Rap1-mediated Lymphocyte Function-associated Antigen-1 Activation by the T Cell Antigen Receptor Is Dependent on Phospholipase C-γ1

The small GTPase, Rap1, is a potent activator of leukocyte integrins and enhances the adhesive activity of lymphocyte function-associated antigen-1 (LFA-1) when stimulated by the T cell receptor (TCR) or chemokines. However, the mechanism by which Rap1 is activated remains unclear. Here, we demonstrate that phospholipase C (PLC)-γ1 plays a critical role in the signaling pathway leading to Rap1 activation triggered by the TCR. In Jurkat T cells, TCR cross-linking triggered persistent Rap1 activation, and SDF-1 (CXCL12) activated Rap1 transiently. A phospholipase C inhibitor, U73122, abrogated Rap1 activation triggered by both the TCR and SDF-1 (CXCL12). PLC-γ1-deficient Jurkat T cells showed a marked reduction of TCR-triggered Rap1 activation and adhesion to intercellular adhesion molecule-1 (ICAM-1) mediated by LFA-1. In contrast, SDF-1-triggered Rap1 activation and adhesion were not affected in these cells. Transfection of these cells with an expression plasmid encoding PLC-γ1 restored Rap1 activation by the TCR and the ability to adhere to ICAM-1, accompanied by polarized LFA-1 surface clustering colocalized with regulator of adhesion and polarization enriched in lymphoid tissues (RAPL). Furthermore, when expressed in Jurkat cells, CalDAG-GEFI, a calcium and diacylglycerol-responsive Rap1 exchange factor, associated with Rap1, and resulted in enhanced Rap1 activation and adhesion triggered by the TCR. Our results demonstrate that TCR activation of Rap1 depends on PLC-γ1. This activity is likely to be mediated by CalDAG-GEFI, which is required to activate LFA-1. The small GTPase, Rap1, is a potent activator of leukocyte integrins and enhances the adhesive activity of lymphocyte function-associated antigen-1 (LFA-1) when stimulated by the T cell receptor (TCR) or chemokines. However, the mechanism by which Rap1 is activated remains unclear. Here, we demonstrate that phospholipase C (PLC)-γ1 plays a critical role in the signaling pathway leading to Rap1 activation triggered by the TCR. In Jurkat T cells, TCR cross-linking triggered persistent Rap1 activation, and SDF-1 (CXCL12) activated Rap1 transiently. A phospholipase C inhibitor, U73122, abrogated Rap1 activation triggered by both the TCR and SDF-1 (CXCL12). PLC-γ1-deficient Jurkat T cells showed a marked reduction of TCR-triggered Rap1 activation and adhesion to intercellular adhesion molecule-1 (ICAM-1) mediated by LFA-1. In contrast, SDF-1-triggered Rap1 activation and adhesion were not affected in these cells. Transfection of these cells with an expression plasmid encoding PLC-γ1 restored Rap1 activation by the TCR and the ability to adhere to ICAM-1, accompanied by polarized LFA-1 surface clustering colocalized with regulator of adhesion and polarization enriched in lymphoid tissues (RAPL). Furthermore, when expressed in Jurkat cells, CalDAG-GEFI, a calcium and diacylglycerol-responsive Rap1 exchange factor, associated with Rap1, and resulted in enhanced Rap1 activation and adhesion triggered by the TCR. Our results demonstrate that TCR activation of Rap1 depends on PLC-γ1. This activity is likely to be mediated by CalDAG-GEFI, which is required to activate LFA-1. The small GTPase, Rap1, is a potent signaling molecule of integrins The adhesion mediated by lymphocyte function-associated T cell cell regulator of adhesion and polarization enriched in lymphoid phospholipase ICAM-1, intercellular adhesion exchange and exchange lymphocyte function-associated T cell cell regulator of adhesion and polarization enriched in lymphoid phospholipase ICAM-1, intercellular adhesion exchange and exchange and by and the of Rap1 is activated by a of and and plays a role in to activate Rap1 activation by TCR the of the the T cell and cells, which on the T cell to Rap1 activation in lymphocyte to cells, and lymphocyte Rap1 is the of T cell