[Participation of annexins in signal transduction, regulation of plasma membrane structure and membrane repair mechanisms].

Cell integrity, assured by plasma membrane continuity, is essential to maintain proper cell functioning and survival. Plasma membrane separates the cell interior from the extracellular milieu and constitutes a barrier due to which the spatial relationship between organelles and the internal membrane network as well as the chemical composition of the cytoplasm are preserved during the cellular life span. Therefore, all cellular processes including intracellular ion homeostasis, exchange of substances between the extracellular environment and the cytoplasm, maintenance of cellular shape, cellular movement, vesicular traffic, cell division and membrane biogenesis, as well as and cellular signaling depend on the integrity, structure and function of the plasma membrane. In the course of these processes the plasma membrane is subjected to dynamic changes that can create a kind of mechanical stress and be a source of cell-threatening injuries. These membrane injuries could be also created upon chemical stress and due to the presence of hydrolytic enzymes or bacterial toxins in the extracellular milieu. All the mentioned factors turn to be deleterious to the membrane permeability, especially that to calcium ions. Many investigators underline that the influx of Ca2+ to the cytoplasm as a result of membrane injury creates a signal interpreted by the cell as an immediate danger. Many calcium-dependent mechanisms have evolved In relation to this. A growing number of evidence suggests that in some of these mechanisms ubiquitous cellular proteins, annexins, may participate as calcium sensors and molecules interacting with the plasma membrane. In this review the data are presented that annexins participate in the regulation of membrane structure and may be involved in the calcium-dependent membrane repair mechanisms.