Secondary massenger

1. SECONDARY
MESSANGERS
Presented by :- Bharti Bhardwaj and Mayank Saini,
Under the guidance of Dr. Sarita Sharma
Maharishi Markandeshwar (Deemed to be
University), Mullana , Ambala

2. INTRODUCTION
Cells communicate by chemical messengers called as Signal
transduction. When a chemical messenger bind with another cell
receptor, so inside the cell there is a system which pass the
message from “receptor to the target proteins” is called as
Intracellular signaling (IS) or secondary messenger system.
There are main 4 steps in intracellular signaling, which are :-
• Binding of the ligand with receptor
• Activation/inactivation occur during downstream of receptors,
also called as “cascade of events”
• Signal reached to the target proteins
• Initiation of response

3. • INTEGRATION
• AMPLIFICATION
OTHER FUNCTIONS OF IS :
One upstream molecule can activate or
generate multiple downstream messengers.
The signal is amplified towards the target
protiens.
The 2nd messenger system allows to converge
or diverge the signals from the 1st messenger.
a) Different ligand receptor combination may
activate the same intracellular signaling
pathway and thereby affect the same
response. Ex. epinephrine and glucagon
cAMP pathway
b) It also allow diversifying responses from
the same first messenger. Ex. acetylcholine
act on
heart cell and pancreas.
a
)
b
)

4. SECOND MESSENGER SYSTEMS IN SIGNAL TRANSDUCTION
On the other hand, “hydrophilic or polar ligands” such as amino acid-
derived hormones cannot pass through the plasma membrane so they
need to transmit the signal to other receptors or messengers through a
process called signal transduction.
“Small and hydrophobic or nonpolar ligands” including steroid
hormones like testosterone and progesterone can permeate the
hydrophobic interior of the plasma membrane so they can bind to
intracellular receptors (or internal receptors) in the cytoplasm and
directly influence DNA.
So, there are Water-soluble second messengers like cAMP which diffuse
through the cytosol, while lipid-soluble second messengers like
diacylglycerol (DAG) diffuse through the inner region of the plasma
membrane where other signaling proteins are embedded.

6. Cyclic adenosine monophosphate (cAMP) is an example of
a second messenger. cAMP is produced by adenylyl
cyclase–an enzyme embedded in the plasma membrane–
from adenosine triphosphate (ATP).
THERE ARE 3 MAJOR CLASSES OF SECOND MESSENGERS :
• cyclic nucleotides (e.g. cAMP and cGMP)
• inositol triphosphate (IP3) and diacyclglycerol (DAG)
• calcium ions (Ca2++)
• Binding of the hormone to its receptor activates
• a G protein which, in turn, activates
• adenylyl cyclase.
• The resulting rise in cAMP turns on the appropriate response in the cell
by either (or both):
⚬ changing the molecular activities in the cytosol, often using Protein
Kinase A (PKA) — a cAMP-dependent protein kinase that
phosphorylates target proteins
⚬ turning on a new pattern of gene transcription
• CYCLIC AMP (cAMP)

7. Cyclic guanosine monophosphate is a cyclic nucleotide
that is synthesised by guanosine triphosphate (GTP) with
the help of the guanylate cyclase enzyme.
Its production is triggered by stimulation of soluble guanylyl cyclase (sGC).
cGMP-induced effects are regulated by endogenous receptor ligands
such as nitric oxide (NO) and natriuretic peptides (NPs).
Once produced cGMP can have a number of effects in cells, but many of
those effects are mediated through the activation of protein kinase G
(PKG).
2.CYCLIC GMP (cGMP)
Active PKG is ultimately responsible for many of the effects of Nitric
Oxide including its effects on blood vessel relaxation (vasodilation).
Activation of PKG by cGMP leads to activation of myosin phosphatase
which in turn leads to release of calcium from intracellular stores in
smooth muscle cells. This in turn leads to relaxation of the smooth
muscle cells.

8. Calcium ions (Ca2+) are often used as a second messenger by cells in
pathways that are activated by both G protein-coupled receptors and
receptor tyrosine kinases.
Cells tend to have very low concentrations of Ca2+ because ion pumps in
the plasma membrane constantly remove it using adenosine-5'-
triphosphate (ATP). When not in use, Ca2+ is stored in cytoplasmic vesicles
in the endoplasmic reticulum or in intracellular storage compartments
outside the cell.
During signal transduction, ligand-gated calcium ion channels allow
larger quantities of Ca2+ present outside the cell to flow into the
cytoplasm, increasing cytoplasmic Ca2+ concentration.
The increase in Ca2+ generates varied cellular responses, depending on
the cell type that is involved. For instance, Ca2+ signaling causes insulin
release in pancreatic β-cells, while an increase in Ca2+ in muscle cells
causes muscular contractions.
3.CALCIUM IONS

9. THANK YOU