Recruitment of JNK to JIP1 and JNK-dependent JIP1 phosphorylation regulates JNK module dynamics and activation.
JIP1 is a scaffold protein that assembles and facilitates the activation of the mixed lineage kinase-dependent JNK module. Results of earlier work led us to propose a model for JIP1-JNK complex regulation that predicts that under basal conditions, JIP1 maintains DLK in a monomeric, unphosphorylated, and catalytically inactive state. Upon appropriate module stimulation, JNK-JIP1 binding affinity increases and DLK-JIP1 affinity decreases. Dissociation of DLK from JIP1 results in subsequent DLK oligomerization, autophosphorylation, and ultimately module activation. Our previous published results suggested the hypothesis that recruitment of JNK to JIP1 and phosphorylation of JIP1 by JNK is prerequisite for activation of the JNK module (Nihalani, D., Meyer, D., Pajni, S., and Holzman, L. B. (2001) EMBO J. 20, 3447-3458). The present study corroborated this hypothesis by demonstrating that JNK binding to JIP1 is necessary for stimulus-induced dissociation of DLK from JIP1, for DLK oligomerization, and for JNK activation. After mapping JNK-dependent JIP1 phosphorylation sites and testing their functional significance, it was observed that phosphorylation by JNK of JIP1 on Thr-103 and not other phosphorylated JIP1 residues is necessary for the regulation of DLK association with JIP1, DLK activation, and subsequent module activation. A refined model of JIP1-JNK module regulation is presented in which JNK phosphorylation of JIP1 is necessary prior to module activation.
Nihalani
Deepak
D
Division of Nephrology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109-0676, USA.
Wong
Hetty N
HN
Holzman
Lawrence B
LB
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D007163:Immunosorbent Techniques; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020930:MAP Kinase Kinase Kinases / Q000737:chemistry / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D009474:Neurons / Q000201:enzymology; D019319:Okadaic Acid / Q000494:pharmacology; D016376:Oligonucleotides, Antisense; D009842:Oligopeptides; D010449:Peptide Mapping; D010455:Peptides / Q000235:genetics; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D020836:Protein Structure, Quaternary; D051381:Rats; D011993:Recombinant Fusion Proteins; D013912:Threonine / Q000378:metabolism; D014162:Transfection
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C110528:Mapk8ip1 protein, rat; D016376:Oligonucleotides, Antisense; D009842:Oligopeptides; D010455:Peptides; D011993:Recombinant Fusion Proteins; D019319:Okadaic Acid; D013912:Threonine; C085706:FLAG peptide; D048031:JNK Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C090757:mitogen-activated protein kinase kinase kinase 12; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases