Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Molecular + Cellular Neuro > Intracellular Signalling > Flashcards

Intracellular Signalling Flashcards

1
Q

Name some of calcium’s roles in signalling (8)

A
  • Synaptic transmission
  • Neuronal excitability
  • Signal amplification - 2nd messenger
  • Synaptic plasticity
  • Regulation of gene expression - (in neuron) regulates TF’s eg Kreb
  • Axonal growth - guidance + branching - steer dev axons to target cells + formation
  • Neuronal survival
  • Regulation of neuronal cytoskeleton
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

EF hand proteins background (4)

A

also known as calcium binding proteins
-120 families of EF hand proteins
- EHelix-loop-Fhelix
- present in wide variety: bacteria to humans
- various roles eg muscle contraction, enzyme activation, gene expression reg, neurotransmitter release

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Name + explain an EF hand protein (3)

A

Eg : calmodulin and parvalbumin

calmodulin:
- found in almost all eukaryotic cells
- regulates the activity of numerous enzymes + other proteins by binding to ca2+ ions and transmitting ca2+ signals to downstream targets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how do EF hand proteins work? (3)

A

1) bind to ca2+
2) confirmational changes to protein
3) = allows them to sense [ca]i changes = sensors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do we measure calcium + eg? (4)

A

using chemical or protein based fluorescent indicators - (has EGTA bound to it)

eg. Indo-1
- emits fluorescence once bound to 2 calcium ions
- usually emits light around 350-380 nm
- shorter + longer wavelengths ratio analysed = monitor changes in [ca]i

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Calcium enters through… (4)

A
  • Voltage operated channels (VOC)
  • Ligand operated channels (LOC) - + other non-selective channels: Ach r’s + ATP r’s = ALLOW INFLUX OF CA2+ INTO CELL
  • Store-operated channels (SOC) - empties ER ca2+ store
  • Transient receptor potential (TRP)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does the removal of excess calcium take place? (3 + 3)

A
  • Plasma membrane Ca2+–ATPase (PMCA) :
  • form phosphorylated intermediates during x cycle + calmodulin binds to c terminal at certain splice variants
  • ca2+ + calmodulin = confirmational changes
  • Na+-Ca2+ exchanger (NCX):
  • at rest: 3na+ for 1ca2+
  • bidirectional
  • voltage dependent = reverse their exchange na+ during AP’s = NA out of cell and Ca into the cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Endoplasmic reticulum background (2)

A
  • Primary intercellular calcium store - spanning large distances = can move ca2+ in and out of cells w/o detrimental effects eg local control as opposed to global - accumulation

3 main compartments:
* Smooth
* Rough
* Nuclear envelope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Calcium retrieval into the ER (4)

A
  • [Ca2+] 100 to 800 mM (microM in cytoplasm)
  • SERCA pump facilitates transfer - energy intensive pump requires the hydrolysation of ATP
  • 2 Ca2+ ions transferred for each ATP –> moves across the gradient

SERCA 1 + 2: muscle
SERCA 3: other tissues eg brain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Release of calcium from ER to cytoplasm (4)

A

From either r:
-Ryanodine (RyR) receptor
- inositol(1,4,5)-triphosphate receptor (IP3R)

==> Both release channels from tetramers of identical subunits + have long Nterminal regions = binding sites for ATP, Ca + proteins (eg calmodulin)

They’re activated by:
-IP3
- calcium
-cyclic ADP ribose (cADPR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What’s the role of the mitochondria on Ca2+ dynamics? (3)

A
  • Can store vast quantities of calcium - but has to be regulated to avoid overproduction of ROS ( +inhibition of ATP + mito depol)
  • positioned in cytoplasm near areas of high [Ca2+]
  • Detect high [Ca2+] and produce energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does the mitochondria detect high [Ca2+] and produce energy? (7)

A

close relationship w/ER - bound by tethering proteins eg microtubules anchoring them together

1) ca release from ER in localised system

2) VDAnionC in atrial membrane supplies ca2+ to transporters in inner mito membrane = accumulation of ca2+ within mito.

3) elevated ca2+ = activates rate limiting step in TCA cycle = increased oxidative phosphorylation + promotes ATP synthesis

4) ADP transported from mito via adenine nucleotide transporter in exchange of ATP

5) Ca2+ exits mito via NA+/Ca2+ or Ca2+/H+ echanges = sequestered in ER by SERCA

6) necrosis occurs when high ca2+ w/ oxidative stress

7) = opening mito transit pores (MTP) = loss of ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a drug - definition? (2)

A

A chemical substance of known structure, other than a nutrient or an essential dietary ingredient which, when administered to a living organism, produces a biological effect.

