Depolymerisation and rearrangement of actin filaments during exocytosis in rat peritoneal mast cells: involvement of ryanodine-sensitive calcium stores.
Cytoskeletal F-actin associated with synaptic vesicles and granules plays an important role during Ca(2+)-mediated exocytosis. In the present work, we have used amperometry and confocal fluorescence to study the role of internal Ca(2+) in the rearrangement of F-actin (visualised with phalloidin-Alexa 546) during exocytosis in rat mast cells. The F-actin-depolymerising drug, latrunculin A, and the ryanodine receptor agonists ryanodine and caffeine that, per se did not induce exocytosis, enhanced the exocytotic responses elicited by compound 48/80 (C48/80). They also induced cortical actin depolymerisation in the presence or absence of external Ca(2+). Degranulation induced by C48/80 was accompanied by the formation of a cytoplasmic F-actin network. Depletion of internal Ca(2+) with cyclopiazonic acid inhibited latrunculin potentiation of C48/80-stimulated exocytosis and completely blocked the formation of the cytoplasmic F-actin network. This indicates that the mobilisation of Ca(2+) from ryanodine-sensitive intracellular stores plays an important role in the depolymerisation of the cortical F-actin barrier and possibly in the formation of the internal F-actin network during exocytotic activation of peritoneal mast cells.
Guzmán
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Lab. Neuroquimica, CBB, IVIC, Apartado 21827, Caracas 1020-A, Venezuela.
Bolaños
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Delgado
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Rojas
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DiPolo
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Caputo
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Jaffe
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D008841:Actin Cytoskeleton / Q000378:metabolism / Q000502:physiology*; D000199:Actins / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015550:Cell Degranulation; D003593:Cytoplasm / Q000378:metabolism; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D010537:Peritoneum / Q000166:cytology; D011108:Polymers / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012433:Ryanodine / Q000494:pharmacology*; D053778:Thiazolidines / Q000494:pharmacology; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D011108:Polymers; D053778:Thiazolidines; D012433:Ryanodine; D002110:Caffeine; D003189:p-Methoxy-N-methylphenethylamine; C037067:latrunculin A; D002118:Calcium