Albumin Is a Major Protein Component of Transverse Tubule Vesicles Isolated from Skeletal Muscle

AbstractWe previously demonstrated that a common dietary protein component, wheat amylase trypsin inhibitors (ATI), stimulate intestinal macrophages and dendritic cells via toll like receptor 4. Activation of these intestinal myeloid cells elicits an inflammatory signal that is propagated to mesenteric lymph nodes, and that can facilitate extraintestinal inflammation. Mice were fed a well-defined high fat diet, with (HFD/ATI) or without (HFD) nutritionally irrelevant amounts of ATI. Mice on HFD/ATI developed only mild signs of intestinal inflammation and myeloid cell activation but displayed significantly higher serum triglycerides and transaminases compared to mice on HFD alone. Moreover, they showed increased visceral and liver fat, and a higher insulin resistance. ATI feeding promoted liver and adipose tissue inflammation, with M1-type macrophage polarization and infiltration, and enhanced liver fibrogenesis. Gluten, the major protein component of wheat, did not induce these pathologies. Therefore, wheat ATI ingestion in minute quantities comparable to human daily wheat consumption exacerbated features of the metabolic syndrome and non-alcoholic steatohepatitis, despite its irrelevant caloric value.

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Anatomical distribution of voltage-dependent membrane capacitance in frog skeletal muscle fibers.

The Journal of General Physiology ◽

10.1085/jgp.93.3.565 ◽

1989 ◽

Vol 93 (3) ◽

pp. 565-584 ◽

Cited By ~ 19

Author(s):

C L Huang ◽

L D Peachey

Keyword(s):

Skeletal Muscle ◽

Muscle Fibers ◽

Fiber Surface ◽

Membrane Capacitance ◽

Hypertonic Solution ◽

Charge Movement ◽

Frog Skeletal Muscle ◽

Transverse Tubule ◽

Skeletal Muscle Fibers ◽

Voltage Dependent

Components of nonlinear capacitance, or charge movement, were localized in the membranes of frog skeletal muscle fibers by studying the effect of 'detubulation' resulting from sudden withdrawal of glycerol from a glycerol-hypertonic solution in which the muscles had been immersed. Linear capacitance was evaluated from the integral of the transient current elicited by imposed voltage clamp steps near the holding potential using bathing solutions that minimized tubular voltage attenuation. The dependence of linear membrane capacitance on fiber diameter in intact fibers was consistent with surface and tubular capacitances and a term attributable to the capacitance of the fiber end. A reduction in this dependence in detubulated fibers suggested that sudden glycerol withdrawal isolated between 75 and 100% of the transverse tubules from the fiber surface. Glycerol withdrawal in two stages did not cause appreciable detubulation. Such glycerol-treated but not detubulated fibers were used as controls. Detubulation reduced delayed (q gamma) charging currents to an extent not explicable simply in terms of tubular conduction delays. Nonlinear membrane capacitance measured at different voltages was expressed normalized to accessible linear fiber membrane capacitance. In control fibers it was strongly voltage dependent. Both the magnitude and steepness of the function were markedly reduced by adding tetracaine, which removed a component in agreement with earlier reports for q gamma charge. In contrast, detubulated fibers had nonlinear capacitances resembling those of q beta charge, and were not affected by adding tetracaine. These findings are discussed in terms of a preferential localization of tetracaine-sensitive (q gamma) charge in transverse tubule membrane, in contrast to a more even distribution of the tetracaine-resistant (q beta) charge in both transverse tubule and surface membranes. These results suggest that q beta and q gamma are due to different molecules and that the movement of q gamma in the transverse tubule membrane is the voltage-sensing step in excitation-contraction coupling.

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Calmodulin and Excitation-Contraction Coupling

Physiology ◽

10.1152/physiologyonline.2000.15.6.281 ◽

2000 ◽

Vol 15 (6) ◽

pp. 281-284 ◽

Cited By ~ 2

Author(s):

Susan L. Hamilton ◽

Irina Serysheva ◽

Gale M. Strasburg

Keyword(s):

Skeletal Muscle ◽

Ion Channels ◽

Sarcoplasmic Reticulum ◽

Release Channel ◽

Excitation Contraction Coupling ◽

Transverse Tubule ◽

Contraction Coupling ◽

Voltage Dependent ◽

Important Regulator ◽

Precise Role

Excitation-contraction coupling in cardiac and skeletal muscle involves the transverse-tubule voltage-dependent Ca2+ channel and the sarcoplasmic reticulum Ca2+ release channel. Both of these ion channels bind and are modulated by calmodulin in both its Ca2+-bound and Ca2+-free forms. Calmodulin is, therefore, potentially an important regulator of excitation-contraction coupling. Its precise role, however, has not yet been defined.

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