Receptors and cell signalling

Question 1

Describe endocrine signalling

Answer 1

long distance signalling;
diffuse through blood;
long-lasting (takes minutes to reach target cell sometimes)

Question 2

Paracrine signalling

Answer 2

acts locally upon (short lived) e.g. neurotransmitters

Question 3

Autocrine signalling

Answer 3

all cells with receptor (including itself) respond to the ligand (growth factors of cancer cells)

Question 4

juxtacrine/direct

Answer 4

to attached cell

Question 5

acetylcholine effects on heart, skeletal muscle, and salivary gland:

Answer 5

heart cells relax, skeletal muscles contract, salivary gland secrete saliva

Question 6

Describe a Guanine exchange factor

Answer 6

receptors on GCPR change a GDP for a GTP on G proteins

Question 7

What is PLC? What is it’s function?

Answer 7

phospholipase C cleaves PIP2 into IP3 and DAG

Question 8

What does Gs protein do?

Answer 8

cAMP pathway

Question 9

How does the Cholera toxin modify the G protein

Answer 9

I keeps Ga in the GTP active form indefinitely by adding a ribose (to G protein);
Cl secretion is constantly turned on

Question 10

another term for turning up a signal

Answer 10

potentiate

Question 11

another term for turning down a signal

Answer 11

attenuate

Question 12

another term for turning down a signal

Answer 12

attenuate

Question 13

What desensitizes a signal?

Answer 13

hormone levels drop;
phosphodiesterases remove cAMP;
receptors are sequestrated (endosome) and destroyed (endosome to lysosome via proteases);
GRK (GCPR kinase) phosphorylate the receptor so that arrestin can bind to it

Question 14

What are the different G proteins and what does each do?

Answer 14

Gaq-PLC, DAG, Ca, PKC
Gai-cAMP inhibition
Gas-cAMP
Ga12-RhoGEFs

Question 15

What receptor is associated with epinephrine?

Answer 15

beta andren…ic

Question 16

What receptor is associated with histamine?

Answer 16

histamine receptor

Question 17

What receptor is associated with epinephrine and norepinephrine?

Answer 17

alpha andrenergic receptor

Question 18

What receptor is associated with dopamine?

Answer 18

Dopamine receptor

Question 19

What receptor is associated with light?

Answer 19

Rhodopsin

Question 20

What is a calcium mediated pathway?

Answer 20

Gqa GCPR

Question 21

Describe the Gqa pathway cascade

Answer 21

ligand binds, GDP->GTP, G with GTP activates PLC, PLC separates PIP2 into DAG and IP3, IP3 binds to Ca channel on ER/SR,
Ca and DAG activate PKC, Ca forms calmodulin complex

Question 22

What is needed to activate PKC?

Answer 22

DAG and Ca

Question 23

What makes an acceptable nuclear hormone signal molecule?

Answer 23

hydrophobic molecules are best (steroid hormones), NO, growth factors

Question 24

How does an intracellular receptor work?

Answer 24

There is a DNA binding domain on a receptor, once ligand binds then an inhibitory protein is released from the receptor and acts like a transcription factor

Question 25

What are some hydrophobic ligands that are nuclear hormone signals?

Answer 25

cortisol, estradol, testosterone, vitamin D3, thyroxine, and retinoic acid

Question 26

If a CpG island is hypermethalated then what is occuring?

Answer 26

promoter region is inaccessible, DNA transcription does not occur

Question 27

How does hypermethylation of miRNA coding regions of DNA result in cancer?

Answer 27

miRNA binds complementary to mRNA to silence genes. If this is not occuring then bad RNA cannot be silenced through that mechanism

Question 28

If the epigenetic is Highly altered what might that indicate?

Answer 28

cancers have their own specific epigenetic patterns, as well as histone modifications

Question 29

If the CpG islands have a lot of methylation on their histones then what does that indicate?

Answer 29

There is likely transcription of this area

Question 30

What is an easier modification: to methylate histone or DNA?

Answer 30

histone

Question 31

What are the two hits that have to occur in order to get cancer?

Answer 31

DNA repair pathways must be mutated | Oncogenes must be expressed

Question 32

place in order of lowest to highest penetrance? Transposon, cell signalling, or DNA repair gene mutations?

Answer 32

Transposon lowest cell signalling DNA repair highest

Question 33

What are some mitogen pathway proteins? What do they do?

Answer 33

src, erb, and ras | If up-regulated they promote cell proliferation

Question 34

What are Growth inhibitor pathway proteins?

Answer 34

rb and apc