With some exceptions, drugs act on target proteins, namely:
* receptors
* enzymes
* carriers
* ion channels.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a receptor - definition? (1)

A

Protein molecules whose function is to recognise and respond to endogenous
chemical signals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the two-state model of receptor activation? (5)

A

(image)
Resting <-> activated r* -> response

  • no ligand: high to low (skewed to resting)
  • ligand/endo r: low to high prob (high affinity for activated state = more likely to produce response)
  • Agonist: affinity R*>R
  • Antagonist: affinity R=R*, reduced availability of binding sites for other ligands
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Drug def (1)

A

Chemical applied to a physiological system that affects its function in a specific way

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Ligand def (1)

A

Any molecule or atom which binds reversibly to a protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Agonist def + types (3)

A

Drugs which ‘activate’ receptors

-full: = activated until r saturation/ max effect
- partial: partially elicits a partial response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Antagonist + types (1 + 4)

A

A drug that binds to the receptor without causing activation

  • neutral: binds but no effect
  • inverse: binds but inverses effect
    -Reversible: compete w/ agonist binding typically at the same site. Binds reversibly
  • Irreversible (covalent): Binds irreversibly to receptor. May change the conformation of the receptor to reduce ability of agonist to bind
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what 2 factors are often considered when looking at conc + effect graphs? (2)

A

Emax
EC50

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What’s Emax? (1)

A

The maximal response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What’s EC50? (2)

A

The concentration of a drug that gives half-maximal response

  • gives drug’s potency
23
Q

Orthosteric site def (1)

A

The primary ligand binding site of a receptor

24
Q

Allosteric site def (1)

A

A site distinct from the endogenous ligand

25
Q

Allosteric modulators

A

–Allosteric modulators impact receptor function by binding at a site distinct from the endogenous ligand

26
Q

How does allosteric modulation impact dose response curves? (affinity vs efficacy) (4)

A

image

  • positive AFF mod: moves left
  • negative AFF mod: moves right
  • positive EFF mod: moves up
  • negative EFF mod: moves down
27
Q

What are G proteins? (4)

A
  • Protein family that act as molecular
    switches inside a cell
  • Heterodimeric complex made up of a, b and g subunits
  • Activated by GCPRs (metabotropic r’s)
  • Many neurotransmitters react w/ both ligand gated ion + GPCRs
28
Q

What’s the heterotrimeric G-protein? (3)

A

αβγ subunits:
alpha
beta
gamma

attached to GDP

29
Q

How do GPCRs flip on a G-protein switch? - MoA (5)

A

1) Agonist (eg LH) binds to the r = causing conformational change in the GPCR

2) Change in r conformation activates heterodimeric G protein (αβγ) : inactive GDP bound –> active GTP bound

3a) GTP bound to α dissociates from βγ
3b) The activated G protein the activates an effector enzyme (e.g. adenylyl cyclase)

4) Effector generates an intracellular 2nd messenger (e.g cAMP)

30
Q

How do you flip off the G-proteins switch (2)

A

5) GTPase activity: α controls GTPA’s activity => binding of subunit to target = catalyses GTP -> GDP (inactivation of α)

6) α reforms w/βγ = αβγ but remains inactive

31
Q

Structure of abg protein (4)

A
  • crystal structure
  • 7 TM domain
  • G Protein binds to 3rd cytoplasmic loop
  • r smaller than G protein
32
Q

Egs of GCPRs (5)

A

Examples include:
* Adrenergic
* Dopaminergic
* Opioid
* Glutamatergic
* GABAergic

33
Q

What do all these GPCRs do? (4)

A

Functions include:
* Light detection
* Odorant detection
* Hormone detection
* Neurotransmission

34
Q

What are the 3 main families / classes of GPCRs + how are they classified? (5)

A

Heterotrimeric G-proteins (αβγ):
Family A
Family B
Family C

  • Genetic: high sequence homology within each family(the genetic sequence of the proteins within each family is very similar)
  • Structural: Each family has a distinct location of agonist binding domain and length of extracellular N-terminus
35
Q

Family A egs (6)

A
  • Adrenergic
  • Rhodopsin
  • Opioids
  • Odorant
  • Adenosine
  • Cytokines
36
Q

Family B egs (3)

A

Receptors for peptide Hormones
* e.g. Glucagon,
* Growth hormone
* Parathyroid hormone

37
Q

Family C egs (4)

A
  • Metabotropic glutamate receptor (mGluR)
  • GABAB receptor
  • Pheromones
  • Taste receptor
38
Q

How do G-proteins transduce and amplify signals? (4)

A

1) 1 ligand binds to 1 r

2) r can signal to eg 4 bound G proteins

3) G proteins go + activate multiple effector enzymes (2 amplifications of the response)

4) effector enzymes further amplified by acting on many diff targets

39
Q

How does each kind of receptor produce a distinct pattern of cellular effects - eg adrenaline? (2)

A
  • Receptors activate different types of G-proteins
  • There is molecular variation in α-subunit of the G-protein
40
Q

Not all G proteins are the same - explain (3)

A

In humans:
16 Gα
5 Gβ
12Gg
-> These can combine to form different heterotrimeric G proteins

