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Moving and positioning the nucleus in skeletal muscle - one step at a time.

ABSTRACT: Nuclear movement and positioning within cells has become an area of great interest in the past few years due to the identification of different molecular mechanisms and functions in distinct organisms and contexts. One extreme example occurs during skeletal muscle development and regeneration. Skeletal muscles are composed of individual multinucleated myofibers with nuclei positioned at their periphery. Myofibers are formed by fusion of mononucleated myoblasts and during their development, successive nuclear movements and positioning events have been described. The position of the nuclei in myofibers is important for muscle function. Interestingly, during muscle regeneration and in some muscular diseases, nuclei are positioned in the center of the myofiber. In this review, we discuss the multiple mechanisms of nuclear positioning that occur during myofiber formation and regeneration. We also discuss the role of nuclear positioning for skeletal muscle function.

SUBMITTER: Cadot B

PROVIDER: S-EPMC4915500 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Moving and positioning the nucleus in skeletal muscle - one step at a time.

Cadot Bruno B Gache Vincent V Gomes Edgar R ER

Nucleus (Austin, Tex.) 20150101 5

Nuclear movement and positioning within cells has become an area of great interest in the past few years due to the identification of different molecular mechanisms and functions in distinct organisms and contexts. One extreme example occurs during skeletal muscle development and regeneration. Skeletal muscles are composed of individual multinucleated myofibers with nuclei positioned at their periphery. Myofibers are formed by fusion of mononucleated myoblasts and during their development, succe ...[more]

PMID: 26338260

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Project description:Striated muscle contraction is the result of sarcomeres, the basic contractile unit, shortening because of hydrolysis of adenosine triphosphate (ATP) by myosin molecular motors. In noncontracting, "relaxed" muscle, myosin still hydrolyzes ATP slowly, contributing to the muscle's overall resting metabolic rate. Furthermore, when relaxed, myosin partition into two kinetically distinct subpopulations: a faster-hydrolyzing "relaxed" population, and a slower-hydrolyzing "super relaxed" (SRX) population. How these two myosin subpopulations are spatially arranged in the sarcomere is unclear, although it has been proposed that myosin-binding protein C (MyBP-C) may stabilize the SRX state. Because MyBP-C is found only in a distinct region of the sarcomere, i.e., the C-zone, are SRX myosin similarly colocalized in the C-zone? Here, we imaged the binding lifetime and location (38-nm resolution) of single, fluorescently labeled boron-dipyrromethene-labeled ATP molecules in relaxed skeletal muscle sarcomeres from rat soleus. The lifetime distribution of fluorescent ATP-binding events was well fitted as an admixture of two subpopulations with time constants of 26 ± 2 and 146 ± 16 s, with the longer-lived population being 28 ± 4% of the total. These values agree with reported kinetics from bulk studies of skeletal muscle for the relaxed and SRX subpopulations, respectively. Subsarcomeric localization of these events revealed that SRX-nucleotide-binding events are fivefold more frequent in the C-zone (where MyBP-C exists) than in flanking regions devoid of MyBP-C. Treatment with the small molecule myosin inhibitor, mavacamten, caused no change in SRX event frequency in the C-zone but increased their frequency fivefold outside the C-zone, indicating that all myosin are in a dynamic equilibrium between the relaxed and SRX states. With SRX myosin found predominantly in the C-zone, these data suggest that MyBP-C may stabilize and possibly regulate the SRX state.

Dataset Information

Moving and positioning the nucleus in skeletal muscle - one step at a time.

Publications

Moving and positioning the nucleus in skeletal muscle - one step at a time.

Similar Datasets

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