biotech 6 : signal transduction 2

how many times do GPCRs span the membrane?

how many times do Enzyme Linked Receptors span the membrane?

7

1

Enzyme linked receptors either have their own intrinsic enzyme (often ___________) or they become bound to ________________

kinase

enzyme

RTKs are the most common enzyme linked receptor families, and usually have their own intrinsic ________________ ____________ activity

tyrose kinase

most RTKs dimerize after a ligand binds to them, what does that mean?

once a ligand binds the receptor pairs up with another receptor (it can be the receptor or a different kind)

what are the four enzyme linked receptors in the Epidural Growth Factor family? Include all of the names they are called

1. EGFR1 - ErbB1 —Her1

2. EGFR2—ErbB2—Her2

3. EGFR3—ErbB3 — Her3

4. EGFR4—ErbB4—-Her4

what ligands bind to EGFR1 (Erb1—Her1)?

EGF

TGF-a (tumor growth factor-a)

what ligands bind to EGFR2 (Her2— Erb2) ?

no ligands bind to EGFR2 but it attaches to other receptors (dimerizes) to strengthen their signals once a ligand binds to them

what ligands bind to EGFR3 (Erb3— Her 3) ?

HRGs

which ligands bind to EGFR4 (Erb4—Her4)?

HRGs

BTC

EREG

what are three pathways activated by RTK

1. MAP kinase

2. P13K, AKT pathway

The ________ module is highly conserved throughout evolution

MAP Kinase

SEQ: GENERAL MAP Kinase Pathway

1. RTK

2. Ras

3. MAPKKK(Raf)

4. MAPKK (MEK)

5. MAPK (ERK)

6. nuclear signals, transcription factors, gene expression

what makes up the kinase cascade (three-component system) of the MAP Kinase cascade?

1. MKKK (Raf)

2. MKK (MERK)

3. MK (ERK)

SEQ: MAP Kinase Pathway

1. Ligand binds to RTK

2. RTK dimerizes and dimers phosphorylate each other

3. Grb2 (adapter protein) binds to phosphorylated RTK

4. Sos, an exchange factor for Ras, binds to Grb2

5. By binding to this complex, Sos gets recruited to the membrane where it activates Ras

6. Ras recruits Raf to membrane

7. Raf(serine/threonine kinase) gets activated through phosphorylation

8. Raf phosphorylates and activates MEK

9. MEK phosphorylates and activates ERK

10. ERK translocates to the nucleus

11. ERK phosphorylates and regulates transcription factors

12. Gene expression is modulated

how does Raf (MAPKKK) get phosphorylated and activate MEK (MAPKK)?

what phosphorylates MEK?

What does MEK (MAPKK) then phosphorylate? specifically, where does it add proteins?

what happens after that?

• autophosphorylation or other kinases

• Raf (MAPKKK)

• ERK (MAPK) on thr and tyr residues

• MAPK translocated to nucleus where it phosphorylates TRANSCRIPTION FACTORS

• gene expression is modulated

how many major MAP kinase pathways are there in mammalian cells? what are they?

3

ERK

JNK

p38

_______is an important signaling protein in the MAP kinase pathway functioning as a MOLECULAR SWITCH

Ras

Ras is apart of a family of monomeric ______ binding proteins

GTP

Which family members of Ras are in charge of relaying signals from RTKs?

H-Ras, K-Ras, N-Ras

Which family members of Ras are in charge of activating mTORs to stimulate cell growth?

Rheb

Which family members of Ras are activated by cyclic-AMP dependent GEF; influences cell adhesion by activating integrins

Rap1

How do MAP kinases play a role in normal cell growth?

regulate genes such as CyclinD which is important for cell cycle progression

Which components of MAP kinase, when improperly activated, can lead to cancer?

