Download - Molecular mechanism of drug action
MOLECULAR MECHANISM OF DRUG
ACTION
• Calcium &
Phosphatidyl-
inositol
• PRESENTED BY :
• SHAVYA SINGH
• M.PHARM 1ST YEAR
• (PHARMACOLOGY)
Calcium :
• Important messenger in all cells .
• Regulate diverse responses including gene
expression ,contraction, secretion, metabolism &
electrical activity.
• Calcium can enter cell through calcium channels
in plasma membrane or released by hormones or
growth factors from intracellular stores.
Types of calcium channels:
In the cell membranes their are three types of
calcium channels:
Voltage-dependent (L, N, P, Q,R, T)
Receptor operating.
Stretch activated.
Calcium channels
L-TYPE
HVA(high voltage activated)
Skeletal muscles ,smooth muscles,bone,dendrites .
P-TYPE
(HVA)
Purkinje neurons in cerebellum/cerebellar
granules cells
N-TYPE
(HVA)
Brain & peripheral nervous system
R-TYPE
Intermediate voltage activated
Cerebellar granule cells & other neurons
T-TYPE
Low voltage activated
Neurons & bones
Calcium channel blockers
• Block calcium channels (L-type) in heart and blood
vessels
• prolong depolarisation
• ↑QRS width
• block SA and AV node conduction
• heart block
• asystole
• vasodilators
• cerebral protection
Calcium channel blockers
• Hypotension
• peripheral vasodilatation and myocardial depression
• Bradycardia
• AV and SA node block
Calcium antagonists reduce coronary and
peripheral vascular resistance, decrease
blood pressure and myocardial oxygen
consumption.
Dihydro pyridines (nifedipine , amlodipine etc)
don’t have negative inotropic , chrono-
tropic and dromotropic effect in comparison to
verapamil and diltiazem, which increase
baroreflex sensibility.
Regulation of intra-cellular calcium
[Ca 2+]ext
(1000mM)
[Ca 2+]cyt
(0.1mM)
Ca 2+
ATPase
CaM
[H+]
[H+] [Na+]
[Na+]
ATPase
[K+]
[K+]
GLUCAGON
a2-ADRENERGIC
b-ADRENERGIC
VASOPRESSIN
-
[Ca 2+]m
( 0.1mM)[CaX]
( 100mmoles)
Pi
H+
[Ca 2+]er
(100mmoles)
Ca2+ATPase
REGULATION OF INTRACELLULAR CALCIUM
[Ca 2+]m [2H+]m
[2H+]c[2Na+]c
[2Na+]m
[Ca 2+]c
[Ca 2+]m
[Ca 2+]c
-180mV
DpH
0.1mM Ca2+
RUTHENIUM
RED
DILTIAZEM
MITOCHONDRIAL CALCIUM TRANSPORT
CYTOSOL
MATRIX
MATRIX CALCIUM PYRUVATE DEHYDROGENASE PHOSPHATASE
(0.8-1mM) ISOCITRATE DEHYDROGENASE
2-OXOGLUTARATE DEHYDROGENASE
PYRUVATE OXIDATION AND TCA CYCLE ACTIVITY
PYROPHOSPHATASE ACTIVITY
INCREASED PYROPHOSPHATE LEADS TO SWELLING, ACTIVATION OF
RESPIRATORY CHAIN, INCREASED ADENINE NUCLEOTIDE CONTENT AND
INCREASED ATP/ADP RATIO.
ELECTROGENICELECTRO-
NEUTRAL0.5mM
CONTROL OF CALCIUM ENTRY INTO CELLS
RYANODINE
RECEPTORS
TRP FAMILY
OF PROTEINS
(Ca2+ CHANNEL)
CIF (IP4?)
The Structure and Function of the
Calcium-Calmodulin Complex
Kinases
Phosphatases
CachannelsCa(intracellular)
Ca -calmodulin complex
Calmodulin
ATP
cAMP
MLCK*MLCK-(PO
Myosin light chain (Myosin-LC)
Myosin-LC- PO Myosin-LC
Actin
Vascular smooth muscle
Contraction Relaxation
Myosin-LC kinase (MLCK)
b agonists
Proteinkinase A
Phosphatidyl inositol
• Phosphatidyl inositol is a negatively
charged phospholipid and a minor component in the
cytosolic side of eukaryotic cell membranes.
• The inositol can be phosphorylated to form phosphatidyl
inositol phosphate (PIP), phosphatidyl inositol bi-
phosphate (PIP2) and phosphatidyl inositol tri-
phosphate (PIP3).
• PIP, PIP2 and PIP3 are collectively called
phosphoinositides.
LOCATION :
• Phosphatidylinositol is especially abundant in brain
tissue, where it can amount to 10% of the phospholipids,
but it is present in all tissues and cell types.
BIOSYNTHESIS :
• PI is formed biosynthetically from precursor cytidine
diphosphate diacylglycerol by reaction with inositol and catalysed
by the enzyme CDP-diacylglycerol inositol phosphatidyl transferase
(phosphatidyl inositol synthase )
• the other product of the reaction is cytidine mono-phosphate (CMP).
