Phosphatidylinositol-3-kinase-dependent phosphorylation of SLP-76 by the lymphoma-associated ITK-SYK fusion-protein.
Recurrent chromosomal translocations have long been implicated in various types of lymphomas and other malignancies. Novel recurrent t(5;9)(q33;q22) has been recently discovered in un-specified peripheral T-cell lymphoma. To elucidate the role of this translocation, the corresponding fusion construct encoding the N-terminal portion of the ITK kinase and the C-terminal catalytic region of the SYK kinase was generated. We herein show that the ITK-SYK fusion-protein is constitutively active. Moreover, we demonstrate that ITK-SYK is phosphorylated on key tyrosine residues and is capable of potently phosphorylating the related adapter proteins BLNK and SLP-76. In transiently transfected cells, SYK was phosphorylated at Y352 but not detectably at the activation-loop tyrosines Y525/Y526. In contrast, ITK-SYK was phosphorylated both at Y212 and the activation-loop tyrosines Y385/Y386, corresponding to Y352 and Y525/Y526 in SYK, respectively. In resting primary lymphocytes, ITK-SYK predominantly localizes to the cell surface. In addition, we demonstrate that following stimulation, the ITK-SYK fusion-protein in cell lines translocates to the cell membrane and, moreover, that this phenomenon as well as SLP-76 phosphorylation are blocked upon phosphatidylinositol-3-kinase (PI3-kinase) inhibition.
Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital, Clinical Research Center, SE-141 86 Huddinge, Sweden. alamdar.hussain@ki.se
Alamdar
A
Hussain
Rani
R
Faryal
Beston F
BF
Nore
Abdalla J
AJ
Mohamed
C I Edvard
CI
Smith
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002895:Chromosomes, Human, Pair 5 / Q000235:genetics; D002899:Chromosomes, Human, Pair 9 / Q000235:genetics; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D016411:Lymphoma, T-Cell, Peripheral / Q000235:genetics / Q000378:metabolism*; D015514:Oncogene Proteins, Fusion / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D000072377:Syk Kinase; D014178:Translocation, Genetic
D048868:Adaptor Proteins, Signal Transducing; D047908:Intracellular Signaling Peptides and Proteins; D015514:Oncogene Proteins, Fusion; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; C113939:B cell linker protein; C092947:SLP-76 signal Transducing adaptor proteins; C000606896:SYK protein, human; C080813:emt protein-tyrosine kinase