activation and an and an The is by exchange and The of Rap1 is to we a that is an regulator in LFA-1 activation and of LFA-1 However, the signaling by which the TCR and Rap1 not the of Rap1, with Rap1 activation to be mediated by and which to In T cells, to a with TCR This in T cells, in which This that the pathway Rap1 activation triggered by the TCR. the to be critical Rap1 activation in cells, cells were to be in Rap1 activation by not a a role of in Rap1 in cells is the of in T cells, to TCR-triggered Rap1 activation and a critical role in Here, we that PLC-γ1 plays a role in Rap1 activation by in LFA-1 demonstrate that Rap1 is associated with and adhesion TCR and were and LFA-1 with and were and T cells and PLC-γ1-deficient Jurkat cells were The cells were by with PLC-γ1 by of and and by and Rap1 and cells were with or T cells were with T cells were stimulated with or or SDF-1 the cells or T cells in were stimulated with or SDF-1 the cells were in Rap1 a were of to in cells were with and in and cells were to in the of or and cells were by and cells were in the a adhesion to in a on which were with The on the of an in of were with or SDF-1 and were were cells, or stimulated with were in with cells were on and with of LFA-1 and cells were with and of LFA-1 and cells were with were with to by to LFA-1 with were with were by with cells were by and cells were with the cell were with were with the and The were with or were to of by expression by Jurkat cells. of were on the to the by and or by and The were a and by of on Rap1 by TCR and the leading to Rap1 activation triggered by TCR and we which to TCR cross-linking and SDF-1 Rap1 activation in Jurkat T cells. TCR-triggered Rap1 activation In contrast, SDF-1 a Rap1 activation, which and The of Rap1 activation in Jurkat T cells to in not not activate Rap1 in Jurkat cells that Rap1 activation TCR and SDF-1 and not to the in the the signaling pathway that TCR to Rap1 activation, Jurkat T cells were with and stimulated Rap1 in Rap1 activation by TCR or SDF-1 by the inhibitor, The not Rap1 activation Rap1 activation in T cells A calcium not Rap1 activation a inhibitor, Rap1 activation, not activation in Rap1 activation triggered by TCR and of Rap1 by the TCR the that activity is critical Rap1 activation, we the of PLC-γ1 a Jurkat cell in which is expression of PLC-γ1 these cells not to and in to TCR in calcium and that activation of Rap1 in the PLC-γ1-deficient Jurkat cells with cells In contrast, Rap1 activation the that Rap1 is in the cells the role of PLC-γ1 in Rap1 activation by the we to PLC-γ1 PLC-γ1 the cells a to that in cells The expression of PLC-γ1 resulted in restored Rap1 activation by the TCR of PLC-γ1 not the of when stimulated with SDF-1 results the critical of PLC-γ1 in Rap1 activation triggered by TCR not of Rap1 activation on PLC-γ1 TCR PLC-γ1 or PLC-γ1-deficient Jurkat cells. The of PLC-γ1 were by with or PLC-γ1-deficient cells with or PLC-γ1 were stimulated with or SDF-1 or and Rap1 activation in Rap1 signaling TCR to activate LFA-1 of we PLC-γ1 adhesion to in TCR not adhesion in PLC-γ1-deficient cells. The expression of LFA-1 in the PLC-γ1-deficient cells to that in cells by cell not In contrast, stimulated adhesion of PLC-γ1-deficient Jurkat cells, which with that of the This the that the adhesion is to of PLC-γ1. The of PLC-γ1 in the cells restored LFA-1 adhesive activity to a to that in cells, that PLC-γ1 TCR-triggered SDF-1-triggered adhesion to in PLC-γ1-deficient Jurkat cells with that of the and not by PLC-γ1 This is with the that showed that Rap1 activation SDF-1 in PLC-γ1-deficient Jurkat cells these results that Rap1 activation by PLC-γ1 is in adhesion by TCR. In the of PLC-γ1 of Rap1 is adhesion of PLC-γ1-deficient Jurkat cells, with that of cells is critical LFA-1 PLC-γ1-deficient Jurkat cells were with the or PLC-γ1. cells were stimulated with or on and The and of with cells stimulated with TCR. PLC-γ1-deficient Jurkat cells with the