Disruption of NF-κB signaling and chemokine gene activation by retroviral mediated expression of IKKγ/NEMO mutants

Phosphorylation Of I kappa Bs-the cytoplasmic inhibitors of the NF-kappaB transcription factors-is the key event which triggers activation of the NF-kappaB cascade. Signal-mediated phosphorylation Of I kappaB alpha is mediated by a multiprotein complex, the I kappaB kinase (IKK) complex, which is composed of at least three identified subunits. Two of these polypeptides, IKK alpha and IKK beta, also known as IKK1 and IKK2, are the catalytic subunits of the kinase complex and phosphorylate I kappaB alpha and I kappaB beta. The third component, NEMO/IKK gamma, does not exhibit kinase activity, but rather constitutes a regulatory subunit, In the present study, C-terminal truncated forms of IKK-gamma-DeltaC-IKK gamma 306 and DeltaC-IKK gamma 261 - were stably expressed in the myeloid calf line U937 by retroviral-mediated gene transfer, Overexpression of DeltaC-IKK gamma resulted in a reduction in IKK kinase activity in vitro, a subsequent decrease in NF-kappaB DNA binding activity, and inhibition of chemokine gene induction in response to TNF alpha stimulation or paramyxovirus infection. This study demonstrates the efficacy of DeltaC-IKK gamma as a repressor of IKK signaling and NF-kappaB activation and suggests a potential gene therapy approach to limit chronic inflammation due to chemokine hyperactivation. (C) 2001 Academic Press.