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Bio 331 Final Exam > Receptor Tyrosine Kinases > Flashcards

Receptor Tyrosine Kinases Flashcards

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Biology 101 flashcards
1
Q

What are the types of receptors

A

Receptor tyrosine kinases (RTKs)

Cytoplasmic protien tyrosine kinases

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2
Q

What are receptor tyrosine kinases

A

They are receptors that are directly activated by extracellular signals

They have a ligand binding domain

The kinase activity is in one part of the receptor

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3
Q

What are cytoplasmic protein kinases

A

They’re indirectly regulated by the ligand

Ex. JAK2

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4
Q

What are the types or RTK activation

A

Ligand mediated activation

Receptor mediated activation

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5
Q

How does ligand mediated activation work

Give a name of a ligand that does this

A

The ligand has 2 binding sites for each subunit of the receptor

The receptor pieces come together and dimerize (to get activated)

(Ex. Platelet derived growth factor) PDGF

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6
Q

How does receptor mediated activation work

Give a name of a ligand that does this

A

Each chain/peice of the receptor binds one ligand

Then the two peices come together as a dimer

Ex. Epidermal growth factor (EGF)

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7
Q

Each receptor has a

A

Kinase domain

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8
Q

What do the kinase domains on receptors do

A

Phosphorylates the other kinase domain of the receptor prince to activate it

Or Phosphorylates other area of the receptor to make docking sites for the signalling protiens to bind

This is called trans autophosphorylation

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9
Q

What is the similar in the structure of all the RTKS

A

They have a domain on the cytoplasmic side of the cell which is the tyrosine kinase domain

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10
Q

What is special about the insulin receptor

A

It’s dimer is held together by disulfide bonds

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11
Q

What is special about the PDGF receptor

A

It has immunoglobulin like domains

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12
Q

What is special about the EGF receptor

A

It has cysteine rich domains

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13
Q

What are autophosphorylation site

A

The receptors have these sites

can regulate the receptors kinase activity

Can serve as binding sites for cytoplasmic signalling molecules

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14
Q

What is the activation loop of a receptor

A

The loop in the kinase domain of the receptor

Has tyrosine residues that get phosphorylated by autophosphorylation

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15
Q

How is the kinase activity of a receptor controlled

A

By autophosphorylation where the tyrosine residues in the activation loop are phosphorylated

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16
Q

What happens after the activation loop is phosphorylated

A

It’s stabilized in a position away from the substrate binding site

This leads to activation of the kinase part of the receptor

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17
Q

After the kinase domain of a receptor is activation what can it do

A

It can phosphorylate other tyrosine residues of the receptors kinase domains that are next to it

These phosphorylated region can then act as binding site for the cell signalling protiens

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18
Q

What are the domains of the protiens that bind to the RTKs called

A

SH2 domain

SH3 domain

PTB

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19
Q

What is the SH2 domain

A

SRC homology domain 2

Domain if orotiens where It interacts with the phosphorylated receptor then itself gets phosphorylated

It binds to the phosphotyrosine domains

ex. STAT molecules have SH2

20
Q

What is the SH3 domain

A

Domain of a protons that Binds to hydrophobic proline amino acids of other protiens

21
Q

What is the PTB binding domain

A

Phosphotyrosine binding domain

Binds phosphotyrosine same as SH2

22
Q

What type of protiens come to the RTKS

A

Adaptor protiens (GRB2 bind to the receptor and brings other protiens to it)

Docking protiens (IRS: insulin receptor substrate)

Transcription factors (STATS)

Signaling enzymes (PLC, lipid kinases, phosphatases, GTPase activation protiens)

23
Q

What is special about GRB2

A

Has a sh2 domain (binds to receptor) and a sh3 domain (binds to protiens)

24
Q

What are accessory protiens

A

They are protiens that help regulate the activity of small g protiens

25
Q

What are the three types of accessory protiens

A

Guanine nucleotide exchange factors (GEFs)

GTPase-activating protiens (GAPs)

