L'actine cytosquelettique et ses protéines associées II. Aspects pathologiques

Abstract

L’actine intervient dans une large variété de processus biologiques. Dans les cellules non musculaires, l’évolution de la bactérie Listeria monocytogenes fournit un exemple de motilité reposant sur l’actine. Les envahisseurs bactériens exploitent activement l’actine de la cellule hôte au cours des phases d’infection et de propagation dans les cellules avoisinantes. In vivo, la régulation de l’association/dissociation continue des molécules d’actine est strictement contrôlée par un grand nombre de protéines dites associées, agissant individuellement ou de concert pour séquestrer les monomères (thymosine β), coiffer (Cap Z), ponter (filamine), réticuler (actinine α), fragmenter (gelsoline), ou stabiliser (tropomyosine) les filaments d’actine. Toute perturbation dans l’expression, la structure ou la fonction de ces protéines induit des changements dans le comportement cellulaire, conduisant à la déstructuration architecturale du réseau d’actine.

The vast variety of cellular processes implicating the actin molecule, as either a component of the cytoskeleton or a major factor in muscle contraction and motility systems, requires the interactions of actin with its associated proteins. A fascinating example of actin-based motility in non-muscle cells is the case of the bacteria Listeria monocytogenes, which can invade eukaryotic cells and actively exploit actin from its host cell during infection and cell-to-cell spreading. Within the cell, the regulation of continuous cycle of assembly/ disassembly of actin is highly controlled by a large repertoire of proteins acting either individually or in concert, by sequestering monomers (beta-thymosin), capping (CapZ), cross-linking (filarain), bundling (alpha-actinin), severing (gelsolin) or stabilizing (tropomyosin) actin filaments. The development and function of multicellular organisms are dependent on the correct spatial and temporal organization of actin cytoskeleton, in response to appropriate environmental cues. Therefore, disruptions in the expression, the structure or the function of these proteins result in changes in cell behavior, leading to perturbation of actin architecture and in many cases, to the appearance of a wide range of pathogenic conditions and diseases. Indeed, disorganization of the actin cytoskeleton is part of the cell death program. [References: 30]