or PLC-γ1 were stimulated with SDF-1 on and were to of adhesion to of and PLC-γ1-deficient Jurkat cells. expression in and cells. PLC-γ1-deficient Jurkat cells with the or PLC-γ1 were stimulated with and LFA-1 and or LFA-1 and The the of on is the Rap1 molecule critical and with LFA-1 and LFA-1 to the leading Rap1 activation the of LFA-1 and in PLC-γ1-deficient Jurkat cells with cells with PLC-γ1. TCR to a of LFA-1 the leading and to a and colocalized with the of LFA-1 In PLC-γ1 Jurkat cells, the of LFA-1 and on the cell surface not TCR in cells not In contrast, the of PLC-γ1 of LFA-1 and TCR colocalized with polarized surface LFA-1. This is with the results in an of LFA-1 and the leading is critical LFA-1 results that PLC-γ1 the of LFA-1 and and the that PLC-γ1 results in Rap1 activation, which in of LFA-1 mediated by Rap1 and PLC-γ1 and the Rap1 and is likely to be in Rap1 activation of PLC-γ1. we CalDAG-GEFI, which is expressed in the the and the be in Rap1 activation triggered by TCR. by in Jurkat cells in Jurkat cells and the on Rap1 activation by TCR were in Rap1 activation TCR in cells, with the of activation in cells. the of Jurkat cells resulted in adhesion to in cells TCR The by U73122, not expression of enhanced Rap1 activation and adhesion to In we that with in when Jurkat cells, Rap1 and an with or Furthermore, TCR However, not with and not with or of the these that be and with TCR-triggered Rap1 of in Rap1 activation by the TCR. of Jurkat cells with or The of were by and The and in or CalDAG-GEFI, were Jurkat cells. The of were by Jurkat cells with the or were stimulated with and Rap1 activation, in Jurkat cells with the or CalDAG-GEFI, with or with or were stimulated with on and The and of with cells stimulated by the TCR. Jurkat cells with Rap1 and or Jurkat cells with Rap1 or were stimulated with and and The were with or and with or or Rap1 we critical Rap1 activation triggered by TCR and SDF-1 and PLC-γ1-deficient Jurkat cells. Our results that PLC-γ1 plays an role in Rap1 activation by the TCR not in activation by The to activate Rap1 to resulted in the of TCR-triggered adhesion to However, on adhesion Our results that be an Rap1 exchange of PLC-γ1 activity triggered by Jurkat cells, we that PLC-γ1 required Rap1 activation and adhesion TCR The Rap1 activation associated with a in polarized and of LFA-1 with in PLC-γ1-deficient Jurkat cells. This is with which that with LFA-1 is critical LFA-1 with PLC-γ1 TCR-triggered Rap1 activation and with LFA-1 colocalized with the leading these results that PLC-γ1 activation the critical signaling leading to of LFA-1 mediated by Rap1 and mechanism of TCR-triggered activation of PLC-γ1 The is that a of activated T and and a of the of PLC-γ1 activation in to TCR signaling is in PLC-γ1 activation TCR with and activation required PLC-γ1 activation by and critical the activation of integrins by the TCR In with PLC-γ1-deficient Jurkat cells to an adhesive to not and T cells were to be in LFA-1 and adhesion to ICAM-1, and cell TCR This adhesion to be to However, LFA-1 to be of an Our the that PLC-γ1 activation in T cells PLC-γ1 likely plays a role in TCR-triggered adhesion mediated by and integrins to to and which in the of is a of that both and of that on Rap1 in to and and is enriched in the and cells and is to Rap1 In contrast, is expressed and a showed that Rap1 with in Jurkat cells, cells stimulated with Our results that expression of activated Rap1 and adhesion to in to TCR This is in with a that is a regulator of and to in CalDAG-GEFI, and likely Rap1 exchange of PLC-γ1 in to TCR that in T cells Rap1 activation by the TCR with the of the to the and and that activated Rap1 required T cell Rap1 activated by cell or TCR in PLC-γ1 Rap1 activation activation restored by the of PLC-γ1. results with a cells in which Rap1 activation on PLC-γ1-deficient Jurkat T cells showed a in Rap1 activation by the In that the pathway an role in results that Rap1 activation