lecture 9

Question 1

signal transduction

Answer 1

• conversion of one signal to another

Question 2

types of signals

Answer 2

growth factors, cytokines, hormones, ECM, neurotransmitters, light sound

Question 3

small signalling molecules

Answer 3

epinephrine, acetylcholine, steroids, peptides

Question 4

large signalling moleucles

Answer 4

growth factors, cytokines, proteins

Question 5

receptors

Answer 5

• cell surface receptors and intracellular receptors

Question 6

Intracellular signaling proteins:

Answer 6

G proteins, protein kinases/phosphatases, etc.

Question 7

Different forms of cell signalling: endocrine, paracrine, autocrine, cell-cell.

Answer 7

endocrine, paracrine, autocrine, cell-cell
signalling molecules act locally or at a distance

Question 8

endocrine

Answer 8

tissue produces the ligand that enters the blood stream to act at a distance

Question 9

paracrine

Answer 9

once cell secretes a ligand that acts on an adjacent target cell and moves only a short distance

Question 10

autocrine

Answer 10

cell produces a ligand and expresses a receptor itself (self-stimulation)

Question 11

signal by plasma membrane attached proteins

Answer 11

cell produces transmembrane protein that can act on adjacent target cell that has cell surface receptor

Question 12

epinephrine

Answer 12

both endocrine and paracrine singlaing

Question 13

EGF

Answer 13

• autocrine, cell-cell or paracrine

Question 14

types of nuclear receptors in nuclear-receptor superfamily

Answer 14

• thyroxine receptor
• rteinoic acid receptor
  ** involves phobic signalling molecules

Question 15

cytoplasmic receptors in nuclear receptor superfamily

Answer 15

• estrogen receptor
• progesterone receptor
• glucoroctioic recepotr

Question 16

Signal Transduction overview of process

Answer 16

Primary messenger or molecules.
Signaling of cell-surface receptors.
Short-term and long-term intracellular responses.
effector proteins (metabolic enzymes to alter metabolism, alter gene expressionn or alter cell shape or movement)
Termination of cellular response.

Question 17

slow behaviour changes in target cell

Answer 17

• gene regulated changes in cell growth and division

Question 18

faster behvaviour hangs in target cell

Answer 18

• changes in ion transport, cell movement, secretion or metabolism

Question 19

what do cell signals tell it

Answer 19

• survive
• grow and divide (mytogenic factors)
• differentiate (response to growth factors)
• die

Question 20

7. Ligand-Receptor Interactions:

Answer 20

Binding specificity based on molecular complementarity.
Triggers receptor conformational change.
Often induces receptor dimerization (which is when interacting with another receptor which is important for signal transaction events to inside of cell)

Question 21

8. Dissociation Constant (Kd):

Answer 21

Measure of receptor-ligand affinity.
Smaller Kd indicates higher affinity.
Determines ligand concentration to occupy 50% of receptors.

Question 22

Functional expression Assay

Answer 22

• use cells that do not have receptor for that ligand
• transfer the cells with cDNA from cell that expresses the receptor for growth factor
• pick the colonies that express that repceotr and that are associated with that phenotype
• deduce the receptor protein sequence from cDNA sequence
• or mutating specific amino acids to determine essential ligand binding domain

Question 23

. Regulation by Kinase/Phosphatase Switch:

.

Answer 23

Tyrosine/Serine/Threonine Kinases.
Tyrosine/Serine/Threonine Phosphatases.
Phospho-specific antibodies reveal pathway activation
- phosphoryalation leads to activation
- not phosprylated = inactive

Question 24

Switching Mechanism of G Proteins:

Answer 24

• proteins that responds to GTP instead of phosphate group
• Existence in active (GTP-bound) and inactive (GDP-bound) forms.
  Activation triggered by signals, assisted by GEF.
  Inactivation through GTP hydrolysis, mediated by GAP or other GTPase (intrinsic)

Question 25

G-protein coupled receptors

Answer 25

- 7 membrane spanning domains - respond to stimuli such as vision, pathogens, smooth muscle relaxation in a arteries, drugs

Question 26

G protein coupled receptor structure

Answer 26

- 7 transmembrane domains that respond to different ligands - used because it can be activated by chemical agonists and inhibited by antagonists

Question 27

heterotimeric G protein comlex

Answer 27

- G alpha and G gamma subunit are lips anchored proteins at the cytoplasmic face - G alpha controls activity of teh complex, is bound to GTP when active - function in single transduction by coupling ligand-bound receptors to specific effector molecules

Question 28

what happens when ligand binds to G protein coupled recptor

Answer 28

- recuritemtnof the g complex - G alpha can inhibit tffector and g beta gamma will activate the effector

Question 29

FRET showing dissociation of G alpha and G beta gamma

Answer 29

- g alpha linked to cFP - g beta gama linked to YFP - excite CGP with 440 nm - emit light to excite YFP indicating that the proteins are interacting - however, when ligand is added, loss of fret signal tdue to dissociation for he complex

Question 30

G alpha s

Answer 30

activates adenylyl cuclase, increase cAMP

Question 31

G alpha I

Answer 31

inhibits adenyl cyclase, decrease cAMP

Question 32

activation of adenylyl cyclase

Answer 32

- stimulatory hormone (ACTH, glucagon, epi) - alpha subunit moves along to activate effector protein (e..g adenylyl cyclase) - this leads to production of secondary molecule cAMP

Question 33

inhibtion of adenelyl cyclase

Answer 33

- inhibitory hormone (PGE, adenosine) - binds to receptor for inhibitory homrone - Galphai subunit to inhibit adenelyl cyclase - no production of cAMP

Question 34

cholera

Answer 34

- bacteria produce toxin in intestine that enters eptithelial cells using GM1 ganglisodie receptor - it maintains the Galphas in activate state, lets to activation of adenylyl cyclase - increase in cAMP - activates PKA - activates CFTR potassium channel - increase in activity of CFTR ion channel - it goes on to activate protein kinase - flux of chloride ions into small intestine lumen and sodium - water enters lumen of small intestine due to salt, diarrhea and dehydration

Question 35

whooping cough

Answer 35

- infectes lung tissue - toxin leads to activation of g alpha I subunit - inhibitn of inhibitory actibity - increase in g alpha s activity, more adenyl cyclase activation, more cAMP, more activation of CFTR - increase cl ion efflux , watery mucous in lung

Question 36

how does cAMP activate PKA

Answer 36

- epinephrine results in cAMP production - PKA has two regulatory and two catalytic subints - cAMP binds to regulatory components, - regulatory are then released from catalytic domains so they can go and phosyrlate other proteins

Question 37

cooperative binding of cAMP to PKA a and b domains on regulatory subunnits

Answer 37

- cAMP binds first to B to lower Kd for binding to A

Question 38

cAMP

Answer 38

- activates PKA

Question 39

cyclic GMP

Answer 39

- activates PKG, and opens cation channels in rod cells

Question 40

DAG

Answer 40

- activates PKCE

Question 41

inositol

Answer 41

opens Ca channels in ER

Question 42

four intracellular secondary messengers

Answer 42

- cAMP - cGMP - diacylglycerol - inositol

Question 43

cAMP and PKA- short term or long term effects

Answer 43

short term, e.g. activity of enzymes modulation and long term (gene activity)

Question 44

gene regulation by pKA

Answer 44

- they must have specific cnuceltoide sequence (TGACGTCA) (this is the cRE)

Question 45

Activation of cREB transcription factor

Answer 45

- by phosphytlation by pKA in nucleus

Question 46

phospholipase C

Answer 46

- cleaves pip2 into DAG and IP3