Cutting edge: Dok-1 and Dok-2 adaptor molecules are regulated by phosphatidylinositol 5-phosphate production in T cells.

Institut National de la Santé et de la Recherche Médicale, Centre de Recherche en Cancérologie de Marseille, France.
The Journal of Immunology (Impact Factor: 5.36). 05/2009; 182(7):3974-8. DOI: 10.4049/jimmunol.0804172
Source: PubMed

ABSTRACT Downstream of tyrosine kinase (Dok) proteins Dok-1 and Dok-2 are involved in T cell homeostasis maintenance. Dok protein tyrosine phosphorylation plays a key role in establishing negative feedback loops of T cell signaling. These structurally related adapter molecules contain a pleckstrin homology (PH) domain generally acting as a lipid/protein-interacting module. We show that the presence of this PH domain is necessary for the tyrosine phosphorylation of Dok proteins and their negative functions in T cells. We find that Dok-1/Dok-2 PH domains bind in vitro to the rare phosphoinositide species, phosphatidylinositol 5-phosphate (PtdIns5P). Dok tyrosine phosphorylation correlates with PtdIns5P production in T cells upon TCR triggering. Furthermore, we demonstrate that PtdIns5P increase regulates Dok tyrosine phosphorylation in vivo. Together, our data identify a novel lipid mediator in T cell signaling and suggest that PH-PtdIns5P interactions regulate T cell responses.

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