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Naranjan S Dhalla - One of the best experts on this subject based on the ideXlab platform.
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effect of β adrenoceptor antagonists on phospholipid n methylation activities of cardiac Sarcolemma
Journal of Cardiovascular Pharmacology and Therapeutics, 1998Co-Authors: Vincenzo Panagia, Yuji Taira, Gregory L Bryson, Paramjit S Tappia, Naranjan S DhallaAbstract:: BACKGROUND: Some beta-adrenoceptor antagonists exert a negative inotropic action by affecting Ca(2+) fluxes in the myocardial cell as a consequence of their interaction with Sarcolemmal and sarcoplasmic reticular membranes. This action may be caused by their effects on the chemicophysical properties of membranes phospholipids. Because phosphatidylethanolamine (PE) N-methylation can influence the chemicophysical properties of membranes, these agents may affect PE N-methylation. This study was undertaken to examine the effects of propranolol, acebutolol, and atenolol on PE-N-methylation in rat heart Sarcolemma (SL). METHODS AND RESULTS: Sarcolemmal membrane was isolated from rat hearts by the hypotonic shock LiBr method. Incorporation of radiolabeled methyl groups from S-adenosyl-l-methionine was assayed at three catalytic sites involved in the PE N-methylation reaction in the presence and absence of these drugs. A biphasic effect of propranolol at site I was noted; low concentrations (10(-8) M) were inhibitor. Acebutolol (10(-9)-10(-3) M) depressed methyl group incorporation in SL at site II in a dose-dependent manner, whereas atenolol showed no effect. Propranolol also exerted a biphasic effect on sarcoplasmic reticular (SR) methylation at site I, whereas acebutolol depressed the SR enzyme activity at site II and atenolol had no effect. The mitochondrial methyltransferase activities at sites I, II, and III were unaltered by any of these drugs. CONCLUSIONS: It is suggested that propranolol and acebutolol alter SL and SR PE N-methyltransferase activity at site I and site II, respectively, either by affecting the enzyme directly or by changing the physiochemical properties of the membrane.
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Regulation of cardiac Sarcolemmal Ca^2+ channels and Ca^2+ transporters by thyroid hormone
Molecular and Cellular Biochemistry, 1993Co-Authors: Enn K. Seppet, Frantisek Kolar, Ian M. C. Dixon, Tomoji Hata, Naranjan S DhallaAbstract:In order to examine the regulatory role of thyroid hormone on Sarcolemmal Ca^2+-channels, Na^+−Ca^2+ exchange and Ca^2+-pump as well as heart function, the effects of hypothyroidism and hyperthyroidism on rat heart performance and Sarcolemmal Ca^2+-handling were studied. Hyperthyroid rats showed higher values for heart rate (HR), maximal rates of ventricular pressure development+(dP/dt)max and pressure fall−(dP/dt)max, but shorter time to peak ventricular pressure (TPVP) and contraction time (CT) when compared with euthyroid rats. The left ventricular systolic pressure (LVSP) and left ventricular end-diastolic pressure (LVEDP), as well as aortic systolic and diastolic pressures (ASP and ADP, respectively) were not significantly altered. Hypothyroid rats exhibited decreased values of LVSP, HR, ASP, ADP, +(dP/dt)max and −(dP/dt)max but higher CT when compared with euthyroid rats; the values of LVEDP and TPVP were not changed. Studies with isolated-perfused hearts showed that while hypothyroidism did not modulate the inotropic response to extracellular Ca^2+ and Ca^2+ channel blocker verapamil, hyperthyroidism increased sensitivity to Ca^2+ and decreased sensitivity to verapamil in comparison to euthyroid hearts. Studies of [^3H]-nitrendipine binding with purified cardiac Sarcolemmal membrane revealed decreased number of high affinity binding sites (B_max) without any change in the dissociation constant for receptor-ligand complex (K_d) in the hyperthyroid group when compared with euthyroid Sarcolemma; hypothyroidism had no effect on these parameters. The activities of Sarcolemmal Ca^2+-stimulated ATPase, ATP-dependent Ca^2+ uptake and ouabain-sensitive Na^+−K^+ ATPase were decreased whereas the Mg^2+-ATPase activity was increased in hypothyroid hearts. On the other hand, Sarcolemmal membranes from hyperthyroid samples exhibited increased ouabain-sensitive Na^+−K^+ ATPase activity, whereas Ca^2+-stimulated ATPase, ATP-dependent Ca^2+ uptake, and Mg^2+-ATPase activities were unchanged. The V_max and K_a for Ca^2+ of cardiac Sarcolemmal Na^+−Ca^2+ exchange were not altered in both hyperthyroid and hypothyroid states. These results indicate that the status of Sarcolemmal Ca^2+-transport processes is regulated by thyroid hormones and the modification of Ca^2+-fluxes across the Sarcolemmal membrane may play a crucial role in the development of thyroid state-dependent contractile changes in the heart.
