Signal Transduction and the Related Disorders Department of Pathophysiology Shanghai Jiao-Tong...
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Transcript of Signal Transduction and the Related Disorders Department of Pathophysiology Shanghai Jiao-Tong...
Signal Transduction and thSignal Transduction and the Related Disorderse Related Disorders
Department of PathophysiologyDepartment of Pathophysiology
Shanghai Jiao-Tong University School of MedicineShanghai Jiao-Tong University School of Medicine
CHAPTER 1CHAPTER 1
General Introduction of Cell Signal TransductiGeneral Introduction of Cell Signal Transductionon
Concept of Cell Signaling
The process in which cells sense the extracellular stimuli through membranous or intracellular receptors, transduce the signals via intracellular molecules, and thus regulate the biological function of the cells
Signal molecules
Physical signals Light, electronic, mechanic, UV, heat, volume or osmotic, etc
Chemical signals Hormones, neurotransmitters, Growthe factors, cytokines, odor molecules, ATP, active oxygen, drugs, toxins, etc
Endocrine: Act on a far away organ via blood circulation Paracrine: Act on a nearby target Autocrine: Act on itself after secreted Synaptic: Presynaptic to postsynaptic,
Autocrine
Endocrine Paracrine
Synaptic
Modes for the function of endogenous signals
The primary pathways of cell signalling
G-protein-mediated pathway Adenylate cyclase mediated pathway
Phospholipase mediated pathway
Small G-protein-mediated pathway
Non-G-protein-mediated pathway Receptor tyrosine kinase mediated pathway
Receptor serine/threonine kinase mediated pathway
Receptor guanilate cyclase mediated pathway
Intracellular (unclear) receptor mediated pathway
G-protein-mediated pathway
High moleular weight G-protein (trimeric GTP-binding regulatory protein)
Low moleular weight G-protein Ras
Classification of G-protein
G-proteins, coupled with members of the seven transmembrane domain of the receptor superfamily, are regulatory proteins that act as molecular switches. They control a wide range of biological processes
Regulation of G-Protein Activity
G protein-coupled receptors exhibit a common structural motif consisting of seven membrane spanning regions. Receptor occupation promotes interaction between the receptor and the G protein on the interior surface of the membrane. This induces an exchange of GDP for GTP on the G protein subunit and dissociation of the subunit from the heterodimer. Depending on its isoform, the GTP- subunit complex mediates intracellular signaling either indirectly by acting on effector molecules such as adenylyl cyclase (AC) or phospholipase C (PLC), or directly by regulating ion channel or kinase function.
Regulation of G-Protein Activity
Regulation of G-Protein Activity
Regulation of G-Protein Activity
Regulation of G-Protein Activity
G-protein-mediated pathway
Adenylate cyclase mediated pathway
Phospholipase mediated pathway
Small G-protein-mediated pathway
G-protein-mediated pathway
cAMP can activate protein kinase A(PKA), which can phosphorylate CREB ( bi
nding protein of cAMP-respones element) and initiate gene transcription.CRE is cAMP response element in DNA.
Adenylate cyclase mediated pathway
Phospholipase C mediated pathway
G-protein-mediated pathway
Non-G-protein-mediated pathway
Receptor tyrosine kinase mediated pathway
Receptor tyrosine kinases transmit signals across the plasma membrane, from the cell exterior to the cytoplasm.
The interaction of the external domain of a receptor tyrosine kinase with the ligand, often a growth factor, up-regulates the enzymatic activity of the intracellular catalytic domain, which causes tyrosine phosphorylation of cytoplasmic signaling molecules.
Receptor tyrosine kinase mediated pathway
Receptor serine/threonine kinase mediated pathway
Receptor guanilate cyclase mediated pathway
Intracellular (unclear) receptor mediated pathway
Receptor tyrosine kinases transmit signals across the plasma membrane, from the cell exterior to the cytoplasm.
The interaction of the external domain of a receptor tyrosine kinase with the ligand, often a growth factor, up-regulates the enzymatic activity of the intracellular catalytic domain, which causes tyrosine phosphorylation of cytoplasmic signaling molecules.
Receptor tyrosine kinase mediated pathway
Mechanism of Tyrosine Kinase Receptors
When hormone binds to the extracellular domain the receptors aggregate
When the receptors aggregate, the tyrosine kinase domains phosphorylate
the C terminal tyrosine residues
Mechanism of Tyrosine Kinase Receptors
This phosphorylation produces binding sites for proteins with SH2 domains. GRB2 is one of these proteins. GRB2, with SOS bound to it, then binds to the receptor complex. This causes the activation of SOS.
