Requirement of functional ryanodine receptor type 3 for astrocyte migration.

Astrocyte motility plays an important role in the response of the brain to injury and during regeneration. We used two in vitro assays, a wound-healing model and a chemotaxis assay, to study mechanisms that control astrocyte motility. Ryanodine receptors (RyR), intracellular calcium-release channels, modulate intracellular Ca2+ levels, and also motility: 1) blocking RyR with antagonizing concentration of ryanodine (200 microM) strongly attenuated motility and 2) motility of astrocytes cultured from homozygous RyR type 3 knockout mice was impaired strongly compared with wild-type. In contrast, MIP-1a-induced chemotaxis was neither impaired in the presence of ryanodine nor in the cells from the knockout animals. Reverse transcription-polymerase chain reaction (RT-PCR) analysis combined with Western blotting and immunocytochemistry confirmed the expression of RyR type 3, but not type 1 or 2 in cultured and acutely isolated astrocytes. RyR in astrocytes are linked to Ca2+ signaling because the RyR agonist 4-chloro-m-cresol induced a release of Ca2+ from intracellular stores. These results indicate that astrocytes express only RyR type 3 and that this receptor is important for controlling astrocyte motility.