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Rat peritoneal mast cells, both intact and permeabilized, have been used widely as model secretory cells. GTP-binding proteins and calcium play a major role in controlling their secretory response. Here we have examined changes in the organization of actin filaments in intact mast cells after activation by compound 48/80, and in permeabilized cells after(More)
BACKGROUND Regulated secretion by mast cells is known to be controlled by GTP-binding proteins, but the proteins involved have not been identified. Rac and Rho, two small GTPases related to the oncoprotein Ras, mediate transmission of signals from cell-surface receptors to the actin cytoskeleton. In rat mast cells, both Rac and Rho participate in effecting(More)
The major part of mast cell actin is Triton-soluble and behaves as a monomer in the DNase I inhibition assay. Thus, actin exists predominantly in monomeric or short filament form, through filamentous actin is clearly apparent in the cortical region after rhodamine-phalloidin (RP) staining. The minimum actin content is estimated to be approximately 2.5(More)
Localized disassembly of cortical F-actin has long been considered necessary for facilitation of exocytosis. Exposure of permeabilized mast cells to calcium/ATP induces cortical F-actin disassembly (calmodulin-dependent) and secretion (calmodulin-independent). The delay in the onset of secretion is characteristic for the calcium/ATP response and is(More)
Secretion is dependent on a rise in cytosolic Ca(2+)concentration and is associated with dramatic changes in actin organization. The actin cortex may act as a barrier between secretory vesicles and plasma membrane. Thus, disassembly of this cortex should precede late steps of exocytosis. Here we investigate regulation of both the actin cytoskeleton and(More)
Permeabilised rat mast cells were exposed to gelsolin and its N-terminal half (S1-3), proteins that sever actin filaments in a calcium-dependent and independent manner, respectively. Gelsolin and S1-3 induced a decrease in cellular F-actin content and an increase in the extent of the secretory response. The calcium sensitivities of both these effects were(More)
A large proportion (60-85%) of the actin present in lysates of cultured baby hamster kidney (BHK) cells is monomeric at low temperature. All this G-actin is accounted for in the fractions obtained by high-speed centrifugation of the lysate in the presence or absence of non-ionic detergent; 98 (+/- 7)% of its reacts as monomer in the deoxyribonuclease assay.(More)
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