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Cell Communication Single cell Multicellular organism

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Page 1: Cell Communication Single cell Multicellular organism

Cell Communication

Single cell

Multicellular organism

Page 2: Cell Communication Single cell Multicellular organism

Budding yeast cellsresponding to matingfactor

One haploid cell

Another haploid cell

Sexual mating (requires many downstream signalpathways to beactivated)

Page 3: Cell Communication Single cell Multicellular organism

GENERAL PRINCIPLES OF CELL COMMUNICATION

Extracellular signal molecules bind to specific receptors

Page 4: Cell Communication Single cell Multicellular organism

Extracellular signal molecules can act over either short or long distance

Page 5: Cell Communication Single cell Multicellular organism
Page 6: Cell Communication Single cell Multicellular organism

Autocrine signaling can coordinate decision by groups of identical cells

“Community effect” in early developmentIn tumor biology---cancer cells stimulate their own proliferation

Page 7: Cell Communication Single cell Multicellular organism

Gap junctions allow signaling information to be shared by neighboring cells

Ca2+, cAMP etc. but not for proteins or nucleic acids

Intracellular electrodes, small water-soluble dyes

Connexin 43 deficiency --- abnormal heart development

Page 8: Cell Communication Single cell Multicellular organism

Each cell is programmed to respond to specific combinations of extracellular signal molecules

Page 9: Cell Communication Single cell Multicellular organism

Different cells can respond differently to the same extracellular signal molecules

Page 10: Cell Communication Single cell Multicellular organism

The concentration of a molecule can be adjusted quickly only if the lifetime of the molecule is short

Page 11: Cell Communication Single cell Multicellular organism

Nitric oxide gas signals by binding directly to an enzyme inside the target cell

Nitroglycerine --- anginaViagra --- PDE inhibitorCO

Page 12: Cell Communication Single cell Multicellular organism

Nuclear receptors are ligand-activated gene regulatory proteins

Page 13: Cell Communication Single cell Multicellular organism

Ligand-binding domain

Page 14: Cell Communication Single cell Multicellular organism
Page 15: Cell Communication Single cell Multicellular organism

The three largest classes of cell-surface receptor proteins are ion-channel-linked, G-proteins-linked, and enzyme-linked receptors

Page 16: Cell Communication Single cell Multicellular organism

Most activated cell-surface receptors relay signals via small molecules and a network of intracellular signaling proteins

Page 17: Cell Communication Single cell Multicellular organism

Some intracellular signaling proteins act as molecular switches

2% of human genes Monomeric GTPaseTrimeric GTPase

Page 18: Cell Communication Single cell Multicellular organism

Signal integration by protein phosphorylation

Page 19: Cell Communication Single cell Multicellular organism

Intracellular signaling complexes enhance the speed, efficiency, and specificity of the response

Page 20: Cell Communication Single cell Multicellular organism

Complex forms transiently

Page 21: Cell Communication Single cell Multicellular organism

Interactions between intracellular signaling proteins are mediated by modular binding domains

Page 22: Cell Communication Single cell Multicellular organism

PDZ Domain Domain binding and function: PDZ domains bind to the C-terminal 4–5 residues of their t

arget proteins, frequently transmembrane receptors or ion channels. These interactions can be of high affinity (nM Kd). The consensus binding sequence contains a hydrophobic residue, commonly Val or Ile, at the very C-terminus. Residues at the –2 and –3 positions are important in determining specificity. PDZ domains can also heterodimerize with PDZ domains of different proteins, potentially regulating intracellular signaling. In addition to engaging in protein-protein interactions, several PDZ domains including those of syntenin, CASK, Tiam1 and FAP are capable of binding to the phosphoinositide PIP2. PIP2-PDZ domain binding is thought to control the association of PDZ domain-containing proteins with the plasma membrane.Structure Reference: Doyle, D.A. et al. (1996) Cell 85(7), 1067–1076.

