Lecture 18 Cell Communication

Question 1

Where does signal transduction occur?

Answer 1

inside the cell

Question 2

What is signal tranduction?

Answer 2

Process in which Extracellular signaling molecules bind to specific receptors in target cells to initiate a chain of events

Question 3

External signals induce what major type of fast response?

Answer 3

Change in activity or function of enzymes or proteins in the cell

Question 4

External signals induce what major type of slow response?

Answer 4

Change in the amounts of proteins by change in expression of genes

Question 5

What is a long distance, long lasting type of signaling?

Answer 5

endocrine signaling
Signal -> bloodstream -> distant target cells
Freely diffusible signals

Question 6

What type of signaling acts locally, affects cells nearby (not as freely diffusable), and short lived?

Answer 6

Paracrine signaling

e.g. neurotransmitters

Question 7

What type of signaling is released to themselves or release to cells of the same type?

Answer 7

Autocrine signaling
Cells secrete signal that feeds back and binds to a receptor on its won surface

E.g growth factor in cancer cells

Question 8

What type of signaling does the immune cell elicit?

Answer 8

Direct cell signaling
Ag-presenting cell to T cells

*also known as juxtacrine signaling

Question 9

What does acetylcholine do to heart muscle cells?

Answer 9

relax them

Question 10

What does acetylcholine do to skeletal muscle cells?

Answer 10

contract them

Question 11

What does acetylcholine do to salivary gland cells?

Answer 11

Cause them to secrete saliva

Question 12

What are signaling cascade components?

Answer 12

signals, receptors, effectors

Question 13

What can make up a cell signaling ligand?

Answer 13

proteins, small peptides, amino acid derivatives, hydrophobic molecules, steroid hormones like estrogen.

Question 14

What are the main categories of cell signaling molecules?

Answer 14

small lipophilic molecules: steroid hormones

water soluble molecules- growth factors

Question 15

What are two types of signaling module receptors?

Answer 15

intracellular receptors and cell surface receptors.

Question 16

What is a specific type of intracellular receptors?

Answer 16

steroid receptor

Question 17

What type of molecules can diffuse across the cytoplamic membrane and bind to intracellular receptors?

Answer 17

small hydrophobic signaling molecules

Question 18

What are most signaling molecules?

Answer 18

hydrophilic and require cell surface receptors

Question 19

What are intracellular ligands and signals?

Answer 19

VART

Question 20

WHat are three main types of cell signaling receptors in the plasma membrane?

Answer 20

gated ion, G protein coupled receptors, enzyme coupled receptors

Question 21

Where are gated ion channels common?

Answer 21

nervous tissue

Question 22

What is special about GCPR?

Answer 22

7 pass transmembrane proteins

Question 23

What does enzyme coupled receptor class include?

Answer 23

receptor tyrosine kinases

Question 24

What is one major class of surface receptors that mediate signals inside the cell?

Answer 24

GPCRs

Question 25

What type of receptors affect olfaction, sight and taste?

Answer 25

GPCRs

Question 26

What type of transmembrane receptors are targets of many drugs?

Answer 26

GPCRs

Question 27

What three parts is the G protein coupled receptors composed of?

Answer 27

extracellular domain- binds to ligand transmembrane domain- anchors receptors cytoplasmic domain- associated with G protieins

Question 28

What are heterotrimeric G proteins?

Answer 28

are guanine nucleotide-binding proteins that consist of three subunits designated αβ γ

Question 29

What have no instrinsic catalytic activity and regulated target enzymes?]?

Answer 29

g protein coupled receptors

Question 30

What is the GPCR activity cascade?

Answer 30

``` GPCR-----> Trimeric G protein----> effector enzyme, adenyl cyclase---> 2nd messenger, cAMP----> Targets of 2nd messenger----> Biological response ```

Question 31

What is GEF?

Answer 31

guanidine exchange factor

Question 32

What causes GTP to change to GDP?

Answer 32

hydrolysis

Question 33

What is the common subunit upstream of cAMP production?

Answer 33

Gsalpha

Question 34

What does cAMP activate?

Answer 34

cAMP- dependent protein kinase, PKA, 4 subunits

Question 35

What can active PKA do?

Answer 35

phosphorylate other proteins

Question 36

What are the 4 consequences of phosphorylation by PKA?

Answer 36

1. form part of structure 2. change enzymatic target 3. change intracellular localization of target protein 4. alterations in abundance of target proteins

Question 37

What does cholera cause you to do what?

Answer 37

pump a lot of water into your gut... lots of diahrea

Question 38

What does cholrea target?

Answer 38

toxin targets a G-protein

Question 39

How does cholera modify G proteins?

Answer 39

by keeping the G alpha in the GTP active form indefinitely... lots of cAMP.... lots of PKA... Lots of secretion of water Continually pumping water and Cl out of the cells

Question 40

What is desensitization?

Answer 40

ability to turn off or reject the signal | can lead to cancer

Question 41

potentiate

Answer 41

turn up

Question 42

attenuate

Answer 42

turn down

Question 43

What happens when hormone levels drop?

Answer 43

decreased adenylyl cyclase activity.... decreased cAMP...

Question 44

What will remove cAMP/ cGMP?

Answer 44

phosphodiesterases

Question 45

How do you sequester the receptors?

Answer 45

endosomes

Question 46

How do you destroy receptors of the cell?

Answer 46

endosomes and lysososmes (proteases)

Question 47

What are G protein receptor kinases?

Answer 47

phosphorylate the receptor such that another protein called arrestin will bind to the 3rd intracellular loop and prevents Galpha from interacting with the third loop - causing desensitiation of signal

Question 48

Phosphoplipase C cleaves PIP2 to produce what?

Answer 48

IP3 and DAG

Question 49

IP3 and DAG triggers?

Answer 49

release of Ca from endoplasmic reticulum

Question 50

What are the two types of secondary messangers

Answer 50

cAMP and Ca

Question 51

What type of enzyme coupled receptors do growth factors use?

Answer 51

tyrosine kinases

Question 52

What is the structure of tyrosine kinases?

Answer 52

single pass transmembrane domain

Question 53

What happens when a protein binds to a tyrosine kinase?

Answer 53

dimerization and then autophopshorylation occurs causing a scaffolding effect.

Question 54

What binds to the SH2 domain of Grb2?

Answer 54

RTK

Question 55

What does SH3 domain of Grb2 bind to?

Answer 55

prolines and SOS

Question 56

What is the first human oncogene?

Answer 56

Ras, plays crucial role in cell dividsion and a frequent mutation in cancer

Question 57

How many steps are involved to get to changes in protein activity in gene expression?

Answer 57

3 steps

Question 58

What is the MAP kinase pathway?

Answer 58

Grb2-Sos- RAS-RAF-Mek-Erk

Question 59

What seperates JAK STAT from tyrosine kinases?

Answer 59

More direct route, not using scaffolding | Goes straight to transcription regulation; however, lacks regulation

Question 60

What is the difference in serine threonine?

Answer 60

Uses serine threonine instead of tyronsine kinases... SMAD controls cell proliferation