Mechanism of Tyrosine Kinase Receptors
SOS is a guanyl nucleotide-release protein (GNRP). When this is activated, it causes certain G proteins to release GDP and exchange it for GTP. Ras is one of these proteins. When ras has GTP bound to it, it becomes active.
Mechanism of Tyrosine Kinase Receptors
Activated ras then causes the activation of a cellular kinase called raf-1
Mechanism of Tyrosine Kinase Receptors
Raf-1 kinase then phosphorylates another cellular kinase called MEK. This cause the activation of MEK
Mechanism of Tyrosine Kinase Receptors
Activated MEK then phosphorylates another protein kinase called MAPK causing its activation. This series of phosphylating activations is called a kinase cascade. It results in amplification of the signal
Mechanism of Tyrosine Kinase Receptors
Among the final targets of the kinase cascade are transcriptions factors (fos and jun showed here). Phosphorylation of these proteins causes them to become active and bind to the DNA, causing changes in gene transcription
Mechanism of Tyrosine Kinase Receptors
Signal Transduction Through Receptor Tyrosine Kinases
(1) Type I and type II receptors for TGF(beta) in a cell prior to binding of the growth factor.
(2) Binding of growth factor results in clustering of type I and type II receptors, and phosphorylation of type I receptors by type II receptors.
(3) The activated type I receptors then phosphorylate particular receptor-mediated Smads.
(4) These Smads then bind to other Smads (co-Smads), and together they enter the nucleus.
Receptor serine/threonine kinase mediated pathway
Intracellular (nuclear) receptor mediated pathway
Basic Structure of nuclear receptor
Hormone-bindind domain
DNA-binding domain
Transcription-activating domain
The signal pathway by steroid hormones
nuclear receptor mediated pathway
The signal pathway by steroid hormones
Networks of Signal Transduction
600 G protein-coupled receptors
Multiple gene families and combinations
of G protein subunits
20G isoforms
6 G isoforms
12 G isoforms
Multiple gene families for selected effector proteins
Adenylyl cyclases
Phospholipases
Ion channels
+
+
The magnitude of amplification within this cellular cascade structure often exceeds 10+4. That is, the binding of one molecule of ligand to a cell-surface receptor leads a change of 10,000-fold in the intracellular concentration of a metabolic product.
Cascade structure of cellular signal pathways
CHAPTER CHAPTER 22
Dysfunction of cellular signal
transduction in diseases
Aberrant Signal in cell signaling
Aberrant Receptor in cell signaling
Aberrant G-protein in cell signaling
Aberrant Intracellular Signaling
Multiple Abnormalities in cell signaling
Aberrant Signal in cell signaling
ischemia, epilepsy, neurodegenerative diseases
extracellular glutamate/aspartic acid
NMDAR activation
Ca2+ influx
[Ca2+]i , activation of enzymes
excitatory intoxication
Receptor-based diseases
Alterations in number, structure or function of receptors will lead to disorder in cellular signal transdution
Up-regulation/hypersensitivity
Down-regulation/desensitization
Receptor Gene Mutation
Aberrant Receptor in cell signaling
Myasthenia Gravis is an autoimmune receptor disorder in which antibodies form against acetylcholine(Ach) nicotinic postsynaptic receptors at the neuromuscular junction
Myasthenia Gravis
Ach
The Neuromuscular Junction
AchR
anti n-AchR
influx of Na
Contraction of muscle fiber
mechanism
manifestations
Drooping of the eyelidsDouble visionDifficulty smiling, speaking, swallowingDifficulty raising the armsDifficulty walkingDifficulty breathing if chest muscle are affected
Autoimmune Thyroid Diseases
hyperthyroidism (Grave's disease)
hypothyroidism (Hashimoto's thyroiditis)
DG
hyperthyroidism
Stimulatory Ab
TSH-R
Gs Gq
AC
cAMP
Thyroid proliferation & secretion
PLC
IP3
Ca2+ PKC
hypothyroidism
Blocking Ab
TSH-R 295~302
385~395
AA residues
Binding of TSH to R↓
mechanism
manifestations
Grave's disease
Stimulatory antibodies mimic the function of TSH Stimulating thyroid hormone synthesis, secretion, a
nd thyroid growth female:male incidence -- 5:1 to 10:1diffusely enlarged goiter
Hashimoto's thyroiditis
manifestations
Inhibitory antibodies antaonize the function of TSH Inhibiting thyroid hormone synthesis, secretion, and thy
roid growth Thyroid gland is gradually destroyed Myxedema
Receptor Gene Mutation--Genetic insulin-resistant diabetes
NIDDM is a chronic metabolic syndrome defined by resistance to the hormone insulin. This leads to inappropriate hyperglycaemia (increased blood sugar levels) and deranged metabolism of carbohydrate, fats and proteins.