The third PDZ domain from PSD-95.

www.cellsignal.com

Page 23: Cell Communication Single cell Multicellular organism

Binding Examples:

PDZ domain proteins

Binding partners domain binding sites

Post-synaptic Density Protein 95 (PSD-95)

NMDA receptor B via PDZ1 and PDZ2 of PSD-95

– IESDV-COOH

Post-synaptic Density Protein 95 (PSD-95)

Kvl1.4 Shaker-type K+ channel via PDZ1 and PDZ2 of PSD-95

– VETDV-COOH

Post-synaptic Density Protein 95 (PSD-95)

Neural Nitric Oxide Synthase (nNOS) via PDZ2

PDZ/PDZ interaction

Page 24: Cell Communication Single cell Multicellular organism

Enriched in cholesterol and glycolipids

Lipid raft

c-Src tyrosine kinase

Page 25: Cell Communication Single cell Multicellular organism

Cells can respond abruptly to a gradually increasing concentration of an extracellular signal

Chicken oviduct cells Stimulated by estradiol

effector/target : 1~16

maximal activation

Page 26: Cell Communication Single cell Multicellular organism

One type of signaling mechanism expected to show a steep thresholdlike response

Page 27: Cell Communication Single cell Multicellular organism

A cell can remember the effect of some signals

Signals trigger muscle cell determinationAutophosphorylation of Ca2+/CaM-kinase II

Page 28: Cell Communication Single cell Multicellular organism

Cells can adjust their sensitivity to a signal

Page 29: Cell Communication Single cell Multicellular organism

SIGNALING THROUGH G-PROTEIN-LINKEDCELL-SURFACE RECEPTORS

1. The largest family of cell-surface receptors2. 5% of the C. elegans genes3. Signal molecules: hormones, neurotransmitters and local medicators4. Rhodopsin-light receptor5. Genome sequencing --- vast numbers of new family members6. Major targets for drug discovery

Page 30: Cell Communication Single cell Multicellular organism

Trimeric G proteins disassemble to relay signals from G-protein-linked receptors

Transducin-G protein in visual transduction

Page 31: Cell Communication Single cell Multicellular organism

The disassembly of a activated G-protein into two signaling components

Page 32: Cell Communication Single cell Multicellular organism

The switching off of the G-protein subunit by the hydrolysis of its bound GTP

RGS proteins --- regulators of G protein signaling, act as subunit-specific GTPase activating proteins (GAPs)

~25 RGS proteins in the human genome

Page 33: Cell Communication Single cell Multicellular organism

Some G-proteins signal by regulating the production of cyclic AMP

Nerve cell culture, preloaded with a fluorescent protein that changes its fluorescence when it binds to cAMP.

>10-6 M~5 X 10-8 M

(Science 260:222-226, 1993)

Page 34: Cell Communication Single cell Multicellular organism

cAMP-dependent protein kinase (PKA) mediate most of the effects of cyclic AMP

Role of cAMP, PKA in glycogenmetabolism

Page 35: Cell Communication Single cell Multicellular organism

How gene transcription is activated by a rise in cAMP concentration

(CRE, cAMP response element)

Role of protein phosphatases?

Page 36: Cell Communication Single cell Multicellular organism

Some G-proteins activate the inositol phospholipid signaling pathway by activating phospholipase C-

(<1% of total phospholipids)

Page 37: Cell Communication Single cell Multicellular organism
Page 38: Cell Communication Single cell Multicellular organism

The two branches of the inositol phospholipid pathway

Page 39: Cell Communication Single cell Multicellular organism

Ca2+ functions as a ubiquitous intracellular messenger

Ca2+ signaling in fertilization of starfish, detected by Ca2+-sensitive fluorescence dye

Page 40: Cell Communication Single cell Multicellular organism

The main ways eucaryotic cells maintain a very low concentration of free Ca2+ in their cytosol

Page 41: Cell Communication Single cell Multicellular organism

The frequency of Ca2+ oscillations influences a cell’s response

In a liver cell

Page 42: Cell Communication Single cell Multicellular organism

Ca2+/calmodulin-dependent protein kinases (CaM-kinases) mediate many of the actions of Ca2+ in animal cells

The structure of Ca2+/calmodulin

A peptide derived from CaM-Kinase II

Page 43: Cell Communication Single cell Multicellular organism

The activation of CaM-kinases II

~2% of total mass in some brain regions, especially in synapses

It can function as a molecular memory device ---(1) Learning defect (where things are in space) in mutant mice that lack the brain-specific subunit of CaM-kinase II(2) Same defect also observed in mutant mice that have their CaM-kinase II mutated at the autophosphorylation site

Page 44: Cell Communication Single cell Multicellular organism

CaM-kinases II as a frequency decoder of Ca2+ oscillations

CaM-kinase II is immobilized on a solid surface +a brain protein phosphatase +repetitive pulse of Ca2+/calmodulin at different frequencyKinase activity assay

What a nice experiment it is!

