Sub-maximally Activated Rat Soleus Fibers Exhibit Stretch Activation

Asynchronous insect flight muscles produce oscillatory contractions and can contract at high frequency because they are activated by stretch as well as by Ca2+. Stretch activation depends on the high stiffness of the fibres and the regular structure of the filament lattice. Cytoskeletal proteins may be important in stabilising the lattice. Two proteins, zeelin 1 (35 kDa) and zeelin 2 (23 kDa), have been isolated from the cytoskeletal fraction of Lethocerus flight muscle. Both zeelins have multiple isoforms of the same molecular mass and different charge. Zeelin 1 forms micelles and zeelin 2 forms filaments when renatured in low ionic strength solutions. Filaments of zeelin 2 are ribbons 10 nm wide and 3 nm thick. The position of zeelins in fibres from Lethocerus flight and leg muscle was determined by immunofluorescence and immunoelectron microscopy. Zeelin 1 is found in flight and leg fibres and zeelin 2 only in flight fibres. In flight myofibrils, both zeelins are in discrete regions of the A-band in each half sarcomere. Zeelin 1 is across the whole A-band in leg myofibrils. Zeelins are not in the Z-disc, as was thought previously, but migrate to the Z-disc in glycerinated fibres. Zeelins are associated with thick filaments and analysis of oblique sections showed that zeelin 1 is closer to the filament shaft than zeelin 2. The antibody labelling pattern is consistent with zeelin molecules associated with myosin near the end of the rod region. Alternatively, the position of zeelins may be determined by other A-band proteins. There are about 2.0 to 2.5 moles of myosin per mole of each zeelin. The function of these cytoskeletal proteins may be to maintain the ordered structure of the thick filament.

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An Embryonic Myosin Isoform Enables Stretch Activation and Cyclical Power in Drosophila Jump Muscle

Biophysical Journal ◽

10.1016/j.bpj.2013.04.057 ◽

2013 ◽

Vol 104 (12) ◽

pp. 2662-2670 ◽

Cited By ~ 7

Author(s):

Cuiping Zhao ◽

Douglas M. Swank

Keyword(s):

Stretch Activation

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Asynchronous muscle: a primer

Journal of Experimental Biology ◽

10.1242/jeb.203.18.2713 ◽

2000 ◽

Vol 203 (18) ◽

pp. 2713-2722 ◽

Cited By ~ 19

Author(s):

R.K. Josephson ◽

J.G. Malamud ◽

D.R. Stokes

Keyword(s):

Time Course ◽

Flight Muscle ◽

Isometric Force ◽

Length Change ◽

Mechanical Activity ◽

Stretch Activation ◽

Passive Stiffness ◽

Schistocerca Americana ◽

Slow Time ◽

Shortening Deactivation

The asynchronous muscles of insects are characterized by asynchrony between muscle electrical and mechanical activity, a fibrillar organization with poorly developed sarcoplasmic reticulum, a slow time course of isometric contraction, low isometric force, high passive stiffness and delayed stretch activation and shortening deactivation. These properties are illustrated by comparing an asynchronous muscle, the basalar flight muscle of the beetle Cotinus mutabilis, with synchronous wing muscles from the locust, Schistocerca americana. Because of delayed stretch activation and shortening deactivation, a tetanically stimulated beetle muscle can do work when subjected to repetitive lengthening and shortening. The synchronous locust muscle, subjected to similar stimulation and length change, absorbs rather than produces work.

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CH Stretch Activation of CH3CHOO: Deep Tunneling to Hydroxyl Radical Products

The Journal of Physical Chemistry A ◽

10.1021/acs.jpca.8b12324 ◽

2019 ◽

Vol 123 (13) ◽

pp. 2559-2569 ◽

Cited By ~ 7

Author(s):

Victoria P. Barber ◽

Shubhrangshu Pandit ◽

Vincent J. Esposito ◽

Anne B. McCoy ◽

Marsha I. Lester

Keyword(s):

Hydroxyl Radical ◽

Stretch Activation

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Stretch-activated potassium channels in renal proximal tubule

