PKCepsilon induces astrocyte stellation by modulating multiple cytoskeletal proteins and interacting with Rho A signalling pathways: implications for neuroinflammation.

Despite the importance of stellation to maintain astrocyte functionality, the intracellular signals controlling morphology in these cells are poorly characterized. Our goal was to examine the implication of protein kinase C epsilon (PKCepsilon) in astrocyte stellation. We found that the morphological transformation of astrocytes induced by exposure to the pro-inflammatory agent lipopolysaccharide is enhanced by adenoviral expression of wild-type PKCepsilon, and that activation of PKCepsilon is sufficient to trigger a dramatic stellation. Such an effect is mediated by the rearrangement of microtubules and filaments of glial fibrillary acidic protein, disorganization of stress fibres, and formation of new actin filaments within growing cellular processes. Furthermore, PKCepsilon regulates actin-interacting elements such as non-muscle myosin and proteins of the ezrin/radixin/moesin family. We also observed that at least part of the actions of PKCepsilon depend on its catalytic activity. Finally, stellation by PKCepsilon could be blocked by the expression of a constitutively active form of Rho A implicated in the stability of the flat astrocytic morphology. In summary, PKCepsilon stands out as a key intracellular regulator of morphological plasticity in astrocytes, affecting a large range of cytoskeletal elements and inactivating Rho A-dependent pathways. These morphological effects of PKCepsilon may play essential roles during the course of neuroinflammation.