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role of sulfhydryl groups in phospholipid methylation reactions of cardiac Sarcolemma
Molecular and Cellular Biochemistry, 1991Co-Authors: Roland Vetter, Vincenzo Panagia, Nasrin Mesaeli, Naranjan S DhallaAbstract:The effect of reagents that modify sulfur-containing amino acid residues in the phosphatidylethanolamine N-methyltransferase was studied in the isolated rat cardiac Sarcolemma by employing S-adenosyl-L-[methyl-3H]methionine as a methyl donor. Dithiothreitol protected the sulfhydryl groups in the membrane and caused a concentration- and time-dependent increase of phospholipid N-methylation at three different catalytic sites. This stimulation was highest (9-fold) in the presence of 1 MM MgCl2 and 0.1 µM S-adenosyl-L-[methyl-3H]methionine at pH 8.0 (catalytic site 1), and was associated with an enhancement of Vmax without changes in Km for the methyl donor. Thiol glutathione was less stimulatory than dithiothreitol; glutathione disulfide inhibited the phosphatidylethanolamine N-methylation by 50%. The alkylating reagents, N-ethylmaleimide and methylmethanethiosulfonate, inhibited the N-methylation with IC5O of 6.9 and 14.1 µM, respectively; this inhibition was prevented by 1 mM dithiothreitol. These results indicate a critical role of sulfhydryl groups for the activity of the cardiac Sarcolemmal phosphatidylethanolamine N-methyltransferase and suggest that this enzyme system in cardiac Sarcolemma may be controlled by the glutathione/glutathione disulfide redox state in the cell.
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stimulation of phospholipid n methylation by isoproterenol in rat hearts
Circulation Research, 1990Co-Authors: Y Taira, Vincenzo Panagia, Robert E. Beamish, K R Shah, Naranjan S DhallaAbstract:Phosphatidylethanolamine (PtdEtn) N-methyltransferase activities were studied in rat heart Sarcolemmal and sarcoplasmic reticular fractions after a single intraperitoneal injection of isoproterenol (0.5-5.0 mg/kg). Three active sites (I, II, and III) for PtdEtn N-methylation were assayed by measurement of [3H]methyl group incorporation from 0.055, 10, and 150 microM S-adenosyl-L-[methyl-3H]methionine into membrane PtdEtn molecules. Total methylation activity for catalytic site I of both Sarcolemma and sarcoplasmic reticulum was stimulated within 2 minutes by isoproterenol in a dose-dependent manner. Although the increased methyltransferase activity in sarcoplasmic reticulum was normalized at 10 minutes, the enzyme activity in Sarcolemma was normalized at 5 minutes but was again increased at 10-30 minutes after isoproterenol injection. No changes in response to isoproterenol were seen for site II and III N-methylation activities in either membrane. Individual N-methylated phospholipids (phosphatidyl-N-monomethylethanolamine, phosphatidyl-N,N-dimethylethanolamine, and phosphatidylcholine), which specifically formed at each site, showed similar behavior. Pretreatment of the animals with a beta-blocking drug, atenolol, for 2 days prevented the isoproterenol-induced changes in hemodynamic parameters and Sarcolemmal methylation without affecting the enhanced methylation activities in sarcoplasmic reticulum. In vitro addition of cyclic AMP-dependent protein kinase (catalytic subunit) plus Mg-ATP enhanced methyltransferase activities in Sarcolemma and sarcoplasmic reticulum from control hearts by 2.7- and 2.3-fold, respectively; however, under the same in vitro conditions, only about 20% activation was seen in both subcellular membranes isolated from the heart of isoproterenol-injected animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Michael Muntener - One of the best experts on this subject based on the ideXlab platform.