• The enzyme is located in the endoplasmic reticulum mainly,
although it may also occur in the plasma membrane in yeasts, and
almost entirely on the cytosolic side of the bilayer.
• PI is then delivered to other membranes either by vesicular transport
or via the agency of specific transfer proteins.
Types of phosphatidyl-inositol
PI-MONOPHOSPHATE
• Phosphatidylinositol 3-phosphate
• Phosphatidylinositol 4-phosphate
• Phosphatidylinositol 5-phosphate
PI-BIPHOSPHATE
• Phosphatidylinositol 3,4-bisphosphate
• Phosphatidylinositol 3,5-bisphosphate
• Phosphatidylinositol 4,5-bisphosphate
PI-TRIPHOSPHATE
• Phosphatidylinositol 3,4,5-triphosphate
Three Types of Inositol phospholipids
PI, PI(4)P, PI(4,5)P2
Phospholipase C-b
(PLC-b) Produces
DAG
(diacylglycerol) and
IP3 (inositol 1,4,5-
trisphosphate (IP3))
Gq->PLC-b
PKCACTIVE
b
g
GTP
H
PHOSPHO-
LIPASE Cb
Active
aq
P
P PIP2
P OH
PHOSPHATIDYL
INOSITOL 4,5-
BISPHOSPHATE
1,2-DIACYL
GLYCEROL
P
P IP3
P
Ca2+
ENDOPLASMIC
RETICULUM
IP3-DEPENDENT
Ca2+ CHANNEL
Ca2+
E + Cal2 + 4Ca2+ ECal2(Ca2+)4
PHYSIOLOGICAL RESPONSE
Ca2+
Ca2+
ARACHIDONIC
ACID
PHOSPHOLIPASE Cb ACTIVATION
OO P1,2-DIACYLGLYCEROL
O
O-PHOSPHATIDYLINOSITOLRAPID BREAKDOWN
FOLLWED BY RESYNTHESIS
OO P1,2-DIACYLGLYCEROL
O
O-
PHOSPHATIDYLINOSITOL-
4 PHOSPHATE
OPO32-
OO P1,2-DIACYLGLYCEROL
O
O-PHOSPHATIDYLINOSITOL-
4,5 BISPHOSPHATE1-2% OF TOTAL INOSITOL
LIPIDS
OPO32-
OPO32-
OH
OH
OHOHOH
OH
OHOHOH
OHOH
OH
SITE OF HYDROLYSIS
HYDROLYSIS OF PHOSPHATIDYL INOSITOL
4,5 BISPHOSPHATE
METABOLISM OF PHOSPHATIDYL INOSITOL
4,5 BISPHOSPHATE
OO P
O
O- OHOHOH
R1
R2OPO3
2-
OPO32-
OHOHOH
OPO32-
OPO32-
2-O3PO
OHOH
OPO32-
OPO32-
2-O3PO
OPO32-
PHOSPHOLIPASE C
PI 4,5P2
Ins (1,4,5)P3
Ins (1,3,4,5)P4
Ca2+-DEPENDENT
KINASE
R1
R2*OH
DIACYLGLYCEROL
*ARACHIDONIC
ACID
OHOHOH
OH
OPO32-
2-O3PO
Ins (1,4,)P2
OHOH
OH
OPO32-
2-O3PO
OPO32-
Ins (1,3,4)P3
PHOSPHATASE
PHOSPHATASE
PtdINS 4,5P2
(RAPID DEPLETION)
Ins 1,4,5 P3
(RAPID ACCUMULATION)
Ins 1,4 P2
(ACCUMULATION)
Ins 1 P(ACCUMULATION)
INOSITOL(SLOW ACCUMULATION)
1,2 DIACYLGLYCEROL(RAPID ACCUMULATION)
PHOSPHATIDATES(ACCUMULATES,
STIMULATED 32P
LABELLING)
PHOSPHATIDYL-CMP
Ptd INOSITOL(DEPLETED, STIMULATED32P LABELLING)
PtdINS 4,P(RAPID DEPLETION)
32P-ATP
RECEPTOR-STIMULATED BREAKDOWN
OF PHOSPHATIDYL INOSITOL 4,5 BISPHOSPHATE
STIMULUS
Ca2+ INDEPENDENTGTP
INHIBITED BY Li+
CALCIUM RELEASE BY INSOSITOL PHOSPHATES
RELEASE OF CALCIUM REQUIRES THE 4,5 PHOSPHATE
GROUPS IN THE MOLECULE
Ins1,4P2 IS INEFFECTIVE
Ins4,5P2 IS WEAK
Ins2,4,5P3 IS EFFECTIVE BUT LESS SO THAN Ins1,4,5P3
HORMONAL STIMULATION RESULTS IN THE PRODUICTION
OF TWO INOSITOL TRIS PHOSPHATES Ins1,4,5 P3 AND
Ins1,3,4 P3