PMID- 10498895
OWN - NLM
STAT- MEDLINE
DCOM- 19991029
LR  - 20131121
IS  - 0950-9232 (Print)
IS  - 0950-9232 (Linking)
VI  - 18
IP  - 39
DP  - 1999 Sep 23
TI  - Phosphorylation at Tyr-838 in the kinase domain of EphA8 modulates Fyn binding to
      the Tyr-615 site by enhancing tyrosine kinase activity.
PG  - 5413-22
AB  - Eph-related receptors and their ephrin ligands are highly conserved protein
      families which play important roles in targeting axons and migrating cells. In
      this study we have examined the functional roles of two major autophosphorylation
      sites, Tyr-615 and Tyr-838, in the EphA8 receptor. Two-dimensional phosphopeptide
      mapping analysis demonstrated that Tyr-615 and Tyr-838 constitute major
      autophosphorylation sites in EphA8. Tyr-615 was phosphorylated to the highest
      stoichiometry, suggesting that phosphorylation at this site may have a
      physiologically important role. Upon conservative mutation of Tyr-838 located in 
      the tyrosine kinase domain, the catalytic activity of EphA8 was strikingly
      reduced both in vitro and in vivo, whereas a mutation at Tyr-615 in the
      juxtamembrane domain did not impair the tyrosine kinase activity. In vitro
      binding experiments revealed that phosphorylation at Tyr-615 in EphA8 mediates
      the preferential binding to Fyn-SH2 domain rather than Src and Ras
      GTPase-activating protein (Ras GAP)-SH2 domains. Additionally, a high level of
      EphA8 was detected in Fyn immunoprecipitates in intact cells, indicating that
      EphA8 and Fyn can physically associate in vivo. In contrast, the association of
      full-length Fyn to EphA8 containing mutation at either Tyr-615 or Tyr-838 was
      greatly reduced. These data indicate that phosphorylation of Tyr-615 is critical 
      for determining the association with Fyn whereas the integrity of Tyr-838
      phosphorylation is required for efficient phosphorylation at Tyr-615 as well as
      other major sites. Finally, it was observed that cell attachment responses are
      attenuated by overexpression of wild type EphA8 receptor but to much less extent 
      by EphA8 mutants lacking phosphorylation at either Tyr-615 or Tyr-838.
      Furthermore, transient expression of kinase-inactive Fyn in EphA8-overexpressing 
      cells blocked cell attachment responses attenuated by the EphA8 signaling. We
      therefore propose that Fyn kinase is one of the major downstream targets for the 
      EphA8 signaling pathway leading to a modification of cell adhesion, and that
      autophosphorylation at Tyr-838 is critical for positively regulating the EphA8
      signaling event.
FAU - Choi, S
AU  - Choi S
AD  - Institute of Environment and Life Science, Hallym University, 1 Okcheon-dong,
      Chuncheon, Kangwon-do, 200-702, Korea.
FAU - Park, S
AU  - Park S
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - England
TA  - Oncogene
JT  - Oncogene
JID - 8711562
RN  - 0 (Proto-Oncogene Proteins)
RN  - 42HK56048U (Tyrosine)
RN  - EC 2.7.10.1 (Receptor Protein-Tyrosine Kinases)
RN  - EC 2.7.10.1 (Receptor, EphA8)
RN  - EC 2.7.10.2 (FYN protein, human)
RN  - EC 2.7.10.2 (Fyn protein, mouse)
RN  - EC 2.7.10.2 (Proto-Oncogene Proteins c-fyn)
SB  - IM
MH  - Amino Acid Sequence
MH  - Animals
MH  - Cell Adhesion
MH  - Cell Line, Transformed
MH  - Enzyme Activation
MH  - Humans
MH  - Mice
MH  - Molecular Sequence Data
MH  - Phosphorylation
MH  - Proto-Oncogene Proteins/chemistry/*metabolism
MH  - Proto-Oncogene Proteins c-fyn
MH  - Receptor Protein-Tyrosine Kinases/*chemistry
MH  - Receptor, EphA8
MH  - Sequence Homology, Amino Acid
MH  - Tyrosine/*metabolism
MH  - src Homology Domains
EDAT- 1999/09/28 00:00
MHDA- 1999/09/28 00:01
CRDT- 1999/09/28 00:00
PHST- 1999/09/28 00:00 [pubmed]
PHST- 1999/09/28 00:01 [medline]
PHST- 1999/09/28 00:00 [entrez]
AID - 10.1038/sj.onc.1202917 [doi]
PST - ppublish
SO  - Oncogene. 1999 Sep 23;18(39):5413-22. doi: 10.1038/sj.onc.1202917.