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fibre type specific concentration of focal adhesion kinase at the Sarcolemma influence of fibre innervation and regeneration
The Journal of Experimental Biology, 2002Co-Authors: Martin Fluck, Rudi Billeter, A Ziemiecki, Michael MuntenerAbstract:SUMMARY In skeletal muscles, focal adhesion complexes (FACs) form part of the costamere, a Sarcolemmal protein complex that enables lateral transfer of forces and ensures the stability of the Sarcolemma. The present investigation tested whether localisation of a major assembly factor of FACs, focal adhesion kinase (FAK), to the Sarcolemma parallels the known modulation of FACs by fibre type (innervation pattern) and fibre regeneration. Immunohistochemical experiments indicated that FAK is preferentially associated with the Sarcolemma in a high proportion (>74 %) of the (slow-twitch) type I and (fast-twitch) type IIA fibres in normal rat soleus (N-SOL) muscle and of the type IIA fibres in extensor digitorum longus (N-EDL) muscle. In contrast, a low proportion (<15 %) of fast-twitch type IIB and type I fibres in N-EDL showed Sarcolemmal FAK immunoreactivity. Cross-reinnervation of slow-twitch rat SOL muscle with the fast EDL nerve induced slow-to-fast fibre transformation and led to a significant reduction in Sarcolemmal FAK immunoreactivity in type I and type IIA fibres. Transplantation of the fast EDL into the slow SOL bed with regeneration and reinnervation of the muscle by the SOL nerve (T-EDL) caused a significant increase in Sarcolemmal FAK immunoreactivity in new type I and hybrid I/II fibres and a corresponding reduction in Sarcolemmal FAK immunoreactivity in `normal9 IIA and IIB fibres. Conversely, Sarcolemmal FAK immunoreactivity in small IIB fibres of T-EDL muscle was increased. Correspondingly, the transplanted and regenerated SOL (reinnervated by the fast EDL nerve) maintained the percentage of FAK-positive Sarcolemma in the (regenerated) type I and IIA fibres. Thus, the expression and association of FAK with the Sarcolemma are regulated (i) by factors that determine the fibre type and (ii) during fibre regeneration. Our data suggest that the integrity of Sarcolemmal FACs is dependent on the fibre type and that FAC turnover is increased during regeneration of muscle fibres.
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Fibre-type specific concentration of focal adhesion kinase at the Sarcolemma: influence of fibre innervation and regeneration
J Exp Biol, 2002Co-Authors: Martin Fluck, Rudi Billeter, A Ziemiecki, Michael MuntenerAbstract:In skeletal muscles, focal adhesion complexes (FACs) form part of the costamere, a Sarcolemmal protein complex that enables lateral transfer of forces and ensures the stability of the Sarcolemma. The present investigation tested whether localisation of a major assembly factor of FACs, focal adhesion kinase (FAK), to the Sarcolemma parallels the known modulation of FACs by fibre type (innervation pattern) and fibre regeneration. Immunohistochemical experiments indicated that FAK is preferentially associated with the Sarcolemma in a high proportion (>74 %) of the (slow-twitch) type I and (fast-twitch) type IIA fibres in normal rat soleus (N-SOL) muscle and of the type IIA fibres in extensor digitorum longus (N-EDL) muscle. In contrast, a low proportion (
James M. Ervasti - One of the best experts on this subject based on the ideXlab platform.
