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Receptors
1. Submitted by:
T. Sri Teja
B. Pharmacy (IV/IV)
Guided by:
P. N. Subrahmanyeswari., M.Pharm
Department of Pharmacology
Vignan Pharmacy College
Vadlamudi, Guntur (Dst), Andhra Pradesh, India ,
Pin : 522213 1
2. Contents
Vignan Pharmacy College, Vadlamudi, Guntur, A.P. 2
S.NO Table of contents Slide Number
1. Introduction 3
2. Protein Targets for Drug Binding 4
3. Ion Channels 5-6
4. Enzymes 7-8
5. Carrier Molecules 9-10
6. Receptors 11
History 12-14
7. Drug Receptor Interactions 15
8. Classification Of receptors 16-33
9. Conclusion 34
10. References 35
11. Acknowledgement 37
3. Introduction (3)
(Targets for
drug binding)
Drug or
medicament
No therapeutic
response
Shows
therapeutic
response
3Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
4. Protein Targets for Drug Binding (1,2)
Protein targets
4Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
5. Ion Channels (1,2)
Type of protein targets open only when agonist binds to receptors.
Ex:
Benzodiazepine Tranquillizers Binds to GABA receptors
Opens chloride channel
Hyper polarisation
5
Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
6. Mechanism of opening of chloride channels
6
Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
7. Enzymes (1,3)
Many drugs are targeted on enzymes.
Ex:
Captopril Acts on Angiotensin Converting Enzyme(ACE)
7
Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
9. Carrier Molecules (1,3)
These are also called Transporters.
As cell membrane is lipophillic, it requires some carriers to facilitate
the transport of ions, organic molecules etc. across the membrane.
Ex:
Nor epinephrine Transporter(NET)
9Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
11. Receptors (1,3)
Receptors are the sensing elements in the system of chemical
communication that co-ordinates the function of all different cells in the
body.
These are macro molecules.
Rece ptors
Receiving Proteins for
drugs
11
Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
12. History (1,2)
Paul Ehrlich – 20th century
John N. Langley- 1878, antagonism of Atropine
and pilocarpine.
1970- Development of Receptor-labelling techniques, helped to extract and
purify the receptor material (nicotinic R).
Extraction is done in 2 methods:
A. From electric organs of many fishes.
B. From venom of snakes of cobra family.
Extracted α-toxins
(Best is α-Bungarotoxin - Bungarus multicinctus)
12
Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
13. Postulates of Receptor Theory (2)
A J Clark – Receptor Theory.
Receptors must possess
Structural and steric specificity
Saturable and finite
High affinity for ligand at physiological concentrations
Early recognizable chemical event must occur
13
Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
14. Lock and Key Mechanism of Receptors
14Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
15. Drug-Receptor Interactions (1)
Affinity: Ability of an agent to bind with the receptors.
Efficacy or Intrinsic Activity: Ability of an agent to activate the
receptors and produce pharmacological action.
Agonist: Affinity + Maximum Intrinsic activity [I.A = +1]
Antagonist: Affinity + No Intrinsic activity [I.A = 0]
Inverse Agonist: Affinity + Negative Intrinsic activity [I .A = -1]
Partial Agonist: Affinity + Sub max. Intrinsic activity [I.A = 0.1-0.9]
15Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
16. Classification of receptors (1)
Based on
molecular
structure and the
nature of the
linkage
Receptor are
distinguished
into 4 super
families
Ligand-
gated ion
channels
G-protein
coupled
receptors
Kinase
linked
receptors
Nuclear
receptors
16Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
17. Ligand-Gated Ion Channels (Ionotropic Receptors) (1,3,4)
Structure
• Pentameric Structure,
contains 2α, β, γ, δ subunits.
• 2 Acetylcholine binding
sites between interface one
of 2α subunits.
