibitors of smooth muscle Myosin Light Chain kinase.
Biochemical and Biophysical Research Communications, 1992Co-Authors: Suzanne Moreland, Mitsuo Ikebe, John T. Hunt, Robert S. MorelandAbstract:Summary Activation of Myosin Light Chain kinase is a prerequisite for smooth muscle activation. In this study, short peptide analogs of the phosphorylation site of the Myosin Light Chain were studied for their effects on several contractile protein systems. The peptides inhibited phosphorylation of isolated ventricular and smooth muscle Myosin Light Chains by smooth muscle Myosin Light Chain kinase, but they were only weak inhibitors of phosphorylation of intact Myosin and actoMyosin. The peptides were also unable to block force development or Myosin Light Chain phosphorylation in glycerol permeabilized fibers of swine carotid media. Apparently, the association of the Myosin Light Chain with Myosin changes its conformation such that substrate analogs which are potent inhibitors of the phosphorylation of isolated Myosin Light Chains by Myosin Light Chain kinase are ineffective at blocking phosphorylation of the intact molecule.
