Cell Communication

Page
8

Formin

P

P

P

Formin

P

Actin

subunit

Microfilament

1

2

3

4

5

Slide 58

Fine-Tuning of the Response

Multistep pathways have two important benefits:

Amplifying the signal (and thus the response)

Contributing to the specificity of the response

Slide 59

Signal Amplification

Enzyme cascades amplify the cell’s response

At each step, the number of activated products is much greater than in the preceding step

Slide 60

The Specificity of Cell Signaling and Coordination of the Response

Different kinds of cells have different collections of proteins

These different proteins allow cells to detect and respond to different signals

Even the same signal can have different effects in cells with different proteins and pathways

Pathway branching and “cross-talk” further help the cell coordinate incoming signals

Slide 61

Fig. 11-17

Signaling

molecule

Receptor

Relay

molecules

Response 1

Cell A. Pathway leads

to a single response.

Response 2

Response 3

Cell B. Pathway branches,

leading to two responses.

Response 4

Response 5

Activation

or inhibition

Cell C. Cross-talk occurs

between two pathways.

Cell D. Different receptor

leads to a different response.

Slide 62

Fig. 11-17a

Signaling

molecule

Receptor

Relay

molecules

Response 1

Cell A. Pathway leads

to a single response.

Cell B. Pathway branches,

leading to two responses.

Response 2

Response 3

Slide 63

Fig. 11-17b

Response 4

Response 5

Activation

or inhibition

Cell C. Cross-talk occurs

between two pathways.

Cell D. Different receptor

leads to a different response.

Slide 64

Signaling Efficiency: Scaffolding Proteins and Signaling Complexes

Scaffolding proteins are large relay proteins to which other relay proteins are attached

Scaffolding proteins can increase the signal transduction efficiency by grouping together different proteins involved in the same pathway

Slide 65

Fig. 11-18

Signaling

molecule

Receptor

Scaffolding

protein

Plasma

membrane

Three