The SH3 domain of Lck modulates T-cell receptor-dependent activation of extracellular signal-regulated kinase through activation of Raf-1.
Engagement of the T-cell antigen receptor (TCR) results in the proximal activation of the Src family tyrosine kinase Lck. The activation of Lck leads to the downstream activation of the Ras/Raf/MEK/ERK signaling pathway (where ERK is extracellular signal-related kinase). Under conditions of weak, but not strong, stimulation through the TCR, a version of Lck that contains a single point mutation in the SH3 (Src homology 3) domain (W97ALck) fails to support the activation of ERK, despite initiating signaling through the TCR, as demonstrated by the robust activation of ZAP-70, PLC-gamma, and Ras. We determined that the signaling lesion in W97ALck-expressing cells lies at the level of Raf-1 activation and is dependent on the presence of tyrosines 340/341 in the Raf-1 sequence. These data demonstrate a second function for Lck in TCR-mediated signaling to ERK. Additionally, we found that a significant fraction of Lck is localized to the Golgi apparatus and that, compared with wild-type Lck, W97ALck displays aberrant Golgi membrane localization. Our results support a model where under conditions of weak stimulation through the TCR, in addition to activated Ras, Golgi apparatus-localized Lck is needed for the full activation of Raf-1.
Li
Manqing
M
Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, Hansen Life Sciences Building, 201 South University Street, West Lafayette, IN 47907, USA.
Ong
Su Sien
SS
Rajwa
Bartek
B
Thieu
Vivian T
VT
Geahlen
Robert L
RL
Harrison
Marietta L
ML
D017252:CD3 Complex / Q000378:metabolism; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D051966:Phospholipase C gamma / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D021381:Protein Transport; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D013379:Substrate Specificity; D051746:ZAP-70 Protein-Tyrosine Kinase / Q000378:metabolism; D018909:src Homology Domains
D017252:CD3 Complex; C121704:CD3 antigen, zeta chain; D011948:Receptors, Antigen, T-Cell; D010768:Phosphoserine; D019000:Phosphotyrosine; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051746:ZAP-70 Protein-Tyrosine Kinase; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D051966:Phospholipase C gamma