EGRR, Ras, Raf

DRUGS MADE TO INHIBIT THEM IF OVERACTIVE

Which component of the MAP kinase pathway is blocked by Krazati (adaqrasib)?

inhibits tumor growth of cells that have mutant K-ras genes

• binds to KRAS locking it in its inactive state (binds to S-IIP region of ras preventing hydrolysis of GTP)

• does not interfere with with wild-type KRAS minimizing side effects

• used to treat metastatic, non-small lung cancer in aduolts

SEQ: P13K / AKT signaling pathway

1. RTK activated by ligand

2. RTK dimerizes and phosphorylates each other on their tyrosine regions

3. P-13 Kinase (P13-K) binds to the phosphorylated RTK via the SH2 domain (on the p-tyr portion region)

4. P-13 translocate to membrane close to substrate PIP2

5. P13 phosphorylates PIP2 resulting in PIP3

6. PDK1 binds to PIP3 via PH domain (binds to phosphoinositide)

7. AKT ALSO binds to PIP3 via PH domain

8. PDK1 phosphorylates AKT

9. activated AKT phosphorylates various targets associated with cell survival

how does Truqdab inhibit the P13K/AKT pathway?

Prevents AKT from being phosphorylated by PDK1

treats hormone-positive Her2 negative breast cancer

how does Joenja inhibit the P13K/AKT pathway?

inhibits overactive P13-K causing abnormal growth of white blood cells

what does mTOR stand for?

Target of Rampamysin

what is rampamysin? what is it used for?

bacterial toxin

• used as immunosuppressant and anti-cancer drug

mTOR is a ________/________ kinase

serine/threonine kinase

mTOR exists in which two protein complexes?

what does each contain?

what does each do?

mTOR1 —raptor—stimulates cell growth

mTOR2 ——rictor—promote survival by activating AKT (also regulates cytoskeleton)

which mTOR promotes survival by activating AKT and also regulates the cytoskeleton?

mTOR 2 —-rictor

which mTOR stimulates cell growth

mTOR1 - raptor

which mTOR stimulates AKT? which mTOR is stimulated BY AKT?

mTOR 2—stimulates AKT

mTOR 1— stimulated BY AKT

mTOR pathways are involved in regulation of various cell processes including

• cell growth

• proliferation

• metabolism

• protein synthesis

• coordinate how cells respond to nutrient availability, growth factors, energy status, and stress conditions

Does Rapamune (rapamycin/sirolimus) inhibit or enhance mTOR? what does it do?

• rapamune INHIBIT mTOR leading to reduction of t-cell activation and proliferation (immunosuppressant)

• used for transplant patients to avoid negative immune response

• treats cancer with other medicines

VEGFR is an example of a

RTK

binding of VEGF to VEGFR on the surface of endothelial cells leads to

angiogenesis (blood vessel growth)

Vabysmo is a drug in the form of a monoclonal antibody that inhibits VEGFR. What happens as a result.

abnormal angiogenesis is blocked treating wet aged-related macular degeneration (wAMD) and diabetic macular edema

what can be used to treat the abnormal growth of blood vessels which extend into the subretinal space (area between retina and outer layers of eye) leading to vision loss?

Inhibitors of VEGFR( promotes angiogenesis) and Ang-2 (helps red blood vessel stability) — don’t want to be stable want to DIE

Herceptin (monoclonal antibody) targets HER2 receptors which are _________. what does this do?

RTKs

treats HER2 positive cancer by inhibiting increased (overexpressed) HER2 receptors to prevent rapid division

Tykerb is also used to treat HER-2 positve breast cancer. What does it do?

Inhibit overexpressed HER2 and EGFR RTKs to prevent rapid cell division

Sutenet is used for several types of cancers including kidney cancer, gastrointestinal stromal cancers, and pancreatic nueroendocrine tumors

what does it target?

RTKs : VEGFR, PDGFR, and KIT

inhibit binding to prevent growth through RTK pathway

what is the difference between Intracellular receptors and RTKs and GPCRs? (where are they found)

RTK and GPCR pathways have membrane receptors

Intracellular receptors are found in CYTOPLASM or on NUCLEAS

what are the substrates/ ligands for intracellular receptors?