AJP Renal Physiology ◽

10.1152/ajprenal.1987.253.6.f1253 ◽

1987 ◽

Vol 253 (6) ◽

pp. F1253-F1262 ◽

Cited By ~ 4

Author(s):

H. Sackin

Keyword(s):

Proximal Tubule ◽

Cell Volume ◽

Negative Pressure ◽

Basolateral Membrane ◽

Cell Volume Regulation ◽

K Channel ◽

Proximal Tubule Cell ◽

Stretch Activation ◽

Membrane Stretch ◽

Excised Patches

A short open-time potassium (K) channel that has previously been identified in the basolateral membrane of Necturus proximal tubule (17) is activated by membrane stretch. Application of between 12 and 20 cmH2O negative pressure to the patch pipette reversibly increases mean number of open basolateral K channels (NP0) by a factor of 5.3 +/- 2 in cell-attached patches (n = 4) and a factor of 13.7 +/- 5 in excised patches (n = 8). This stretch activation does not alter channel selectivity or conductance and depends on neither the direction of K current nor the orientation of the patch ("inside-out" vs. "outside-out"). The increase in NP0 occurs within seconds after applying negative pressure to the patch and is proportional to applied negative pressure. Stretch activation of the basolateral potassium channel may play an important role in proximal tubule cell volume regulation. For example, if swelling stretches the basolateral membrane, the resulting increase in NP0 could restore cell volume by loss of K (with an accompanying anion) followed by osmotic exit of water.

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ATP masks stretch activation of epithelial sodium channels in A6 distal nephron cells

AJP Renal Physiology ◽

10.1152/ajprenal.00147.2001 ◽

2002 ◽

Vol 282 (3) ◽

pp. F501-F505 ◽

Cited By ~ 47

Author(s):

He-Ping Ma ◽

Li Li ◽

Zhen-Hong Zhou ◽

Douglas C. Eaton ◽

David G. Warnock

Keyword(s):

Patch Clamp ◽

Sodium Channel ◽

Sodium Channels ◽

Mechanical Stretch ◽

Stretch Activation ◽

Distal Nephron ◽

Epithelial Sodium Channels ◽

Open Probability ◽

The Mean ◽

Epithelial Sodium Channel Enac

The mechanosensitivity of the epithelial sodium channel (ENaC) is controversial. Using cell-attached patch-clamp techniques, we found that mechanical stretch stimulated ENaC in A6 distal nephron cells in only three of nine cell-attached patches. However, stretch consistently activated ENaC after apical ATP was scavenged with apical hexokinase plus glucose or after P2receptors in the patch were blocked. The mean open probability ( P o) of ENaC was increased from 0.31 ± 0.04 to 0.61 ± 0.06 ( P < 0.001; n = 9) when patch pipettes contained hexokinase and glucose, or from 0.24 ± 0.05 to 0.55 ± 0.11 ( P < 0.01; n = 7) when patch pipettes contained suramin, respectively. A poorly hydrolyzable ATP analog, ATPγS, in the patch pipettes inhibited ENaC, reducing the P o from 0.41 ± 0.06 to 0.19 ± 0.05 ( P < 0.01; n = 8). Pretreatment of A6 cells with the phospholipase C (PLC) inhibitor U-73122 abolished the effect of ATP on ENaC activity. These data together suggest that ATP, acting through a PLC-dependent purinergic pathway, masks stretch-induced ENaC activation.

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Calcium and Stretch Activation Modulate Power Generation in Drosophila Flight Muscle

Biophysical Journal ◽

10.1016/j.bpj.2011.09.034 ◽

2011 ◽

Vol 101 (9) ◽

pp. 2207-2213 ◽

Cited By ~ 14

Author(s):

Qian Wang ◽

Cuiping Zhao ◽

Douglas M. Swank

Keyword(s):

Power Generation ◽

Flight Muscle ◽

Stretch Activation

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Activation Dependence of Stretch Activation in Mouse Skinned Myocardium: Implications for Ventricular Function

The Journal of General Physiology ◽

10.1085/jgp.200509432 ◽

2006 ◽

Vol 127 (2) ◽

pp. 95-107 ◽

Cited By ~ 62

Author(s):

