Costamere
Encyclopedia
The costamere is a structural-functional component of striated muscle
cells which connects the sarcomere of the muscle to the cell membrane.
Costameres are sub-sarcolemmal protein assemblies circumferentially aligned in register with the Z-disk of peripheral myofibril
s. They physically couple force-generating sarcomeres with the sarcolemma
in striated muscle cells and are thus considered one of several "Achilles' heel
s" of skeletal muscle, a critical component of striated muscle morphology which, when compromised, is thought to directly contribute to the development of several distinct myopathies.
The dystrophin-associated glycoprotein (DAG) complex contains various integral and peripheral membrane proteins such as dystroglycans and sarcoglycans, which are thought to be responsible for linking the internal cytoskeletal system of individual myofibers to structural proteins within the extracellular matrix (such as collagen
and laminin
). Therefore it is one of the features of the sarcolemma which helps to couple the sarcomere
to the extracellular connective tissue. Desmin protein may also bind to the DAG complex, and regions of it are known to be involved in signaling.
Striated muscle
Striated muscle tissue is a form of fibers that are combined into parallel fibers. More specifically, it can refer to:* Cardiac muscle .* Skeletal muscle* Branchiomeric muscles...
cells which connects the sarcomere of the muscle to the cell membrane.
Costameres are sub-sarcolemmal protein assemblies circumferentially aligned in register with the Z-disk of peripheral myofibril
Myofibril
A myofibril is a basic unit of a muscle. Muscles are composed of tubular cells called myocytes or myofibers. Myofibers are composed of tubular myofibrils. Myofibrils are composed of long proteins such as actin, myosin, and titin, and other proteins that hold them together...
s. They physically couple force-generating sarcomeres with the sarcolemma
Sarcolemma
The sarcolemma is the cell membrane of a muscle cell . It consists of a true cell membrane, called the plasma membrane, and an outer coat made up of a thin layer of polysaccharide material that contains numerous thin collagen fibrils...
in striated muscle cells and are thus considered one of several "Achilles' heel
Achilles' heel
An Achilles’ heel is a deadly weakness in spite of overall strength, that can actually or potentially lead to downfall. While the mythological origin refers to a physical vulnerability, metaphorical references to other attributes or qualities that can lead to downfall are common.- Origin :In Greek...
s" of skeletal muscle, a critical component of striated muscle morphology which, when compromised, is thought to directly contribute to the development of several distinct myopathies.
The dystrophin-associated glycoprotein (DAG) complex contains various integral and peripheral membrane proteins such as dystroglycans and sarcoglycans, which are thought to be responsible for linking the internal cytoskeletal system of individual myofibers to structural proteins within the extracellular matrix (such as collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
and laminin
Laminin
Laminins are major proteins in the basal lamina , a protein network foundation for most cells and organs...
). Therefore it is one of the features of the sarcolemma which helps to couple the sarcomere
Sarcomere
A sarcomere is the basic unit of a muscle. Muscles are composed of tubular muscle cells . Muscle cells are composed of tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as dark and light bands...
to the extracellular connective tissue. Desmin protein may also bind to the DAG complex, and regions of it are known to be involved in signaling.