Role of myosin light-chain phosphorylation and microtubules in stress fiber morphology in cultured mesangial cells

1985 ◽  
Vol 249 (2) ◽  
pp. F227-F235 ◽  
Author(s):  
J. I. Kreisberg ◽  
M. A. Venkatachalam ◽  
R. A. Radnik ◽  
P. Y. Patel
Keyword(s):  
Light Chain ◽  
Myosin Light Chain ◽  
Mesangial Cells ◽  
Shape Change ◽  
Stress Fiber ◽  
Model Systems ◽  
Stress Fibers ◽  
Intracellular Camp ◽  
Fiber Morphology ◽  
Physiological Basis

Induced elevations in intracellular cAMP caused remarkable shape changes in cultured mesangial cells that were prevented by prostaglandin E2 (PGE2). The purpose of this study was to determine the morphological and physiological basis for these alterations. Coincident with elevated levels of cAMP and shape change there was rapid dissolution of stress fibers. Cytochalasin B treatment also caused shape change and stress fiber dissolution. Stress fibers were visualized by fluorescence microscopy after appropriate staining. In such cells, microtubules were intact. PGE2 prevented stress fiber loss as well as shape change if it was included in the medium from the outset, or restored stress fibers and normal morphology within 30 min if it was added following shape change. Agents that depolymerize microtubules also prevented both stress fiber loss and shape change. Coincident with stress fiber loss and shape change induced by elevations of cAMP, there was a decrease in the rate of [32P]-orthophosphate incorporation into myosin light chain; this was also prevented or reversed by PGE2. Remarkably, PGE2 alone caused an increase in the rate of [32P]orthophosphate incorporation into myosin light chain in cells that were otherwise untreated. Phosphorylation of the light chain of myosin may be an important factor in the maintenance of stress fiber morphology. The results of this study point out complex interrelationships between microtubules, and stress fibers in the maintenance of cell shape needing further study. The model systems that are presented seem suited for such investigation.

Vasoactive agents affect mesangial cell adhesion

1986 ◽  
Vol 251 (4) ◽  
pp. C505-C511 ◽  
Author(s):  
J. I. Kreisberg ◽  
M. A. Venkatachalam
Keyword(s):  
Cell Adhesion ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Mesangial Cell ◽  
Cultured Cells ◽  
Mesangial Cells ◽  
Stress Fibers ◽  
Vasoactive Agents ◽  
Substrate Adhesion ◽  
Adhesive Contacts

The formation and maintenance of stress fibers in cultured mesangial cells is associated with myosin light chain phosphorylation [Kreisberg et al. Am. J. Physiol. 249 (Renal Fluid Electrolyte Physiol. 18): F227-F235, 1985], a biochemical indicator for activation of actin-myosin interactions. Agents that elevate intracellular levels of adenosine 3',5'-cyclic monophosphate (cAMP) (e.g., isoproterenol) fragment stress fibers and cause myosin light chain dephosphorylation, whereas the addition of contractile agents such as arginine vasopressin (AVP) and prostaglandin E2 (PGE2) reverses these changes. Because stress fiber development in cultured cells is correlated with tight cell to substrate adhesion, we wanted to examine whether vasoactive agents have an effect on mesangial cell adhesion. Both isoproterenol and dibutyryl cAMP (DBcAMP) reduced mesangial cell adherence as measured by a trypsin assay (% detached cells: control 11 +/- 2.4%; isoproterenol plus isobutylmethylxanthine (IBMX) = 48.3 +/- 7.4%; DBcAMP = 29.3 +/- 3.7%; DBcAMP-IBMX = 73 +/- 4.4%). The areas of focal (adhesive) contacts between the cell and substratum as observed by interference-reflexion microscopy were also reduced, being replaced by areas of greater separation (% of the surface in contact with the substratum: control = 7.4 +/- 0.8%; isoproterenol-IBMX = 2.9 +/- 1.1%). Addition of PGE2 or AVP to the incubation medium containing the cAMP-elevating agents prevented the above changes. PGE2 or AVP alone increased mesangial cell adhesion (% detached cells: control 11 +/- 2.4%; PGE2 = 6.8 +/- 0.5%; AVP = 5.1 +/- 1.2%).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Myosin light chain kinase-regulated endothelial cell contraction: the relationship between isometric tension, actin polymerization, and myosin phosphorylation.

