Hormone Action/insulin/glucose

Front 1

What are hormones?

Back 1

Chemical messegers that transport signals from one cell to another through the bloodstream

Front 2

What are the major hormone producers?

Back 2

Pineal gland, ovaries, testes, thymus, thyroid gland, pituitary gland, adrenal gland

Front 3

What are the two types of hormones?

Back 3

1)Polypeptide
2)Steroid

Front 4

What are the differences between polypeptide hormones and steroid hormones? Examples?

Back 4

Polypeptide hormones: polar, water soluble, hydrophilic, large proteins. Ex: Epinephrine/dopamine (amino acid derivatives)
Steroid hormones: apolar, hydrophobic, water insoluble Ex: testosterone, estrogen (cholesterol derivatives) Need a carrier to go trough the blood

Front 5

What is the method of action for peptide hormones?

Back 5

Hormone binds receptor on the cell, causes a conformational change of the receptor, activates 2nd messenger. Get a signal cascade and 2nd messenger will enter nucleus and alter gene transcription

Front 6

What is the method of action of Steroid hormones?

Back 6

Diffuse across the cell mb, where they interact with cytoplasmic factors, which transport them or make them soluble. They end up in the nucleus and bind nuclear hormone receptors. Fct as TF

Front 7

Which hormone is faster acting? Why?

Back 7

-Peptide hormone.
-Meet their receptor earlier and cause rapid cascade (instead of ghaving to diffuse across the mb)

Front 8

What are the hormone classifications (3)?

Back 8

1) Endocrine: Source far away from target
2) Paracrine: Source close to target
3)Autocrine: act on same cell or same cell type

Front 9

What are the mechanisms of action for signal transduction? (4)

Back 9

1) Specificity: Hormones very specific. One molecule for one receptor. Receptor has very high affinity for its ligand. Also cooperativity and amplification between the ligand and the receptor (small change in [ligand] drastically changes receptor activation)
2) Amplification: activation of downstream effectors. Small change in conc causeshuge cascade
3)Desensitization: Negative feedback signal. Output signal: response from hormone binding receptor can turn off the hormone
4) Integration:2 dif hormones activate 2 dif paths that work tog to modulate a response

Front 10

What are the different receptors that mediate the mechanism of action of teh hormones? (6)

Back 10

1)Gated ion channels
2)Receptor Enzymes
3)GPCR/Serpentine receptors
4)Steroid receptors
5)Receptor w/ no intrinsic enz activity
6) Adhesion Receptors

Front 11

What are two methods to measure hormone concentration?

Back 11

-RIA
-RRA

Front 12

What does RIA involve?

Back 12

-Need radiolabelled hormone and specific antibody
-have unknown [hormone] and perform binding competition btw labelled and unlabelled hormone to a known amount of antibody.
-Plot a standard curve using unbound:bound ratio

Front 13

What is RRA?
What can it be used for?

Back 13

Same as RIA, but uses a receptor instead of an antibody
-Can be used to determine the [hormone], the receptor density and the affinity of the receptor for its hormone

Front 14

What ae the three major types of experiments? Describe them.

Back 14

1)Kinetic: Measures the association and dissociation rate constants
R + L<---> RL
K1 (K on): depends on [unbound hormone] and [unbound receptor]
K-1 (K off): depends on bound RL complex
2)Saturation:Measure max binding and diss't constant (Kd)
Kd=(K off)/(K on)=[R][L]/[RL]
Smaller the Kd, higher the affinity of the ligand for its receptor
Kd= [] at which 1/2 the binding sites are occupied
3)Inhibition: determine Ki
Ki= [inhibitor] at which 1/2 of the receptor sites are occupied by the inhibitor

Front 15

Describe the Scatchard plot.

Back 15

-Slope= -1/Kd
-X-intercept= Bmax (receptor density)
Y= -B/Kd + Bmax/Kd

Front 16

When is the Scatchard plot linear? Curved? Examples.

Back 16

Linear: when binding of hormone to receptor is independent (independent receptor site)
Curved: can be positive or negative curve. Indicates cooperativity
Positive curve: binding of hormone to one receptor, increases the receptor's affinity to attract other hormones (Hb and O2)
Negative curve: binding of hormone tothe receptor decreases the receptor's affinity for other hormones (Insulin)

Front 17

What is diabetes?

Back 17

Insullin resistant syndrome

Front 18

What is the difference between type I and type II diabetes?

Back 18

Type I: Insulin dependent, pancreatic cells don't produce enough insulin
Type II; Insulin independent. Can be making enough insulin, but insulin receptors are insensitive to insulin and don't recognize it. Type II is considered a disorder of FA metabolism

Front 19

How can you mediate type I diabetes? Type II?

