Related Experiment Video

Updated: Jul 13, 2026

Tyramide Signal Amplification for the Immunofluorescent Staining of ZBP1-Dependent Phosphorylation of RIPK3 and MLKL After HSV-1 Infection in Human Cells
09:15

Tyramide Signal Amplification for the Immunofluorescent Staining of ZBP1-Dependent Phosphorylation of RIPK3 and MLKL After HSV-1 Infection in Human Cells

Published on: October 20, 2022

Hypophosphorylated TCR/CD3zeta signals through a Grb2-SOS1-Ras pathway in Lck knockdown cells

Trond Methi1, Jacob Ngai, Torkel Vang

  • 1The Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway.

European Journal of Immunology
|August 9, 2007
PubMed

Insights

Even with reduced Lck kinase activity, T cell responses increase due to alternative signaling pathways. This study reveals Grb2-SOS1 recruitment and enhanced Ras-ERK activation, highlighting a novel T cell activation mechanism.

Area of Science:

  • Immunology
  • Cell Signaling
  • Molecular Biology

Background:

  • T cell activation typically relies on Lck kinase activity.
  • Paradoxical augmentation of T cell responses occurs despite Lck knockdown.
  • Alternative T cell activation pathways may exist or low Lck levels induce unique signals.

Purpose of the Study:

  • To investigate the molecular mechanisms behind augmented T cell responses in Lck-deficient T cells.
  • To identify alternative signaling pathways involved in T cell activation.
  • To elucidate the role of Lck in regulating Ras signaling and feedback mechanisms.

Main Methods:

  • T cells with siRNA-mediated Lck knockdown were used.
  • Prolonged anti-CD3 (OKT3) stimulation was applied.
  • Recruitment of Grb2-SOS1 to CD3zeta, ITAM phosphorylation, Ras and ERK1/2 activation, and Ras-GAP phosphorylation were analyzed.

Main Results:

  • Grb2-SOS1 was recruited to CD3zeta in Lck knockdown T cells.
  • Grb2 bound to incompletely phosphorylated ITAM1 (pY-Y), while ZAP-70 was excluded.
  • Ras and ERK1/2 activation, and NFAT-AP-1 activity were augmented.
  • Ras-GAP phosphorylation was suppressed, indicating Lck-dependent Ras negative feedback.

Conclusions:

  • Alternative Lck-independent pathways contribute to T cell activation.
  • Grb2-SOS1 recruitment to partially phosphorylated ITAMs is a key event.
  • Lck is crucial for a negative feedback mechanism regulating Ras signaling.

More Related Videos

Phospho Flow Cytometry with Fluorescent Cell Barcoding for Single Cell Signaling Analysis and Biomarker Discovery08:38

Phospho Flow Cytometry with Fluorescent Cell Barcoding for Single Cell Signaling Analysis and Biomarker Discovery

Published on: October 4, 2018

Identification of Mediators of T-cell Receptor Signaling via the Screening of Chemical Inhibitor Libraries08:49

Identification of Mediators of T-cell Receptor Signaling via the Screening of Chemical Inhibitor Libraries

Published on: January 22, 2019

Related Concept Videos

Amplifying Signals via Enzymatic Cascade01:22

Amplifying Signals via Enzymatic Cascade

When a ligand binds to a cell-surface receptor, the receptor's intracellular domain changes shape, which may either activate its enzyme function or allow its binding to other molecules. The initial signal is amplified by most signal transduction pathways. This means that a single ligand molecule can activate multiple molecules of a downstream target. Proteins that relay a signal are most commonly phosphorylated at one or more sites, activating or inactivating the protein. Kinases catalyze the...
The JAK-STAT Signaling Pathway01:20

The JAK-STAT Signaling Pathway

Several cytokine receptors have tightly bound Janus kinase or JAK proteins attached at their cytosolic tail. Small signaling molecules such as cytokines, growth hormones, or prolactins bind to the cytokine receptors and initiate their dimerization. The dimerization brings the cytosolic JAKs together that trans-phosphorylate and activates each other. The activated JAKs now phosphorylate cytosolic tails of the cytokine receptors, which serve as binding sites for adaptor proteins such as  SH2...
TGF - β Signaling Pathway01:16

TGF - β Signaling Pathway

The TGF-β signaling pathway regulates cell growth, differentiation, adhesion, motility, and development. TGF-β ligands that induce TGF-β signaling are synthesized in their latent form. Several proteases or cell surface receptors such as integrins act upon the latent form, releasing the active ligand. There are three types of mammalian TGF-βs: (TGF-β1, TGF-β2, and TGF-β3) that bind as homodimers or heterodimers to TGF-β receptors. The TGF-β receptors are of three kinds RI, RII, and RIII. The RI...
Receptor Tyrosine Kinases01:26

Receptor Tyrosine Kinases

Receptor tyrosine kinases or RTKs are membrane-bound receptors that phosphorylate specific tyrosine on protein substrates. RTKs regulate cellular growth, differentiation, survival, and migration. They contain an extracellular ligand binding domain, a transmembrane domain, and a cytosolic tail with intrinsic kinase activity. Several extracellular signaling molecules activate RTKs in one or more ways and relay the signal downstream. Ligands such as platelet-derived growth factor (PDGF) or...
MAPK Signaling Cascades01:07

MAPK Signaling Cascades

Mitogen-activated protein kinase, or MAPK pathway, activates three sequential kinases to regulate cellular responses such as proliferation, differentiation, survival, and apoptosis. The canonical MAPK pathway starts with a mitogen or growth factor binding to an RTK. The activated RTKs stimulate Ras, which recruits Raf or MAP3 Kinase (MAPKKK), the first kinase of the MAPK signaling cascade. Raf further phosphorylates and activates MEK or MAP2 Kinases (MAPKK), which in turn phosphorylates MAP...
PI3K/mTOR/AKT Signaling Pathway01:22

PI3K/mTOR/AKT Signaling Pathway

The mammalian target of rapamycin  (mTOR) is a serine/threonine kinase that regulates growth, proliferation, and cell survival in response to hormones, growth factors, or nutrient availability. This kinase exists in two structurally and functionally distinct forms: mTOR complex 1  (mTORC1) and mTOR complex 2  (mTORC2). The first form (mTORC1) is composed of a rapamycin-sensitive Raptor and proline-rich Akt substrate, PRAS40. In contrast,  mTORC2 consists of a rapamycin-insensitive companion...