Ankrd2: a link between the sarcomere and the nucleus in skeletal muscle

Ankrd2 is an ankyrin repeat protein mainly expressed in skeletal muscle and heart and localized in the sarcomeric I-line, adjacent to the Z-line. Z-lines define the boundaries of each sarcomere, the contractile units of the myofibril and are composed by a highly intricate network of protein-protein interactions. Nowadays it has clearly emerged that several sarcomeric components are moving between this district and other subcellular compartments, such as the nucleus. Hence the sarcomere and in particular the Z-line are considered to be central nodes in which signals arrive and from which signals depart. Since Ankrd2 is detectable both in the sarcomere and in the nucleus, it is supposed to shuttle between these two compartments to transmit a still unknown signal. Moreover Ankrd2 expression increases after skeletal muscle stretch and during the myoblasts differentiation into multinucleated myotubes. Therefore it has been hypothesized an Ankrd2 involvement in hypertrophy or in myogenesis.