Serine 6 of Lck tyrosine kinase: a critical site for Lck myristoylation, membrane localization, and function in T lymphocytes.
Lck is a member of the Src family kinases expressed predominantly in T cells, and plays a pivotal role in TCR-mediated signal transduction. Myristoylation of glysine 2 in the N-terminal Src homology 4 (SH4) domain of Lck is essential for membrane localization and function. In this study, we examined a site within the SH4 domain of Lck regulating myristoylation, membrane localization, and function of Lck. A Lck mutant in which serine 6 (Ser6) was substituted by an alanine was almost completely cytosolic in COS-7 cells, and this change of localization was associated with a drastic inhibition of myristoylation in this mutant. To assess the role of Ser6 of Lck in T cell function, we established stable transfectants expressing various Lck mutants using Lck-negative JCaM1 cells. The Lck mutant of Ser6 to alanine, most of which did not target to the plasma membrane, was not able to reconstitute TCR-mediated signaling events in JCaM1 cells, as analyzed by tyrosine phosphorylation of intracellular proteins and CD69 expression. These results demonstrate that Ser6 is a critical factor for Lck myristoylation, membrane localization, and function in T cells, presumably because the residue is important for N-myristoyl transferase recognition.
Yasuda
K
K
Biomedical Research Center and School of Allied Health Sciences, Faculty of Medicine, Osaka University Medical School, Osaka, Japan.
Kosugi
A
A
Hayashi
F
F
Saitoh
S
S
Nagafuku
M
M
Mori
Y
Y
Ogata
M
M
Hamaoka
T
T
D000409:Alanine / Q000235:genetics; D019943:Amino Acid Substitution / Q000235:genetics / Q000276:immunology; D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000201:enzymology / Q000235:genetics; D002522:Chlorocebus aethiops; D006801:Humans; D019169:Jurkat Cells; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D019814:Myristic Acid / Q000378:metabolism*; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D013601:T-Lymphocytes / Q000201:enzymology* / Q000378:metabolism; D014162:Transfection
D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell; C054979:antigen T cell receptor, zeta chain; D019814:Myristic Acid; D012694:Serine; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D000409:Alanine