The importance of three membrane-distal tyrosines in the adaptor protein NTAL/LAB.
NTAL (non-T cell activation linker)/LAB (linker for activation of B cells) is a LAT (linker for activation of T cells)-like molecule that is expressed in B cells, mast cells, natural killer cells, and monocytes. Upon engagement of the B cell receptor or Fc receptors, it is phosphorylated and interacts with Grb2. LAB is capable of rescuing thymocyte development in LAT(-/-) mice. In this study, we utilized various LAB Tyr to Phe mutants to map the phosphorylation and Grb2-binding sites of LAB. We also examined the function of these mutants by investigating their ability to rescue signaling defects in LAT-deficient Jurkat cells and thymocyte development in LAT(-/-) mice. Our results indicated that human LAB was primarily phosphorylated on three membrane-distal tyrosines, Tyr(136), Tyr(193), and Tyr(233). Mutation of these three tyrosines abolished Grb2 binding and LAB function. Our data suggested that these tyrosines are the most important tyrosines for LAB function.
Koonpaew
Surapong
S
Department of Immunology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Janssen
Erin
E
Zhu
Minghua
M
Zhang
Weiguo
W
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D002460:Cell Line; D051380:GRB2 Adaptor Protein; D006801:Humans; D019169:Jurkat Cells; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D010766:Phosphorylation; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013950:Thymus Gland / Q000378:metabolism; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism* / Q000502:physiology*
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C495949:Grb2 protein, mouse; C419196:LAT2 protein, human; C488163:LAT2 protein, mouse; D008565:Membrane Proteins; D010750:Phosphoproteins; D011506:Proteins; D014443:Tyrosine