Redistribution of F-actin and large dense-cored vesicles in the human neuroblastoma SH-SY5Y in response to secretagogues and protein kinase Cα activation

Our previous studies have shown that noradrenaline release is enhanced by activation of protein kinase Cα in SH-SY5Y cells. In the present study, we report that activation of protein kinase Cα leads to (a) partial redistribution of the F-actin cytoskeleton and (b) a 2.5-fold increase in the number of large dense-cored vesicles within 100 nm of the plasma membrane. This redistribution can be prevented by down-regulation of protein kinase Cα by up to 48 h exposure to phorbol dibutyrate. Treatment with the secretagogues 100 mM KCl, the Ca2+ ionophore A23187 (20 μM) and 1 mM carbachol also leads to a partial disassembly of the F-actin cytoskeleton. This is accompanied by an increase in the number of large dense cored vesicles at the plasma membrane following exposure to KCl and A23187 but not following exposure to carbachol. These results are discussed in relation to the hypothesis that a key step in the enhancement of noradrenaline release following activation of protein kinase Cα and elevation of intracellular calcium is the movement of large dense cored vesicles to the plasma membrane following partial disassembly of the F-actin cytoskeleton.