[Pathology of the cytoskeleton]

In the last years, considerable advances have been made in the study of the proteins and polypeptides of the cytoskeleton, and its three main components: microfilaments (MF), intermediate filaments (IMF) and microtubules (MT). The principal properties of these elements and those of many associated proteins are recalled. The actin MF are mainly involved in cell contractility, the IMF in cell shape, while the MT and their associated proteins are involved in intracellular transport. Some pathological modifications of the cytoskeleton will be considered. In the liver, accumulations of keratin result in the formation of Mallory's hyalin, found in several types of cirrhosis and hepatomas. In muscle, accumulations of desmin are observed in various myopathies. An accumulation of alpha-actinin at the Z bands characterizes nemalin myopathy. In several forms of hemolytic anemias, alterations of the membranous cytoskeletal components of the red blood cells--spectrin, ankyrin, actin--may explain their abnormal shape and excessive fragility. In the nervous system, many pathological conditions are related to abnormal cytoskeletal components. In Parkinson's disease, Lewy bodies are an accumulation of neurofilaments (IMF). In Alzheimer's disease, and some related conditions, the intraneuronal tangles are associated with modifications of MT and neurofilaments. The role of MT and in particular of the MT-associated protein tau, as demonstrated recently, confirms the involvement of the MT. The observed disturbances of MT-related axonal flow may explain some of the known functional changes in these forms of dementia.