Transcript Cell signaling

Cell signaling
Prof.Dr.Gönül Kanıgür
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
• 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
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.
signaling molecules
• Extracellular molecules
• Intracellular molecules
1. Extracellular molecules
protein & peptides: Hormone, cytokine
AA & its derivatives: Gly, Glu, adrenaline,
thyroxine
Steroid: Sex Hormone,
glucocorticosteroid
Fatty acid derivatives: prostaglandin
2. Intracellular molecule
• Ca2+
ions
• DG, ceramide
• IP3
lipid derivatives
carbohydrate
derivatives
• cAMP cGMP
nucleotides
• Ras, JAK, Raf
proteins
Proteins and peptides:
Effect by
membrane
receptors
Hormones, cytokines
Amino acid derivatives:
Catecholamines
Fatty acid derivatives:
Extracellular
molecules
Prostaglandins
Effect by
intracellular
receptors
Signal
molecules
Intracellular
molecules
Steroid hormones,
Thyroxine, VD3
cAMP, cGMP, IP3, DG, Ca2+
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.
Signaling molecule
Receptor of target cell
Intracellular molecule
biological effect
Signal
transduction
Cell Cell signaling is divided into three
general categories
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Endocrine
Paracrine
Autochrine
signaling based on the distance over which
signals are transmitted
(1) Endocrine signal
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Secreted by endocrine cells.
Reach target cells by blood circulation.
Time of action is long.
Such as insulin, thyroxine, adrenalin
(2) Paracrine signaling
(local chemical mediators)
• Secreted by common cells.
• Reach neighboring target cells by
passive diffusion.
• Time of action is short.
(3) Synaptic signal (neurotransmitters)
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Secreted by neuronal cells.
Reach another neuron by synaptic gap.
Time of action is short.
Such as Acetylcholine (Ach), noradrenaline
(4) Gaseous signal
• Simple structure, half life is short and
active in chemistry .
• Such as NO, CO.
• NO is amajor paracrine signaling molecule
in the nervous,immune and circulary
system
• .NO is synthesized from the aa arginine by
the enzyme nitric oxide synthase.
(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
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
Function of receptor
(1) Recognize the special ligand
(2) Binding to special ligand
(3) Signal transduction
effect
biological
ligand
A small molecule that binds specifically
to a larger one; for example, a hormone is
the ligand for its specific protein receptor.
• Membrane receptors
membrane
Glycoprotein
• Intracellular receptors
Cytosol or nuclei
DNA binding protein
Properties of binding of Hormone and
Receptor
• highly specificity
• highly affinity
• saturation
• reversible binding
• special function model