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TCR activation kinetics and feedback regulation in primary human T cells.

Poltorak M, Arndt B, Kowtharapu BS, Reddycherla AV, Witte V, Lindquist JA, Schraven B, Simeoni L - Cell Commun. Signal (2013)

Bottom Line: In fact, upon iAbs stimulation TCR-mediated signaling is prolonged by a positive feedback loop involving Erk, whereas sAbs strongly activate inhibitory molecules that likely terminate signaling.We additionally found that, by enhancing the phosphorylation of Src family kinases under proliferation-inducing conditions, signaling and T-cell activation are terminated.In summary, our analysis documents TCR signaling kinetics and feedback regulation under conditions of stimulation inducing either unresponsiveness or proliferation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Molecular and Clinical Immunology, Otto-von-Guericke University, Leipziger Str, 44, 39120, Magdeburg, Germany. luca.simeoni@med.ovgu.de.

ABSTRACT

Background: Signaling through the TCR is crucial for the generation of different cellular responses including proliferation, differentiation, and apoptosis. A growing body of evidence indicates that differences in the magnitude and the duration of the signal are critical determinants in eliciting cellular responses.

Results: Here, we have analyzed signaling dynamics correlating with either unresponsiveness or proliferation induced upon TCR/CD28 ligation in primary human T cells. We used two widely employed methods to stimulate T cells in vitro, antibodies either cross-linked in solution (sAbs) or immobilized on microbeads (iAbs). A comparative analysis of the signaling properties of iAbs and sAbs revealed that, under proliferation-inducing conditions, feedback regulation is markedly different from that leading to an unresponsive state. In fact, upon iAbs stimulation TCR-mediated signaling is prolonged by a positive feedback loop involving Erk, whereas sAbs strongly activate inhibitory molecules that likely terminate signaling. We additionally found that, by enhancing the phosphorylation of Src family kinases under proliferation-inducing conditions, signaling and T-cell activation are terminated.

Conclusions: In summary, our analysis documents TCR signaling kinetics and feedback regulation under conditions of stimulation inducing either unresponsiveness or proliferation.

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Related in: MedlinePlus

Feedback regulation of TCR-mediated signaling. sAbs stimulation triggers strong phosphorylation of Src kinases, such as Lck, and leads to strong activation of downstream signaling pathways. In addition to the activation of positive regulators, sAbs also induce inhibitory molecules (c-Cbl, Dok2), which might imbalance TCR-mediated signaling, thus rapidly terminating T-cell activation (left side). On the other hand, iAbs stimulation results in the activation of an Erk-Lck positive feedback loop, which is required to sustain signaling (right side).
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Figure 6: Feedback regulation of TCR-mediated signaling. sAbs stimulation triggers strong phosphorylation of Src kinases, such as Lck, and leads to strong activation of downstream signaling pathways. In addition to the activation of positive regulators, sAbs also induce inhibitory molecules (c-Cbl, Dok2), which might imbalance TCR-mediated signaling, thus rapidly terminating T-cell activation (left side). On the other hand, iAbs stimulation results in the activation of an Erk-Lck positive feedback loop, which is required to sustain signaling (right side).

Mentions: In summary, we have shown that stimulation with iAbs induces different feedback regulation than sAbs treatment (Figure 6). sAbs lead to strong and rapid activation of Src kinases and subsequently to the phosphorylation of inhibitory molecules (e.g. c-Cbl, Dok2), which terminate signaling. On the other hand, iAbs induce only slight increase in kinase activity and an Erk-Lck positive feedback loop, which may be required to prevent rapid Lck dephosphorylation by SHP-1 or other phosphatases, and therefore lead to sustained activation.


TCR activation kinetics and feedback regulation in primary human T cells.

Poltorak M, Arndt B, Kowtharapu BS, Reddycherla AV, Witte V, Lindquist JA, Schraven B, Simeoni L - Cell Commun. Signal (2013)

Feedback regulation of TCR-mediated signaling. sAbs stimulation triggers strong phosphorylation of Src kinases, such as Lck, and leads to strong activation of downstream signaling pathways. In addition to the activation of positive regulators, sAbs also induce inhibitory molecules (c-Cbl, Dok2), which might imbalance TCR-mediated signaling, thus rapidly terminating T-cell activation (left side). On the other hand, iAbs stimulation results in the activation of an Erk-Lck positive feedback loop, which is required to sustain signaling (right side).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3842781&req=5

Figure 6: Feedback regulation of TCR-mediated signaling. sAbs stimulation triggers strong phosphorylation of Src kinases, such as Lck, and leads to strong activation of downstream signaling pathways. In addition to the activation of positive regulators, sAbs also induce inhibitory molecules (c-Cbl, Dok2), which might imbalance TCR-mediated signaling, thus rapidly terminating T-cell activation (left side). On the other hand, iAbs stimulation results in the activation of an Erk-Lck positive feedback loop, which is required to sustain signaling (right side).
Mentions: In summary, we have shown that stimulation with iAbs induces different feedback regulation than sAbs treatment (Figure 6). sAbs lead to strong and rapid activation of Src kinases and subsequently to the phosphorylation of inhibitory molecules (e.g. c-Cbl, Dok2), which terminate signaling. On the other hand, iAbs induce only slight increase in kinase activity and an Erk-Lck positive feedback loop, which may be required to prevent rapid Lck dephosphorylation by SHP-1 or other phosphatases, and therefore lead to sustained activation.

Bottom Line: In fact, upon iAbs stimulation TCR-mediated signaling is prolonged by a positive feedback loop involving Erk, whereas sAbs strongly activate inhibitory molecules that likely terminate signaling.We additionally found that, by enhancing the phosphorylation of Src family kinases under proliferation-inducing conditions, signaling and T-cell activation are terminated.In summary, our analysis documents TCR signaling kinetics and feedback regulation under conditions of stimulation inducing either unresponsiveness or proliferation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Molecular and Clinical Immunology, Otto-von-Guericke University, Leipziger Str, 44, 39120, Magdeburg, Germany. luca.simeoni@med.ovgu.de.

ABSTRACT

Background: Signaling through the TCR is crucial for the generation of different cellular responses including proliferation, differentiation, and apoptosis. A growing body of evidence indicates that differences in the magnitude and the duration of the signal are critical determinants in eliciting cellular responses.

Results: Here, we have analyzed signaling dynamics correlating with either unresponsiveness or proliferation induced upon TCR/CD28 ligation in primary human T cells. We used two widely employed methods to stimulate T cells in vitro, antibodies either cross-linked in solution (sAbs) or immobilized on microbeads (iAbs). A comparative analysis of the signaling properties of iAbs and sAbs revealed that, under proliferation-inducing conditions, feedback regulation is markedly different from that leading to an unresponsive state. In fact, upon iAbs stimulation TCR-mediated signaling is prolonged by a positive feedback loop involving Erk, whereas sAbs strongly activate inhibitory molecules that likely terminate signaling. We additionally found that, by enhancing the phosphorylation of Src family kinases under proliferation-inducing conditions, signaling and T-cell activation are terminated.

Conclusions: In summary, our analysis documents TCR signaling kinetics and feedback regulation under conditions of stimulation inducing either unresponsiveness or proliferation.

Show MeSH
Related in: MedlinePlus