Striated Muscle Cytoarchitecture: An Intricate Web of Form and Function

Abstract

Striated muscle is an intricate, efficient, and precise machine that contains complex interconnected cytoskeletal networks critical for its contractile activity. The individual units of the sarcomere, the basic contractile unit of myofibrils, include the thin, thick, titin, and nebulin filaments. These filament systems have been investigated intensely for some time, but the details of their functions, as well as how they are connected to other cytoskeletal elements, are just beginning to be elucidated. These investigations have advanced significantly in recent years through the identification of novel sarcomeric and sarcomeric-associated proteins and their subsequent functional analyses in model systems. Mutations in these cytoskeletal components account for a large percentage of human myopathies, and thus insight into the normal functions of these proteins has provided a much needed mechanistic understanding of these disorders. In this review, we highlight the components of striated muscle cytoarchitecture with respect to their interactions, dynamics, links to signaling pathways, and functions. The exciting conclusion is that the striated muscle cytoskeleton, an exquisitely tuned, dynamic molecular machine, is capable of responding to subtle changes in cellular physiology.

Age-related changes and nutritional regulation of myosin heavy-chain composition in longissimus dorsi of commercial pigs

“…The variability of muscle fibres is due to the existence of multiple isoforms of each myofibrillar component (Clark et al, 2002). The diversity of a protein isoform is based on gene regulation through two main mechanisms (Bottinelli and Reggiani, 2000).…”

Variations in the abundance of 24 protein biomarkers of beef tenderness according to muscle and animal type

“…However, this is not consistent with the literature data on this protein. It is a protein of the thick myosin filament that binds to the myosins (Clark et al, 2002), controlling the polymerisation and the assembly of the thick filament. This protein participates in the regulation of muscle contraction by inhibiting the myosin ATPase activity.…”

“…CapZ-b, a capping protein of the thin actin filament at the barbed and pointed ends, has a role in the organisation of the thin filament and its anchor to the Z-line (Clark et al, 2002). The CapZ protein is a heterodimer of CapZ-a and CapZ-b.…”

Drastic increase of myosin light chain MLC-2 in senescent skeletal muscle indicates fast-to-slow fibre transition in sarcopenia of old age

“…This is not a trivial point, since the biomolecules forming the thick and thin filaments of the basic contractile units in skeletal muscles exist in numerous fibre type-specific isoforms (Pette and Staron, 1990). Skeletal muscle myosin forms a hexameric structure consisting of 2 myosin heavy chains (MHCs) and various MLCs (Clark et al, 2002;Bozzo et al, 2005). Molecular coupling between the myosin head structure and actin filaments, in the presence of ATP, causes the sliding of thin filaments past thick filaments resulting in sarcomeric shortening (Gordon et al, 2000;Fitts, 2008).…”