T cell receptor and co-stimulatory signaling (Homo sapiens)
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- Takahashi K, Yan I, Haga H, Patel T; ''Long non-coding RNA in liver diseases.''; Hepatology, 2014 PubMed Europe PMC Scholia
- Srikanth S, Gwack Y; ''Orai1-NFAT signalling pathway triggered by T cell receptor stimulation.''; Mol Cells, 2013 PubMed Europe PMC Scholia
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| Name | Type | Database reference | Comment |
|---|---|---|---|
| AP-1 | Protein | (cFos, JunB) | PIP2 is a membrane lipid. |
| Akt | Protein | Protein kinase B (PKB) | Akt is a serine/threonine-specific protein kinase that plays a key role in many cellular processes such as glucose metabolism, apoptosis, cell proliferation, transcription, and cell migration. Akt is recruited to the membrane by PIP3. Here Akt can be activated / phosphorylated (indirectly) by P13K and can then phosphorylate a variety of downstream pathways. Noteably, Akt promotes cell survival by inhibiting the cell death pathway and stimulates cell metabolism by increasing the utilization of glucose. |
| Bcl-xL | Protein | B-cell lymphoma-extra large | Bcl-xL is a transmembrane protein in the mitochondria. It is a anti-apoptosis protein because it prevents release of cytochrome c from the mitochondria. |
| CARMA1 | Protein | CARMA1 is a large membrane-localized scaffold protein which can form a multi-subunit complex with other proteins (MALT1m BCL10) upon phosphorylation by PKC. | |
| CD28 | GeneProduct | 940 (Entrez Gene)  | CD28 is a co-stimulatory surface receptor. It bind B7-1 and B7-2. After CD28 binds its ligand, it is phosphorylated by Lck. The effect of this phosphorylation activates P13K to generate PIP3 which recruits Itk to the cell membrane where Lck can phosphorylate it. Then Itk-P can recruit PLC-g |
| CTLA-4 | Protein | Cytotoxic T-lymphocyte-associated protein 4 | Expression is enhanced by IL-2.
Function is controlled largely by regulation of its surface expression. Initially CTLA-4 is in the intracellular membrane but moves to the cell surface after T-cell receptor signaling. When CTLA-4 cytoplasmic tail is NOT phosphorylated it binds to AP-2 (clathrin adapter molecule) and is removed from the surface. When the tail is phosphorylated AP-2 cannot bind and CTLA-4 is expressed on the surface. CTLA-4 competes with CD28 for B7 ligand, and it has a higher affinity of B7 in part because CTLA-4 binds B7 in a dimer. CTLA-4 interfers with the formation of lipid rafts, TCR:ZAP70 microclusters, and central supramolecular activation complex. |
| Ca2+ | Metabolite | Calcium ions | Calcium ions are second messengers, small-molecule biochemical mediators. Calcium is released from the ER by IP3. It diffuses throughough the cell enabling the signal to activate a variety of taget proteins. A certain calcium ion concentration must be acheived before targets can be activated. |
| Calcineurin | Protein | Calcineurin is a protein phosphatase that acts on NFAT. | |
| Calmodulin | Protein | Calmodulin is a calcium binding protein. Binding Ca ions induces a conformational change allowing calmodulin to bind to and regulate a variety of effector proteins. | |
| DAG | Protein | Diacyglycerol | Produced from PIP2 cleaveage by PLC-g. DAG is a membrane protein which can now recruit other signaling molecules to the membrane by serving as a binding target. |
| Elk-1 | Protein | Elk-1 is a TF that cooperates with another TF to initiate transcription of the FOS gene. | |
| Erk | Protein | MAPK | Erk is MAP kinase that is phosphorylated by MAPKK, Mek. SHP's and PP2A may also dephosphorylate Erk to some extent. |
| Fos | Protein | Elk-1 inititates transcription of FOS gene leading to production of Fos protein. | |
| GTP | Protein | Guanosine triphosphate | |
| Gads | Protein | Grb2-related adapter protein | an adapter protein which brings LAT and SLP-76 together, so that the conplex can recruit PLC-g Gads contains both an SH2 and an SH3 binding domain. |
| Grb2 | Protein | Grb2 is an adapter protein that binds to phosphorylated residues on LAT/SLP-76 and links to Sos | |
| IKK | Protein | IkB kinase complex | IKK is a complex of serine kinases. It phosphorylates IkB, stimulating IkB's ubiquitination which targets IkB for degradation by the proteasome. |
| IL-2 | Protein | All three TFs (NFAT, AP-1, and NFkB) a needed to initiate IL-2 transcription. | |
| IP3 | Protein | Inositol triphosphate | IP3 is generated when PLC-g cleaves PIP2. IP3 is a second messanger that diffuses into the cytosol and binds to IP3 receptors on the ER therey opening calcium channels. |
| IkB | Protein | inhibitor of kB | IkB is an inhibitory protein which when bound to NFkB holds it in an inactive state. |
| Itk | Protein | Interleukin-2-inducible T cell kinase | Itk is a membrane associated tryosine kinase. It binds to phosphorylated LAT and SLP-76 scafflods. From here is activates PLC-g by phosphorylation |
| JNK | Protein | Jun kinase | JNK phosphorylates Jun which cause AP-1 activation. |
| Jun | Protein | Jun protein associates with Fos protein to form inactive AP-1 | |
| KSR | Protein | kinase suppressor of Ras | KSR is a scaffold protein that is associates with Raf, Mek, and Erk during T cell signaling and loarcalizes itself and its cargo to the membrane. |
| LAT | Protein | Linker for Activation of T cells | LAT is a transmembrane scaffold protein. It can be phosphorylated by Zap-70. |
| LcK / Fyn | Protein | lymphcyte-specific protein tyrosine kinase (Lck) | Cytoplasmic tyrosine kinase - Lck in its inactive state is bound to CD4/CD8 cytoplasmic tail and it's terminal tyrosine is phosphorylated. Dephosphorylation of this amino acid (by tyrosine phosphotase CD45 -- CD4/CD8 binding its ligand) causes a conformations change in LcK and it becomes an active tyrosine kinase.
