Signal transduction

GENERAL IDEA OF SIGNAL TRANSDUCTION
DEFINATION
WHAT DOES THE TERM SIGNAL TRANSDUCTION MEANS
HISTORY
BASIC ELEMENTS IN SIGNAL TRANSDUCTION
TYPES OF SIGNAL TRANSDUCTION
SIGNALLING MOLECULE
RECEPTOR MOLECULE
MODES OF CELL CELL SIGNALING
SECOND MESSENGER
SIGNAL TRANSDUCTION PATHWAY
SOME SIGNALING PATHWAYS
SIGNIFICANCE
CONCLUSION
REFERENCE

1. •By
•KAUSHAL KUMAR SAHU
•Assistant Professor (Ad Hoc)
•Department of Biotechnology
•Govt. Digvijay Autonomous P. G. College
•Raj-Nandgaon ( C. G. )
•

2. SYNOPSIS
•GENERAL IDEA OF SIGNAL TRANSDUCTION
•DEFINATION
•WHAT DOES THE TERM SIGNAL TRANSDUCTION MEANS
•HISTORY
•BASIC ELEMENTS IN SIGNAL TRANSDUCTION
•TYPES OF SIGNAL TRANSDUCTION
•SIGNALLING MOLECULE
•RECEPTOR MOLECULE
•MODES OF CELL CELL SIGNALING
•SECOND MESSENGER
•SIGNAL TRANSDUCTION PATHWAY
•SOME SIGNALING PATHWAYS
•SIGNIFICANCE
•CONCLUSION
•REFERENCE

3. “ It isthe process by which an extra cellular
signaling molecule activates a membrane
receptor, which in turn alters intercellular
molecules creating a response.” The stimulus
received at the cell surface is entirely
different from the signal released to the cell
interior, the signal received is amplified.

4. .
•In 1970 Martin Rod bellFirstly examined Signal
Transduction, through effect of glucagons on a rat’s liver
cell.
glucagons
+bind
Guano sine triphosphate disassociated glucagons
↓
stimulates G-protein
↓
strongly influences the cell metabolism

5. BASICELEMENTS IN SIGNAL TRANSDUCTION
•Ligands:-also known as signals or first
messenger.
•Receptor:-transmembrane protein that
binds to the ligand
•Second messenger

6. SIGNALING MOLECULES
•There are two kinds of signaling molecules.
1.Some signaling molecules cross the plasma membrane and bind
to the receptors on the target cell.eg. Steroid hormones.
2.Another signaling molecules can’t enter the plasma membrane
and thus binds to the receptors on the plasma membrane.
e.g..Gprotein
E.g. of signaling molecule
1.STEROID HORMONE
2.NITRIC OXIDE
3.CARBON MONOXIDE
4.NEUROTRANSMITTER
5.PEPTIDE HORMONE

7. RECEPTOR MOLECULE
RECEPTORS
CELL SURFACE
RECEPTOR
INTRACELLULAR
RECEPTOR
G-PROTEIN
COUPLED RECEPTOR
ENZYME LINKED
RECEPTOR
ION CHANNEL LINKED
RECEPTOR
NUCLEAR RECEPTOR
STEROID
RECEPTOR
ESTROGEN
RECEPTOR
KETOSTEROID
RECEPTOR

8. G-PROTEIN LINKED RECEPTOR
•This protein was discovered and characterized by Red bell and
his colleagues at the National Institute of health in the early
1970’s.
•G-protein coupled receptors are a family of integral membrane
proteins
•It is also known as seven transmembrane domain receptors as it
possess seven membrane spanning domains.
•It is linked to a guanine nucleotide binding protein.
•Two pathways involve G-protein coupled receptor:
•cAMP pathway
•Phosphatidylinositol pathway
•The G-protein linked receptors are coupled to their target
enzymes in the plasma membrane through trimeric GTP binding
proteins, called G proteins

9. •G
protein
undergoe
s
change
•
GProtein
binds to
receptor
•GTP
replaces
GDP
•Disassoc
iation of
G
protein
•ßϒ+ἀ
+GTP
•ἀgives
the msg
to target
•GTP
hydrolysi
s
•G
protein
linked
receptor
•Ligand
binds to
receptor
•GProtein
original
form

10. ION LINKED CHANNEL RECEPTORS
•Hydrophobic molecules-Rapidly diffuse
•Uncharged small polar molecules-Rapidly diffuse
•Uncharged large polar molecules-moves through pores using carrier
protein
•Charged molecules-ion channels or active transport
E.g.

