Recruitment of activated p56lck on endosomes of CD2-triggered T cells, colocalization with ZAP-70.
We have previously established that upon CD2 activation of T cells, p56(lck) showed a transient increase in its kinase activity and was partially internalized. Here we studied the possibility that p56(lck) could retain its kinase activity in the endosomes of CD2-triggered cells. T cells were fractionated on a sucrose gradient, and the endosomal fraction was isolated. In CD2-triggered cells, part of Lck was internalized and presented a maximal kinase activity in the endosome-enriched fraction after 5 min, decreasing thereafter. In the endosomal fraction of activated cells, four tyrosine-phosphorylated proteins of apparent molecular masses of 30, 40, 56, and 70 kDa were detected. We demonstrated that the protein tyrosine kinase ZAP-70 was recruited to the endosomal fraction upon CD2 stimulation with kinetics similar to that of p56(lck), suggesting that recruitment of protein tyrosine kinases to endosomal vesicles could promote specific transduction signals at the intracellular level.
Marie-Cardine
A
A
INSERM U332, Institut Cochin de Génétique Moléculaire, 75014 Paris.
Fischer
S
S
Gorvel
J P
JP
Maridonneau-Parini
I
I
D018801:CD2 Antigens / Q000502:physiology*; D002451:Cell Compartmentation; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism*; D006801:Humans; D008213:Lymphocyte Activation; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D010750:Phosphoproteins / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism* / Q000648:ultrastructure; D014407:Tumor Cells, Cultured; D051746:ZAP-70 Protein-Tyrosine Kinase; D019061:src-Family Kinases / Q000378:metabolism*
D018801:CD2 Antigens; D010750:Phosphoproteins; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; D019061:src-Family Kinases