Test 3: Lecture 55

Question 1

plasma membrane hormone receptors are for ___ hormones

Answer 1

amino acid derived

Question 2

intracellular hormone receptors are for ___ hormones

Answer 2

steroid

Question 3

all protein derived hormones bind plasma membrane of the target cell but do not ___

Answer 3

enter the target cell

Question 4

Three classes of plasma membrane bound hormone receptors

Answer 4

• G protein coupled receptors (GPCRs)
• Ion channel-linked receptors
• Enzyme-linked receptors

Question 5

G-protein Coupled Receptors

Answer 5

• Common type of receptor that starts intracellular signal transduction cascades upon ligand (e.g. a hormone) binding
• Has 7 hydrophobic plasma membrane spanning domains (Serpentine Receptors)
• Hormone binding site is extracellular
• Coupled with heterotrimeric GTP binding proteins in the cytoplasm (G proteins)

Question 6

___ is a common type of receptor that starts intracellular signal transduction cascades upon ligand (e.g. a hormone) binding

Answer 6

G protein coupled recetptors

Question 7

___ has 7 hydrophobic plasma membrane spanning domains (___ Receptors)

Answer 7

G protein coupled receptors

Serpentine

Question 8

For G protein coupled receptors the hormone binding site is ___

Answer 8

extracellular

Question 9

G protein coupled receptors are coupled with ___ binding proteins in the cytoplasm

Answer 9

heterotrimeric GTP (G proteins)

Question 10

Key concept of G protein coupled receptors: Ligand-induced conformational change in the receptor facilitates interactions that initiate ___ signal transduction

Answer 10

intracellular

changes outside will cause changes inside cell

Question 11

three classes of G proteins

Answer 11

•G_s stimulates adenyl cyclase converting ATP to cAMP

• G_i inhibits adenyl cyclase decreasing cAMP levels
• G_q activates Phospholipase C: PIP2 >>> DAG + IP3

Question 12

•G_s stimulates adenyl cyclase converting ATP to ___

Answer 12

cAMP

Question 13

•G_i inhibits ___ decreasing cAMP levels

Answer 13

adenyl cyclase

Question 14

•G_q activates ___: PIP2 >>> DAG + IP3

Answer 14

Phospholipase C

Question 15

how does GPCR work

Answer 15

ligand binds

intracellular changes and binds to inactive heterotrimer G protein bounded to GDP

this causes GDP to break off and GTP binds and actives heterotrimer into active alpha with GTP bound

this will bind to effector protein and cause down stream activating

whole thing gets reversed to turn off

Question 16

how does tyrosine kinase receptors work?

Answer 16

enzyme linked receptors

ligand will bind and will bring two receptors closer to each other

they will phosphorylate each other

Grb2 will bind and trigger RAS pathway

Raf→ Mek → Map

this will trigger down stream intracellular response = growth of cell

Question 17

example of enzyme linked receptors

Answer 17

insulin receptor

Question 18

example of ion channels hormone receptors

Answer 18

GABA receptor

amino acid derived hormone will bind and cause rate of ions through channel to increase

least common type of receptor

Question 19

Binding of peptide hormones to receptors initiates a __

Answer 19

signal

Question 20

In plasma membrane receptors for amino acid derived hormones, the signal is passed on to a ___ which typically amplifies it.

Answer 20

second messenger,

Question 21

characteristics of second messengers of peptide hormone receptors (membrane bound receptors)

Answer 21

• Are small easily diffusible chemicals/intermediates
• Have very short half life
• They relay signals received at the receptors on the cell surface
• Serve to enhance the strength of the signal
• Affect more than one pathway and/ or protein
• Cause divergence of the signal

Question 22

3 types of second messengers

Answer 22

Cyclic nucleotides (eg. cyclic AMP and cyclic GMP)

Phospholipid derivatives (eg. Diacyl glycerol, Inositol triphosphate)

Ions (eg. Ca²⁺)

second messengers help increase signal from membrane bound receptors for protein derived hormones

Question 23

how does cAMP work as a second messenger

Answer 23

cAMP will bind to R which is attached to inactive PKA (protein kinase A)

R will let go of PKA and will activate PKA

active PKA can then lead to gene expression

Question 24

why have second messanger system

Answer 24

will greatly enhance the signal.

1→ many very quickly

Question 25

phospholipid derivative second messanger

Answer 25

phospholipase C will cut PIP into DAG and IP3 DAG will activate calcium channels in the cell membrane. influx of calcium will act as additional second messanger IP3 will active intracellular Ca channels

Question 26

•Ultimately, second messengers and downstream signal transducers activate, repress, or modulate ___ programs

Answer 26

gene expression

Question 27

**Signal transduction activates \_\_\_**

Answer 27

**transcription factors**

Question 28

\_\_\_ is the main way that cells generate a response to hormone binding. (Though not the only way – some signals stay in the cytoplasm)

Answer 28

second messanger (membrane bound receptors for amino acid derived hormones)

Question 29

•Gene expression programs are executed by \_\_\_

Answer 29

transcription factors

Question 30

example of nuclear hormone receptors

Answer 30

**used for steroid hormones** **glucocorticoid receptor** (21 carbon steroid hormone produced by adrenal cortex in response to stress) GR lives in cytoplasm, ligand (cortisol) comes into cell and binds and triggers GR to move to nucleus and causes gene expression

Question 31

how does GR move to nucleus

Answer 31

* GR is held in cytoplasm by **heat shock protein** complexes * Intracellular ligand binding (**eg. cortisol)** induces conformational change that frees GR from heat shock protein complex * Nuclear localization signal on GR induces translocation to nucleus will bind to GRE in the nucleus act as transcription factor

Question 32

nuclear receptors are used for ___ hormones

Answer 32

steroid

Question 33

•GR is expressed \_\_\_in most tissues

Answer 33

ubiquitiously

Question 34

•There are the same number of GR DNA binding motifs in the same genomic locations in \_\_\_, Y**et GR activation has different ___ in different tissues.**

Answer 34

all cells **effects** motif are different inside DNA. (DNA might be the same but it is wound or open in different spots- epigenome is different between cells)