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the dystrophin complex forms a mechanically strong link between the Sarcolemma and costameric actin
Journal of Cell Biology, 2000Co-Authors: Inna N. Rybakova, Jitandrakumar R. Patel, James M. ErvastiAbstract:The absence of dystrophin complex leads to disorganization of the force-transmitting costameric cytoskeleton and disruption of Sarcolemmal membrane integrity in skeletal muscle. However, it has not been determined whether the dystrophin complex can form a mechanically strong bond with any costameric protein. We performed confocal immunofluorescence analysis of isolated Sarcolemma that were mechanically peeled from skeletal fibers of mouse hindlimb muscle. A population of γ-actin filaments was stably associated with Sarcolemma isolated from normal muscle and displayed a costameric pattern that precisely overlapped with dystrophin. However, costameric actin was absent from all Sarcolemma isolated from dystrophin-deficient mdx mouse muscle even though it was localized to costameres in situ. Vinculin, α-actinin, β-dystroglycan and utrophin were all retained on mdx Sarcolemma, indicating that the loss of costameric actin was not due to generalized membrane instability. Our data demonstrate that the dystrophin complex forms a mechanically strong link between the Sarcolemma and the costameric cytoskeleton through interaction with γ-actin filaments. Destabilization of costameric actin filaments may also be an important precursor to the costamere disarray observed in dystrophin-deficient muscle. Finally, these methods will be broadly useful in assessing the mechanical integrity of the membrane cytoskeleton in dystrophic animal models lacking other costameric proteins.
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The dystrophin complex forms a mechanically strong link between the Sarcolemma and costameric actin
Journal of Cell Biology, 2000Co-Authors: Inna N. Rybakova, Jitandrakumar R. Patel, James M. ErvastiAbstract:The absence of dystrophin complex leads to disorganization of the force-transmitting costameric cytoskeleton and disruption of Sarcolemmal membrane integrity in skeletal muscle. However, it has not been determined whether the dystrophin complex can form a mechanically strong bond with any costameric protein. We performed confocal immunofluorescence analysis of isolated Sarcolemma that were mechanically peeled from skeletal fibers of mouse hindlimb muscle. A population of gamma-actin filaments was stably associated with Sarcolemma isolated from normal muscle and displayed a costameric pattern that precisely overlapped with dystrophin. However, costameric actin was absent from all Sarcolemma isolated from dystrophin-deficient mdx mouse muscle even though it was localized to costameres in situ. Vinculin, alpha-actinin, beta-dystroglycan and utrophin were all retained on mdx Sarcolemma, indicating that the loss of costameric actin was not due to generalized membrane instability. Our data demonstrate that the dystrophin complex forms a mechanically strong link between the Sarcolemma and the costameric cytoskeleton through interaction with gamma-actin filaments. Destabilization of costameric actin filaments may also be an important precursor to the costamere disarray observed in dystrophin-deficient muscle. Finally, these methods will be broadly useful in assessing the mechanical integrity of the membrane cytoskeleton in dystrophic animal models lacking other costameric proteins.
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dystrophin glycoprotein complex is highly enriched in isolated skeletal muscle Sarcolemma
Journal of Cell Biology, 1991Co-Authors: Kay Ohlendieck, James M. Ervasti, Joseph B Snook, Kevin P CampbellAbstract:mAbs specific for protein components of the surface membrane of rabbit skeletal muscle have been used as markers in the isolation and characterization of skeletal muscle Sarcolemma membranes. Highly purified Sarcolemma membranes from rabbit skeletal muscle were isolated from a crude surface membrane preparation by wheat germ agglutination. Immunoblot analysis of subcellular fractions from skeletal muscle revealed that dystrophin and its associated glycoproteins of 156 and 50 kD are greatly enriched in purified Sarcolemma vesicles. The purified Sarcolemma was also enriched in novel Sarcolemma markers (SL45, SL/TS230) and Na+/K(+)-ATPase, whereas t-tubule markers (alpha 1 and alpha 2 subunits of dihydropyridine receptor, TS28) and sarcoplasmic reticulum markers (Ca2(+)-ATPase, ryanodine receptor) were greatly diminished in this preparation. Analysis of isolated Sarcolemma by SDS-PAGE and densitometric scanning demonstrated that dystrophin made up 2% of the total protein in the rabbit Sarcolemma preparation. Therefore, our results demonstrate that although dystrophin is a minor muscle protein it is a major constituent of the Sarcolemma membrane in skeletal muscle. Thus the absence of dystrophin in Duchenne muscular dystrophy may result in a major disruption of the cytoskeletal network underlying the Sarcolemma in dystrophic muscle.
Martin Fluck - One of the best experts on this subject based on the ideXlab platform.
