Post on 03-Jan-2017
Chapter 15
Cellular Signal Transduction
The biochemistry and molecular biology department of CMU
When environment changes: Monad——responds directly.
Multicellular organisms——signal through elaborate system of intercellular or intracellular communication , and consequently regulate functions of organisms.
Signaling molecule
Receptor of target cell
Intracellular molecule
biological effect
Signaltransduction
§1 Signaling Molecules
Signaling molecules
• Signaling molecules, which are released by signal-producing cells, reach and transfer biological signals to their target cells to initiate specific cellular responses.
• Extracellular molecules
• Intracellular molecules
1. Extracellular moleculesprotein & peptides: Hormone, cytokine
AA & its derivatives: Gly, Glu, adrenaline, thyroxine
Steroid: Sex Hormone, glucocorticosteroid
Fatty acid derivatives: prostaglandin
(1) Paracrine signaling (local chemical mediators)• Secreted by common cells.• Reach neighboring target cells by
passive diffusion.• Time of action is short.• Such as GF, PG
(2) Endocrine signal
• Secreted by endocrine cells.• Reach target cells by blood circulation.• Time of action is long.• Such as insulin, thyroxine, adrenalin
(3) Synaptic signal (neurotransmitters)
• Secreted by neuronal cells.• Reach another neuron by synaptic ga
p.• Time of action is short.• Such as Acetylcholine (Ach), noradren
aline
(4) Gaseous signal
• Simple structure, half life is short and active in chemistry .
• Such as NO, CO.
GAS MOLECULE
(5) Autocrine signal
• Act back to their own cells.• Such as GF, cytokine, interferon,
interleukin.
2. Intracellular molecule• Ca2+ ions
• DG, ceramide lipid derivatives• IP3 carbohydrate derivatives
• cAMP cGMP nucleotides
• Ras, JAK, Raf proteins
Second messenger: Small molecules synthesized in cells
in response to an external signal are the second messengers, which are responsible for intracellular signal transduction.
Such as Ca2+, DG, Cer, IP3, cAMP, cGMP
Third messengers:
Third messengers are the molecules which transmit message from outside to inside of nucleous or from inside to outside of nucleous, also called DNA binding protein.
Effect by membrane receptors
Effect by intracellular receptors
Intracellular molecules
Extracellular molecules
Signal molecules
cAMP, cGMP, IP3, DG, Ca2+
Proteins and peptides:Hormones, cytokines
Amino acid derivatives:Catecholamines
Fatty acid derivatives:Prostaglandins
Steroid hormones, Thyroxine, VD3
§2 Receptor
Receptor Receptors are specific membrane protei
ns, which are able to recognize and bind to corresponding ligand molecules, become activated, and transduce signal to next signaling molecules.
Glycoprotein or Lipoprotein
ligand A small molecule that binds specifi
cally to a larger one; for example, a hormone is the ligand for its specific protein receptor.
• Membrane receptors
membrane
Glycoprotein
• Intracellular receptors
Cytosol or nuclei
DNA binding protein
(1) Ligand-gate ion channels type
(cyclic receptor)
ligand→receptor→ion channel open or close
1. membrane receptors
1) 7-helices transmembrane receptor
(2) G Protein-Coupled Receptors (serpentine R)
Cytosolicside
Oligosaccharideunit
• G protein refers to any protein which binds to GDP or GTP and act as signal transduction.• G proteins consist of three different subunits (, , -subunit). • -subunit carries GTPase activity, binding and hydrolysis of GTP.
