Rho GTPases link cytoskeletal rearrangements and activation processes induced via the tetraspanin CD82 in T lymphocytes.
Activation of T lymphocytes requires the engagement of the T-cell receptor and costimulation molecules through cell-to-cell contacts. The tetraspanin CD82 has previously been shown to act as a cytoskeleton-dependent costimulation molecule. We show here that CD82 engagement leads to the tyrosine phosphorylation and association of both the Rho GTPases guanosine exchange factor Vav1 and adapter protein SLP76, suggesting that Rho GTPases participate in CD82 signaling. Indeed, broad inactivation of all Rho GTPases, or a specific blockade of RhoA, Rac1 or Cdc42, inhibited the morphological changes linked to CD82 engagement but failed to modulate the inducible association of CD82 with the actin network. Rho GTPase inactivation, as well as actin depolymerization, reduced the ability of CD82 to phosphorylate Vav and SLP76 and to potentiate the phosphorylation of two early TcR signaling intermediates: the tyrosine kinases ZAP70 and membrane adapter LAT. Taken together, this suggests that an amplification loop, via early Vav and SLP76 phosphorylations and Rho-GTPases activation, is initiated by CD82 association with the cytoskeleton, which permits cytoskeletal rearrangements and costimulatory activity. Moreover, the involvement of CD82 in the formation of the immunological synapse is strongly suggested by its accumulation at the site of TcR engagement. This novel link between a tetraspanin and the Rho GTPase cascade could explain why tetraspanins, which are known to form heterocomplexes, are involved in cell activation, adhesion, growth and metastasis.
Delaguillaumie
Alix
A
U332--Institut National de la Santé et la Recherche Médicale, Institut Cochin de Génétique Moléculaire, 22 rue Méchain, 75014 Paris, France.
Lagaudrière-Gesbert
Cécile
C
Popoff
Michel R
MR
Conjeaud
Hélène
H
D048868:Adaptor Proteins, Signal Transducing; D015703:Antigens, CD; D018797:Cell Cycle Proteins; D021961:Cell Membrane Structures / Q000201:enzymology* / Q000276:immunology; D003599:Cytoskeleton / Q000201:enzymology* / Q000276:immunology; D006801:Humans; D019169:Jurkat Cells; D051861:Kangai-1 Protein; D008213:Lymphocyte Activation / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000276:immunology / Q000378:metabolism*; D010750:Phosphoproteins / Q000276:immunology / Q000378:metabolism; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000276:immunology / Q000378:metabolism; D051567:Proto-Oncogene Proteins c-vav; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology; D014443:Tyrosine / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000276:immunology / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000276:immunology / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000276:immunology / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D015703:Antigens, CD; C497688:CD82 protein, human; D018797:Cell Cycle Proteins; D051861:Kangai-1 Protein; D008562:Membrane Glycoproteins; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D017260:Receptor-CD3 Complex, Antigen, T-Cell; C092947:SLP-76 signal Transducing adaptor proteins; C496618:VAV1 protein, human; D014443:Tyrosine; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins