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module 102: T3 molecular cell biology > intracellular signalling > Flashcards

intracellular signalling Flashcards

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1
Q

What are some types of intracellular signals?

A
  • ions
  • proteins
  • dissolved gases
  • second messengers
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2
Q

What are the two types of proteins used in signal transduction and where are they found?

A
  • hydrophobic proteins (membrane-associated)
  • hydrophilic proteins (cytosol)
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3
Q

What are the 3 ways signalling molecules are controlled?

A
  • by post translational modification
  • by regulating whether a G protein has bound (GDP or GTP)
  • by provision of activators
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4
Q

What is kinase and what does it do?

A
  • enzyme
  • phosphorylates proteins
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5
Q

What is phosphatase and what does it do?

A
  • enzyme
  • dephosphorylates proteins
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6
Q

What are the 2 enzymes involved in protein phosphorylation?

A
  • kinase (phosphorylates)
  • phosphatase (dephosphorylates)
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7
Q

What are the two types of kinases?

A
  • serine/threonine kinases
  • tyrosine kinases (non receptor and receptor)
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8
Q

What are GEFs and what do they do?

A
  • guanine exchange factors
  • promote exchange of GDP for GTP
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9
Q

What is Ras? Why is it significant?

A
  • a small GTPase
  • Ras mutations found in a large proportion of adenocarcinomas
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10
Q

What are voltage gated Na+ channels composed of?

A
  • alpha subunit
  • 4 beta subunits
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11
Q

How do voltage gated Na+ channels stop other ions from getting through?

A
  • too small for K+ ions to cross
  • contains negatively charged amino acids to stop Cl- ions passing
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12
Q

What do the alpha subunits in voltage gated Na+ channels do?

A
  • opens in response to a change in voltage
  • contains 4 homologous domains that form the pore
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13
Q

What do the beta subunits in voltage gated Na+ channels do?

A

traffic the channel and regulate its kinetic properties

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14
Q

How do the alpha subunits detect voltage?

A
  • 4 homologous domains have 6 transmembrane regions
  • region 4 has AA with positive R-groups which sense the voltage
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15
Q

How does the nicotinic acetylcholine receptor work?

A
  • 2 acetylcholine molecules bind the alpha subunits
  • causes movement of the M2 helices (opens channel)
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16
Q

Describe the structure of the nicotinic acetylcholine receptor

A
  • 5 subunits (2 alpha, beta, gramma, delta)
  • transmembrane region M2 of each subunit forms channel
17
Q

How are the effects of Ca2+ mediated?

A
  • kinases (e.g CAM kinase)
  • phosphatases (e.g Calcineurin)
18
Q

What types of channels are Ca2+ channels?

A

ligand gated or voltage gated

19
Q

What is the structure of a G-protein coupled receptor

A
  • typically has 7 transmembrane domains
20
Q

How does G-protein coupled receptor activation work?

A
  • ligand binds to receptor, and affinity for G-protein increases (may already be coupled)
  • receptor activation changes conformation of internal portion of receptor, releasing GDP
21
Q

How does the GPCR initiation of signalling work

A
  1. GDP attached to alpha subunit is replaced by GTP
  2. alpha subunit and beta-gamma complex dissociate (can each initiate further signalling)
  3. GTP then hydrolysed to GDP and beta-gamma recombine with alpha subunit
22
Q

What are the types of GTP-binding proteins?

A
  • small GTPases
  • heterotrimeric G proteins (in GPCR signalling)
23
Q

How is GTP-binding protein activity regulated?

A
  • guanine exchange factors (GEFs)
  • intrinsic GTPase activity
  • GTPase-activating proteins speed up hydrolysis of GTP
24
Q

Which 3 subunits to G-proteins consist of?

A

alpha beta gamma

25
Q

What are the steps happening the beta adrenergic receptor (relaxation of blood vessels in skeletal muscle)?

A
  1. GPCR
  2. GTP binds to G-alpha S on G protein
  3. adenylyl/andenylate cyclase converts ATP to cAMP
  4. cAMP activates PKA
26
Q

How does cholera affect us?

A
  1. cholera toxins inhibit GTPase activity of subunit G-alpha S
  2. prolonged signalling causes water and Cl- to move out of the cells lining the intestine (cAMP activates the cystic fibrosis transmembrane conductance regulator CFTR)
  3. results in diarrhoea, severe dehydration and death
27
Q

How does whopping cough come about?

A
  1. bordetella pertussis bacterium releases an active adenylyl cyclase domain
  2. pertussis toxin renders G-alpha i inactive (inhibitor for adenylyl cyclase)
  3. prolonged signal stimulates coughing

module 102: T3 molecular cell biology (16 decks)

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