2) G protein (Guanylate binding protein)
Gs→ s→AC→cAMP↑
Gi→ i→AC→cAMP↓
Gq→ q →PI-PLC→IP3+DAG
Go→ o→ion channel
Gt→ t →cGMP PDE→cGMP→ Rhodopsin
3) Classes of G protein
Glucagon
-adrenaline →s →AC↑
ACTH -adrenaline
angiotensin Ⅱacetylcholine(M2 M4)
GF release inhibitory factor
→i→AC↓
Ribosylation of Arg of G
G s -ATP Gs -ADP
AC
cAMP Cl- + H2O Cavity of intestinediarrheaHCO3
-
Cholera toxin
ATPase
Pertussis toxin
i -ADP-ribosylation
Gi
AC↑
allergy of histamine
cAMP ↑
AC
cGMP PDE (phosphodiesterase ) PLC
PLA2
Channel protein
4) Effect proteins of G protein
cAMP
ATP
5) Pathway of G protein linked receptor
H R G protein Es
secondary messeger
Protein kinase
Phophorylation of Es or functional protein
Biological effect
(3) Single transmembrane α-helix receptor
• Tyrosine protein kinase Receptor (catalytic receptor)
IGF - R, EGF - R
• Non tyrosine protein kinase Receptor Growth Hormone R, interferon R
Tyrosine protein kinase Receptoror receptor tyrosine kinase (RTK)
Cys-richdomain
Immunoglobulin-like
domain
EGFR IGF-1R PDGFR FGFR
Intracellularinsulin effectsCytosol
Insulin
Non-receptor tyrosine kinase (NRTK)
Domain of Downstream molecules of TPKR
SH2 domain (Scr homology 2 domain)
SH3 domain
PH domain (pleckstrin homology domain)
Membrane receptor –ANP
Soluble receptor – NO, CO
(4) Guanylate cyclase (GC) receptor
2. Intracellular receptor (transcription regulated recepto
r) Intracellular R is trans-acting
elememt cis-acting element gene expression
Localized in the cytosol and/or in the nucleus.
ligand: Steroid H, VD3, Thyroxine
3. Properties of binding of H and R
• highly specificity
• highly affinity
• saturation
• reversible binding
• special function model
4. Control of receptor activity
• Phosphorylation or dephosphorylation of R
• Phospholipid of membrane
• Enzyme catalyzed hydrolysis
• G protein regulation
(1) Recognize the special ligand
(2) Binding to special ligand
(3) Signal transduction biological effect
5. Function of receptor
§3 Pathway of Signal Transduction
Signal transduction mediated by membrane receptor
• cAMP dependent-protein kinase A pathway
• cGMP dependent PKG pathway • Ca2+ dependent PK pathway • Tyrosine protein Kinase pathway• NF-κB pathway • TGF- βpathway
1. cAMP dependent-protein kinase A pathway
H R
G protein
Phosphorylation of Es or functional proteins
Biological effects
PKA
cAMPAC
(1) cAMP metabolism
ATPMg2+
PPi
cAMP
H2OMg2+ 5'-AMP
AC PDE
AC : Adenylate cyclase
PDE : Phosphodiesterase
PDE
H2O
N
N N
N
NH2
O
HOHOH
CH2
HH H
OPO
O
O
PO
O
O
P
O
O
O ATP
ACPPi
N
N N
N
NH2
O
HOHO
CH2
HH H
O
PO
O
cAMP
N
N N
N
NH2
O
HOHOH
CH2
HH H
OPO
O
O
5'-AMP
(2) Mechanism of cAMP effect
Activate cAMP-dependent protein kinase (PKA).