in of T cell with the inhibitor, U73122, Rap1 activation by TCR and However, SDF-1 to Rap1 activation in PLC-γ1-deficient Jurkat cells, a that with the role of PLC-γ1 in Rap1 of cells with SDF-1 resulted in the activation of Rap1 and activation by to with In both and cell in not in likely to Rap1 activation in the critical role of PLC-γ1 a regulator of adhesion This in the of the in of PLC-γ1 T cell and the The small GTPase, Rap1, is a potent signaling molecule of integrins The adhesion mediated by lymphocyte function-associated T cell cell regulator of adhesion and polarization enriched in lymphoid phospholipase ICAM-1, intercellular adhesion exchange and exchange lymphocyte function-associated T cell cell regulator of adhesion and polarization enriched in lymphoid phospholipase ICAM-1, intercellular adhesion exchange and exchange and by and the of Rap1 is activated by a of and and plays a role in to activate Rap1 activation by TCR the of the the T cell and cells, which on the T cell to Rap1 activation in lymphocyte to cells, and lymphocyte Rap1 is the of T cell activation and Rap1 an and an The is by exchange and The of Rap1 is to we a that is an regulator in LFA-1 activation and of LFA-1 However, the signaling by which the TCR and Rap1 not the of Rap1, with Rap1 activation to be mediated by and which to In T cells, to a with TCR This in T cells, in which This that the pathway Rap1 activation triggered by the TCR. the to be critical Rap1 activation in cells, cells were to be in Rap1 activation by not a a role of in Rap1 in cells is the of in T cells, to TCR-triggered Rap1 activation and a critical role in Here, we that PLC-γ1 plays a role in Rap1 activation by in LFA-1 demonstrate that Rap1 is associated with and adhesion TCR and were and LFA-1 with and were and T cells and PLC-γ1-deficient Jurkat cells were The cells were by with PLC-γ1 by of and and by and Rap1 and cells were with or T cells were with T cells were stimulated with or or SDF-1 the cells or T cells in were stimulated with or SDF-1 the cells were in Rap1 a were of to in cells were with and in and cells were to in the of or and cells were by and cells were in the a adhesion to in a on which were with The on the of an in of were with or SDF-1 and were were cells, or stimulated with were in with cells were on and with of LFA-1 and cells were with and of LFA-1 and cells were with were with to by to LFA-1 with were with were by with cells were by and cells were with the cell were with were with the and The were with or were to of by expression by Jurkat cells. of were on the to the by and or by and The were a and by and were and LFA-1 with and were and T cells and PLC-γ1-deficient Jurkat cells were The cells were by with PLC-γ1 by of and and by and Rap1 and cells were with or T cells were with T cells were stimulated with or or SDF-1 the cells or T cells in were stimulated with or SDF-1 the cells were in Rap1 a were of to in cells were with and in and cells were to in the of or and cells were by and cells were in the a adhesion to in a on which were with The on the of an in of were with or SDF-1 and were were cells, or stimulated with were in with cells were on and with of LFA-1 and cells were with and of LFA-1 and cells were with were with to by to LFA-1 with were with were by with cells were by and cells were with the cell were with were with the and The were with or were to of by expression by Jurkat cells. of were on the to the by and or by and The were a and by of on Rap1 by TCR and the leading to Rap1 activation triggered by TCR and we which to TCR cross-linking and SDF-1 Rap1 activation in Jurkat T cells. TCR-triggered Rap1 activation In contrast, SDF-1 a Rap1 activation, which and The of Rap1 activation in Jurkat T cells to in not not activate Rap1 in Jurkat cells that Rap1 activation TCR and SDF-1 and not to the in the the signaling pathway that TCR to Rap1 activation, Jurkat T cells were with and stimulated Rap1 in Rap1 activation by TCR or