CYTOKINE RECEPTORS CYTOKINE RECEPTORS AND SIGNAL AND SIGNAL

TRANSDUCTIONTRANSDUCTION

Survival factorSurvival factor(eg. IGF-1)(eg. IGF-1)

ChemokinesChemokinesHormonesHormonesTransmittersTransmitters(e.g. Interleukins(e.g. Interleukinsserotonin etc.)serotonin etc.)

Growth factorsGrowth factors(eg TGFa) (eg TGFa)

ExtracellularExtracellularmatrixmatrix

WntWnt

Hedgehog Hedgehog

Death factorsDeath factors(eg TNF)(eg TNF)

Cytokines Cytokines

What is Cytokine? What is Cytokine?

Secreted polypeptide or low molecular weight protein involved in cell-to-cell signaling.

Acts in paracrine or autocrine fashion through specific cellular receptors.

Can be produced by cells of any tissue and act on many cells involved in immune and inflammatory response.

Cytokines, like hormones, can Cytokines, like hormones, can act in autocrine, paracrine, or act in autocrine, paracrine, or

endocrine fashionendocrine fashion

Cytokine nomenclatureCytokine nomenclature LymfokinesLymfokines - produced by activated T lymphocytes direct the immune system response by signaling between its cells

InterleukinsInterleukins -- presumed targets are principally leukocytes.

ChemokinesChemokines - specific class of cytokines. Mediates

chemoattraction (chemotaxis) between cells, stimulate leukocyte movement and regulate the migration of leukocytes from the blood to tissues.

MonokinesMonokines - derived primarily from mononuclear cells such as macrophages.

Cytokines: main functions Cytokines: main functions HematopoiesisHematopoiesis (ex. CSFs, colony stimulating factors). Inflammatory reactionInflammatory reaction (ex. IL1, TNF). ChemotaxisChemotaxis (ex. IL8, MIP1- macrophage inflammatory protein 1,

BLC – B-lymphocyte chemoatractant). ImmunostimulationImmunostimulation (ex. IL12, IFN). SuppressionSuppression (ex. IL10). AngiogenesisAngiogenesis (ex. VEGFs - vacsular endothelial growth factor). EEmbryogenesismbryogenesis (ex. TGF-, LT - lymphotoxin).

Type I cytokine receptorType I cytokine receptor oror hematopoietinhematopoietin receptorreceptor familyfamily : : IL 2, IL 3, IL 4, IL 5, IL 6, IL7, IL 9, IL 13, IL 15, GM-IL 2, IL 3, IL 4, IL 5, IL 6, IL7, IL 9, IL 13, IL 15, GM-CSFCSF (G(Granulocyte-ranulocyte-MMacrophage Colony-Stimulating Factoracrophage Colony-Stimulating Factor)) and G-CSF and G-CSF ((Granulocyte-Colony Stimulation FactorGranulocyte-Colony Stimulation Factor))

Type II cytokine receptorsType II cytokine receptors or or interferoninterferon receptorsreceptors

Transforming gTransforming growth factorrowth factor receptorreceptor Tumor necrosis factorTumor necrosis factor receptor receptor IImmunoglobulin superfamilymmunoglobulin superfamily (IgSF) (IgSF) ChemokineChemokine receptorsreceptors (seven transmembrane helix) (seven transmembrane helix)

Classification Classification

Type I cytokine receptorType I cytokine receptor

Transmembrane receptorsTransmembrane receptors expressed on the surface of expressed on the surface of cellscells..

These receptors are also These receptors are also known under the name known under the name hematopoetin hematopoetin receptorsreceptors, , and share a and share a Trp-Ser-X-Ser-Trp-Ser-X-Ser-TrpTrp motif ( motif (WWSSXXWWSS) in the ) in the extracellular portion extracellular portion adjacent to the cell adjacent to the cell membrane. membrane.

Common Common chain chain

The The chain (green), common to all, mediates chain (green), common to all, mediates intracellular signaling.intracellular signaling.

Signaling through cytokine receptorSignaling through cytokine receptorPhosphorylation through kinases: The addition of a phosphate molecule to a polar R-

group of Tyr can turn a hydrophobic portion of protein into a polar and extreme hydrophilic portion of molecule.– Kinase is a type of enzyme that transfers phosphate group

(PO4) from high-energy donor molecules, such as ATP to specific target molecules (substrates).

– The opposite, an enzyme that removes phosphate groups from targets, is known as a phosphatase.

