Cell communication

1
Cell communication

• Chapter 11

2
Figure 11.2 Communication between mating yeast
cells
3
Cell to cell contact

• Can involve communication (signaling) between
  cells
• Can be local or distant
• Direct or mediated
• Can involve adhesion between cells
• Cell-Cell Adhesion
• Can be strong or weak
• Can be regulated

4
Figure 11.4 Local and long-distance cell
communication in animals
5
Figure 11.5 Overview of cell signaling
6
Hormonal signaling

• Hormones can be of different molecular type,
  e.g. proteins, steroids, catecholamines, small
  organic molecules, NO

7
Hormonal signaling

• Two types of receptors
• (a) Cell surface receptors (hormone does not
  enter cells)
• 3 types
• Ion Channel linked
• Enzyme linked
• G-protein linked
• (b) Intracellular receptors (hormone enters cells)

Figure 45.3
8
Extracellular (cell-surface) receptors

• Receptor must be present in cell membrane
• Receptor determines specificity of response
• Hormone binds to transmembrane receptor protein
• Causes intracellular change such as levels of
  second messenger such as cAMP or calcium

Figure 11.15
9

• A single signal (Acetylcholine) can affect
  different cells in different ways

10
Figure 11.7 The structure and function of a
G-protein-linked receptor
Cell Surface Receptor
11
Figure 11.7 The structure and function of a
tyrosine-kinase receptor
Insulin receptor
12
Figure 11.7 A ligand-gated ion-channel receptor
Acetylcholine gated sodium channel
13
Figure 11.8 A phosphorylation cascade
14
Figure 11.16 A scaffolding protein
15
Second messengers

• Hormone binding to cell surface receptor causes
  second messenger levels to change inside the cell
• cAMP levels
• Ca2 levels
• IP3/Diacylglycerol (DAG)

• Second messengers can change cell function
• Eg. Epinephrine causes elevation in cAMP which
  activates kinase that activates glycogen
  breakdown that provides energy to muscle cells

16
Figure 11.9 Cyclic AMP
17
Figure 11.10 cAMP as a second messenger
General overview Specific example
18
cAMP stimulates protein kinase A
19
Second messengers

• Hormone binding to cell surface receptor causes
  second messenger levels to change inside the cell
• cAMP levels
• Ca2 levels
• IP3/Diacylglycerol (DAG)

• Second messengers can change cell function
• Eg. Epinephrine causes elevation in cAMP which
  activates kinase that activates glycogen
  breakdown that provides energy to muscle cells

20
Figure 11.11 The maintenance of calcium ion
concentrations in an animal cell
Calcium as a second messenger
21
(No Transcript)
22
Figure 11.11 The maintenance of calcium ion
concentrations in an animal cell
Calcium as a second messenger
10-4mM
1mM
1mM
1mM
10-4mM
23
Figure 11.12 Calcium and inositol triphosphate
in signaling pathways (Layer 1)
1mM
10-4mM
PIP2- Phosphoinositol bisphosphate IP3- Inositol
triphosphate DAG- Diacylglycerol
24
(No Transcript)
25
Figure 11.12 Calcium and inositol triphosphate
in signaling pathways (Layer 2)
26
Figure 11.12 Calcium and inositol triphosphate
in signaling pathways (Layer 3)
27
(No Transcript)
28
Figure 11.14 Nuclear response to a signal the
activation of a specific gene by a growth factor
Cell surface receptors can also regulate
transcription
29
Hormonal signaling

• Two types of receptors
• Cell surface receptors (hormone does not enter
  cells)
• 3 types
• Ion Channel linked
• Enzyme linked
• G-protein linked
• Intracellular receptors (hormone enters cells)

Figure 45.3
30
Intracellular receptors-the hormone enters the
cell!

• Ligand binding to intracellular protein.
• (eg steroid hormones, thyroid hormone, vitamin D,
  retinoic acid)
• Protein/hormone complex binds to DNA binding site
  (enhancer)
• Usually work as dimers
• Regulates gene expression (can be ve or -ve)
• Steroid hormone receptor superfamily

31
(No Transcript)
32
(No Transcript)
33
Three of the major types of DNA-binding domains
in transcription factors
34
(No Transcript)
35
Cytoplasmic response to a signal the stimulation
of glycogen breakdown by epinephrine
Signal Amplification