Abstract
The MLK (mixed lineage) ser/thr kinases are most closely related to the MAP kinase kinase kinase family. In addition to a kinase domain, MLK1, MLK2 and MLK3 each contain an SH3 domain, a leucine zipper domain and a potential Rac/Cdc42 GTPase-binding (CRIB) motif. The C-terminal regions of the proteins are essentially unrelated. Using yeast two-hybrid analysis and in vitro dot-blots, we show that MLK2 and MLK3 interact with the activated (GTP-bound) forms of Rac and Cdc42, with a slight preference for Rac. Transfection of MLK2 into COS cells leads to strong and constitutive activation of the JNK (c-Jun N-terminal kinase) MAP kinase cascade, but also to activation of ERK (extracellular signal-regulated kinase) and p38. When expressed in fibroblasts, MLK2 co-localizes with active, dually phosphorylated JNK1/2 to punctate structures along microtubules. In an attempt to identify proteins that affect the activity and localization of MLK2, we have screened a yeast two-hybrid cDNA library. MLK2 and MLK3 interact with members of the KIF3 family of kinesin superfamily motor proteins and with KAP3A, the putative targeting component of KIF3 motor complexes, suggesting a potential link between stress activation and motor protein function.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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14-3-3 Proteins
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3T3 Cells
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Adaptor Proteins, Signal Transducing*
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Amino Acid Sequence
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Animals
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COS Cells
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Calcium-Binding Proteins / metabolism
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Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
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Carrier Proteins / metabolism
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Cell Cycle Proteins / metabolism
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Cell Movement
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Cytoskeletal Proteins*
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Enzyme Activation
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GTP-Binding Proteins / metabolism
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Hippocalcin
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JNK Mitogen-Activated Protein Kinases
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Kinesins / metabolism*
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MAP Kinase Kinase Kinases*
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Mice
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Microinjections
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Microtubules / enzymology*
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Mitogen-Activated Protein Kinases*
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Molecular Sequence Data
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Nerve Tissue Proteins*
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Protein Serine-Threonine Kinases / metabolism*
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Proteins / metabolism
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Recombinant Proteins / metabolism
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Sequence Homology, Amino Acid
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Substrate Specificity
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Tyrosine 3-Monooxygenase*
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cdc42 GTP-Binding Protein, Saccharomyces cerevisiae
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rac GTP-Binding Proteins
Substances
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14-3-3 Proteins
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Adaptor Proteins, Signal Transducing
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Calcium-Binding Proteins
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Carrier Proteins
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Cell Cycle Proteins
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Cytoskeletal Proteins
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KIFAP3 protein, human
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Kif3a protein, mouse
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Nerve Tissue Proteins
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Proteins
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Recombinant Proteins
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Hippocalcin
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Kifap3 protein, mouse
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Tyrosine 3-Monooxygenase
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Protein Serine-Threonine Kinases
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Calcium-Calmodulin-Dependent Protein Kinases
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JNK Mitogen-Activated Protein Kinases
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Mitogen-Activated Protein Kinases
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MAP Kinase Kinase Kinases
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Map3k10 protein, mouse
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GTP-Binding Proteins
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Kinesins
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cdc42 GTP-Binding Protein, Saccharomyces cerevisiae
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rac GTP-Binding Proteins