Guanine nucleotide dissociations inhibitors (GDIs)

26
Q

What are GEFs

A

They stimulate the dissociations of the gdp on the g protiens and promote binding to GTP

The activate the G protein

27
Q

What are gaps

A

The stimulate hydrolysis of the GTP on the g protien and decrease the duration of the signal

They inactivate the g protien

28
Q

What are GDIs

A

The inhibit/stop the release of the bound gdp

This keeps the GDP on the g protien and keeps it inactive

29
Q

What protien does the GRB2 bind to

A

At its SH3 domain it binds to SOS (the son of seven less)

30
Q

What is SOS

A

A GEF for the RAS g protien

31
Q

What is RAS

A

A G protien that helps in growth and proliferation of cells

32
Q

How do the accessory protiens help regular the activity of RAS g protien in the MAPK pathway

A

GAP: shortens the active time of RAS

GEF: stimulates the exchange of GDP to GTP which makes RAS active

GDI: inhibits the release of GDP to keep RAS inactive when there’s no need for a signal

33
Q

What is the whole point of a g protiens

A

To act as a molecular switch to regulate signal transduction

34
Q

What is special about the docking protien IRS

A

Gives versatility

It gives extra site of phosphorylation once bound to the RTK of the receptor. The receptor phosphorylates it to give it these extra sites

It bind to the receptor via a PTB/SH2 domain

35
Q

What protiens does the docking protien IRS recruit

A

Shp2: tyrosine phosphatase

PI3K: lipid kinase that phosphorylated inositol rings in the 3rd position

36
Q

What is an example of a signalling protien that goes to the nucleus after being activated

A

STATs

They have an SH2 domain where they need to bind to the receptor and each other to get tyrosine phosphorylated and activated

Only then can they go from cytoplasm into the nucleus and act as transcription factor to bind to dna

37
Q

How can the signal from STATs be shut off

A

By protiens with cytokine inducible SH2 domains that can bind to the receptor and block docking of STATS

Ex. CIS

38
Q

What are the names of the signalling enzymes that can bind to the receptor and get activated

A

Shp2

PI3K

Pi-PLC

All have SH2 domains

39
Q

What is the point of the mapk pathway

A

To signal proliferation of cells

40
Q

What is the first step in the mapk pathway

A

A ligand binds to the RTK

Phosphotyrosines from autophosphorylation on the receptor are used as docking sites for sh2 containing protiens

So GRB2-SOS gets bound to the receptor on the inner surface of the membrane

Then SOS which is a GEF activate the small g protien RAS

41
Q

What happens after RAS gets phosphorylated

A

A phosphorylation cascade where

MAPKKK GETS P from RAS

THEN MAPKK

THEN MAPK

42
Q

Once the last kinase (MAPK) is phosphorylated what happens

A

It activates transcription factors ex. Fos and Jun

They then go to the nucleus to transcribe the genes for cyclin D1 which makes the cell cycle go from G1 to S phase

In the end cell cycle occurs and more cells are made

43
Q

How does the Mapk pathway get turned off

A

MKP-1 eventually gets transcribed by the active Fos or jun

MKP-1 is a MAPK phosphatase that dephosphorylates and inactivated MAPK

This make Fos and jun inactive

44
Q

What is convergence

A

Signals from Unrelated receptors (ex. GPCR AND tyrosine kinase receptors) lead to the activation of a common effector

Ex. Ex. GPCRS, RTK, and integrins all bind to diff ligands but they can all lead to a docking site for GRB2

45
Q

What is divergence

A

A signal from one receptor can lead to activation a a variety of effectors

46
Q

What is crosstalk

A

Includes convergence and divergence where Signals can be passed back and forth between pathways

Ex.

In a GPCR, PKA from cAMP can block RAS from activating MapKKK and then it can just go into the nucleus and regulate the genes it wants to

But then in a RTK, RAS wants to activate mapKKK to make Fos or Jim go in the nucleus and regulate its own gene that it regulates

Bio 331 Final Exam (17 decks)

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