Cell Communication

Page
7

The cell’s response to an extracellular signal is sometimes called the “output response”

Slide 50

Nuclear and Cytoplasmic Responses

Ultimately, a signal transduction pathway leads to regulation of one or more cellular activities

The response may occur in the cytoplasm or may involve action in the nucleus

Many signaling pathways regulate the synthesis of enzymes or other proteins, usually by turning genes on or off in the nucleus

The final activated molecule may function as a transcription factor

Slide 51

Fig. 11-14

Growth factor

Receptor

Phosphorylation

cascade

Reception

Transduction

Active

transcription

factor

Response

P

Inactive

transcription

factor

CYTOPLASM

DNA

NUCLEUS

mRNA

Gene

Slide 52

Other pathways regulate the activity of enzymes

Slide 53

Fig. 11-15

Reception

Transduction

Response

Binding of epinephrine to G protein-coupled receptor (1 molecule)

Inactive G protein

Active G protein (102 molecules)

Inactive adenylyl cyclase

Active adenylyl cyclase (102)

ATP

Cyclic AMP (104)

Inactive protein kinase A

Active protein kinase A (104)

Inactive phosphorylase kinase

Active phosphorylase kinase (105)

Inactive glycogen phosphorylase

Active glycogen phosphorylase (106)

Glycogen

Glucose-1-phosphate

(108 molecules)

Slide 54

Signaling pathways can also affect the physical characteristics of a cell, for example, cell shape

Slide 55

Fig. 11-16

RESULTS

CONCLUSION

Wild-type (shmoos)

∆Fus3

∆formin

Shmoo projection forming

Formin

P

Actin

subunit

P

P

Formin

Formin

Fus3

Phosphory-

lation

cascade

GTP

G protein-coupled

receptor

Mating

factor

GDP

Fus3

Fus3

P

Microfilament

1

2

3

4

5

Slide 56

Fig. 11-16a

RESULTS

Wild-type (shmoos)

∆Fus3

∆formin

Slide 57

Fig. 11-16b

CONCLUSION

Mating

factor

G protein-coupled

receptor

GDP

GTP

Phosphory-

lation

cascade

Shmoo projection

forming

Fus3

Fus3

Fus3

Formin