Depletion of T-tubules and specific subcellular changes in sarcolemmal proteins in tachycardia-induced heart failure

Ravi C. Balijepalli, Andrew J. Lokuta, Nathan Maertz, Jennifer M. Buck, Robert A. Haworth, Hector H. Valdivia, Timothy J. Kamp

Research output: Contribution to journalArticle

130 Citations (Scopus)

Abstract

Objective: The T-tubule membrane network is integrally involved in excitation-contraction coupling in ventricular myocytes. Ventricular myocytes from canine hearts with tachycardia-induced dilated cardiomyopathy exhibit a decrease in accessible T-tubules to the membrane-impermeant dye, di8-ANNEPs. The present study investigated the mechanism of loss of T-tubule staining and examined for changes in the subcellular distribution of membrane proteins essential for excitation-contraction coupling. Methods: Isolated ventricular myocytes from canine hearts with and without tachycardia-induced heart failure were studied using fluorescence confocal microscopy and membrane fractionation techniques using a variety of markers specific for sarcolemmal and sarcoplasmic reticulum proteins. Results: Probes for surface glycoproteins, Na/K ATPase, Na/Ca exchanger and Cav1.2 demonstrated a prominent but heterogeneous reduction in T-tubule labeling in both intact and permeabilised failing myocytes, indicating a true depletion of T-tubules and associated membrane proteins. Membrane fractionation studies showed reductions in L-type Ca2+ channels and β-adrenergic receptors but increased levels of Na/Ca exchanger protein in both surface sarcolemma and T-tubular sarcolemma-enriched fractions; however, the membrane fraction enriched in junctional complexes of sarcolemma and junctional sarcoplasmic reticulum demonstrated no significant changes in the density of any sarcolemmal protein or sarcoplasmic reticulum protein assayed. Conclusion: Failing canine ventricular myocytes exhibit prominent depletion of T-tubules and changes in the density of a variety of proteins in both surface and T-tubular sarcolemma but with preservation of the protein composition of junctional complexes. This subcellular remodeling contributes to abnormal excitation-contraction coupling in heart failure.

Original languageEnglish (US)
Pages (from-to)67-77
Number of pages11
JournalCardiovascular Research
Volume59
Issue number1
DOIs
StatePublished - Jul 1 2003
Externally publishedYes

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Tachycardia
Sarcolemma
Heart Failure
Muscle Cells
Excitation Contraction Coupling
Sarcoplasmic Reticulum
Membranes
Canidae
Proteins
Membrane Proteins
Membrane Glycoproteins
Dilated Cardiomyopathy
Fluorescence Microscopy
Confocal Microscopy
Adrenergic Receptors
Coloring Agents
Staining and Labeling

Keywords

  • Ca-channel
  • E-c coupling
  • Heart failure
  • Remodeling
  • Sarcolemma

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

Cite this

Depletion of T-tubules and specific subcellular changes in sarcolemmal proteins in tachycardia-induced heart failure. / Balijepalli, Ravi C.; Lokuta, Andrew J.; Maertz, Nathan; Buck, Jennifer M.; Haworth, Robert A.; Valdivia, Hector H.; Kamp, Timothy J.

In: Cardiovascular Research, Vol. 59, No. 1, 01.07.2003, p. 67-77.

Research output: Contribution to journalArticle

Balijepalli, Ravi C. ; Lokuta, Andrew J. ; Maertz, Nathan ; Buck, Jennifer M. ; Haworth, Robert A. ; Valdivia, Hector H. ; Kamp, Timothy J. / Depletion of T-tubules and specific subcellular changes in sarcolemmal proteins in tachycardia-induced heart failure. In: Cardiovascular Research. 2003 ; Vol. 59, No. 1. pp. 67-77.
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AU - Balijepalli, Ravi C.

AU - Lokuta, Andrew J.

AU - Maertz, Nathan

AU - Buck, Jennifer M.

AU - Haworth, Robert A.

AU - Valdivia, Hector H.

AU - Kamp, Timothy J.

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N2 - Objective: The T-tubule membrane network is integrally involved in excitation-contraction coupling in ventricular myocytes. Ventricular myocytes from canine hearts with tachycardia-induced dilated cardiomyopathy exhibit a decrease in accessible T-tubules to the membrane-impermeant dye, di8-ANNEPs. The present study investigated the mechanism of loss of T-tubule staining and examined for changes in the subcellular distribution of membrane proteins essential for excitation-contraction coupling. Methods: Isolated ventricular myocytes from canine hearts with and without tachycardia-induced heart failure were studied using fluorescence confocal microscopy and membrane fractionation techniques using a variety of markers specific for sarcolemmal and sarcoplasmic reticulum proteins. Results: Probes for surface glycoproteins, Na/K ATPase, Na/Ca exchanger and Cav1.2 demonstrated a prominent but heterogeneous reduction in T-tubule labeling in both intact and permeabilised failing myocytes, indicating a true depletion of T-tubules and associated membrane proteins. Membrane fractionation studies showed reductions in L-type Ca2+ channels and β-adrenergic receptors but increased levels of Na/Ca exchanger protein in both surface sarcolemma and T-tubular sarcolemma-enriched fractions; however, the membrane fraction enriched in junctional complexes of sarcolemma and junctional sarcoplasmic reticulum demonstrated no significant changes in the density of any sarcolemmal protein or sarcoplasmic reticulum protein assayed. Conclusion: Failing canine ventricular myocytes exhibit prominent depletion of T-tubules and changes in the density of a variety of proteins in both surface and T-tubular sarcolemma but with preservation of the protein composition of junctional complexes. This subcellular remodeling contributes to abnormal excitation-contraction coupling in heart failure.

AB - Objective: The T-tubule membrane network is integrally involved in excitation-contraction coupling in ventricular myocytes. Ventricular myocytes from canine hearts with tachycardia-induced dilated cardiomyopathy exhibit a decrease in accessible T-tubules to the membrane-impermeant dye, di8-ANNEPs. The present study investigated the mechanism of loss of T-tubule staining and examined for changes in the subcellular distribution of membrane proteins essential for excitation-contraction coupling. Methods: Isolated ventricular myocytes from canine hearts with and without tachycardia-induced heart failure were studied using fluorescence confocal microscopy and membrane fractionation techniques using a variety of markers specific for sarcolemmal and sarcoplasmic reticulum proteins. Results: Probes for surface glycoproteins, Na/K ATPase, Na/Ca exchanger and Cav1.2 demonstrated a prominent but heterogeneous reduction in T-tubule labeling in both intact and permeabilised failing myocytes, indicating a true depletion of T-tubules and associated membrane proteins. Membrane fractionation studies showed reductions in L-type Ca2+ channels and β-adrenergic receptors but increased levels of Na/Ca exchanger protein in both surface sarcolemma and T-tubular sarcolemma-enriched fractions; however, the membrane fraction enriched in junctional complexes of sarcolemma and junctional sarcoplasmic reticulum demonstrated no significant changes in the density of any sarcolemmal protein or sarcoplasmic reticulum protein assayed. Conclusion: Failing canine ventricular myocytes exhibit prominent depletion of T-tubules and changes in the density of a variety of proteins in both surface and T-tubular sarcolemma but with preservation of the protein composition of junctional complexes. This subcellular remodeling contributes to abnormal excitation-contraction coupling in heart failure.

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KW - E-c coupling

KW - Heart failure

KW - Remodeling

KW - Sarcolemma

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