El citoesquleto: Funciones estructurales y de regulación de las proteinas de membrana

Abstract

The cytoskeleton is a network of proteic filaments which occupy the interior of all vegetable and animal cells. It has a special relevance in the latter, which lack a rigid cellular wall, because it maintains the structure and shape of the cell. It acts as a support for the organization and fixation of organelles and enzymes. In many cells, the cytoskeleton is not a permanent structure, but instead it is continuously being dismantled and reconstructed. It is formed by three main types of proteic filaments: microtubules, actin filaments and intermediate filaments, bound together and to other cellular structures. The controlled polymerization of actin and tubulin is responsible for both the mobility and shape of eukaryotic cells. The movement of eukaryotic cells is the result of the coordinated action of the formation of extensions, adhesions and retractions of the membrane, where the actin network and the interactions between these and molecular motors play a key role. The microtubules control the spatial distribution of these activities, creating a polarization of the cell which determines the direction of movement. Recent studies of our laboratory (Vanagas and col, 2007, 2008) show that monomeric actin activates calcium transport in the membrane of red blood cells, whereas polymeric or filamentous actin inhibits it. This phenomenon seems to be a general property of all membrane proteins in which the cytoskeleton is no longer restricted to a merely mechanical function, but rather would produce the modulation of the activity of the integral proteins to which it is related to.