1995 ◽  
Vol 130 (3) ◽  
pp. 613-627 ◽  
Author(s):  
Z M Goeckeler ◽  
R B Wysolmerski
Keyword(s):  
Endothelial Cell ◽  
Light Chain ◽  
Isometric Contraction ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Myosin Ii ◽  
Isometric Tension ◽  
Stress Fibers ◽  
Light Chains ◽  
Myosin Light Chains

The phosphorylation of regulatory myosin light chains by the Ca2+/calmodulin-dependent enzyme myosin light chain kinase (MLCK) has been shown to be essential and sufficient for initiation of endothelial cell retraction in saponin permeabilized monolayers (Wysolmerski, R. B. and D. Lagunoff. 1990. Proc. Natl. Acad. Sci. USA. 87:16-20). We now report the effects of thrombin stimulation on human umbilical vein endothelial cell (HUVE) actin, myosin II and the functional correlate of the activated actomyosin based contractile system, isometric tension development. Using a newly designed isometric tension apparatus, we recorded quantitative changes in isometric tension from paired monolayers. Thrombin stimulation results in a rapid sustained isometric contraction that increases 2- to 2.5-fold within 5 min and remains elevated for at least 60 min. The phosphorylatable myosin light chains from HUVE were found to exist as two isoforms, differing in their molecular weights and isoelectric points. Resting isometric tension is associated with a basal phosphorylation of 0.54 mol PO4/mol myosin light chain. After thrombin treatment, phosphorylation rapidly increases to 1.61 mol PO4/mol myosin light chain within 60 s and remains elevated for the duration of the experiment. Myosin light chain phosphorylation precedes the development of isometric tension and maximal phosphorylation is maintained during the sustained phase of isometric contraction. Tryptic phosphopeptide maps from both control and thrombin-stimulated cultures resolve both monophosphorylated Ser-19 and diphosphorylated Ser-19/Thr-18 peptides indicative of MLCK activation. Changes in the polymerization of actin and association of myosin II correlate temporally with the phosphorylation of myosin II and development of isometric tension. Activation results in a 57% increase in F-actin content within 90 s and 90% of the soluble myosin II associates with the reorganizing F-actin. Furthermore, the disposition of actin and myosin II undergoes striking reorganization. F-actin initially forms a fine network of filaments that fills the cytoplasm and then reorganizes into prominent stress fibers. Myosin II rapidly forms discrete aggregates associated with the actin network and by 2.5 min assumes a distinct periodic distribution along the stress fibers.

Role of Rho and myosin phosphorylation in actin stress fiber assembly in mesangial cells

1997 ◽  
Vol 273 (2) ◽  
pp. F283-F288 ◽  
Author(s):  
J. I. Kreisberg ◽  
N. Ghosh-Choudhury ◽  
R. A. Radnik ◽  
M. A. Schwartz
Keyword(s):  
Cell Shape ◽  
Mesangial Cells ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Stress Fibers ◽  
Actin Stress Fiber ◽  
Glomerular Mesangial Cells ◽  
Fiber Assembly ◽  
Camp Elevation ◽  
Actin Stress Fibers

Treatment of renal glomerular mesangial cells with adenosine 3',5'-cyclic monophosphate (cAMP)-elevating agents induces actin stress fiber disassembly, myosin light chain (MLC) dephosphorylation, loss of adhesion to the substratum and cell shape change [J. I. Kreisberg and M. A. Venkatachalam. Am. J. Physiol. 251 (Cell Physiol. 20): C505-C511, 1986]. Thrombin and vasopressin block the effects of cAMP. Because these agents are known to promote stress fiber formation via the small GTP-binding protein Rho, we investigated the effect of an activated variant of Rho on the response to cAMP elevation. Microinjecting V14-Rho completely blocked the effect of cAMP elevation on cell shape and the actin cytoskeleton, whereas inactivating Rho with botulinum C3 exoenzyme induced stress fiber disruption and cell retraction that was indistinguishable from that caused by elevations in intracellular levels of cAMP. Disruption of actin stress fibers by cAMP has previously been ascribed to MLC dephosphorylation; however, both C3 and cytochalasin D also caused dephosphorylation of MLC, whereas blocking MLC dephosphorylation failed to block the cAMP-induced loss of actin stress fibers. We conclude that Rho can modulate the effects of cAMP elevation and suggest that MLC dephosphorylation may be a consequence of actin stress fiber disassembly.