Julian E. Stelzer ◽

Lars Larsson ◽

Daniel P. Fitzsimons ◽

Richard L. Moss

Keyword(s):

Isometric Force ◽

Force Characteristic ◽

Stretch Activation ◽

Thin Filaments ◽

Cross Bridge ◽

Steady Level ◽

Myocardial Stretch ◽

Myosin Subfragment 1 ◽

Activation Response ◽

Cross Bridges

Recent evidence suggests that ventricular ejection is partly powered by a delayed development of force, i.e., stretch activation, in regions of the ventricular wall due to stretch resulting from torsional twist of the ventricle around the apex-to-base axis. Given the potential importance of stretch activation in cardiac function, we characterized the stretch activation response and its Ca2+ dependence in murine skinned myocardium at 22°C in solutions of varying Ca2+ concentrations. Stretch activation was induced by suddenly imposing a stretch of 0.5–2.5% of initial length to the isometrically contracting muscle and then holding the muscle at the new length. The force response to stretch was multiphasic: force initially increased in proportion to the amount of stretch, reached a peak, and then declined to a minimum before redeveloping to a new steady level. This last phase of the response is the delayed force characteristic of myocardial stretch activation and is presumably due to increased attachment of cross-bridges as a consequence of stretch. The amplitude and rate of stretch activation varied with Ca2+ concentration and more specifically with the level of isometric force prior to the stretch. Since myocardial force is regulated both by Ca2+ binding to troponin-C and cross-bridge binding to thin filaments, we explored the role of cross-bridge binding in the stretch activation response using NEM-S1, a strong-binding, non-force–generating derivative of myosin subfragment 1. NEM-S1 treatment at submaximal Ca2+-activated isometric forces significantly accelerated the rate of the stretch activation response and reduced its amplitude. These data show that the rate and amplitude of myocardial stretch activation vary with the level of activation and that stretch activation involves cooperative binding of cross-bridges to the thin filament. Such a mechanism would contribute to increased systolic ejection in response to increased delivery of activator Ca2+ during excitation–contraction coupling.

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A cloned renal epithelial Na+ channel protein displays stretch activation in planar lipid bilayers

AJP Cell Physiology ◽

10.1152/ajpcell.1995.268.6.c1450 ◽

1995 ◽

Vol 268 (6) ◽

pp. C1450-C1459 ◽

Cited By ~ 92

Author(s):

M. S. Awayda ◽

I. I. Ismailov ◽

B. K. Berdiev ◽

D. J. Benos

Keyword(s):

Hydrostatic Pressure ◽

Pressure Gradient ◽

Lipid Bilayers ◽

Single Channel ◽

Na Channel ◽

Planar Lipid Bilayers ◽

Stretch Activation ◽

Hydrostatic Pressure Gradient ◽

Epithelial Na Channel

We have previously cloned a bovine renal epithelial channel homologue (alpha-bENaC) belonging to the epithelial Na+ channel (ENaC) family. With the use of a rabbit nuclease-treated in vitro translation system, mRNA coding for alpha-bENaC was translated and the polypeptide products were reconstituted into liposomes. On incorporation into planar lipid bilayers, in vitro-translated alpha-bENaC protein 1) displayed voltage-independent Na+ channel activity with a single-channel conductance of 40 pS, 2) was mechanosensitive in that the single-channel open probability was maximally activated with a hydrostatic pressure gradient of 0.26 mmHg across the bilayer, 3) was blocked by low concentrations of amiloride [apparent inhibitory constant of amiloride (K(i)amil approximately 150 nM], and 4) was cation selective with a Li+:Na+:K+ permselectivity of 2:1:0.14 under nonstretched conditions. These pharmacological and selectivity characteristics were altered to a lower amiloride affinity (K(i)amil > 25 microM) and a lack of monovalent cation selectivity in the presence of a hydrostatic pressure gradient. This observation of stretch activation (SA) of alpha-bENaC was confirmed in dual electrode recordings of heterologously expressed alpha-bENaC whole cell currents in Xenopus oocytes swelled by the injection of 15 nl of a 100 mM KCl solution. We conclude that alpha-bENaC, and by analogy other ENaCs, represent a novel family of cloned SA channels.

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