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fibre type specific concentration of focal adhesion kinase at the Sarcolemma influence of fibre innervation and regeneration
The Journal of Experimental Biology, 2002Co-Authors: Martin Fluck, Rudi Billeter, A Ziemiecki, Michael MuntenerAbstract:SUMMARY In skeletal muscles, focal adhesion complexes (FACs) form part of the costamere, a Sarcolemmal protein complex that enables lateral transfer of forces and ensures the stability of the Sarcolemma. The present investigation tested whether localisation of a major assembly factor of FACs, focal adhesion kinase (FAK), to the Sarcolemma parallels the known modulation of FACs by fibre type (innervation pattern) and fibre regeneration. Immunohistochemical experiments indicated that FAK is preferentially associated with the Sarcolemma in a high proportion (>74 %) of the (slow-twitch) type I and (fast-twitch) type IIA fibres in normal rat soleus (N-SOL) muscle and of the type IIA fibres in extensor digitorum longus (N-EDL) muscle. In contrast, a low proportion (<15 %) of fast-twitch type IIB and type I fibres in N-EDL showed Sarcolemmal FAK immunoreactivity. Cross-reinnervation of slow-twitch rat SOL muscle with the fast EDL nerve induced slow-to-fast fibre transformation and led to a significant reduction in Sarcolemmal FAK immunoreactivity in type I and type IIA fibres. Transplantation of the fast EDL into the slow SOL bed with regeneration and reinnervation of the muscle by the SOL nerve (T-EDL) caused a significant increase in Sarcolemmal FAK immunoreactivity in new type I and hybrid I/II fibres and a corresponding reduction in Sarcolemmal FAK immunoreactivity in `normal9 IIA and IIB fibres. Conversely, Sarcolemmal FAK immunoreactivity in small IIB fibres of T-EDL muscle was increased. Correspondingly, the transplanted and regenerated SOL (reinnervated by the fast EDL nerve) maintained the percentage of FAK-positive Sarcolemma in the (regenerated) type I and IIA fibres. Thus, the expression and association of FAK with the Sarcolemma are regulated (i) by factors that determine the fibre type and (ii) during fibre regeneration. Our data suggest that the integrity of Sarcolemmal FACs is dependent on the fibre type and that FAC turnover is increased during regeneration of muscle fibres.
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Fibre-type specific concentration of focal adhesion kinase at the Sarcolemma: influence of fibre innervation and regeneration
J Exp Biol, 2002Co-Authors: Martin Fluck, Rudi Billeter, A Ziemiecki, Michael MuntenerAbstract:In skeletal muscles, focal adhesion complexes (FACs) form part of the costamere, a Sarcolemmal protein complex that enables lateral transfer of forces and ensures the stability of the Sarcolemma. The present investigation tested whether localisation of a major assembly factor of FACs, focal adhesion kinase (FAK), to the Sarcolemma parallels the known modulation of FACs by fibre type (innervation pattern) and fibre regeneration. Immunohistochemical experiments indicated that FAK is preferentially associated with the Sarcolemma in a high proportion (>74 %) of the (slow-twitch) type I and (fast-twitch) type IIA fibres in normal rat soleus (N-SOL) muscle and of the type IIA fibres in extensor digitorum longus (N-EDL) muscle. In contrast, a low proportion (
Robert J Bloch - One of the best experts on this subject based on the ideXlab platform.
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biomechanics of the Sarcolemma and costameres in single skeletal muscle fibers from normal and dystrophin null mice
Journal of Muscle Research and Cell Motility, 2011Co-Authors: Karla P Garciapelagio, Robert J Bloch, Alicia Ortega, H L GonzalezserratosAbstract:We studied the biomechanical properties of the Sarcolemma and its links through costameres to the contractile apparatus in single mammalian myofibers of Extensor digitorum longus muscles isolated from wild (WT) and dystrophin-null (mdx) mice. Suction pressures (P) applied through a pipette to the Sarcolemma generated a bleb, the height of which increased with increasing P. Larger increases in P broke the connections between the Sarcolemma and myofibrils and eventually caused the Sarcolemma to burst. We used the values of P at which these changes occurred to estimate the tensions and stiffness of the system and its individual elements. Tensions of the whole system and the Sarcolemma, as well as the maximal tension sustained by the costameres, were all significantly lower (1.8–3.3 fold) in muscles of mdx mice compared to WT. Values of P at which separation and bursting occurred, as well as the stiffness of the whole system and of the isolated Sarcolemma, were ~2-fold lower in mdx than in WT. Our results indicate that the absence of dystrophin reduces muscle stiffness, increases Sarcolemmal deformability, and compromises the mechanical stability of costameres and their connections to nearby myofibrils.