Functional arginine vasopressin system in early heart maturation

2007 ◽  
Vol 293 (4) ◽  
pp. H2262-H2270 ◽  
Author(s):  
Jolanta Gutkowska ◽  
Malgorzata Miszkurka ◽  
Bogdan Danalache ◽  
Natig Gassanov ◽  
Donghao Wang ◽  
...  
Keyword(s):  
Stem Cells ◽  
Light Chain ◽  
Arginine Vasopressin ◽  
Transcriptional Control ◽  
Myosin Light Chain ◽  
Coronary Vessels ◽  
Intracellular Camp ◽  
Specific Marker ◽  
Adult Rats ◽  
Cardiovascular Tissue

Since the neurohypophyseal hormone 8-arginine vasopressin (AVP) is involved in cardiovascular tissue hypertrophy and myocyte differentiation, it is possible that local AVP plays a role in heart maturation. AVP-specific RIA, RT-PCR, and immunoblot measurement of AVP receptors (VR) were used to investigate heart tissues from newborn and adult rats. To test AVP's role in differentiation and specialization into ventricle-like cardiomyocytes, we studied GFP-P19Cl6 stem cells, which express green fluorescence protein (GFP) reporter under transcriptional control of the myosin light chain-2v promoter. VR1 transcripts and proteins were higher in adult than in newborn rat hearts. In contrast, VR2 increased from postnatal day 1 to 5 and was barely detected in the adult rat heart. In cardiomyocytes expressing troponin C, immunofluorescence revealed VR2 and VR1. Intracellular cAMP increased 6.5- and 8.9-fold in response to the selective VR2 agonist 1-desamino-8-d-AVP (DDAVP) after 1 and 24 h, respectively. Cardiac AVP was high in 1- and 5-day-old (330 ± 26 and 276 ± 53 pg/mg protein, respectively) but low in 66-day-old (98 ± 15 pg/mg protein) rats. AVP immunostaining was detected in the tunica adventitia and endothelium of the coronary vessels. The possible role of AVP in cardiomyogenesis was indicated by DDAVP-AVP-dependent differentiation of GFP-P19Cl6 stem cells into contracting cells displaying GATA-4, a cardiac-specific marker, and ventricle-specific myosin light chain. Together, it is suggested that the AVP system is implicated in postnatal cardiac maturation.

scholarly journals Regulation of rat myosin light-chain synthesis in heterokaryons between 5-bromodeoxyuridine-blocked rat myoblasts and differentiated chick myocytes.

1983 ◽  
Vol 96 (6) ◽  
pp. 1571-1579 ◽  
Author(s):  
W E Wright ◽  
J Aronoff
Keyword(s):  
Light Chain ◽  
Myosin Light Chain ◽  
Gene Dosage ◽  
Indirect Evidence ◽  
Model Systems ◽  
Direct Result ◽  
Gene Dosage Effects ◽  
Dosage Effects ◽  
Inducing Factors ◽  
Chain Synthesis

Terminal cell differentiation in a variety of model systems is inhibited by the thymidine analogue 5-bromodeoxyuridine (BUdR). We investigated the mode of action of BUdR by forming heterokaryons between undifferentiated BUdR-blocked rat myoblasts and differentiated chick skeletal myocytes. We analyzed newly synthesized proteins on two-dimensional polyacrylamide gels. The induction of rat skeletal myosin light-chain synthesis was reduced fivefold, as compared with controls, when chick myocytes were fused to BUdR-blocked rat myoblasts. This indicates that plasma membrane effects cannot be the proximate cause for the inhibition of myogenesis by BUdR, since BUdR is able to block the effect of chick inducing factors even when a differentiated chick myocyte is in direct cytoplasmic continuity with the BUdR-blocked rat nucleus. The observation that chick cells required an 80% substitution of BUdR for thymidine to block myogenesis, whereas L6 rat myoblasts required only a 20% substitution led to a hypothesis involving a DNA-mediated action of BUdR. This model yielded three testable predictions: (a) putative chick inducing molecules should be present in limiting quantities, (b) exploiting gene-dosage effects to increase the quantity of putative chick inducing factors might overcome the inhibition produced in the rat myoblasts by a 35% BUdR for thymidine substitution, and (c) these gene-dosage effects should be abolished by increasing the level of BUdR substitution in the rat myoblast to 60-80%. All three of these predictions have been verified, providing strong indirect evidence that the inhibition of myogenesis produced by BUdR is a direct result of its incorporation into cellular DNA.