– Kinase enzymes that specifically phosphorylate tyrosine amino acids are termed tyrosine kinases.

Signaling through cytokine receptorSignaling through cytokine receptor

The ligand-activated receptor (The ligand-activated receptor (RR) attracts a Janus (JAK) kinase () attracts a Janus (JAK) kinase (KK). ). KK phosphorylates both phosphorylates both itself and the receptor. A itself and the receptor. A SSignal ignal TTransducer and ransducer and AActivator of ctivator of TTranskription (STAT) protein (ranskription (STAT) protein (SS) ) binds to tyrosine-phosphorylated receptor-kinase binds to tyrosine-phosphorylated receptor-kinase ccomplex. After being phosphorylated by omplex. After being phosphorylated by JAK, the STATs form JAK, the STATs form active dimersactive dimers that translocate into the nucleus to regulate transkription. that translocate into the nucleus to regulate transkription.

Protein hormones with antiviral activity.

Secrete by cells in a response to variety of stimuli.

Type I and type II IFN and IFN-like cytokines.

Effects are mediated through cell receptors.

IFN activate cellular signalling pathway (gene induction or repression).

Type II cytokine receptorsType II cytokine receptors

Interferons (IFN)Interferons (IFN)

Type I IFNs consist of seven classes:IFN-, IFN-, IFN-, IFN-, IFN- IFN-and

IFN-

Type I IFNs are major components of the innate immune system. Protect against viral infection. The expression of type I IFNs is induced by viral challenge.

Type II IFN consist of IFN- only.

IFN- (immune interferon) is produced by certain activated T-cells and NK cells. IFN- is made in response to antigen (including viral antigens) or mitogen stimulation of lymphocytes.

Type I IFNsType I IFNs Produced by macrophages, neutrophils and other somatic cells in response to infection by viruses or bacteria.  Inducer is double strand RNA provided by viral genom itself. Receptors are expressed on most cell types.

IFN-IFN- IFN- is produced in activated TH1 and NK cells,

particularly in response to IL-2 and IL-12.  Binding of IFN- to its receptor increases the expression of class I MHC on all somatic cells.  IFN- may also activate macrophages, neutrophils and NK cells.

Initiation and regulation of variety responses

antiviral

antiproliferative activity (ability to arrest cell growth) – treatment for cancer

control of apoptosis

immunomodulatory (INF- predominantly modulates immune response, main antiviral cytokine).

Function of IFNs:Function of IFNs:

http://www.virtualsciencefair.org/2007/sank7b2/fig1b.jpg

IFN-IFN- receptor receptor

Expression of on the surface almost of all cell types.

High affinity receptors are located in the T- and B-lymphocytes, NK-cells, monocytes, macrophages, neutrophiles, fibroblasts, endotelial cells and smooth muscle cells.

Receptor is expressed only in response to stimulus by antigen, only in cells of lymphoid origin (NK cells, macrophages, and some T cells).

IFN- R2 - 62 kDa glycoprotein (315 amino acid residues)Extracellular domain – 226 amino acid residuesTransmembrane domain – 23 amino acid residuesIntracellular domain – 65 amino acid residues.

Ligand binds to extracellular domain of IFN-R1 only (in absence of IFN-R1, IFN-R2 cannot bind IFN

IFN-R1 - 90 kDa glycoprotein (472 amino acid residues)Extracellular domain – 228 amino acid residuesTransmembrane domain – 24 amino acid residuesIntracellular domain – 220 amino acid residues

IFNreceptor has two components:R1 and R2

JakJak proteins are brought into close after ligand-receptor complex formation. Transphosphorylation between Jak1Jak1 and Jak2Jak2 proteins (Jak2 Jak2 phosphorylates Jak1Jak1, Jak1Jak1 transphosphorylates Jak2Jak2). phosphorylation of IFN-R1 (TyrTyr 440440). Binding of STAT1STAT1 protein to each IFN-R1. Bound SSis phosphorylated by Jak. Dissociation of dimer from the receptor and formed dimer translocates to the nucleus. Induction of transcription of many genes.

Signal transduction is carried out through a series of tyrosine phosphorylation events and culminates with the activation and nuclear translocation of STAT protein and new mRNA synthesis is induced.

IFNIFN rreceptoreceptor

IFN-R1 - 530 amino acid residues (409 residues of protein are extracellular, 100 residues are intracellular.

IFN-R2 - 217 AA residues in extracellular space, 251 AA residues in intracellular space.

