CD8+ T cell cytolytic activity independent of mitogen-activated protein kinase / extracellular regulatory kinase signaling (MAP kinase / ERK)

The cytoskeletal adaptor protein paxillin localizes to the microtubule organizing center (MTOC) in T cells and, upon target cell binding, is recruited to the supramolecular activation complex (SMAC). We mapped the region of paxillin that associates with both the MTOC and SMAC to the leucine-aspartic acid (LD) domains and showed that a protein segment containing LD2–4 was sufficient for MTOC and SMAC recruitment. Examination of the localization of paxillin at the SMAC revealed that paxillin localizes to the peripheral area of the SMAC along with LFA-1, suggesting that LFA-1 may contribute to its recruitment. LFA-1 or CD3 engagement alone was insufficient for paxillin recruitment because there was no paxillin accumulation at the site of CTL contact with anti–LFA-1– or anti-CD3–coated beads. In contrast, paxillin accumulation was detected when beads coated with both anti-CD3 and anti–LFA-1 were bound to CTL, suggesting that signals from both the TCR and LFA-1 are required for paxillin accumulation. Paxillin was shown to be phosphorylated downstream of ERK, but when we generated a mutation (S83A/S130A) that abolished the mobility shift as a result of phosphorylation, we found that paxillin still bound to the MTOC and was recruited to the SMAC. Furthermore, ERK was not absolutely required for MTOC reorientation in CTL that require ERK for killing. Finally, expression of the LD2–4 region of paxillin substantially reduced MTOC reorientation. These studies demonstrated that paxillin is recruited, through its LD domains, to sites of integrin engagement and may contribute to MTOC reorientation required for directional degranulation.

Section: Discussioncontrasting

confidence: 99%

Paxillin Associates with the Microtubule Cytoskeleton and the Immunological Synapse of CTL through Its Leucine-Aspartic Acid Domains and Contributes to Microtubule Organizing Center Reorientation

Robertson

Ostergaard

2011

“…Other molecules that are established to have a role in the regulation of granule exocytosis-mediated cytotoxicity in mouse CD8 ϩ T cells are ERK1/2 and PI3K (13)(14)(15)(16)(17)(18)(19). These kinases are components of general TCR-mediated signaling cascade and are, in addition to the regulation of lytic function, involved in control of the other aspects of T cell function, including activation, proliferation, differentiation, and cytokine production (31).…”

Section: Discussionmentioning

confidence: 99%

“…In addition to these two events, there have been only a few signaling molecules whose role in the regulation of CTL granule exocytosis is well documented. Those include PI3K and MAPK/ERK (13)(14)(15)(16)(17)(18)(19). The extent to which each of these kinases contribute to the regulation of CD8 ϩ T cell degranulation has not been established completely, and the order in which they make their contributions to the signaling cascade leading to CTL degranulation is not known.…”

Section: T He Cd8mentioning

confidence: 99%

Protein Kinase Cδ Regulates Antigen Receptor-Induced Lytic Granule Polarization in Mouse CD8+ CTL

Jennifer

Monu

Shen

et al. 2007

Self Cite

T cell receptor (TCR)‐induced activation of protein kinase C (PKC) has long been known to be critical for regulation of granule exocytosis mediated cytotoxicity in CD8+ T cells. However, the mechanism by which PKC regulates this effector function is not clear. In addition, it is not known which PKC family members are involved in the regulation of this process. By combining the use of pharmacological inhibitors and mice with targeted gene deletions, we showed that Protein Kinase C □elta is required for granule exocytosis mediated lytic function in mouse CD8+T cells. We studied lysosomal/lytic granule movements in CD8+ T cells responding to target cell recognition by confocal microscopy and live imaging and demonstrated that PKC □elta regulates TCR induced lytic granule polarization. In summary, our studies identified Protein Kinase C □elta, a member of the family of diacylglycerol dependent, calcium independent PKC isoforms, as a novel regulator of TCR mediated lytic granule release in mouse CD8+CTL. This work was supported by the NIH grants RO1AI48837 and RO1AI41573 to SV and by NIH, NCI F32CA101449‐02 and Research Advisory Council grant to SR.

“…Three major signaling pathways were implicated in selective regulation of granule exocytosis in CD8 ϩ T lymphocytes. These involve protein kinase C (17, 41), mitogen-activated protein kinase extracellular signal-regulated kinase 1/2 (42,43), and phosphoinositol 3-kinase (44). In contrast, calcineurin is, in general, involved in cytokine secretion (45), but not in perforin/granzyme-mediated cytolysis (46), suggesting the selective involvement of calcineurin in cytokine responses.…”

Section: Discussionmentioning

confidence: 99%

Modulation of CD8+ T Cell Response to Antigen by the Levels of Self MHC Class I

Santori

Arsov

Vukmanović

2001

Self Cite

The response of H-Y-specific TCR-transgenic CD8+ T cells to Ag is characterized by poor proliferation, cytolytic activity, and IFN-γ secretion. IFN-γ secretion, but not cytotoxic function, can be rescued by the B7.1 molecule, suggesting that costimulation can selectively enhance some, but not all, effector CD8+ T cell responses. Although the H-Y epitope binds H-2Db relatively less well than some other epitopes, it can induce potent CTL responses in nontransgenic mice, suggesting that the observed poor responsiveness of transgenic CD8+ T cells cannot be ascribed to the epitope itself. Previously reported reactivity of this TCR to H-2Ab is also not the cause of the poor responsiveness of the H-Y-specific CD8+ T cells, as H-Y-specific CD8+ T cells obtained from genetic backgrounds lacking H-2Ab also responded poorly. Rather, reducing the levels of H-2b class I molecules by breeding the mice to (C57BL/6 × B10.D2)F1 or TAP1+/− backgrounds partially restored cytotoxic activity and enhanced proliferative responses. These findings demonstrate that the self MHC class I gene dosage may regulate the extent of CD8+ T cell responsiveness to Ag.