g protein coupled receptors, ion channels, types of receptors, wnt signalling, cell signalling, tranduction pathway, disorders regarding the signalling

1. Signal Transduction andSignal Transduction and
the Related Disordersthe Related Disorders
RVS Chaitanya KoppalaRVS Chaitanya Koppala
Assistant professorAssistant professor
Lovely Professional University, PunjabLovely Professional University, Punjab

2. General Introduction of Cell SignalGeneral Introduction of Cell Signal
TransductionTransduction

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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 α
subunit and dissociation of the α subunit from the βγ heterodimer. Depending
on its isoform, the GTP-α 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.

9. Regulation of G-Protein Activity

10. Regulation of G-Protein Activity

11. Regulation of G-Protein Activity

12. Regulation of G-Protein Activity

14. G-protein-mediated pathway
Adenylate cyclase mediated pathway
Phospholipase mediated pathway
Small G-protein-mediated pathway

15. G-protein-mediated pathway
cAMP can activate protein kinase A(PKA), which can phosphorylate
CREB （ binding protein of cAMP-respones element ） and initiate gene
transcription.
Adenylate cyclase mediated
pathway

16. Phospholipase C mediated pathway
G-protein-mediated pathway

17. 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

18. 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

19. Mechanism of Tyrosine Kinase Receptors
When hormone binds to the extracellular domain the receptors aggregate

20. When the receptors aggregate, the tyrosine kinase domains phosphorylate
the C terminal tyrosine residues
Mechanism of Tyrosine Kinase Receptors

21. 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

22. 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

23. Activated ras then causes the activation of a cellular kinase called raf-1
Mechanism of Tyrosine Kinase Receptors

24. Raf-1 kinase then phosphorylates another cellular kinase called
MEK. This cause the activation of MEK
Mechanism of Tyrosine Kinase Receptors

25. 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

26. 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

27. Signal Transduction Through Receptor Tyrosine Kinases

28. (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

29. Intracellular (nuclear) receptor mediated pathway
Basic Structure of nuclear receptor
Hormone-bindind
domain
DNA-binding
domain
Transcription-
activating domain

30. The signal pathway by steroid hormones
nuclear receptor mediated pathway

31. The signal pathway by steroid hormones

32. Networks of Signal Transduction
600 G protein-coupled receptors
Multiple gene families and combinations
of G protein subunits
20Gα isoforms
6 Gβ isoforms
12 Gγ isoforms
Multiple gene families for selected effector proteins
Adenylyl cyclases
Phospholipases
Ion channels
+
+

33. 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

34. 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

35. Aberrant Signal in cell signaling
ischemia, epilepsy, neurodegenerative diseases
extracellular glutamate/aspartic acid
NMDAR activation
Ca2+
influx
[Ca2+
]i , activation of enzymes
excitatory intoxication

36. 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

37. Myasthenia Gravis is an autoimmune receptor disorder in
which antibodies form against acetylcholine(Ach) nicotinic
postsynaptic receptors at the neuromuscular junction
Myasthenia Gravis

38. Ach
The Neuromuscular
Junction
AchR
anti n-AchR
influx of Na
Contraction of
muscle fiber
mechanism

39. manifestations
Drooping of the eyelids
Double vision
Difficulty smiling, speaking, swallowing
Difficulty raising the arms
Difficulty walking
Difficulty breathing if chest muscle are affected

40. Autoimmune Thyroid
Diseases
hyperthyroidism (Grave's disease)
hypothyroidism (Hashimoto's thyroiditis)

41. 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

42. manifestations
Grave's disease
Stimulatory antibodies mimic the function of TSH
Stimulating thyroid hormone synthesis, secretion,
and thyroid growth
female:male incidence -- 5:1 to 10:1
diffusely enlarged goiter

43. Hashimoto's thyroiditis
manifestations
Inhibitory antibodies antaonize the function of TSH
Inhibiting thyroid hormone synthesis, secretion, and
thyroid growth
Thyroid gland is gradually destroyed
Myxedema

44. 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

45. The cause of Diabetes Mellitus Type 2 is not known, but it may involve a defect
or change in the insulin receptor (IR).
mechanism

46. Disturbances in
synthesis
transfer to the membrane
affinity to insulin
RPTK activation
proteolysis
Genetic insulin-resistant diabetes
IR gene mutations
Diabetes Mellitus Type 2

47. 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

48. mechanism
Gsα gene mutation
GTPase activity
Persistent activation of Gsα
Persistent activation of AC
cAMP
Acromegaly or Gigantism
Pituitary proliferation and secretion

49. manifestations

50. G-protein modification——
cholera
lumen of intestine
GsCT
AC
cAMP ↑ ↑ ↑
Cl-H2O Na+
CT--Cholera toxin Gsα ribosylation at Arg201

51. manifestations
Diarrhea
Dehydration
Circulation failure

52. Aberrant Intracellular Signaling
The intracellular signaling involves various messengers,
transducers and transcription factors. Disorders can occur in
any of these settings.

53. WNT sinal pathway

54. 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

55. 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

56. 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

57. 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
（—）

58. 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

59. Chr.9
abl
bcr
Chr.22
Chr.9+
bcr-abl
Ph
FUSION PROTEIN
WITH TYROSINE
KINASE ACTIVITY
The Philadelphia Chromosome:
t(9;22) Translocation

60. Structure of BCR-ABL Fusion Proteins

61. 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

62. Gleevec®-Tyrosine Kinase Inhibitor
Bcr-Abl
ATP
Substrate
STI571
Y = Tyrosine
P = Phosphate
Bcr-Abl
Substrate
P
P
P
P
Bcr-Abl
ATP
Substrate
STI571
Y = Tyrosine
P = Phosphate
Bcr-Abl
Substrate
P
P
P
P
Goldman JM. Lancet. 2000;355:1031-1032.