The cytoskeleton as a barrier to exocytosis in secretory cells

摘要: Chromaffin cells of the adrenal medulla synthesize, store and secrete catecholamines. These contain numerous electron-dense secretory granules which discharge their contents into extracellular space by exocytosis. The subplasmalemmal area chromaffin cell is characterized presence a highly organized cytoskeletal network. F-Actin seems to be exclusively localized in this together with specific actin-binding proteins forms dense viscoelastic gel; fodrin, vinculin caldesmon, three actin cross-linking proteins, gelsolin, an actin-severing protein, are found region. Since fodrin-, caldesmon- alpha-actinin-binding sites exist on granule membranes, filaments can also link granules. entrapped lattice thus cytoskeleton acts as barrier preventing When stimulated, molecular rearrangements take place: F-actin depolymerizes fodrin reorganizes patches. In addition, introduction monospecific antifodrin immunoglobulins digitonin-permeabilized blocks exocytosis, demonstrating crucial role protein. bacterial toxin-permeabilized cells, experiments using actin-perturbing agents such cytochalasin D DNAase I suggest that exocytosis part controlled cytoskeleton. intracellular signal governing reorganization (associated exocytosis) calcium. Calcium inhibits some activates other consequently causes dissolution This should result detachment permit free access exocytotic plasma membrane.