Author/Editor     Chowdhury-Haque, Helena
Title     Aktinski citoskelet in dinamika sprememb površine membrane podganje hipofizne celice v kulturi
Type     monografija
Place     Ljubljana
Publisher     Univerza v Ljubljani, Medicinska fakulteta
Publication year     2000
Volume     str. 45
Language     slo
Abstract     The membrane area dynamics is changing due to vesicle transport, thus due to exocytosis and endocytosis. The mechanisms of exocytosis and endocytosis regulation are not yet completely established, but both processes are important in maintaining subcellular integrity and allow the transport of proteins and lipids within the cell and between the cell and its environment. Both processes are important for us to understand physiological and pathophysiological processes. It is already known that actin cytoskeleton plays important role in exocytosis and endocytosis, yet exact mechanism is not known. We hypothesized that actin cytoskeleton acts as a barrier for secretory granules translocation from cytoplasm to the plasma membrane and that it is essential for endocytosis. Actin cytoskeleton was disaggregated by pretreating cells with Clostridium spiroforme toxin (CST), which specifically ADP-ribosylates cellular actin. We monitored the secretory activity of single rat melanotrophs by the "patch-clamp" membrane capacitance (Cm) measurements. Capacitance increases are a direct measure of increases in the area of the plasma membrane. To investigate membrane area dynamics in greater detail, we used "cell-attached patch-clamp" method to measure microscopic changes in Cm, which enable us to distinguish exocytosis from endocytosis. We found that pretreatment of cells by CST reduces the amount of phalloidin stained subcortical actin, indicating a depolymerisation of F-actin. In stimulated, CST treated cells Cm was increasing more rapidly than in control cells, which indicate an inhibitory role of actin cytoskeleton in exocytosis. This was also confirmed with microscopic measurements of Cm. In conditions, where endocytosis was determined the time- course of Cm, the CST-treatment resulted in an increase in Cm, while in control cells Cm was decreasing. This indicates that endocytosis was inhibited.
Descriptors     PITUITARY GLAND
CYTOSKELETON
EXOCYTOSIS
ENDOCYTOSIS
ACTINS
RATS
BACTERIAL TOXINS
CELL MEMBRANE
CLOSTRIDIUM
PATCH-CLAMP TECHNIQUES