(3) PKA effect
Phosphorylate specifically Ser/Thr residues in several proteins
( 1 ) Regulation of metabolism
( 2 ) Regulation of gene expression
hormons: glucagon, epinephrine
inactive AC active AC
ATP cAMP
inactive PKA active PKA
phosphorylase b kinase
phosphorylase b kinaseP
ATP
ADP
H2O
Pi
phosphorylase b
P
P
ATP ADP
Pi
H2OATP ADP
glycogen synthase
glycogen synthase
P
H2OPi protein phosphatase-1
(active) (inactive)
inhibitor-1 (active)
inhibitor-1 (inactive)
phosphorylase a
ATP
CRE : cAMP response element (TGACGTCA)
CREB: CRE binding protein
DNACRE
CREBPKA
P
TranscriptionmRNA
CREBPKA
PCREB P
CREBP
CR
EB
P
CREBP
CR
EBP
CR
EB
P
2. Ca2+ dependent PK pathway (1) Ca2+ -DAG -dependent PKC pathway
H RPIP2
G protein PLC
IP3 DG ER
PKCCa2+ PS
Biological effects
Phosphorylation of Es or functional proteins
[Ca 2+]i 0.01-1 mol/L ( 10-7 mol/L )[Ca 2+]o 2.5mmol/L ( 10-3 mol/L ) 5000~10000×
1 ) Function of DG and IP3
IP3 + R→open of Ca2 + channel →[Ca2 + ]↑
PS, Ca2 +DG PKC ↑
2 ) Function of PKC
• regulation of metabolismPKC →Ser/Thr-P of R, enzyme,
Protein of Mb. • Gene expression
Late response:
Trans-acting factor-P
Third messengerImmediate early genes
Third messenger-P
Activate genes
Cell proliferation
PKC
PKC
Early response:
(2) Ca2 + -CaM dependent protein kinase pathway
H R G protein PLC
IP3
Ca2+ CaM
CaMK
Biological effects
Phosphorylation of Es or functional proteins
Calmodulin (CaM ): Ca2 + binding protein
4 Ca2 + + CaM → Ca2 + - CaM
↓ CaM kinase↑
↓ Ser/Thr - P ↓
Ca2 + pump, AC ↑ GC ↑ Es (glycogen synthase, phosphorylase
kinase)
3. cGMP-dependent PKG pathway
Biological effects
Phosphorylation of Es or functional proteins
ANPNO, CO
Soluble GC
PKG
cGMPReceptor-linked GC
(1) cGMP
(2) Function of PKG Ser/Thr- P of protein and E
Mg2+
PPi H2OMg2+GTP cGMP 5'-GMP
GC PDE
GC: Guanylate cyclase
ANP ( atrial natriuretic peptides ) ↓ GC NO ↓ cGMP ↓ PKG ↓ Vascular dilatation
cis-acting elementnucleus
expression
cell memberane
phosphorylation of enzymes or proteins effects
CaM-PK
Ca2+-CaMCa2+
IP3 DGcAMP cGMP
PKA PKG PKC
ATP GTP PIP2(PC)
G AC GC G PL
peptide hormonesneurotransmitters AFP
neurotransmittershypothalamic pituitrin
Ptrans-acting factor
4. Tyrosine-protein kinase pathway (TPK)
• TPK receptor is related to proliferation, differentiation, dissociation, carcinomatous change.
• TPK :receptor TPK : Mb.non receptor TPK : cytosol
(1) Receptor TPK - Ras - MAPK pathway
• GRB2, SOS, Ras, Raf• Small G protein: Ras• MAPK (mitogen-activated protein kinas
e) :MAPK 、 MAPKK 、 MAPKKK
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EGF, PDGF
receptor TPK Ras - GTPSOS - PGRB2 - P
Raf - P
MAPKK - P
MAPK - Ptrans-acting factor
expression
nucleus
- P
(2) JAKs - STAT pathway
ligand
non TPK receptor
JAKs STAT
gene expression
• JAKs• STAT: Signal transductors and activa
tor of transcription
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JAK
11391
84
48
113P
91P 84 P
48
113
91 84P P
P
interferons
inactive STAT
Plasma membrane
STAT complex
Nuclear membrane
geneInterferons response element
transcription
Dimerization of Receptor
Interferon
Autophosphorylation of JAK
Phosphorylation of STAT
Nuclear translocation of STAT
Interferon response element
Expression of gene
5. Nuclear factor-κB pathway
6. TGF-βpathway
Intracellular receptor (DNA transcription regulated
receptor)
• Steroid H, VD3, Thyroxine
• Cytosolic R: glycocorticosteroid H
• Nuclear R: thyroxine, estrogen, androgen, progesterone
Serum binding proteinWith bound bormone