Modulation of interleukin-1 transcriptional response by the interaction between VRK2 and the JIP1 scaffold protein.
BACKGROUND
Cellular biological responses to specific stimulation are determined by a balance among signaling pathways. Protein interactions are likely to modulate these pathways. Vaccinia-related kinase-2 (VRK2) is a novel human kinase that can modulate different signaling pathways.


RESULTS
We report that in vivo, the activity of JIP1-JNK complexes is downregulated by VRK2 in response to interleukin-1beta. Also the reduction of endogenous VRK2 with shRNA increases the transcriptional response to IL-1beta. The JIP1 scaffold protein assembles three consecutive members of a given MAPK pathway forming signaling complexes and their signal can be modulated by interactions with regulatory proteins that remain to be identified. Knocking-down JIP1 with siRNA resulted in elimination of the AP1 transcriptional response to IL-1beta. VRK2, a member of novel Ser-Thr kinase family, is able to stably interact with JIP1, TAK1 and MKK7, but not JNK, and can be isolated forming oligomeric complexes with different proportions of TAK1, MKK7beta1 and JNK. JIP1 assembles all these proteins in an oligomeric signalosome. VRK2 binding to the JIP1 signalosome prevents the association of JNK and results in a reduction in its phosphorylation and downregulation of AP1-dependent transcription.


CONCLUSIONS
This work suggests that the intracellular level of VRK2 protein can modulate the flow through a signaling pathway and alter the response from a receptor that can be distributed by more than one pathway, and thus contribute to the cellular specificity of the response by forming alternative signaling complexes. Furthermore, the effect might be more general and affect other signaling routes assembled on the JIP1 scaffold protein for which a model is proposed.
Blanco
Sandra
S
Programa de Oncología Traslacional, Instituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Salamanca, Salamanca, Spain.
Sanz-García
Marta
M
Santos
Claudio R
CR
Lazo
Pedro A
PA
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D015536:Down-Regulation / Q000235:genetics; D006801:Humans; D053583:Interleukin-1beta / Q000502:physiology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D018808:Transcription Factor AP-1; D014158:Transcription, Genetic
D048868:Adaptor Proteins, Signal Transducing; D053583:Interleukin-1beta; C490666:MAPK8IP1 protein, human; D018808:Transcription Factor AP-1; D017346:Protein Serine-Threonine Kinases; C109891:VRK2 protein, human; D048031:JNK Mitogen-Activated Protein Kinases