Inhibitors of myosin light chain kinase and phosphodiesterase reduce ventilator-induced lung injury

2000 ◽  
Vol 89 (6) ◽  
pp. 2241-2248 ◽  
Author(s):  
James C. Parker ◽  
Keyword(s):  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Control Group ◽  
Signal Pathways ◽  
Intracellular Camp ◽  
Ventilator Induced Lung Injury ◽  
Capillary Fluid ◽  
Fluid Leak ◽  
Camp Levels

Alveolar overdistension due to high peak inflation pressures (PIP) is associated with an increased capillary filtration coefficient ( K fc). To determine which signal pathways contribute to this injury, we perfused isolated rat lungs with 5% bovine albumin in Krebs solution and measured K fc after successive 30-min periods of ventilation with peak inflation pressures (PIP) of 7, 20, 30, and 35 cmH2O. In a high-PIP control group, K fc increased significantly after ventilation with 30 and 35 cmH2O PIP, but significant increases were prevented by treatment with 100 μM trifluoperazine, an inhibitor of Ca2+/calmodulin, 500 nM ML-7, an inhibitor of myosin light chain kinase (MLCK), a combination of isoproterenol (20 μM) and rolipram (10 μM) to enhance intracellular cAMP levels, and a dose of KT-5720 (2 μM), which inhibits MLCK and protein kinase C. These studies suggest that the Ca2+/calmodulin-MLCK pathway augments capillary fluid leak after a modest high-PIP injury and that this is attenuated by kinase inhibition and increased intracellular cAMP.

scholarly journals Activation of ROCK and MLCK tunes regional stress fiber formation and mechanics via preferential myosin light chain phosphorylation

2017 ◽  
Vol 28 (26) ◽  
pp. 3832-3843 ◽  
Author(s):  
Elena Kassianidou ◽  
Jasmine H. Hughes ◽  
Sanjay Kumar
Keyword(s):  
Light Chain ◽  
Viscoelastic Properties ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Kinase Activity ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Myosin Regulatory Light Chain ◽  
Regional Stress ◽  
Stress Fiber Formation

The assembly and mechanics of actomyosin stress fibers (SFs) depend on myosin regulatory light chain (RLC) phosphorylation, which is driven by myosin light chain kinase (MLCK) and Rho-associated kinase (ROCK). Although previous work suggests that MLCK and ROCK control distinct pools of cellular SFs, it remains unclear how these kinases differ in their regulation of RLC phosphorylation or how phosphorylation influences individual SF mechanics. Here, we combine genetic approaches with biophysical tools to explore relationships between kinase activity, RLC phosphorylation, SF localization, and SF mechanics. We show that graded MLCK overexpression increases RLC monophosphorylation (p-RLC) in a graded manner and that this p-RLC localizes to peripheral SFs. Conversely, graded ROCK overexpression preferentially increases RLC diphosphorylation (pp-RLC), with pp-RLC localizing to central SFs. Interrogation of single SFs with subcellular laser ablation reveals that MLCK and ROCK quantitatively regulate the viscoelastic properties of peripheral and central SFs, respectively. The effects of MLCK and ROCK on single-SF mechanics may be correspondingly phenocopied by overexpression of mono- and diphosphomimetic RLC mutants. Our results point to a model in which MLCK and ROCK regulate peripheral and central SF viscoelastic properties through mono- and diphosphorylation of RLC, offering new quantitative connections between kinase activity, RLC phosphorylation, and SF viscoelasticity.

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