Title: T-Tubule Function in Mammalian Cardiac Myocytes | Circulation Research
Headings: T-Tubule Function in Mammalian Cardiac Myocytes
T-Tubule Function in Mammalian Cardiac Myocytes
Abstract
Occurrence and Morphology of the T-Tubules
T-Tubule Development Is Labile
Proteins Present in the T-Tubule Membrane
Ca2+-Handling Proteins
Na+-Handling Proteins
K+-Handling Proteins
Anion-Handling Proteins
Second-Messenger Pathways
Interpretation of Immunohistochemical Data
Protein Colocalization Within, and With Proteins Adjacent to, the T-Tubules
Localization of Function
Cells Lacking T-Tubules
Diffusion Studies
Scanning Pipette
Detubulation
Functional Role
Electrical Properties of T-Tubules
Coupling of Ca 2+ Entry and Ca 2+ Release
Ca 2+ Efflux
Signal Transduction
Changes During Development and Disease
T-Tubule Development and Morphology in Hypertrophy and Failure
Changes in Protein Expression in Development, Hypertrophy, and Failure
Relevance of Changes in T-Tubule Structure and Protein Expression to Function
Conclusions and Unanswered Questions
Footnotes
References

Content: 2003;92:1182–1192
Abstract
The transverse tubules (t-tubules) of mammalian cardiac ventricular myocytes are invaginations of the surface membrane. Recent studies have suggested that the structure and function of the t-tubules are more complex than previously believed; in particular, many of the proteins involved in cellular Ca 2+ cycling appear to be concentrated at the t-tubule. Thus, the t-tubules are an important determinant of cardiac cell function, especially as the main site of excitation-contraction coupling, ensuring spatially and temporally synchronous Ca 2+ release throughout the cell. Changes in t-tubule structure and protein expression occur during development and in heart failure, so that changes in the t-tubules may contribute to the functional changes observed in these conditions. The purpose of this review is to provide an overview of recent studies of t-tubule structure and function in cardiac myocytes. The transverse tubules (t-tubules) of mammalian cardiac ventricular myocytes are invaginations of the surface membrane that occur at the Z line and have both transverse and longitudinal elements. Many of the proteins involved in excitation-contraction coupling appear to be concentrated at the t-tubules. Therefore, it has been suggested that the t-tubules play a central role in cell activation. In the present review, we will consider the immunohistochemical and functional evidence for protein localization at the t-tubules, potential problems in the interpretation of such data, and the functional consequences of such localization.