SDF-1 by the inhibitor, The not Rap1 activation Rap1 activation in T cells A calcium not Rap1 activation a inhibitor, Rap1 activation, not activation in Rap1 activation triggered by TCR and of Rap1 by the TCR the that activity is critical Rap1 activation, we the of PLC-γ1 a Jurkat cell in which is expression of PLC-γ1 these cells not to and in to TCR in calcium and that activation of Rap1 in the PLC-γ1-deficient Jurkat cells with cells In contrast, Rap1 activation the that Rap1 is in the cells the role of PLC-γ1 in Rap1 activation by the we to PLC-γ1 PLC-γ1 the cells a to that in cells The expression of PLC-γ1 resulted in restored Rap1 activation by the TCR of PLC-γ1 not the of when stimulated with SDF-1 results the critical of PLC-γ1 in Rap1 activation triggered by TCR not Rap1 signaling TCR to activate LFA-1 of we PLC-γ1 adhesion to in TCR not adhesion in PLC-γ1-deficient cells. The expression of LFA-1 in the PLC-γ1-deficient cells to that in cells by cell not In contrast, stimulated adhesion of PLC-γ1-deficient Jurkat cells, which with that of the This the that the adhesion is to of PLC-γ1. The of PLC-γ1 in the cells restored LFA-1 adhesive activity to a to that in cells, that PLC-γ1 TCR-triggered SDF-1-triggered adhesion to in PLC-γ1-deficient Jurkat cells with that of the and not by PLC-γ1 This is with the that showed that Rap1 activation SDF-1 in PLC-γ1-deficient Jurkat cells these results that Rap1 activation by PLC-γ1 is in adhesion by TCR. In the of PLC-γ1 of Rap1 is adhesion of PLC-γ1-deficient Jurkat cells, with that of cells is critical LFA-1 PLC-γ1-deficient Jurkat cells were with the or PLC-γ1. cells were stimulated with or on and The and of with cells stimulated with TCR. PLC-γ1-deficient Jurkat cells with the or PLC-γ1 were stimulated with SDF-1 on and were to of adhesion to of and PLC-γ1-deficient Jurkat cells. expression in and cells. PLC-γ1-deficient Jurkat cells with the or PLC-γ1 were stimulated with and LFA-1 and or LFA-1 and The the of on is the Rap1 molecule critical and with LFA-1 and LFA-1 to the leading Rap1 activation the of LFA-1 and in PLC-γ1-deficient Jurkat cells with cells with PLC-γ1. TCR to a of LFA-1 the leading and to a and colocalized with the of LFA-1 In PLC-γ1 Jurkat cells, the of LFA-1 and on the cell surface not TCR in cells not In contrast, the of PLC-γ1 of LFA-1 and TCR colocalized with polarized surface LFA-1. This is with the results in an of LFA-1 and the leading is critical LFA-1 results that PLC-γ1 the of LFA-1 and and the that PLC-γ1 results in Rap1 activation, which in of LFA-1 mediated by Rap1 and PLC-γ1 and the Rap1 and is likely to be in Rap1 activation of PLC-γ1. we CalDAG-GEFI, which is expressed in the the and the be in Rap1 activation triggered by TCR. by in Jurkat cells in Jurkat cells and the on Rap1 activation by TCR were in Rap1 activation TCR in cells, with the of activation in cells. the of Jurkat cells resulted in adhesion to in cells TCR The by U73122, not expression of enhanced Rap1 activation and adhesion to In we that with in when Jurkat cells, Rap1 and an with or Furthermore, TCR However, not with and not with or of the these that be and with TCR-triggered Rap1 of in Rap1 activation by the TCR. of Jurkat cells with or The of were by and The and in or CalDAG-GEFI, were Jurkat cells. The of were by Jurkat cells with the or were stimulated with and Rap1 activation, in Jurkat cells with the or CalDAG-GEFI, with or with or were stimulated with on and The and of with cells stimulated by the TCR. Jurkat cells with Rap1 and or Jurkat cells with Rap1 or were stimulated with and and The were with or and with or or Rap1 The of on Rap1 by TCR and the leading to Rap1 activation triggered by TCR and we which to TCR cross-linking and SDF-1 Rap1 activation in Jurkat T cells. TCR-triggered Rap1 activation In contrast, SDF-1 a Rap1 activation, which and The of Rap1 activation in Jurkat T cells to in not not activate Rap1 in Jurkat cells that Rap1 activation TCR