LcK is activated when the extracellular part of CD8 binds its (MHC:peptide) ligand. Lck is a Src family kinase that is constitutively expressed. It phosphorylates all TCR ITAMS. Rephosphorylation of this carboxyl-terminal tyrosine by Csk returns Lck to the inactive state. Basically, Lck is bound to CD8. When CD8 binds MHC:peptide, Lck gets activated and can phosphorylate nearby ITAMs. |
| Mek | Protein | MAPKK | PIP2 is a membrane lipid. |
| NFAT | Protein | PIP2 is a membrane lipid. | |
| NFkB | Protein | PIP2 is a membrane lipid. | |
| P13K | Protein | Phosphatidylinositol 3-kinase | P13K converts membrane lipid PIP2 to PIP3 by adding a phosphate. P13K activity is dependent upon CD28 co-stimulation because P13K can bind to phosphorylated ITIMs on CD28. PI3K can also bind ICOS |
| PD-1 | Protein | Programmed Cell Death 1 | PD-1 is repressed by pro-inflammatry cytokines. It's ligand, PD-L1, is constitutively expressed on T-cells. PD-1 contains a ITIM (immunoreceptor tyrosine-based inhibitory motif) in its cytoplasmic tail. When this ITIM is phosphorylated, it recruits either of 2 inhibitory phosphatases called SHP |
| PIP2 | Protein | Phosphatidylinositol 3,4-bisphosphate | PIP2 is a membrane lipid. |
| PIP3 | Protein | Phosphatidylinositol 3,4,5-triphophats | PIP3 is a membrane lipid generated from PIP2 by the enzyme P13K. PIP3 has a PH binding domain that can be recognized by PLC-g, Itk, and Atk. |
| PKC | Protein | PIP2 is a membrane lipid. | |
| PLC-g | Protein | Phospholipase C | PLC-g is a phospholipase, a class of enzymes that cleave phospholipids just before the phosphate group.
PLC-g is initially brought to the plasma membrane by binding of its PH domain to membrane lipid PIP3. PLC-g then binds to LAT and SLP-76 and can be activated by Itk mediated phosphorylation. PLC-g ultimately produces 3 different second messangers to activate 3 paths leading to different TFs that lead to IL-2 transcription |
| PP2A | Protein | protein phosphatase 2 | PP2A is a serine/threorine phosphatase which results in inhibtion of Akt thereby inhibiting CD28-mediated induction of glucose uptake, etc. PP2A may bind to CTLA-4 cytoplasmic tail and inhibit its signlaing function. Activation of TCR causes phosphorylation of PP2A when it's bound to CTLA-4. This causes PP2A to dissociate from CTLA-4's cytoplasmic tail and allow CTLA-4 signaling. |
| Raf | Protein | MAPKKK | Raf is a MAPKKK - an effector of mitogenic ras signaling |
| Ras-Gap | Protein | Ras GTPase | Ras-GAP rapidly downregulates the activity of Ras by converting its bound GTP to GDP |
| RasGRP | Protein | gunanyl nucleotide-releasing protein | RasGRP binds to DAG in the membrane where it can activate Ras |
| Ras | Protein | RAS | Ras is a small G protein of GTPase. It is located in the membrane, and it acts as a molecular switch. It is inactive when bound to GDP, but becomes active when GDP is switched for GTP. Binding the GTP induces a conformational change in Ras thus enabling it to bind to and do other things. |
| SHP | Protein | SHP-1/2 are tyrosine phosphatases. Here, SHP removes phosphates from PIP3 reverting it back to PIP2. (reverses the work of tyrosine kinase P13K) SHP is recruited to the PD-1 cytoplasmic tail when PD-1 ITIMs are phosphorylated. | |
| SLP-76 | Protein | Lymphocyte cytosolic protein 2 (also known as LCP2) | An adapter, cytosolic protein that becomes linked to LAT (after they are both phosphorylated by Zap-70) through the adapter protein Gads. |
| Sos | Protein | Guanine nucleotide exchange factor | Sos causes Ras to release GDP and bind to GTP. |
| TAK1 | Protein | kinase | TAK1 is recruited when TRAF-6 builds a ubiquitin scaffold. TAK1 phosphorylates IKK. |
| TCR | Complex | T cell receptor complex | |
| TRAF-6 | Protein | E3 ligase | TRAF-6 is an E3 ligase that bings to the CARMA1 scaffold and produces a polyubiquitin scaffold on itself and the IKKg-subunit (called NEMO) |
| Zap-70 | Protein | Zeta-chain-associated protein kinase 70 | ZAP-70 is kinase that becomes activated after phosphorylation. It contains to tandem SH2 domains that bind to phosphorylated ITAMs on the TCR complex cytoplasmic tails.
It docks at the TCR (requires both ITAM positions to be phosphorylated), is then phosphorylated by Lck, and then recruits other signaling proteins. |
Annotated Interactions
No annotated interactions