Page 45: Cell Communication Single cell Multicellular organism

Smell and vision depend on G-protein-linked receptors that regulate cyclic-nucleotide-gated ion channels

Page 46: Cell Communication Single cell Multicellular organism

Cyclic GMPA rod photoreceptor cell

Page 47: Cell Communication Single cell Multicellular organism

The response of a rod photoreceptor cell to light

Page 48: Cell Communication Single cell Multicellular organism

Extracellular signals are greatly amplified by the use of small intracellular mediators and enzymatic cascades

Amplification in the light-induced

catalytic cascade in vertebrate rods

Page 49: Cell Communication Single cell Multicellular organism

G-protein-linked receptors desensitization depends on receptor phosphorylation

Page 50: Cell Communication Single cell Multicellular organism

SIGNALING THROUGH ENZYME-LINKEDCELL-SURFACE RECEPTORS

Six classes:

1. Receptor tyrosine kinases2. Tyrosine kinase-associated receptors3. Receptorlike tyrosine phosphatases4. Receptor serine/threonine kinases5. Receptor guanylyl cyclases6. Histidine-kinase-associated receptors

Page 51: Cell Communication Single cell Multicellular organism

Activated tyrosine kinases phosphorylate themselves

angiogenesiscell/axon migration

Page 52: Cell Communication Single cell Multicellular organism

Three ways in which signaling proteins can cross-link receptor chains

Monomeric vs. dimeric ligand

Page 53: Cell Communication Single cell Multicellular organism

Inhibition of signaling through normal receptor tyrosine kinases by an excess of mutant receptors

As a tool for determining normal function of receptor

Page 54: Cell Communication Single cell Multicellular organism

Phosphorylated tyrosine serves as docking sites for proteins with SH2 domains

Page 55: Cell Communication Single cell Multicellular organism

The binding of SH2-containing intracellular signaling proteins to an activated PDGF receptor

determine the binding specificity

Page 56: Cell Communication Single cell Multicellular organism

Ras is activated by a guanine nucleotide exchange factor

GEF: guanine nucleotide exchange factorGAP: GTPase-activating protein

In cells [GTP] > [GDP] ~10 fold

Page 57: Cell Communication Single cell Multicellular organism

The activation of Ras by an activated receptor tyrosine kinase

Page 58: Cell Communication Single cell Multicellular organism

The MAP-kinase serine/threonine phosphorylation pathway activated by Ras

Page 59: Cell Communication Single cell Multicellular organism

The organization of MAP-kinase pathway by scaffold proteins in budding yeast

Page 60: Cell Communication Single cell Multicellular organism

PI 3-kinase produces inositol phospholipid docking sites in the plasma membrane

Cell division vs. cell growthPI 3 kinase is one of the major cell growth signaling transduces

Page 61: Cell Communication Single cell Multicellular organism

The recruitment of signaling proteins with PH domains to the plasma membrane during B cell activation

SH2domain

Mutation of BTKleads to severely deficiency in Abproduction

Page 62: Cell Communication Single cell Multicellular organism

The PI 3-kinase/protein kinase B signaling pathway can stimulate cells to survive and grow

Page 63: Cell Communication Single cell Multicellular organism

Brief summarization

Page 64: Cell Communication Single cell Multicellular organism

Signal proteins of the TGF- superfamily act through receptor serine/threonine kinases and Smads

Page 65: Cell Communication Single cell Multicellular organism

Kinase catalytic domain ~250 amino acids

Page 66: Cell Communication Single cell Multicellular organism

SIGNALING PATHWAY THAT DEPEND ON REGULATED PROTEOLYSIS

1. Notch2. Wnt3. Hedgehog4. NF-kB

Page 67: Cell Communication Single cell Multicellular organism

The receptor protein Notch is activated by cleavage

In Drosophila, mutation in Delta leads to produce a huge excess of neurons at the expense of epidermal cells

Page 68: Cell Communication Single cell Multicellular organism

The processing and activation of Notch by proteolytic cleavage

Inhibit neural differentiation

Page 69: Cell Communication Single cell Multicellular organism

Wnt proteins bind to Frizzled receptors and inhibit the degradation of -catenin

(c-Myc protein)(APC, adenomatous polyposis coli,a tumor suppressor )

Page 70: Cell Communication Single cell Multicellular organism

Multiple stressful and proinflammatory stimuli act through an NF-B-dependent signaling pathway

inflammationdevelopmentcancer