•2 α helices are present
which are responsible for
formation of gate
•Molecular weight of each
subunit is 40-58 KDa. 17
Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
26. Location Receptor Shows Action
on
Inhibition/
Stimulation
Pharmacological
Action
Cardiac
Muscle
Gs Adenylate
Cyclase
Stimulation Increase Cardiac
output
Bronchi Gs Adenylate
Cyclase
Stimulation Relaxation &
bronchodilation
Heart Gi Adenylate
Cyclase
Inhibition Decrease force of
contraction
Uterus Gi Adenylate
Cyclase
Inhibition Contraction
Glands Gq Phospholipase C Stimulation Increase Secretions
Small
Intestine
Gq Phospholipase C Stimulation Contraction
(Motility of S.I)
26Vignan Pharmacy College, Vadlamudi, Guntur, A.P.Table:2
27. Kinase Linked Receptors (or) Enzymatic Receptors (1)
Structure:
Possess a single chain of 1000 residues
Extracellular N-terminal, Intracellular C-terminal
Here the receptors are coupled to enzymes.
These receptors are mainly helpful in Cellular growth, cell division, etc.
Types of Enzymatic receptors:
A. Receptor tyrosine Kinase
B. Serine/ Threonine Kinase
C. Cytokine Receptor
D. Guanylyl- Cyclase Kinase
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Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
29. Mechanism of receptor Tyrosine Pathway (1)
1) Binding of Ligand
2) Dimerisation
of reseptor
-OH -OH -OHTyr kinase
domain
(Janus kinase)
Phosphoryl of Tyr
O P O P
STATS
protein
O P O P STATS
protein 1) Phosphoryl. of STAT
2) Release of STAT in cytoplasma
3) STATto cell nucleus
4) Intitation of transcription
Ras
GDP
GTP
Ref
P
Mek
P
Map Kinase
P
Various Transcription
factors
P
Gene Transcription
29
Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
32. Mechanism of Action
Ligand binds to receptor
Change in Gene Expression
Synthesis of Specific Protein by mRNA
Shows Pharmacological Action
Stimulatory Inhibitory
Based on type of protein Synthesized
32
Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
33. Name of the Receptors Examples
Ligand Gated Ion Channels Nicotinic AcH Receptors
GABA Receptors
NMDA Type of glutamate Receptors
G- Protein Coupled
Receptors
Muscarnic AcH Receptors
Adreno Receptors
Opiate Receptors
Kinase Linked Receptors Growth Factors
Cytokines
Hormones like Insulin, Leptin
Nuclear Receptors Steroidal Receptors
Aldosterone Receptors
Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
33
34. Conclusion
Extensive research done on receptor pharmacology lead to discovery
of new drug targets for treatment of several diseases.
Still requires discovery of new receptor types and mechanism of
many orphan receptors that can result in effective treatment of many
diseases.
Requires development of receptor crystallization.
Must to be discovered about the nuclear receptors.
Vignan Pharmacy College, Vadlamudi, Guntur, A.P. 34
35. References:
Rang and Dale; Pharmacology; Pg.no: 20-22, 24-52
Dr. S. S. Kadam; Principles of Medicinal Chemistry; Pg.no: 43-44
KD. Tripathi; Essentials Of Medical Pharmacology; Pg.no: 37-60
Wilson And Griswold; Text Book of Organic, Medicinal And
Pharmaceutical Chemistry pg.no; 524-545, 548-580
35
Vignan Pharmacy College, Vadlamudi, Guntur, A.P.
37. Vignan Pharmacy College, Vadlamudi, Guntur dist. A.P. 37
I would like to express my gratitude to all those who gave me the
possibility to complete this seminar .
I express my sincere gratitude to my guide P.N.Subrahmanyeswari
madam, who suggested with great patience.
A special thanks to the Principal sir, Dr. P. Srinivasa Babu garu
and special thanks to Sowjanya madam and seminar committee
whose encouragement contributed immensely to complete my
seminar.