Human homologue of Drosophila CNK interacts with Ras effector proteins Raf and Rlf.
Connector enhancer of KSR (CNK) is a multidomain protein that participates in Ras signaling in Drosophila eye development. In this report we identify the human homologue of CNK, termed CNK2A, and a truncated alternatively spliced variant, CNK2B. We characterize CNK2 phosphorylation, membrane localization, and interaction with Ras effector molecules. Our results show that MAPK signaling appears to play a role in the phosphorylation of CNK2 in vivo. CNK2 is found in both membrane and cytoplasmic fractions of the cell. In MDCK cells, full-length CNK2 is localized to the lateral plasma membrane. Consistent with previous reports, we show CNK2 interacts with Raf. CNK2 interaction was mapped to the regulatory and kinase domains of Raf, as well as to the carboxyl-terminal half of CNK2. CNK2 also interacts with the Ral signaling components, Ral GTPase, and the RalGDS family member Rlf. CNK2 interaction was mapped to the GEF domain of Rlf. The ability of CNK2 to interact with both Ras effector proteins Raf and Rlf suggests that CNK2 may integrate signals between MAPK and Ral pathways through a complex interplay of components.
Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0606, USA.
Thomas M
TM
Lanigan
Albert
A
Liu
Yang Z
YZ
Huang
Lin
L
Mei
Ben
B
Margolis
Kun-Liang
KL
Guan
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D002460:Cell Line; D016764:Cell Polarity; D029721:Drosophila Proteins; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D020935:MAP Kinase Signaling System; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D008969:Molecular Sequence Data; D010766:Phosphorylation; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors; D020725:ral GTP-Binding Proteins / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C115753:CNK protein, Drosophila; C479421:CNKSR2 protein, human; D002352:Carrier Proteins; D029721:Drosophila Proteins; D020662:Guanine Nucleotide Exchange Factors; D008565:Membrane Proteins; C097542:RLF protein, human; D014157:Transcription Factors; D019908:Proto-Oncogene Proteins c-raf; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D020725:ral GTP-Binding Proteins