Back 19

Type I: Insulin shots
Type II: Weight loss/exercise

Front 20

What is Hypoglycemia shock?

Back 20

Overdose of insulin, body's cells takes up too much glucose to quickly, not enough glucose left in the blood

Front 21

What are the targets of glucose for storage?

Back 21

Fat cells
Liver cells
Muscle cells

Front 22

What are some properties of Insulin?

Back 22

-Secreted in response to high [glucose]
-Enhances glucose transport from blood to body cells
-Stimulates glycogen synthase
-Inc oxidation of glucose to CO2
-Enhances ptn synthesis
-Blocks gluconeogenesis (inhibits Pyruvate carboxylase and fructose diphosphate)
-Works at very low concentrations
-Interacts w/ insulin receptor

Front 23

How is insulin processed?

Back 23

-Starts as preproinsulin
-Preproinsulin's signal seq is cleaved by proteolysis to become Proinsulin
-Proinsulin is stored in the pancreatic cells
-Proinsulin is cleaved to get mature form of insulin

Front 24

In what form is insulin stored?
What form is it active in?

Back 24

Stored as a Hexamer (cuz its more stable, stabilized by a Zinc molecule)
Active as a monomer

Front 25

Describe the Insulin receptor.

Back 25

-Heterotetrameric tyrosine kinae receptor.
-2 extracell. alpha subunits, held tog by di-S bonds
-2 beta transmb subunits that have phosphotyrosine kinase activity'
-Has CR, KD, JM and CT domains
CR: binds insulin at alpha part
of receptor
JM: P sites
KD: kinase domain, gets P
CT: also gets P

Front 26

Describe the negative cooperativity of insulin binding its receptor.

Back 26

-When RIA performed, got curved scatchard plot
-insulin initially binds receptor with high affinity
-Max bio. response when 2% of receptors are bound (when more then this, binding becomes much less efficient)

Front 27

Why is the max biological response only 2%?

Back 27

-Glucose uptake=fast response
-want to slow down glucose uptake to counteract rapidity of this response otherwise can get hypoglycemic shock
.: need lots of spare receptors to have efficient insulin binding

Front 28

How does negative cooperativity affect people with type II diabetes?

Back 28

Ppl with type II already have low amt of receptors, so when just a little insulin in the blood, already surpass the 2%,insulin receptors are locked in low affinity conform.

Front 29

How does insulin induce negative cooperativity through binding?

Back 29

Insulin binds the two alpha chains assymetrically (binds site 1 on a1 and site 2 on a2) this disrupt the molec so receptor can't accept more insulin. cnfor change in a leads to conf. change in beta
-first binding with high affinity
-subsequent bindings=low affinity (cuz first binding pulls the 2 a-chains apart)

Front 30

What happens when insulin binds the insulin receptor?

Back 30

-Auto-P of 3 tyrosines in the kinase dom of the beta chain
-active site is stabilized and opened
-other tyrosines are P i the insulin receptor and downstream targets

Front 31

Whattype of downstream events does insulin activate?

Back 31

-Metabolism: glucose transport and glycogen synthesis
-Cellular growth and differentiation: RNA/DNA/Ptn synthesis

Front 32

What is IRS-1? What are its domain?

Back 32

Insulin receptor substrate-1. Has a role in mediating the effects of intracellular insulin
-PHD:anchors IRS-1 to mb
-PTB: Interacts with Y190 when its P, localizes it to insulin receptor
-C-terminus: has multiple Tyrosine P sites that are docking sites for SH2 domain containing ptns

Front 33

How is IRS-1 activated?
How does it activate glucose uptake?

Back 33

1)Tyr 960 (of JM) is P
2) 3 sites on KD are P (stabilize and keep KD open)
3)P of JM recruits IRS-1 thru PTB, which can then be P on 5 sits by KD (these P sites used to recruit other ptns)
4) IRS1-P recruits p85a of P13k which will bring catalytic subunit p110 (p110+p85=P13k)
5)P13k P PIP@ and makes it PIP3
6)PIP3 gets PKB
7)PDK1 P PKB
8) PKB-P recruits glucose transporter
9)PKB-P P GSK3
10)GSK3-P cant P glycogen synthase .: gluc-> glycogen
11)PKB stimulates mov't of vesicles to alow shuttle of glucose into the cell

Front 34

How does insulin activate/regulate gene transcription?

