An antisense oligodeoxynucleotide targeted to chromaffin cell scinderin gene decreased scinderin levels and inhibited depolarization-induced corticalF-actin disassembly and exocytosis

Chromaffin cell secretion requires cortical F-actin disassembly and it has been suggested that scinderin, a Ca2+-dependent F-actin severing protein, c ontrols cortical actin dynamics. An antisense oligodeoxynucleotide targetin g the scinderin gene was used to decrease the expression of the protein and access its role in secretion. Treatment with 2 muM scinderin antisense oli godeoxynucleotide for 4 days produced a significant decrease in scinderin e xpression and its mRNA levels. The expression of gelsolin, another F-actin severing protein, was not affected. Scinderin decrease was accompanied by c oncomitant and parallel decreases in depolarization-evoked cortical F-actin disassembly and exocytosis. Similar treatment with a mismatched oligodeoxy nucleotide produced no effects. Scinderin antisense oligodeoxynucleotide tr eatment was also a very effective inhibitor of exocytosis in digitoninperme abilized cells stimulated with increasing concentrations of Ca2+. This rule d out scinderin antisense interference with stimulation-induced depolarizat ion or Ca2+ channel activation. Scinderin antisense treatment decreased the maximum (B-max) secretory response to Ca2+ without modifying the affinity (K-m) of the cation for the exocytotic machinery. Moreover, the antisense t reatment did not affect norepinephrine uptake or the expression of dopamine beta -hydroxylase, suggesting that the number and function of chromaffin v esicles was not modified. In addition, scinderin antisense treatment did no t alter the expression of proteins involved in vesicle-plasma membrane fusi on, such as synaptophysin, synaptotagmin or syntaxin, indicating a lack of effects on the fusion machinery components. These observations strongly sug gest that scinderin is a key player in the events involved in the secretory process.