and SDF-1 and not to the in the the signaling pathway that TCR to Rap1 activation, Jurkat T cells were with and stimulated Rap1 in Rap1 activation by TCR or SDF-1 by the inhibitor, The not Rap1 activation Rap1 activation in T cells A calcium not Rap1 activation a inhibitor, Rap1 activation, not activation in Rap1 activation triggered by TCR and of Rap1 by the TCR the that activity is critical Rap1 activation, we the of PLC-γ1 a Jurkat cell in which is expression of PLC-γ1 these cells not to and in to TCR in calcium and that activation of Rap1 in the PLC-γ1-deficient Jurkat cells with cells In contrast, Rap1 activation the that Rap1 is in the cells the role of PLC-γ1 in Rap1 activation by the we to PLC-γ1 PLC-γ1 the cells a to that in cells The expression of PLC-γ1 resulted in restored Rap1 activation by the TCR of PLC-γ1 not the of when stimulated with SDF-1 results the critical of PLC-γ1 in Rap1 activation triggered by TCR not PLC-γ1 Rap1 signaling TCR to activate LFA-1 of we PLC-γ1 adhesion to in TCR not adhesion in PLC-γ1-deficient cells. The expression of LFA-1 in the PLC-γ1-deficient cells to that in cells by cell not In contrast, stimulated adhesion of PLC-γ1-deficient Jurkat cells, which with that of the This the that the adhesion is to of PLC-γ1. The of PLC-γ1 in the cells restored LFA-1 adhesive activity to a to that in cells, that PLC-γ1 TCR-triggered SDF-1-triggered adhesion to in PLC-γ1-deficient Jurkat cells with that of the and not by PLC-γ1 This is with the that showed that Rap1 activation SDF-1 in PLC-γ1-deficient Jurkat cells these results that Rap1 activation by PLC-γ1 is in adhesion by TCR. In the of PLC-γ1 of Rap1 is adhesion of PLC-γ1-deficient Jurkat cells, with that of cells the of on is the Rap1 molecule critical and with LFA-1 and LFA-1 to the leading Rap1 activation the of LFA-1 and in PLC-γ1-deficient Jurkat cells with cells with PLC-γ1. TCR to a of LFA-1 the leading and to a and colocalized with the of LFA-1 In PLC-γ1 Jurkat cells, the of LFA-1 and on the cell surface not TCR in cells not In contrast, the of PLC-γ1 of LFA-1 and TCR colocalized with polarized surface LFA-1. This is with the results in an of LFA-1 and the leading is critical LFA-1 results that PLC-γ1 the of LFA-1 and and the that PLC-γ1 results in Rap1 activation, which in of LFA-1 mediated by Rap1 and PLC-γ1 and the Rap1 and is likely to be in Rap1 activation of PLC-γ1. we CalDAG-GEFI, which is expressed in the the and the be in Rap1 activation triggered by TCR. by in Jurkat cells in Jurkat cells and the on Rap1 activation by TCR were in Rap1 activation TCR in cells, with the of activation in cells. the of Jurkat cells resulted in adhesion to in cells TCR The by U73122, not expression of enhanced Rap1 activation and adhesion to In we that with in when Jurkat cells, Rap1 and an with or Furthermore, TCR However, not with and not with or of the these that be and with TCR-triggered Rap1 we critical Rap1 activation triggered by TCR and SDF-1 and PLC-γ1-deficient Jurkat cells. Our results that PLC-γ1 plays an role in Rap1 activation by the TCR not in activation by The to activate Rap1 to resulted in the of TCR-triggered adhesion to However, on adhesion Our results that be an Rap1 exchange of PLC-γ1 activity triggered by Jurkat cells, we that PLC-γ1 required Rap1 activation and adhesion TCR The Rap1 activation associated with a in polarized and of LFA-1 with in PLC-γ1-deficient Jurkat cells. This is with which that with LFA-1 is critical LFA-1 with PLC-γ1 TCR-triggered Rap1 activation and with LFA-1 colocalized with the leading these results that PLC-γ1 activation the critical signaling leading to of LFA-1 mediated by Rap1 and mechanism of TCR-triggered activation of PLC-γ1 The is that a of activated T and and a of the of PLC-γ1 activation in to TCR signaling is in PLC-γ1 activation TCR with and activation required PLC-γ1 activation by and critical the activation of integrins by the TCR In with PLC-γ1-deficient Jurkat cells