A critical role for palladin in astrocyte morphology and response to injury.

Astrocytes respond to injury of the CNS with a dramatic change in morphology, contributing to the formation of a glial scar. We recently identified a novel actin-associated protein named palladin, which possesses the features of a potent cytoskeletal scaffold. Palladin expression was assayed in two populations of cultured astrocytes, polygonal versus stellate, and was detected at high levels in polygonal astrocytes and low levels in stellate astrocytes. When stellate astrocyte monolayers were wounded, palladin was rapidly upregulated along the edge of the wound, coordinate with an increase in actin assembly. Palladin upregulation occurred along a similar rapid time course following injury to the cerebral cortex of adult rats. To explore palladin function more directly, palladin cDNA was transfected into stellate astrocytes, which acquired a spread morphology and prominent actin bundles. These results suggest that palladin upregulation following injury may be a key step in the acquisition of the reactive astrocyte morphology.