A proteomic analysis of PKCε targets in astrocytes: implications for astrogliosis

Astrocytes are glial cells in the central nervous system (CNS) that play key roles in brain physiology, controlling processes, such as neurogenesis, brain energy metabolism and synaptic transmission. Recently, immune functions have also been demonstrated in astrocytes, influencing neuronal survival in the course of neuroinflammatory pathologies. In this regard, PKCepsilon (PKCε) is a protein kinase with an outstanding role in inflammation. Our previous findings indicating that PKCε regulates voltage-dependent calcium channels as well as morphological stellation imply that this kinase controls multiple signalling pathways within astrocytes, including those implicated in activation of immune functions. The present study applies proteomics to investigate new protein targets of PKCε in astrocytes. Primary astrocyte cultures infected with an adenovirus that expresses constitutively active PKCε were compared with infection controls. Two-dimensional gel electrophoresis clearly detected 549 spots in cultured astrocytes, and analysis of differential protein expression revealed 18 spots regulated by PKCε. Protein identification by mass spectrometry (nano-LC-ESI-MS/MS) showed that PKCε targets molecules with heterogeneous functions, including chaperones, cytoskeletal components and proteins implicated in metabolism and signalling. These results support the notion that PKCε is involved in astrocyte activation; also suggesting that multiple astrocyte-dependent processes are regulated by PKCε, including those associated to neuroinflammation.