Signal Transduction

Question 1

endocrine signals

Answer 1

produced far from target tissues, which they reach through the circulatory system

Question 2

paracrine signals

Answer 2

diffusible and act over a short range

Question 3

juxtacrine signals

Answer 3

require physical contact btw sending and receiving cells

Question 4

autocrine signals

Answer 4

act on the same cell that produces them

Question 5

coreceptor

Answer 5

help facilitate the interaction of receptor with its ligand

Question 6

second messengers

Answer 6

any of several substances that transmit signals from extracellular signaling ligands to the cell interior

Question 7

signal transduction

Answer 7

ability of a cell to respond to ligand-receptor binding by altering behaviour or gene expression

Question 8

Dissociation constant (Kd)

Answer 8

concentration of free ligand needed to produce a state where HALF the receptors are occupied
(high ligand affinity = low Kd)

Question 9

agonist

Answer 9

drugs that activate the receptor they bind to

Question 10

antagonists

Answer 10

bind receptor without triggering a change and prevent the messenger from activating the receptor

Question 11

receptor desensitization

Answer 11

cell adapts to receptors that have been occupied for long periods of time and no longer responds

Question 12

4 types of signalling pathways

Answer 12

1- ligand-gated ion channels
2- G protein-coupled receptors (GPCR)
3- Enzyme coupled receptors
4- Nuclear receptors

Question 13

G protein

Answer 13

guanine-nucleotide binding protein

Question 14

G protein-coupled receptors

Answer 14

ligand binding changes receptor conformation and activates G protein which binds a target protein to alter its activity

Question 15

GRKs

Answer 15

regulate the activity by phosphorylation of AA which inhibits the receptor

Question 16

Gs vs Gi

Answer 16

Gs are stimulators and Gi are inhibitors of signal transduction

Question 17

regulator g protien signalling proteins (RGS)

Answer 17

GTPase activating proteins that enhance Gprotein activity

Question 18

cyclic AMP (cAMP)

Answer 18

secondary messenger activated by binding of G protein

Question 19

phosphodiesterase

Answer 19

degrades remaining cAMP

Question 20

protein kinase A (PKA)

Answer 20

main target of cAMP that phosphorylates a variety of proteins

Question 21

Cholera and Whooping cough

Answer 21

diseases caused by inhibition of G protein

Question 22

IP3 and DAG

Answer 22

second messengers generated through binding of G protein formed through cleavage of PIP2

Question 23

Calcium

Answer 23

plays an important role in regulating cell functions

Question 24

phospholipase C

Answer 24

cleaves PIP2 to form IP3 and DAG

Question 25

calcium ionophores

Answer 25

result in release of Ca in the absense of stimulus

Question 26

calmodulin

Answer 26

mediates calcium activated processes by binding 4 Ca to form calcium-calmodulin complex and binding proteins to alter their activity

Question 27

PKC

Answer 27

Main target protein for Ca and DAG

Question 28

enzyme coupled receptors

Answer 28

usually kinase receptors that send signals throuhg a phosphorylation cascade

Question 29

growth factors

Answer 29

messengers in blood serum that stimulate growth of cells

Question 30

serum

Answer 30

fluid remaining after blood clots, when platelets secrete growth factors

Question 31

RTK (receptor tyrosine kinase)

Answer 31

type of enzyme coupled receptor that trigger chain eventts that alter cell growth, proliferation, and specialization

Question 32

autophosphorylation

Answer 32

occurs when receptors like RTK phosphyorylate the same type of receptor as themselves

Question 33

SH2 domain

Answer 33

AA domain on RTK that recognizes nearby residues on the receptor that can recruit SH2 proteins

Question 34

Ras

Answer 34

small monomeric g protien that is activated by Sos and phosphorylates a series of proteins (Raf, MEK, MAP)

Question 35

Sos

Answer 35

guanine-nucleotide exchange factor (GEF) that binds to GRB2 to cause GTP binding to Ras

Question 36

Sos/GRB2/Ras/Raf/MEK/MAPK

Answer 36

series of binding and phosphorylation events leading to formation of transcription factors to alter gene expression and cause cell division or growth

Question 37

GTPase activating protein (GAP)

Answer 37

facilitates hydrolysis of GTP to GDP (inactivates Ras)

Question 38

dominant negative mutation

Answer 38

normal receptor function is disrupted because one mutant receptor prevents autophosphorylation

Question 39

constitutively active mutation

Answer 39

receptors are active in signaling when not bound to ligands (remain active all the time)

Question 40

transforming growth factor B (TGFB)

Answer 40

serine-threonine kinase growth factors that phosphorylate Smad proteins

Question 41

R-Smad

Answer 41

receptor regulated

Question 42

Smad4

Answer 42

forms multiprotein complex with R-Smads that can enter the nucleus

Question 43

other Smad

Answer 43

inhibit the TGF B pathway

Question 44

guanylyl cylcase

Answer 44

enzyme coupled receptors that produce cyclic GMP (cGMP)

Question 45

multiprotein complexes

Answer 45

signaling components form these in order to make signal cascades more efficient (yeast mating)

Question 46

signaling crosstalk

Answer 46

activated components from one pathway affect components of the other pathways

Question 47

integration

Answer 47

several pathways can converge and lead to the same molecule or product (ie: IP3 and Ca are second messengers to multiple paths)