Parvovirus interference with intracellular signalling:: mechanism of PKCη activation in MVM-infected A9 fibroblasts

Autonomous parvoviruses are strongly dependent on the phosphorylation of the major non-structural protein NS1 by members of the protein kinase C (PKC) family. Besides being accompanied with changes in the overall phosphorylation pattern of NS1 and acquiring new modifications at consensus PKC sites, ongoing minute virus of mice (MVM) infections lead to the appearance of new phosphorylated cellular protein species. This prompted us to investigate whether MVM actively interferes with phosphoinositol-dependent kinase (PDK)/PKC signalling. The activity, subcellular localization and phosphorylation status of the protein kinases PDK1, PKC eta and PKC lambda were measured in A9 cells in the presence or absence of MVM infection. Parvovirus infection was found to result in activation of both PDK1 and PKC eta, as evidenced by changes in their subcellular distribution and overall (auto)phosphorylation. We show evidence that activation of PKC eta by PDK1 is driven by atypical PKC lambda. By modifying the hydrophobic motif of PKC eta, PKC lambda appeared to control docking and consecutive phosphorylation of PKC eta's activation-loop by PDK1, a process that was inhibited in vivo in the presence of a dominant-negative PKC lambda mutant.