The role of the cytoskeleton in capacitative calcium entry in myenteric glia

Capacitative calcium entry (CCE) is the process by which intracellular calcium is replenished from the external milieu upon depletion of intracellular stores. CCE is thought to participate in chemotaxis, proliferation and cell signalling. A physical interaction between intracellular stores and the plasma membrane is postulated to regulate CCE. We hypothesized that cytoskeletal disruption alters this interaction, inhibiting CCE in enteric glia. Cultured myenteric glia from neonatal guinea-pigs were treated with cytochalasin D (10 μmol L^-1), a microfilament disrupting agent, nocodazole (20 μmol L^-1), a microtubule disrupting agent, or vehicle (dimethyl sulphoxide). Intracellular calcium changes were measured using fura-2 microfluorimetry. To evaluate the rate of cation re-entry, barium was substituted for calcium because barium is not sequestered internally. Cytochalasin D-treated glia had diminished CCE responses (57 ± 3 nmol L^-1) compared with controls (97 ± 7 nmol L^-1) as did nocodazole-treated glia (30 ± 2 nmol L^-1) vs controls (77 ± 6 nmol L^-1). The proportion of cells demonstrating CCE abolition was greater in the cytochalasin (50 ± 8%) and nocodazole-treated (89 ± 2%) groups compared with controls (21 ± 2%, 40 ± 9%, respectively). Cytochalasin D and nocodazole treatment diminished the rate of cation re-entry based on diminished barium entry in treated vs control cells. From this study, we conclude that disruption of cytoskeletal elements diminishes calcium influx essential to calcium store repletion in myenteric glia.