T cell receptor activation leads to two distinct phases of Pyk2 activation and actin cytoskeletal rearrangement in human T cells.
The tyrosine kinase Pyk2 integrates receptor-mediated signals controlling actin cytoskeletal rearrangement, events needed for the activation and function of T cells. Induction of the T cell receptor (TCR) leads to the phosphorylation of Pyk2, but the timing of these events is controversial and not fully understood. In this study, the TCR-induced phosphorylation kinetics of Pyk2 tyrosines 402 and 580 were characterized in human T cells. Interestingly, the early TCR-mediated phosphorylation of Pyk2 was more rapid and transient than ZAP-70, whose phosphorylation kinetics were similar to other T cell signaling proteins. Unexpectedly, Pyk2 had a second burst of phosphorylation 30-60 min after TCR stimulation. Pyk2 was enzymatically active during the two separate bursts of phosphorylation, since both paxillin phosphorylation, a known substrate of Pyk2, and TCR-induced actin polymerization showed similar kinetics. The second burst of Pyk2 phosphorylation did not require actin cytoskeleton rearrangement or PI3K function, but was dependent on the enzymatic activity of Fyn and/or Lck. Collectively, these observations suggest that signaling pathways downstream of TCR activation are hard-wired to induce two separate periods of Pyk2 activation and actin cytoskeletal rearrangement.
Collins
Michaela
M
Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
Bartelt
Rebekah R
RR
Houtman
Jon C D
JC
D000199:Actins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism; D004789:Enzyme Activation; D051418:Focal Adhesion Kinase 2 / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D019169:Jurkat Cells; D007700:Kinetics; D051419:Paxillin / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism*; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism; D051746:ZAP-70 Protein-Tyrosine Kinase / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
D000199:Actins; C496061:PXN protein, human; D051419:Paxillin; D011948:Receptors, Antigen, T-Cell; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; D051418:Focal Adhesion Kinase 2; C103547:PTK2B protein, human; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; D019061:src-Family Kinases