Title: T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases | Skeletal Muscle | Full Text
Headings: T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases
Abstract
Introduction
T-tubule plasticity
Morphological aspects of triad biogenesis
Sarcoplasmic reticulum
Transverse tubule
Molecular mechanisms involved in T-tubule biogenesis and triad formation and maintenance
Table 1 Proteins implicated in triad organization, roles and associated human diseasesa
Caveolin 3
Amphiphysin 2 (BIN1)
Dysferlin
Mitsugumins
Junctophilins
Myotubularin
The RyR-DHPR complex
Conclusion
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Content: Indeed, muscle fibers contain large internal calcium stores with the ability to quickly release and retrieve calcium (Figure 1, right panel). For a fast and fine-tuning of muscle contraction, these stores are maintained under the control of the action potential, which ensures calcium release simultaneously within the whole interior of the muscle fiber. As myofibers are 50-100 μm in diameter and several millimeters to centimeters long, a highly specialized structure named the triad is necessary to overcome spatial limits in using calcium as secondary messenger, and connect the sarcolemma with the calcium stores. The sarcolemma forms regular invaginations which insert between myofibrils, termed transverse tubules (T-tubules). In skeletal muscle, T-tubules tightly associate with the sarcoplasmic reticulum (SR), in a region called terminal cisternae/junctional SR. The close association of one T-tubule with two terminal cisternae on both sides of the tubule forms the triad (Figure 1 ). Figure 1
Triad organization in skeletal muscle. Left: Electron micrograph of a triad junction. A central T-tubule is flanked on both sides by a terminal cisternae element from the sarcoplasmic reticulum.