Both components bind type-IFNs cooperatively. Receptor has ability to bind multiple ligands (all subspecies of IFN- and IFN- and other types of IFN-type I). Interferon ligand is boud to IFN-R1 and than to IFN-R2 which stabilizes the complex.

Tyk2 associates with IFN-R1Jak1, STAT1 and STAT2 associate with IFN-R2.

Jak1 transphosphorylates Tyk2 (1). Tyk2 in turn phosphorylates Jak1 and IFN-R1 (2).

Phosphorylation of IFN-R1 allows STAT2 to bind to IFN-R2.

STAT2 phoshorylates STAT1.

STAT1-STAT2 complex dissociates from receptor.

Dimer STAT1-STAT2 associates with interferon regulatory factor to form the transcription complex.

Signal transduction goes through Jak/STAT pathway.Signal transduction goes through Jak/STAT pathway.Involves two different ligand binding proteins Involves two different ligand binding proteins (kinases)(kinases)

Tyk2 and Jak1.Tyk2 and Jak1.

Induces inflammatory reaction.

Induces antibacterial effect (activation of neutrophils, NK cells and macrophages, increased their ability to recognize, kill, and digest foreign materials or microbes).

Normal expression of is important in preventing the development of cancer.

Effect of signalling through IFN-Effect of signalling through IFN- receptor receptor

Effect of signalling through IFN-Effect of signalling through IFN-// receptor receptor

Antiviral defence (protects the cell from viral replication).

IImmunoglobulin superfamilymmunoglobulin superfamily (IgSF) (IgSF)

The The immunoglobulin superfamilyimmunoglobulin superfamily (IgSF) (IgSF) -- a large group of cell surface and soluble a large group of cell surface and soluble proteins that are involved in the recognition, proteins that are involved in the recognition, binding, orbinding, or adhesionadhesion processes of processes of cells.cells.

Molecules are categorized as members of Molecules are categorized as members of this this superfamilysuperfamily based on shared structural based on shared structural features withfeatures with immunoglobulinsimmunoglobulins ( (antibodies); antibodies); they all possess a domain known as an they all possess a domain known as an immunoglobulin domain or fold.immunoglobulin domain or fold.

AAssociated with roles in the immune ssociated with roles in the immune system. system.

Tumor Tumor NNecrosis ecrosis FFactoractor receptor receptor

Typical structure of a Typical structure of a chemokine receptorchemokine receptor, , with seven transmembrane domains. with seven transmembrane domains. Chemokine receptors are usually linked to a Chemokine receptors are usually linked to a G-proteinG-protein through which they signal. through which they signal. Interaction with their specific chemokine Interaction with their specific chemokine ligand, chemokine receptors trigger a flux in ligand, chemokine receptors trigger a flux in intracellular calcium (Ca2+) ions (calcium intracellular calcium (Ca2+) ions (calcium signaling) and cause cell response signaling) and cause cell response (chemotaxis). (chemotaxis).

http://en.wikipedia.org/wiki/Chemokine_receptorhttp://en.wikipedia.org/wiki/Chemokine_receptor

CysteineCysteine-rich-rich common extracellular common extracellular binding domain binding domain

Chemokine receptorChemokine receptor

www.nature.com/.../v2/n8/fig_tab/nrc866_F3.html

After ligand binding, After ligand binding, ((PDGFR or PDGFR or EGFR receptor tyrosine kinases (RTKs) EGFR receptor tyrosine kinases (RTKs) dimerize,dimerize, undergo autophosphorylation undergo autophosphorylation ((PP) and recruit adaptor proteins (such ) and recruit adaptor proteins (such as as GRB2 GRB2 and and SHCSHC) that activate ) that activate various downstream effectors. various downstream effectors.

RASRAS is an important is an important downstream downstream effectoreffector and functions as a molecular and functions as a molecular switch by cycling between the active switch by cycling between the active GTP-bound form and the inactive GDP-GTP-bound form and the inactive GDP-bound form. RAS activity is regulated bound form. RAS activity is regulated positively by positively by guanosine exchange guanosine exchange factorsfactors ( (GEFsGEFs), such as ), such as SOSSOS, and , and negatively by negatively by GTPase-activating GTPase-activating proteinsproteins ( (GAPsGAPs).).

At least three downstream effectors At least three downstream effectors can be activated by RAS. The can be activated by RAS. The RAFRAF--mediated signalling cascademediated signalling cascade..

Transforming GTransforming Growth rowth Factor ReceptorFactor Receptor

The EndThe End

Thank you