  • There are 4 Ga subunit families that are classified by sequence, effector targets and GPCRs
  • Gαi/o
  • Gαs
  • Gαq
  • Gα12/13
41
Q

2nd messengers egs (3)

A
  • Membrane associated, water insoluble
    e.g. diacylglycerol (DAG)
  • Cytosolic location, water-soluble
    e.g. cAMP, cGMP and Ca2+
  • Gases
    e.g. nitric oxide
42
Q

Properties of Metabotropic Glutamate Receptors (6)

A

Depending on subtype can be pre- and/or postsynaptically localised

Generally play a modulatory role in synaptic transmission

Postsynaptic group I mGlu receptors mediate slow depolarization (EPSP)

Presynaptic group II and III mGlu receptors decrease neurotransmitter release

Involved in the modulation of signalling through K+ and Ca2+– control excitability of
neurones

Metabotropic glutamate receptors were desirable targets for drug
discovery.

43
Q

Metabotropic Glutamate Receptor Family (mGlu1-8) subtypes (3)

A

Group I: mGlu1 & mGlu5
Group II: mGlu2 & mGlu3
Group III: mGlu4, mGlu6, mGlu7, mGlu8

R’s placed into 3 groups according to AA sequence
homology, signal transduction mechanism and agonist pharmacology

44
Q

Group selective
Agonists for mGluR (3)

A

I: DHPG
II: LY404039
III: L-AP4

45
Q

Group I: Gq (4)

A

ca2+ dependent

1) glut binds to 1/2/5 r = dissociation of alpha subunit (GDP-> GTP)

2) GTP binds to PLC =
breakdown of PIP2 into IP3 + DAG

3) IP3 acts on IP3r in ER
DAG activates phosphokinase C

= inc. [Ca2+]I

46
Q

Groups II + III: Gi/Go (4)

A

cAMP dependent

Activation of Gi/o coupled receptors:
bind - dissociation of alpha subunit (GDP-> GTP)
1) Inhibits cAMP production
2) Activates GIRK K+ channels
3) Inhibits voltage-sensitive Ca2+
channels

47
Q

mGlu Receptor structure (4)

A
  • Bi-lobed N-terminal extracellular domain - glutamate binding site (orthosteric site)
  • Cysteine rich domain = maintains
    tertiary structure
  • 7-TMD in
    common with other GPCR families (allosteric
    modulators bind at sites in the TMD)
  • 2nd intracellular loop involved in G-protein
    coupling and in determining transduction
    mechanism
48
Q

X-ray crystallography of the ligand binding region reveals a homodimeric structure for mGlu1(6)

A

The ligand binding region (LBR) of mGlu1 has been expressed in
soluble form

X-ray crystallographic analysis showed mGlu1= homodimeric

The 2 protomers connected by a disulphide bridge b/w cysteine residues present on both LB1s of the LBRs

Bilobed structures (LB1 + LB2) of each protomer are flexible +can form open or closed conformations

X-ray structure showed Glu bound to both protomers one with
lobes closed and one with lobes open – corresponds to an activated state

Research suggests that lobes should be closed in both protomers for fully activated state.

49
Q

Describe the constitutive activation of group I mGluRs + eg (2)

A

Spontaneous lobe closure in the absence of the agonist can lead to mGlu receptor activation (constitutive activity) + basal activity of the receptor

e.g. basal levels of phosphoinositide hydrolysis – blocked by inverse agonists

50
Q

What does glutamate binding do to mGluRs? (1)

A

Glutamate binding stabilises the activated statewhile orthosteric antagonists bind to the resting state to prevent the lobe closure that would lead to receptor activation

51
Q

Explain how MPEP is a Negative Allosteric Modulator of mGlu5 (3)

A

MPEP = Negative Allosteric Modulators
(NAMs)

binds to TM region AA residues ii + iii in mGlu5 to inhibit the glutamate-stimulated rise in intracellular [Ca2+]

Increasing concentrations of MPEP decrease the maximum response of a glutamate conc response curve on rat mGlu5

52
Q

Positive Allosteric Modulators (PAMs) e.g.
Ro 01-6128 (3)

A

binds to AA residues in TMIII and TMV

Concentration-response curves for the effect of (S)-DHPG on mGlu1 are shifted to the left in the presence of Ro 01-6128

A 5-fold decrease in EC50 value and a 1.2-fold increase in the maximum response was observed in the presence of Ro 01-6128 i.e. change in efficacy of orthosteric agonist DHPG

53
Q

Why is there a Slow EPSP from mGlu1 Receptor compared to ionotrophic r’s? (3)

A

because they’re not largely driven by an ion chance but the release of ca2+ from stores

= longer time to see ESPC (slower + more mediated = cant see)

==>biphasic distribution seen:
- fast depol by AMPAr + glut r
- much slower depol by mGlutr

Molecular + Cellular Neuro (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions