Cellular Signaling

Montarop YamabhaiSuranaree University of Technology

Out line

I. Principle of Cellular SignalingII. Nuclear ReceptorIII. G Protein-Couple Receptors (GPCR) and

Second MessengersIV. Receptor Tyrosine KinasesV. Other Signaling PathwayVI. Interaction and Regulation of Signaling

PathwayVII. Target intervention in Signal

Transduction

I. Principle of cellular signaling

• Extracellular signal molecules bind to specific receptors

• There are two types of receptors• There are 5 types of intercellular signaling• Identification and purification of cell surface

receptor• Responses from cellular signaling• There are three majors classes of cell-surface

receptor• Multiple steps of cell signaling • Different types of intracellular signaling proteins• Methods that are used to study protein-protein

interaction

There are two types of receptors:

Ligands that bind to intracellular receptors

Ligands that bind to cell surface receptors

• Water soluble hormone and neuro transmitters– Peptide hormones– Small charged hormones and neurotransmitters

• Prostaglandin and other eicosanoid hormones

Small molecules that function as neurotransmitters

Eicosanoid hormones

5 Types of Intercellular Signaling

1. Endocrine signaling

2. Paracrine signaling

3. Synaptic signaling

4. Autocrine signaling

5. Signaling by plasma membrane-attached proteins

Identification of cell surface receptor

Purification of cell surface receptor

Basic Components and Responses of Cellular Signaling

Activation/repression ofDNA/RNA synthesis

Chage in ion permeability

3 Types of Cell-Surface-Receptors

1. Ion-channel-linked receptors

2. G-protein-coupled receptors

3. Enzyme-linked receptors

Multi steps of signaling pathway

• Recognition of stimulus by cell surface receptor

• Transfer of signal across plasma membrane

• Transmission of the signal to specific targets inside the cells

• Cessation of the responses

Types of Signaling Protiens

1. Proteins Kinases / Phosphatases. These are proteins that involve in phosphorylation reactions

2. Proteins or GTP-binding proteins3. Adaptor and scaffold proteins

Protein Kinases & Phosphatases

Final Target

G-Protein

Accessory proteins 1. GTPase-activating proteins (GAPs)2. Guanine nucleotide-exchange factors (GEFs)3. Guanine nucleotide-dissociation inhibitors (GDIs)

Adaptor Protein

Scaffold Proteins

Detection of Protein-Protein Interaction by Yeast two-hybrid system

Detection of Protein-Protein Interaction by Phage Display Technology

Nuclear Receptor(Ligand-activated Gene Regulartory Protein)

Responses induced by the activation of a nuclear hormone

G Protein-Couple Receptors (GPCR) and Second

Messengers

1. Structure and Function of G protein-couple receptor

2. Second messengers3. The specificity of G protein-coupled

responses4. The role of G-protein-coupled receptors

in sensory perception

G protien-coupled receptor

Seven membrane spanning helices

G protein binds to guanine nucleotides, eitherGDP or GTP. It consists of three different polypeptide subunits, called , , and .

Mechanism of activation of GPCR

1. activation of the G protein by the receptor- Activation of adenylate cyclase to generate cAMP- Activation of phospholipase C to generate IP3

and DAG

2. relay of the signal from G protein to effector3. ending of the response

I. Activation of the G protein by the receptor

II. Relay of the signal from G protein to effector

III. Ending of the response

The synthesis and degradation of cAMP

-adrenergic receptors mediate the induction of epinephrine-initiated cAMP

synthesis

Agonist and of the -adrenergic receptors

-Epinephrine-isoproterenol

Antagonist of the -adrenergic receptors

-Alprenolol-Propranolol-Practolol

Hormone-induced activation and inhibition of adenylate

cyclase

Activation of cAMP-dependent protein kinase (PKA) by cAMP

Table 1

A sample of known PKA substrates

• Muscle glycogen synthase (Ia)• Phosphorylase kinase • Protein phosphatase-1• Pyruvate kinase• CREB• Liver tyrosine hydroxylase• Acetylcholine receptor • Protein phosphatase inhibitor -1• S6 ribosomal proteins• Rabbit heart troponin• Hormone sensitive lipase• Phosphofructokinase• Myosin light-chain kinase• Fructose biphosphatase• Phosphorylase kinase • Musle glycogen synthase• Acetyl CoA carboxylase

