A vinculin-containing cortical lattice in skeletal muscle: transverse lattice elements ("costameres") mark sites of attachment between myofibrils and sarcolemma.

Abstract

Vinculin is localized at the sarcolemma of [chicken] skeletal muscle cells in a 2-dimensional orthogonal lattice. Perpendicular to the longitudinal axis of the cell, bands of vinculin encircle corresponding to the subjacent sarcomeres. Because of their appearance and probable function, the transverse elements of the lattice are called costameres. Costameres have a substructure consisting of densely clustered patches of vinculin; the patches are segregated into 2 rows which flank the Z line and overlie the I band of the underlying sarcomere. The costameres are physically coupled to the underlying myofibrils because the costameres broaden and narrow in concert with the underlying I band in stretched and contracted muscle, and because adjacent but misaligned myofibrils are mirrored by corresponding discontinuities in the overlying costameres. The sarcolemmal lattice, detected because vinculin is 1 of its molecular components, integrates the contractile apparatus with the sarcolemma during lengthening and shortening of the muscle cells.