Back 34

1)Insulin binds its receptor, which auto-P on tyr residues
2)Insulin receptor P IRS-1 on its tyr residues
3)Grb2 recog. other 3 P sites on IRS-1 and binds. Grb2 ass't w/ SOS, which kicks out GDP for GTP and acivates Ras
4)Ras activates Raf
5)Map kinase path... eventually ERK-P, translocates into nucleus where it P SRF and Elk1
they dimerize and turn on DNA syn

Front 35

How can the insulin receptor be regulated/turned off?

Back 35

1) Neg. fdbck, serine/threonine kinases turn off insulin receptor
2)Receptor mediated endocytosis: degrades receptor
3)Recycle the receptor

Front 36

How is glucose transported into RBC?

Back 36

GLUT1
1)GLucose binds to extracell part of GLUT1
2)Conform change of GLUT1
3)Outside of GLUT1 closes and inside opens
4)Glucose is transfered into the cell

Front 37

What happens to GLUT1 when insulin is present? Absent?

Back 37

When insulin is present, GLUT1 migrates to plasma mb
When insulin is absent, GLUT1 remain in the cell

Front 38

How do glucose transporters work?

Back 38

1)They're initially stored in cytosolic vesicles
2)Insulin binds receptor and transporter fuses with the mb
3)When glucse lvls dec, inslin lvls dec and transporters are recycled or degraded

Front 39

Does insulin increase exo or endocytosis of glucose transporters?

Back 39

Inc exocytosis of GLUT4 by 10-20 fold (and also dec its endocytosis)

Front 40

What are the 3 main kinases thatmediate glucose transport?

Back 40

-PDK1
-PKB
-PKC

Front 41

What does the lipid raft do?

Back 41

Stabilizes the signalling complex

Front 42

Wht is GLUT2?

Back 42

Glucose transporter in the B-islets of Langerhams cells in the pancreas.
When lots of glucose in the blood, GLUT 2 stimulated, leads to excretion of insulin

Front 43

What does insulin activate?

Back 43

1)Recruitment of glucose transporters (series of P, including PKB and PDK1)
2)other paths, including the regulation of lipid rafts using caveolin and flotilin

Front 44

When insulin levels are high, how is glucose stored?

Back 44

1)Glycogen (muscle and liver)
2)TAG: triacylglycerol (adipose tissue)

Front 45

WHat is the counteracting hormone to insulin?

Back 45

Glucagon

Front 46

What makes glucagon?

Back 46

alpha islet of Langerhans in the pancreas

Front 47

What does glucagon do?

Back 47

Stimulates glucose synthesis and glycogen breakdown in the liver
(glucagon released when low levels of glucose in the blood)

Front 48

What happens durig starvation?

Back 48

-Liver becomes main source of glucose
-Glycogen in the liver is broken down. G1P-> G6P-> glucose
-Ptns and TAG degraded and used in gluconeogenesis
-Excess acetyl CoA i transported out of iver to be made into ketone bodies (i.e. for the brain)

Front 49

What determines if glucose will be produced or degraded in the liver? How?

Back 49

-Ratio of insulin to glucagon
Itcontrols rates of gluconeogenesis and glycogenolysis?

Front 50

Describe GPCR.

Back 50

-Hepta helica transmb receptor
-Binds heterotrimeric G-ptn (which has alpha, beta and gamma subunits)
-When glucagon binds, G-ptn is recruited to GPCR and exchanges GDP for GTP
-G-alpha subunit can vary:
->Gs:stimulates adenylyl cyclase to get cAMP
->Gi:inhibis adenylyl cyclase
->Gq: stimulates phospholipase C

Front 51

What is epinephrine?

Back 51

-aa derivative hormone
-not a peptide hormone
-hormone and NT
--als known as adrenalin, fight or flight response

Front 52

How does epinephrine act?

Back 52

Breakdown glycogen in the liver and release lipids from fat cells to inc glucose lvls

Front 53

Describe the epinephrine receptor.

Back 53

-Beta adregnic receptor
-Also a GPCR
-hepta transmb helices
-when epinephrin binds, G-ptn recruited to the GPCR

Front 54

How is the epinephrine signal transduced?

Back 54

1) Epinephrine binds its receptor
2) Gs-GDP => Gs-GTP (active)
3) Gs activates adenylyl cyclase
4)Adenylyl cyclase causes conversion of ATP to cAMP
5) cAMP activates PKA
6) PKA P cell ptns and causes a cell response
7) cAMP is degraded, stopping the response, no more active PKA

Front 55

How are the glucagon receptor and epinephrine receptor (adrenergic receptor) related?

Back 55

-Effects of gluagon and epinephrine are additive (tho both receptors are found in different proportions)
-High epinephrine and glucagon leads to rapid glyconeolysis and .: glucose is released

Front 56

How is PKA regulatory?

