cell signaling discription

1. Cellsignaling
Pritam Prajapati
B.Tech Biotechnology
Ashoka Institute of Technology & Management
Varanasi, Uttar Pradesh

2. Cell Signaling
All cells receive and respond to signals from their
surroundings
Signaling molecules that are secreted on the surface of
one cell and bind to receptors expressed by the other
cells
The binding of most signaling molecules to their
receptors initiates a series of intracellular reactions that
regulate of the cell behaviour including
metabolism,movement,proliferation and differentiation

3. The ligand is the signaling molecule.
It may be a hormone,a growth factor/cytokine ,a
steroid,a polypeptide,or other type of molecule.It has no
activity of its own,but must bind to a macromolecule
Which is known as a receptor
Receptor when activated by ligand ,the receptor causes
a change in the target cell in which it is expressed

4. Signaling molecules
 Signaling molecules, which are released by signal-
producing cells, reach and transfer biological
signals to their target cells to initiate specific
cellular responses.

5. Signaling Molecules
 Extracellular molecules
 Intracellular molecules

6. 1. Extracellular molecules
 Protein & Peptides: Hormone, cytokine
 AA & its derivatives: Gly, Glu, adrenaline,thyroxine
 Steroid: Sex Hormone,glucocorticosteroid
 Fatty acid derivatives: prostaglandin

7. 2.Intracellular molecule
 Ca2+ ions
 DG, ceramide lipid derivatives
 IP3 carbohydrate derivatives
 cAMP cGMP nucleotides
 Ras, JAK, Raf proteins

8. Cell Cell signaling
 Most signaling molecules are secreted by one
cell and bind to cell surface
receptorsexpressed by a target cell.
 The steroid hormones are small hydrophobic
molecules that diffuse across the plasma
membrane of their target cells and bind to
intracellular receptors.

9. Signaling molecule
Receptor of target cell
Intracellular molecule
biological effect
Signal
transduction

10. Cell Cell signaling is divided into three
general categories
 Endocrine
 Paracrine
 Autochrine
 Signaling based on the distance over which
signals are transmitted

11. (1) Endocrine signal
 Secreted by endocrine cells.
 Reach target cells by blood circulation.
 Time of action is long.
 Such as insulin, thyroxine, adrenalin

12. (2) Paracrine signaling
(local chemical mediators)
 Secreted by common cells.
 Reach neighboring target cells by passive
diffusion.
 Time of action is short.

13. (3) Synaptic signal
(neurotransmitters)
 Secreted by neuronal cells.
 Reach another neuron by synaptic gap.
 Time of action is short.
 Such as Acetylcholine (Ach),
noradrenaline

14. (4) Gaseous signal
 Simple structure, half life is short and active
in chemistry .
 Such as NO, CO.
 NO is a major paracrine signaling molecule
in the nervous,immune and circulary
system
 NO is synthesized from the aa arginine by
the enzyme nitric oxide synthase.

15. (5) Autocrine signal
 Act back to their own cells.
 Such as GF, cytokine, interferon, interleukin.
 Direct cell to cell signaling,some signaling
molecules remain bound to the cell surface and
act as a ligands.these kinds off signaling take
place during embryonic development

16. Receptor
 Receptors are specific membrane or
intracellular proteins, which are able to
recognize and bind to corresponding ligand
molecules,
 Receptor when activated by ligand ,the
receptor causes a change in the target cell in
which lt is expressed.
 Glycoprotein or Lipoprotein

17. Function of receptor
(1) Recognize the special ligand
(2) Binding to special ligand
(3) Signal transduction biological effect

18. ligand
 A small molecule that binds specifically to a
larger one; for example, a hormone is the
ligand for its specific protein receptor.

19. Membrane receptors
 Membrane
 Glycoprotein
Intracellular receptors
 Cytosol or nuclei
 DNA binding
protein

20. Properties of binding of
Hormone and Receptor
 highly specificity
 highly affinity saturation
 reversible binding
 special function model