A variety of responses from cAMP signaling

• Plasma membrane: transport• Microtubule: assembly and disassembly• Endoplasmic recticulum: protein synthesis• Nucleus: DNA synthesis, gene expression• Mitochondria and cytosol: glycogen break

down (phosphorylase) in liver, glycogen synthase, triglyceride lipase (fatty acid formation in fat cells

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Activation of gene transcription by a rise in cAMP

Regulation of glycogen breakdown and synthesis by cAMP in liver and muscle cells

The role of cAMP in glucose metabolism in liver cells

Amplification of the signal via cAMP signaling pathway

The generation of phosphatidyl inositol-derived second messengers

Protein Kinase C (PKC) is activated by inositol phospholipid pathway

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Elevation of Ca2+ via the inositol lipid signaling pathway

Table 20-4. Cellular Responses to Hormone-Induced Rise in Inositol 1,4,5-Trisphosphate (IP3) and Subsequent Rise in Cytosolic Ca2+ in Various Tissues

Tissue Hormone Inducinga Rise in IP3

Cellular Response

Pancreas (acinar cells)

Acetylcholine Secretion of digestive enzymes, such as amylase and trypsinogen

Parotid (salivary gland)

Acetylcholine Secretion of amylase

Pancreas ( cells of islets)

Acetylcholine Secretion of insulin

Vascular or stomach smooth muscle

Acetylcholine Contraction

Liver Vasopressin Conversion of glycogen to glucose

Blood platelets Thrombin Aggregation, shape change, secretion of hormones

Mast cells Antigen Histamine secretion

Fibroblasts Peptide growth factors, such as bombesin and PDGF

DNA synthesis, cell division

Sea urchin eggs Spermatozoa Rise of fertilization membrane

SOURCE: M. J. Berridge, 1987, Ann. Rev. Biochem. 56:159; M. J. Berridge and R. F. Irvine, 1984, Nature

Ca2+ Calmodulin mediates many cellular responses

The specificity of G protein-coupled responses

• GPCRs link to different G protein

• G protein regulate different effector proteins

Table 20-5. Properties of Mammalian G Proteins Linked to GPCRs

G Subclass Effect Associated Effector Protein 2nd Messenger

Gs Adenylyl cyclase cAMP

Ca2+ channel Ca2+

Na+ channel Change in membrane potential

Gi Adenylyl cyclase cAMP

K+ channel Change in membrane potential Ca2+ channel Ca2+

Gq Phospholipase C IP3, DAG

Go Phospholipase C IP3, DAG

Ca2+ channel Ca2+

Gt cGMP phosphodiesterasec GMP

G Phospholipase C IP3, DAG

Adenylyl cyclase cAMP

The specificity of G protein-coupled responses

G protein in receptor sensory

Response of a rod photoreceptor cell to light

Receptor Tyrosine Kinases (RTKs)

Activation of RTKs

Ras function downstream of RTKs

Activation of Ras by RTKs

Ras activate MAP Kinase Cascade

Insulin Signaling Pathway

IV Other Signaling Pathways

• Other enzyme-linked signaling pathway– Jak-STAT signaling pathway– TGF-b signaling pathway

• Signaling pathways that depend on regulated proteolysis– Wnt signaling pathway– TNF-a signaling pathway

• Nitric oxide signaling pathway• Apoptotic pathway• Signaling from contacts between cell

surface and the substratum

Activation of Jak-STAT pathway by Cytokine Receptors

TGF- Pathway

Wnt Signaling Pathway

TNF- signaling Pathway

Nitric Oxide (NO) Signaling

Apoptotic Pathway

Signaling from contacts between cell surface and the substratum