Back 56

-P glycogen synthase and inhibits it (.: don't synthesize glycogen)
-P phosphorylase kinase and activates it.
-Phosp. kinase-P P glycogen phosphorylase, making it active so glycogen can be degraded to glucose.

Front 57

What is receptor desensitizaion?

Back 57

Receptor will stop responding after prolonged exposure to its hormone

Front 58

How is the B-adrenergic receptor desensitized?

Back 58

1)Epinephrine binds its receptor, causing Gs to diss't from the Gs/B/gamma
2)Free GsB/gamma recruits the B-adrenergic receptor kinase (BARK) which blocks further binding of G-ptns at the receptor and also P 2 serine residues on the receptor
BARK recruited cuz of Gs: prod adenylyl cyclase: ATP-> cAMP, activates PKA, P BARK
3) B-arrestin is recruited. It blocks further ass't with G-ptns and it induces endocytois of the B-adernergic-receptor
4)Arrestin allows receptor to diis't, be de-P and returned to the cell surface

Front 59

What is leptin important for?

Back 59

Appetite and weight (energy metabolism)
Satiety hormone

Front 60

How is leptin affected in ob/ob mice? In db/db mice?

Back 60

ob/ob: Leptin is mutated, since when paired with any other mice, they lose weight
db/db: Leptin receptor is mtated, since when paired with any other mice, still couldn't lose weight
=>defect in db or ob gene leads to obesity

Front 61

Properties of Leptin.

Back 61

-Protein/peptide hormone
-produced mostly by fat cells
-fct: regulate storage of fuel
-ssensed by hypothalamus

Front 62

What happens when adipocytes taking p a lot of FA?

Back 62

-Adipocytes get bigger and this is sensed by leptin
-leptin interacts with its receptor in the hypothalamus and tells brain to stop eating
-Leptin inhibits FA synthesis
-Leptin activates FA oxidation
-Adipocyte size starts to dec, .: produce less leptin
-Stomach releases another hormone that says fat stores have been used up

Front 63

Wht processes does leptin effect?

Back 63

Appetite
Metabolism (thru FA oxid)

Front 64

What are some properties of Leptin?

Back 64

-prevents accumulation of non-oxid FA
-Protects vs lipotoxicity
=> generates antilipogenic hormone that stops prod'n of lipids
-Prevents loos of fct/viability due to too much fat

Front 65

What's the difference between the insulin receptor and the leptin receptor?

Back 65

LR does not have intrinsic Tyr kinase activity, must recruit a kinase

Front 66

Which tyrosine kinase does leptin recruit?

Back 66

JAK-2

Front 67

What is the mechanism of leptin signal transductiokn in the hypothalamus?

Back 67

1)Leptin binds LR and causes dimerization, which recruits JAK kinases
2)When JAKs are close, they auto-P each other
3)JAK-P then P the LR
4)STAT is then recruited to the P-part of LR. (STAT has SH2 domain, which binds phosphotyrosine residues)
5)STAT is then P by JAK-P
6)STAT-P travel through cytosol as homo/hetero dimer
7)Translocation of STAT into the nucleuswhere it acts as a TF and activates specific genes

Front 68

How do insulin and leptincooperate to reduce food intake?

Back 68

-Leptin makes liver and muscle cells more sensitive to insulin
-Cross talk btw insulin kinases and leptin kinases
(Letin-LR activates JAK; Insulin Receptor has its own kinase activity. Both kinases can P IRS2, which goes on to activate PIP Kinase => inhibition of food intake and incorporaion of glucose inside the cells)

Front 69

What kind of receptor is the nicotinic acetylcholine receptor?

Back 69

Ligand-gated receptor

Front 70

What is Acetylcholine?

Back 70

-NT in nervous system
-Acts on neurons and muscle cells
-Activates nicotinic acetylcholine receptor
-Released by motor neurons

Front 71

How does acetylcholine work?

Back 71

-Released from motor neuron
-Diffuses acroos synaptic cleft
-Hits dendrites and binds nic.acetylcholine receptor
-triggers conform. change in receptor, get depolarization and then muscle contraction

Front 72

Which ions are involved in the response of the acetylcholine receptor to Ach?

Back 72

Na+, K+, Ca2+

Front 73

Describe the nicotinic ACh receptor.

Back 73

-It has 5 subunits (2 identical alpha, 1 beta. gamma, delta)
-4 transmb helical segments (M1-M4)
-M2 helices are amphipathic and interact with charged ions
-M2 helices always point inwards so +-ions can pass thru
-M1,3 and 4 are hydrophobix and stay on the inside, deal with lipids

Front 74

What happens if you don't have fctnal ACh receptors?

Back 74

Diseases: paralysis, stiff muscles