title: Identification of structural and functional domains in mixed lineage kinase dual leucine zipper-bearing kinase required for complex formation and stress-activated protein kinase activation.
abstract: Accumulating evidence suggests that mitogen-activated protein kinase signaling pathways form modular signaling complexes. Because the mixed lineage kinase dual leucine zipper-bearing kinase (DLK) is a large modular protein, structure-function analysis was undertaken to examine the role of DLK domains in macromolecular complex formation. DLK mutants were used to demonstrate that a DLK leucine zipper-leucine zipper interaction is necessary for DLK dimerization and to show that DLK dimerization mediated by the leucine zipper domain is prerequisite for DLK activity and subsequent activation of stress-activated protein kinase (SAPK). Heterologous mixed lineage kinase family members can be co-immunoprecipitated. However, the DLK leucine zipper domain interacted specifically only with the DLK leucine zipper domain; in contrast, DLK NH(2)-terminal region was sufficient to co-immunoprecipitate leucine zipper kinase and DLK. DLK has been shown to associate with the putative scaffold protein JIP1. This association occurred through the DLK NH(2)-terminal region and occurred independently of DLK catalytic activity. Although the DLK NH(2)-terminal region associated directly with JIP-1, this region did not interact directly with either DLK or leucine zipper kinase. Therefore, DLK may interact with heterologous mixed lineage kinase proteins via intermediary proteins. The NH(2)-terminal region of overexpressed DLK was required for activation of SAPK. These results provide evidence that protein complex formation is required for signal transduction from DLK to SAPK.
authors.affiliation: Division of Nephrology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, 48109-0676, USA.
authors.forename: D
authors.initials: D
authors.lastname: Nihalani
authors.forename: S
authors.initials: S
authors.lastname: Merritt
authors.forename: L B
authors.initials: LB
authors.lastname: Holzman
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins / Q000378:metabolism; D019281:Dimerization; D004789:Enzyme Activation; D048031:JNK Mitogen-Activated Protein Kinases; D016350:Leucine Zippers; D020930:MAP Kinase Kinase Kinases / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C490666:MAPK8IP1 protein, human; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C109162:MAP3K13 protein, human; C090757:mitogen-activated protein kinase kinase kinase 12