to an adhesive to not and T cells were to be in LFA-1 and adhesion to ICAM-1, and cell TCR This adhesion to be to However, LFA-1 to be of an Our the that PLC-γ1 activation in T cells PLC-γ1 likely plays a role in TCR-triggered adhesion mediated by and integrins to to and which in the of is a of that both and of that on Rap1 in to and and is enriched in the and cells and is to Rap1 In contrast, is expressed and a showed that Rap1 with in Jurkat cells, cells stimulated with Our results that expression of activated Rap1 and adhesion to in to TCR This is in with a that is a regulator of and to in CalDAG-GEFI, and likely Rap1 exchange of PLC-γ1 in to TCR that in T cells Rap1 activation by the TCR with the of the to the and and that activated Rap1 required T cell Rap1 activated by cell or TCR in PLC-γ1 Rap1 activation activation restored by the of PLC-γ1. results with a cells in which Rap1 activation on PLC-γ1-deficient Jurkat T cells showed a in Rap1 activation by the In that the pathway an role in results that Rap1 activation in of T cell with the inhibitor, U73122, Rap1 activation by TCR and However, SDF-1 to Rap1 activation in PLC-γ1-deficient Jurkat cells, a that with the role of PLC-γ1 in Rap1 of cells with SDF-1 resulted in the activation of Rap1 and activation by to with In both and cell in not in likely to Rap1 activation in the critical role of PLC-γ1 a regulator of adhesion This in the of the in of PLC-γ1 T cell and the In we critical Rap1 activation triggered by TCR and SDF-1 and PLC-γ1-deficient Jurkat cells. Our results that PLC-γ1 plays an role in Rap1 activation by the TCR not in activation by The to activate Rap1 to resulted in the of TCR-triggered adhesion to However, on adhesion Our results that be an Rap1 exchange of PLC-γ1 activity triggered by TCR. Jurkat cells, we that PLC-γ1 required Rap1 activation and adhesion TCR The Rap1 activation associated with a in polarized and of LFA-1 with in PLC-γ1-deficient Jurkat cells. This is with which that with LFA-1 is critical LFA-1 with PLC-γ1 TCR-triggered Rap1 activation and with LFA-1 colocalized with the leading these results that PLC-γ1 activation the critical signaling leading to of LFA-1 mediated by Rap1 and The mechanism of TCR-triggered activation of PLC-γ1 The is that a of activated T and and a of the of PLC-γ1 activation in to TCR signaling is in PLC-γ1 activation TCR with and activation required PLC-γ1 activation by and critical the activation of integrins by the TCR In with PLC-γ1-deficient Jurkat cells to an adhesive to not and T cells were to be in LFA-1 and adhesion to ICAM-1, and cell TCR This adhesion to be to However, LFA-1 to be of an Our the that PLC-γ1 activation in T cells PLC-γ1 likely plays a role in TCR-triggered adhesion mediated by and integrins In to to and which in the of is a of that both and of that on Rap1 in to and and is enriched in the and cells and is to Rap1 In contrast, is expressed and a showed that Rap1 with in Jurkat cells, cells stimulated with Our results that expression of activated Rap1 and adhesion to in to TCR This is in with a that is a regulator of and to in CalDAG-GEFI, and likely Rap1 exchange of PLC-γ1 in to TCR that in T cells Rap1 activation by the TCR with the of the to the and and that activated Rap1 required T cell Rap1 activated by cell or TCR in PLC-γ1 Rap1 activation activation restored by the of PLC-γ1. results with a cells in which Rap1 activation on PLC-γ1-deficient Jurkat T cells showed a in Rap1 activation by the In that the pathway an role in results that Rap1 activation in of T cell with the inhibitor, U73122, Rap1 activation by TCR and However, SDF-1 to Rap1 activation in PLC-γ1-deficient Jurkat cells, a that with the role of PLC-γ1 in Rap1 of cells with SDF-1 resulted in the activation of Rap1 and activation by to with In both and cell in not in likely to Rap1 activation in This the critical role of PLC-γ1 a regulator of adhesion This in the of the in of PLC-γ1 T cell and the PLC-γ1 and