The direct activation of MIK, a germinal center kinase (GCK)-like kinase, by MARK, a maize atypical receptor kinase, suggests a new mechanism for signaling through kinase-dead receptors.
Signaling by receptor protein kinases (RPKs) involves their dimerization and transphosphorylation. However, atypical RPKs with kinase-defective domains have been described recently. Some of them are essential for proper signaling in animal systems, although the precise mechanism involved is unknown in most cases. Here we describe the cloning and characterization of an atypical plant receptor kinase from maize, MARK, which does not phosphorylate in vitro. A yeast two-hybrid approach has allowed us to identify a new germinal center kinase (GCK)-related protein, MIK, that interacts with MARK. Interestingly, the interaction of the intracellular domain of MARK with the regulator domain of MIK strongly induces MIK kinase activity. As some GCK-related proteins connect cell-surface receptors to the intracellular MAPK cascades, the activation of MIK by direct interaction with MARK could illustrate a new mechanism for signaling through atypical RPKs.
Llompart
Blanca
B
Departament de Genètica Molecular, IBMB-CSIC, Jordi Girona 18, 08034 Barcelona, Spain.
Castells
Enric
E
Río
Adolfo
A
Roca
Ramon
R
Ferrando
Alejandro
A
Stiefel
Virginia
V
Puigdomenech
Pere
P
Casacuberta
Josep M
JM
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D019556:COS Cells; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation; D000081410:Germinal Center Kinases; D005982:Glutathione Transferase / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010802:Phylogeny; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014162:Transfection; D020798:Two-Hybrid System Techniques; D003313:Zea mays / Q000201:enzymology*
D018076:DNA, Complementary; D000081410:Germinal Center Kinases; D011994:Recombinant Proteins; D005982:Glutathione Transferase; D017346:Protein Serine-Threonine Kinases