Telethonin and other new proteins of the Z-disc of skeletal muscle.

This brief review outlines some of the most relevant proteins of the Z-disc and the complex network of interactions that link them together in a stable structure. Apart from the well-known Z-disc proteins such as actin, cap-Z, titin, nebulin, and alpha-actinin 2, several other Z-disc proteins have been recently discovered, including telethonin and myotilin that have been linked to limb girdle muscular dystrophies. Some proteins including ALP and ZASP have known interaction domains (PDZ and LIM motifs), whereas others like FATZ have no canonical interaction domains, although they are known to bind several proteins. Another new Z-disc protein is gamma-filamin that could provide a link between the plasma membrane and myofibrils because it binds directly to gamma- and delta-sarcoglycans and indirectly to alpha-actinin 2 via FATZ and myotilin. A greater knowledge of Z-disc proteins and their interactions is essential for understanding their role in the structure and function of muscle.