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erratum to differential distribution of dystrophin and β spectrin at the Sarcolemma of fast twitch skeletal muscle fibers
Journal of Muscle Research and Cell Motility, 2010Co-Authors: Mcrae W Williams, Robert J BlochAbstract:We used double label immunofluorescence and confocal microscopy to examine the organization of β-spectrin and dystrophin at the Sarcolemma of fast twitch myofibers in the Extensor Digitorum Longus (EDL) of the rat. Both β-spectrin and dystrophin are concentrated in costameres, a rectilinear Sarcolemmal array composed of longitudinal strands and transverse elements overlying Z and M lines. In contrast, intercostameric regions, lying between these linear structures, contain significant levels of dystrophin but little detectable β-spectrin. The dystrophin-associated proteins, syntrophin and β-dystroglycan, are also concentrated at costameres but, like dystrophin, are present in intercostameric regions as well. Dystrophin is present at costameres and intercostameric regions in fast twitch muscles of the mouse but is absent from all regions of the Sarcolemma in the mdx mouse, which lacks dystrophin. Areas of the Sarcolemma near myonuclei also contain dystrophin without β-spectrin, consistent with the idea that the distribution of dystrophin at the Sarcolemma is not dependent on β-spectrin. We conclude that dystrophin is present under all areas of the Sarcolemma. The increased fragility of the Sarcolemma in patients with Duchennes muscular dystrophy may be explained in part by the absence of dystrophin not only from costameres, but also from intercostameric regions.
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Elastic Properties of the Sarcolemma‐Costamere Complex of Muscle Cells in Normal Mice
AIP Conference Proceedings, 2006Co-Authors: Karla P. García-pelagio, Robert J Bloch, Alicia Ortega, Hugo Gonzalez-serratosAbstract:Costameres at the Sarcolemma of skeletal myofibers are thought to mediate the lateral transmission of force from the myofibrils to the extracellular matrix. We applied elastimetry to single myofibers from the Extensor digitorum longus muscles of mice to measure the biomechanical properties of the Sarcolemma and the costameres as a function of sarcomere length. Suction pressure (P) applied by the elastimeter to the Sarcolemma generated a bleb of variable height, which depended on P and sarcomere length. Connections between the Sarcolemma and nearby myofibrils broke as P increased. Pressure, tension, force and stiffness (k) were calculated using the displacement pressure curves. With Laplace’s and Hooke’s equations, we estimated tensions generated by the Sarcolemma attached to the myofibrils (Tc+s) and the Sarcolemma after detachment (Ts). Tc+s − Ts = Tc, the maximal tension sustained by the costameres. The Sarcolemma‐costamere complex was represented as a lumped elastic model, in which the elasticity of ea...
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The Sarcolemma in the largemyd mouse
Muscle & Nerve, 2004Co-Authors: Patrick W. Reed, Katherine D. Mathews, K. A. Mills, Robert J BlochAbstract:In the Largemyd mouse, dystroglycan is incompletely glycosylated and thus cannot bind its extracellular ligands, causing a muscular dystrophy that is usually lethal in early adulthood. We show that the Largemyd mutation alters the composition and organization of the Sarcolemma of fast-twitch skeletal muscle fibers in young adult mice. Costameres at the Sarcolemma of the tibialis anterior muscle of Largemyd mice contain reduced levels of several membrane cytoskeletal proteins, including dystrophin and β-spectrin. In the quadriceps, longitudinally oriented costameric structures tend to become thickened and branched. More strikingly, proteins of the dystrophin complex present between costameres in controls are absent from Largemyd muscles. We propose that the absence of the dystrophin complex from these regions destabilizes the Sarcolemma of the Largemyd mouse and thereby contributes to the severity of its muscular dystrophy. Thus, the positioning of Sarcolemmal proteins may have a profound effect on the health of skeletal muscle. Muscle Nerve, 2004