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MBB 231 > Chapter 15 Part 1 > Flashcards

Chapter 15 Part 1 Flashcards

Cell Signalling and Transduction

1
Q

extracellular response sequence (eight principles)

A

1) synthesis of signalling molecule
2) release of the molecule by exocytosis
3) movement of molecules to target cell
4) the molecules act as ligands to bind to the protein receptor on the target cell
5) binding causes a conformational change in the receptor
6) that initiates intracellular pathways
7) the receptor then gets deactivated and the ligand is removed

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2
Q

List the 4 types of intracellular signalling

A
  • endocrine
  • paracrine
  • autocrine
  • justacrine
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3
Q

What is endocrine signalling

A

the message molecules go through the bloodstream to be delivered to the target cell (ex. insulin)

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4
Q

What is paracrine signalling?

A

the message molecules only travel a short distance through extracellular space to target cell

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5
Q

what is autocrine signalling?

A

the cell itself releases messages molecules that go to receptors of the surface of the cell

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6
Q

What is juxtacrine signalling?

A

aka contact depending signalling. the target and secretary cells are adjacent to each other and most be physically in contact with each other. The secretory protein releases plasma membrane attached proteins to the target cell

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7
Q

What are the 3 types of cell surface receptors

A
  • enzymes linked
  • g protein coupled
  • ion channel linked
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8
Q

What is an intercellular receptor?

A

it is when the small hydrophobic molecules diffuse through the membranes and bind to the receptor protein in the nucleus or the cytoplasm

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9
Q

What is a first messenger molecule?

A

it is an extracellular ligand that will bind to the transmembrane to activate a second messenger response or turns it’s domain into a recruiting centre for cellular signalling proteins

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10
Q

What are the 2 different signalling pathways?

A
  • initiate a second messenger response
  • turn its domain to a recruiting centre for cellular signalling proteins
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11
Q

What is a second messenger molecule?

A

in one type of signalling pathway, the transmembrane receptor will signal an enzyme called an effector to generate a second messenger molecule

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12
Q

What can a second messenger molecule do?

A
  • it can activate or deactivate a protein by modifying the protein
  • it diffuse through the cytosol or get imbedded int he lipid bilayer
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13
Q

Which amino group residues are usually phosphorylated?

A
  • serine
  • threonine
  • tyrosine (sometimes)
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14
Q

What is amplification

A

when one small ligand can illicit a large response in a cell (usually each step the amount of molecules gets multiplied)

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15
Q

What are the types of receptors?

A
  • G protein coupled receptor
  • ligand gated coupled receptor
  • receptor kinase
  • nuclear kinase
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16
Q

What does it mean when protein domain dock?

A

allows domains of the receptor and other domains to interact

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17
Q

What does kinase mean?

A

phosphorylate

18
Q

What does phosphorylate mean?

A

dephorsphorylate

19
Q

What regulates phosphorylation and dephospohorylation?

A

first messenger ligands

20
Q

What are GTPases

A

an enzyme that hydrolyzes GTP to GDP changing the protein from active to inactive
- it usually has help from some GTPase regulatory proteins like GAPs, RGSs, GDI & GEF

21
Q

what is GAP?

A

it is a GTPase activating protein
- changes GTP to GDP by increasing the hydrolyzing power thus shorten the protein mediated response

22
Q

What is RGS

A

regulators of G protein signalling
- similar to GAP but done in a different location
- can deactivate a g protien

23
Q

What is GDI?

A

its a guanine nucleotide dissociation inhibitor
- doesn’t allow the GdP to dissociate so protein remains in an inactive state

24
Q

What is GEF

A

guanine nucleotide exchange factor
- factor needed to change form inactive to active by stimulating dissociation of g proteins

(inactive to active: GDP to GTP and active to inactive: GTP to GDP)

25
Q

Examples of GTPases

A
  • Rho
  • Ran
26
Q

What is a G protein and what are the names of the subunits?

A

is a protein composed of 3 subunits (Alpha, beta, and gamma) that is covalently bonded to membrane

27
Q

what are the other names for G protein?

A
  • large G protein
  • heterotrimeric G protein
28
Q

What is the structure of a GPCR

A

it is a receptor that has 7 transmembrane helices and a ligand binding spot and is coupled with a G protein

29
Q

What is special about the alpha subunit?

A

it is a GTPase

30
Q

How does signal transduction get started with a GPCR?

A

it is called activation
- the ligand will bind to the extracellular part of the domain and change the confirmation of the intracellular domain
- that increases the receptor affinity to the G protein

31
Q

What is GRK and what does it do?

A

it is the G protein coupled receptor kinase phosphorylation site
- its located in the cytosol and its the site for downregulation

32
Q

What is PKA?

A

Protein kinase A phosphorlaytion site used for down regulation

33
Q

What are the movement of proteins during signal transduction in GPCR

A

1) ligand binds inducing a conformational change in the receptor
2) This change increases the affinity to a G protien
3) Binding causes change in Ga triggering dissociation of GDP
4) GTP binds and the Ga dissociates
5) Ga binds to the effector activating it
6) GTP is hydrolyzes causing dissocation with the effector and rebinds to the other subunits

34
Q

What is desensitization?

A

the activated GCPR will make the GRK phosphorylate itself allowing arrestin to bind and desensitize the GCPR

35
Q

What is inactivation?

A

termination of the response and its usually caused by desensitization

36
Q

What is arrestin and what does it do?

A

they are proteins that compete with G protein’s spot on the receptor causing the receptors to be inactivated even if a ligand has binded

37
Q

how does a cell get resensitized?

A

the receptor is recycled and returned o the surface of the cell

38
Q

what is a effector?

A

it is the enzymes that catalyze the formation of then second messengers

39
Q

What is adenyl cyclase and what does it do?

A

it is a effector that makes cyclic AMP (cAMP)

40
Q

How is cAMP generated?

A

by adenylyl cyclase as a second messenger response

41
Q

How is cAMP related to PKA

A

cAMP activates protein kinase A

42
Q

what is AKAP?

A

it is a kinase anchoring protein that can be cell/tissue specific and it can confine PKA to
- microtubules
- ion channels
- mitochondria
- nucleus

MBB 231 (11 decks)

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