Diabetes Mellitus Type 1
Diabetes Mellitus Type 2
Non-Insulin dependent diabetes mellitus, NIDDM
The cause of Diabetes Mellitus Type 2 is not known, but it may involve a defect or change in the insulin receptor (IR).
mechanism
Disturbances in
synthesis
transfer to the membrane
affinity to insulin
RPTK activation
proteolysis
Genetic insulin-resistant diabetes
IR gene mutations
Diabetes Mellitus Type 2
G protein-based disease
pituitary tumor
GHRH--Growth-hormone-releasing hormone
GH--Growth-hormone
GHRHGHRH
Pituitary
GHRH Receptor
GsαGsα(+)cAMPcAMP GH secretionGH secretion(-)
somatostatinsomatostatin
GiGi
mechanism
Gs gene mutation
GTPase activity
Persistent activation of Gs
Persistent activation of AC
cAMP
Acromegaly or Gigantism
Pituitary proliferation and secretion
manifestations
G-protein modification——cholera
lumen of intestine
GsCTCTAC
cAMP ↑ ↑ ↑
Cl-H2O Na+
CT--Cholera toxin Gs ribosylation at Arg201
manifestations
Diarrhea
Dehydration
Circulation failure
Aberrant Intracellular Signaling
The intracellular signaling involves various messengers, transducers and transcription factors. Disorders can occur in any of these settings.
WNT sinal pathway
Wnt-1 was found as an oncogene activated by the Mouse Mammary Tumor Virus in murine breast cancer. APC was first isolated as a tumor suppressor gene in human colon cancer. After establishing that APC and beta-catenin bind to each other activating mutations in the human beta-catenin gene were found in human colon cancer and melanomas .These mutations alter specific beta-catenin residues important for GSK3 phosphorylation and stability .The role for Frat/GBP in cancer is illustrated by its activation by proviral insertion in mouse lymphomas. Interestingly, mutations in the human AXIN1 gene were reported in human hepatocellular carcinomas. TCF1 can also act as a tumor suppressor gene , as Tcf1 mutant mice develop adenomas in the gut and mammary glands
Cancer
Multiple Abnormalities in Signaling Pathway
In the development of diseases, the aberrant cellular signal transduction usually involves multiple molecules or pathways. Such diseases include type-2 diabetes mellitus, cancers, hypertension, and so on
Multifactor Aberrancies and Cancer (Enhancement of proliferating signals)
Ligands (GFs)
Receptors (overexpression, activation of TPK)
Intracellular transducers:
Ras mutation Ras-GTPase Ras activation Raf MEK ERK Proliferation
Cancer
Multifactor Aberrancies and Cancer (Deficits in proliferation-inhibiting signal)
Smad2 SARA
Smad2
Smad2Smad4
Smad4
P300
Fast2P300
Smad4 Smad2
Fast2
-P
-P
-P
P15、P21
Smad6,7
Cell memberane
Cytosal
Nuclear membrane
Ⅱ Ⅰ Ⅱ Ⅰ
GS
(TGF-β )2
(—)
Principles for Treatment
To regulate the level of extracellular molecules
To regulate the structure and the function of receptors
To regulate the level and modifications of intracellular
messenger molecules and transducers
To regulate the level of nuclear transcription factors
Target Therapy
Chr.9
abl
bcr
Chr.22
Chr.9+
bcr-abl
Ph
FUSION PROTEINWITH TYROSINEKINASE ACTIVITY
The Philadelphia Chromosome: t(9;22) Translocation
Structure of BCR-ABL Fusion Proteins
p210Bcr-Abl Fusion Protein Tyrosine Kinase
Extracellular space
Y177
BAP-1 GRB2
Cytoplasm
SH3 SH2 SH1
CBL SHC CRKL
Extracellular space
Y177
BAP-1 GRB2
Cytoplasm
SH3 SH2 SH1
CBL SHC CRKL
Gleevec®-Tyrosine Kinase Inhibitor
Bcr-Abl
ATP
Substrate
STI571
Y = TyrosineP = Phosphate
Bcr-Abl
Substrate
PPP
P
Bcr-Abl
ATP
Substrate
STI571
Y = TyrosineP = Phosphate
Bcr-Abl
Substrate
PPP
P
Goldman JM. Lancet. 2000;355:1031-1032.