1. steroid hormones

2. thyroid hormones

3. retinoids

4. vitamin D

do the ligands that bind to intracellular receptors typically travel the blood stream freely?

NO since they are LIPID soluble they require carrier proteins to be carried throughout the blood to get to their intended cell

activation of intracellular receptors leads to an activation of ___________________________ and regulation of target _____________

activate transcription factors

regulate target genes

intracellular receptor ligands:

_________________: responsible for secondary sex characteristics

_____________: main glucocorticoid! regulates blood sugar levels, suppresses inflammation, responds to stress

___________: regulates Ca2+ metabolism, uptake, and excretion, important for bone health (promotes bone reabsorption)

____________: increases metabolic rate of many cell types

______________: regulate growth and differentiation

• steroid sex hormones

• cortisol

• vitamin D

• thyroid

• retinoids

an overproduction in which intracellular receptor is seen in some types of breast cancers

Estrogen Receptor (ER)

What are the major categories of drugs that can treat ER+ breast cancer?

1. SERMS

2. SERDS

3. Aromatase Inhibitors

how do SERMs treat ER+ breast cancer?

Selective Estrogen Receptor Modulators bind to Estrogen receptors and block the effects of estrogen

COMPETITIVE INHIBITOR OF ESTROGEN

how do SERDS treat ER+ breast cancer?

Selective Estrogen Receptor Down-regulators bind to estrogen receptors and PROMOTE THEIR DEGREDATION

how to aromatase inhibitors treat ER+ breast cancer?

inhibit aromatase which is an enzyme that helps synthesize estrogen

prevents estrogen from being made and binding to overactive/expressed ERs

example of SERM

tamoxifen binds to ER

selective estrogen receptor modulator PREVENTs estrogen from binding to estrogen receptor

example of SERDs

orsedu and faslodex used to treat ER+/HER2- metastatic breast cancer

orsedu used with SERM

how do arimidex, aromasin, and femara work?

inhibit aromatase which is used to synthesize estrogen

Glucocorticoids:

• steroid hormones that are produced in the ________________

• what is the primary glucocorticoid in humans? how does it work?

• adrenal gland (above kidney)

• cortisol (hydrocortisone

SEQ pathway of cortisol:

1. cortisol binds to Glucocorticoid receptor in cytosol

2. glucocorticoid receptor / cortisol complex translocate to nucleas

3. still bound to its receptor, cortisol binds to GRE at the promoters of target genes

Functions of glucocorticoids:

• ______- inflammatory and immuno________________ effects

• regulates the metabolism of___________

• released in response to ________ . _____________ blood pressure and modulate the immune system to prepare the body for _____________ situations

• ANTI- inflammatory and imunoDEFICIENT effects

• carbohydrates, proteins, lipids

• stress— higher blood pressure fight or flight

are Deltasone (prednisone), Decadron (dexamethasone), and Cortef (hydrocortisone) synthetic agonists or antagonists for glucocorticoids?

what can they treat

agonists!

• inflamatory disorders such as allergies, rheumatoid arthritis, asthma, and inflammatory bowel disease

• can be used to suppress immune system after TRANSPLANT

what kind of receptor is AhR (aryl hydrocarbon receptor) ?

intracellular

SEQ AhR signalling

1. environmental chemicals bind to AhR

2. AhR dimerizes with ARNT and form transcriptional factor complex

3. complex binds to XRE on promoter of target genes regulating gene expression

4. decreased inflammation, oxidative stress, and sometimes detoxification!

what can happen if there are issues with AhR signalling?

psoriasis (thickening of skin / inflammation)

the drug tapinarof has been shown to induce the expression of _______ barrier genes related to __________ differentiation that are downregulated in psoriasis

does tapinarof act as an AcH antagonist or agonist?

skin

keratinocyte

AGONIST will lead to decreased inflammation and oxidative stress