Requirement of the SH4 and tyrosine-kinase domains but not the kinase activity of Lyn for its biosynthetic targeting to caveolin-positive Golgi membranes.
BACKGROUND
The Src-family non-receptor-type tyrosine kinase Lyn, which is often associated with chemotherapeutic resistance in cancer, localizes not only to the plasma membrane but also Golgi membranes. Recently, we showed that Lyn, which is synthesized in the cytosol, is transported from the Golgi to the plasma membrane along the secretory pathway. However, it is still unclear how Golgi targeting of newly synthesized Lyn is regulated.


METHODS
Subcellular localization of Lyn and its mutants was determined by confocal microscopy.


RESULTS
We show that the kinase domain, but not the SH3 and SH2 domains, of Lyn is required for the targeting of Lyn to the Golgi, whereas the N-terminal lipids of the Lyn SH4 domain are not sufficient for its Golgi targeting. Although intact Lyn, which colocalizes with caveolin-positive Golgi membranes, can traffic toward the plasma membrane, kinase domain-deleted Lyn is immobilized on caveolin-negative Golgi membranes.


CONCLUSIONS
Besides the SH4 domain, the Lyn kinase domain is important for targeting of newly synthesized Lyn to the Golgi, especially caveolin-positive transport membranes. Our results provide a novel role of the Lyn catalytic domain in the Golgi targeting of newly synthesized Lyn in a manner independent of its kinase activity.
Ikeda
Kikuko
K
Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba 260-8675, Japan.
Nakayama
Yuji
Y
Ishii
Mayuko
M
Obata
Yuuki
Y
Kasahara
Kousuke
K
Fukumoto
Yasunori
Y
Yamaguchi
Naoto
N
D000818:Animals; D001665:Binding Sites / Q000235:genetics; D019556:COS Cells; D020134:Catalytic Domain / Q000235:genetics; D022461:Caveolins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D003513:Cycloheximide / Q000494:pharmacology; D006056:Golgi Apparatus / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D018613:Microscopy, Confocal; D009154:Mutation; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D018909:src Homology Domains / Q000235:genetics; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism*
D022461:Caveolins; D011500:Protein Synthesis Inhibitors; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D003513:Cycloheximide; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases