Les compartiments membranaires de la cellule eucaryote

Abstract

Les données issues du décryptage du génome humain puis de la protéomique naissante doivent être intégrées dans les structures de la cellule vivante si l’on veut parvenir à une meilleure compréhension de son fonctionnement normal et pathologique. L’organisation compartimentée de la cellule eucaryote, pressentie dès la fin du XIXe siècle, est maintenant définitivement établie dans l’ensemble du monde vivant. Cet article situe dans une perspective historique les données de base indispensables à la compréhension des recherches modernes sur les mécanismes du transport intracellulaire.

The existence of an intracellular reticulum in eukaryotic cells was revealed at the middle of the XXth century by electron microscopic observations performed on living fibroblasts and then on cell thin sections. Two compartments were morphologically distinguished in this reticulum: the rough endoplasmic reticulum and the smooth endoplasmic reticulum which was identified to the “apparatus” previously described, by the end of the XIXth century, at the light microscope by Golgi. An important progress was then accomplished due to functional studies that demonstrated that these compartments are in continuous communication and that they are the site of the intracellular transport of exported proteins. This led to the concept of membrane traffic and to the hypothesis put forward by Palade of the existence of intracellular transport vesicles, budding and pinching off from donor membranes and fusing with acceptor membranes. Biochemical, molecular and genetic studies performed during the last quarter of the XXth century aimed at elucidating the structural features and functions of the various intracellular compartments. At the same time they have revealed the unicity of organization of all eukaryotic cells. The present chapter surveys the main properties of the intracellular membrane compartments and subcompartments involved in the exportation of proteins (the biosynthetic pathway) or in their importation (endocytic pathway). This knowledge represents necessary basis to the understanding of the most recent studies on the molecular mechanisms of intracellular transport.