Desmin - Putative Functions

Putative Functions

The function of desmin has been deduced through studies in knockout mice, but the underlying mechanism of its action is not known. These possibilities may be the result of interactions with other proteins and not desmin itself. More research needs to be done on desmin's expression and interactions in the muscle cell in order to determine its exact function.

Desmin is one of the earliest protein markers for muscle tissue in embryogenesis as it is detected in the somites. Although it is present early in the development of muscle cells, it is only expressed at low levels, and increases as the cell nears terminal differentiation. A similar protein, vimentin, is present in higher amounts during embryogenesis while desmin is present in higher amounts after differentiation. This suggests that there may be some interaction between the two in determining muscle cell differentiation. However desmin knockout mice develop normally and only experience defects later in life. Since desmin is expressed at a low level during differentiation another protein may be able to compensate for desmin's function early in development but not later on.

Desmin is also important in muscle cell architecture and structure since it connects many components of the cytoplasm. The sarcomere is a component of muscle cells composed of actin and myosin motor proteins which allow the cell to contract. Desmin forms a scaffold around the Z-disk of the sarcomere and connects the Z-disk to the subsarcolemmal cytoskeleton (the cytoplasmic part of the muscle cell plasma membrane). It links the myofibrils laterally by connecting the Z-disks. Through its connection to the sarcomere Desmin connects the contractile apparatus to the cell nucleus, mitochondria, and post-synaptic areas of motor endplates. These connections maintain the structural and mechanical integrity of the cell during contraction while also helping in force transmission and longitudinal load bearing. There is some evidence that desmin may also connect the sarcomere to the extracellular matrix (ECM) through desmosomes which could be important in signalling between the ECM and the sarcomere which could regulate muscle contraction and movement.

Finally, desmin may be important in mitochondria function. When desmin is not functioning properly there is improper mitochondrial distribution, number, morphology and function. Since desmin links the mitochondria to the sarcomere it may transmit information about contractions and energy need and through this regulate the aerobic respiration rate of the muscle cell.