11. NUCLEAR RECEPTOR
•STEROID RECEPTOR
•It is located primarily within the cytosol
•In the absence of ligands they are associated with chaperons.
steroid hormone
↓
chaperone activates the receptor
↓
protein folds
↓
signal enters into the nucleus

12. SECOND MESSENGER
•Link between first messenger and target cell.
•They are generated when first messenger binds to the receptor.
•They are water soluble and relatively smaller in size.
•E.g. Calcium ion, Nitric oxide
CALCIUM ION AS SECOND MESSENGER
•It is present in limited amount inside the cell.
•Present in endoplasmic reticulum in muscles and nervous tissue
•It is inactive when present in its original site.
•It is active when released in the cytosol.

13. ACTIVATION OF Ca2+
Calcium (Inactive state)
↓
First messenger comes and binds to receptor
↓
This interaction induces a conformational change in proteins
↓
Protein specific to calcium channels open the channels for Ca
↓
Calcium ions exit from intracellular storage sites into the cytoplasm
↓
Calcium (active state)
↓
Carries message to the target site
↓
Triggers target site for response
FUNCTION: Muscle contraction, vision in retina cells,proliferation of cells

14. •NITRIC OXIDE AS SECOND MESSENGER
It acts as a second messenger in many processes such as
•Relaxation of blood vessels
•Regulation of neurotransmitters
•Cellular immune response
•Production and maintenance of penile erections
•Activation of apoptosis
•It also plays an important role in generation of cGMP
In high concentration NO is Toxic, It may result in stroke

15. MODES OF CELL SIGNALING
•Cell
Signaling
•Endocrine
signaling
•Paracrine
signaling
•Autocrine
signaling

16. ENDOCRINE SIGNALING

17. PARACRINE SIGNALING

18. AUTOCRINE SIGNALING

19. SIGNAL TRANSDUCTION
PATHWAY
•It consists of five many steps:
•RECEPTION
•TRANSDUCTION
•AMPLIFICATION
•INDUCTION
•RESPONSE

20. .mechanism

21. SOME EXAMPLES OF PATHWAY SIGNALING
•cAMP pathway-It contains five main characteristics:
•Stimulative hormone receptor (Rs)
Inhibitory hormone receptor (Ri)
•Stimulative regulative G-protein (Gs)-binds with
Stimulative receptor
Inhibitory regulative G-protein (Gi) -binds with Inhibitory
receptor
•Adenylyl cyclase-12-transmembrane glucoprotein that
catalyses ATP to form cAMP with the help of Ca.
•Protein kinase A
•cAMP phosphodiesterase

23. RAS MEDIATED SIGNAL TRANSDUCTION PATHWI
It contains four main characteristics:
•Receptor Tyrosine Kinase
•Growth factor
•Ras proteins
•MAP-kinase
•They are products of proto oncogenes c-ras.
•They are active only when bound to GTP and inactive when boundedwith GDP.
•Two classes of signalling proteins that regulate Ras activity include the following:
•GTPase activating proteins (GAPs) -it increases the rate of hydrolysis of bound GTP by Ras
resulting in inactivated Ras.
•Guanine nucleotide releasing proteins (GNRPs) -it promotes the release of GDP and uptake of
GTP resulting in activated Ras.
•Thus Tyrosine kinase activates Ras proteins either by inhibiting GAP or activating
•GNRP
•Ras proteins when active initiate a cascade of phosphorylation which leads to MAP-kinase
(mitogen activated protein) which finally relays signals to nucleus.

25. •Every single way our body reacts depend on the way
our receptors catches signals and transducts them to
the target cells.
•Our life susceptibility depends on signal transduction
•Errors in cellular information processing are
responsible for many diseases such as cancer, heart
problems etc.
•Full study of signal transduction helps in creating
synthetic drugs,
•And also artificial tissue.

26. CONCLUSION
•Cell signalling is a most important function in
all animals and plant cells
•Numbers of research being carried out
indicate that all organisms share certain basic
signalling mechanism but certain pathways are
unique to each major kingdom.
•The scientist world has recognize the
significance of signal transduction mainly in
drug production but still many of its areas are
left to be explored.

27. REFERENCE
•THE CELL-A Molecular Approach-By M.Cooper &
Geoffery (2006)
•Text Book of cell Biology-By Karp (2007)
•Cell And Molecular Biology-By P.K.Gupta (2008)
•Gene viii-By Lewin & Benjamin(2006)
•Genetics-By B.D. Singh