Published online 1 June 2004. doi:10.1083/jcb.200403011
The Rockefeller University Press, 0021-9525 $8.00
JCB, Volume 165, Number 5, 641-652
Trafficking of Lyn through the Golgi caveolin involves the charged residues on
E and
I helices in the kinase domain
Kousuke Kasahara,
Yuji Nakayama,
Kikuko Ikeda,
Yuka Fukushima,
Daisuke Matsuda,
Shinya Horimoto, and
Naoto Yamaguchi
Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan
Address correspondence to Naoto Yamaguchi, Dept. of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba 260-8675, Japan. Tel./Fax: 81-43-226-2868. email: nyama{at}p.chiba-u.ac.jp
Src-family kinases, known to participate in signaling pathways of a variety of surface receptors, are localized to the cytoplasmic side of the plasma membrane through lipid modification. We show here that Lyn, a member of the Src-family kinases, is biosynthetically transported to the plasma membrane via the Golgi pool of caveolin along the secretory pathway. The trafficking of Lyn from the Golgi apparatus to the plasma membrane is inhibited by deletion of the kinase domain or Csk-induced "closed conformation" but not by kinase inactivation. Four residues (Asp346 and Glu353 on
E helix, and Asp498 and Asp499 on
I helix) present in the C-lobe of the kinase domain, which can be exposed to the molecular surface through an "open conformation," are identified as being involved in export of Lyn from the Golgi apparatus toward the plasma membrane but not targeting to the Golgi apparatus. Thus, the kinase domain of Lyn plays a role in Lyn trafficking besides catalysis of substrate phosphorylation.
Key Words: FRAP; intracellular localization; secretory pathway; open conformation; Src-family tyrosine kinase
Abbreviations used in this paper: BFA, brefeldin A; CHX, cycloheximide; GalT, ß-1,4-galactosyltransferase; NEM, N-ethyl-maleimide; SH, Src homology.

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