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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Mitogen-activated protein kinase kinase kinase kinase 4 as a putative effector of Rap2 to activate the c-Jun N-terminal kinase.

Little is known about the specific signaling roles of Rap2, a Ras family small GTP-binding protein. In a search for novel Rap2-interacting proteins by the yeast two-hybrid system, we isolated isoform 3 of the human mitogen-activated protein kinase kinase kinase kinase 4 ( MAP4K4), a previously described but uncharacterized isoform. Other isoforms of MAP4K4 in humans and mice are known as hematopoietic progenitor kinase (HPK)/germinal center kinase (GCK)-like kinase and Nck-interacting kinase, respectively. MAP4K4 belongs to the STE20 group of protein kinases and regulates c-Jun N-terminal kinase ( JNK). MAP4K4 interacted with Rap2 through its C-terminal citron homology domain but did not interact with Rap1 or Ras. Interaction with Rap2 required the intact effector region of Rap2. MAP4K4 interacted preferentially with GTP- bound Rap2 over GDP-bound Rap2 in vitro. In cultured cells, MAP4K4 colocalized with Rap2, while a mutant MAP4K4 lacking the citron homology domain failed to do so. Furthermore, Rap2 enhanced MAP4K4- induced activation of JNK. These results suggest that MAP4K4 is a putative effector of Rap2 mediating the activation of JNK by Rap2.[1]

References

  1. Mitogen-activated protein kinase kinase kinase kinase 4 as a putative effector of Rap2 to activate the c-Jun N-terminal kinase. Machida, N., Umikawa, M., Takei, K., Sakima, N., Myagmar, B.E., Taira, K., Uezato, H., Ogawa, Y., Kariya, K. J. Biol. Chem. (2004) [Pubmed]
 
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