M2 Material

Question 1

What cytoskeletal component makes up the space under the PSD

Answer 1

Actin

Question 2

What is endocytic zone

Answer 2

Area neighboring PSD, hot spots for nt receptor endocytosis

Question 3

Types of glutamate receptors? Subtypes of ionotropic?

Answer 3

• Ionotropic (ligand-gated) (NMDA, AMPA, Kainate)
• Metabotropic (G protein-coupled)

Question 4

AMPA receptors:

Answer 4

• they are responsible for bulk of fast excitatory synaptic transmission through CNS, their modulation is mechanism that underlies plasticity of excitatory neurotransmission in brain
• can increase postsynaptic response to stimulus by: increasing amount of AMPA receptors, or increasing channel conductance (how long they’re open for)

Question 5

NMDA receptors:

Answer 5

• inactive at resting membrane potentials because pf voltage-dependent block of channel pore by Mg ions, preventing ions from flowing through
• sustained activation of AMPA receptors , depolarizes postsynaptic cells, releasing channel inhibition and allowing NMDA activation
• unlike AMPA receptors, NMDA receptors are permeable to calcium ions (and other ions). So NMDA receptor activation leads to a calcium influx into postsynaptic cell, a signal that is instrumental in the activation of a number of signaling cascades

Question 6

Kainate receptors:

Answer 6

• been implicated in epilepsy
• important in synaptic plasticity, shown to be important in LTP.

Question 7

G-protein coupled receptors:

Answer 7

INSERT IMAGE alpha subunit, depending on which G protein can activate 3 diff signaling pathways:
1. Alpha s activates adenyl cyclase, more cAMP, activate PKA, phosphorylates PKA targets

2. Alpha I has opposite effect, inhibits adenyl cyclase, effects on ion channels and proteins
3. Alpha q activate PLC (phospholipids C), breaks PIP2 down into 2 molecules, DAG and IP3. DAG activates PKC (phosphorylates targets), IP3 molecule binds to IP3 receptor on ER, leads to release on calcium from ER.

Question 8

Types of GABA receptors:

Answer 8

• GABAA: Ligand gated ion channels (ionotropic receptors)
• GABAB: G protein-coupled (metabotropic) receptors

Question 9

GABAa receptors:

Answer 9

• 5 subunits, 2 alpha, 2 beta and 1 gamma
• Allows chloride to flow through, cause hyperpolarization (inhibitory)
• Synaptic: involved in fast inhibition. Extra synaptic (next to active zone): involved in tonic inhibition

Question 10

How does activation of GABAa receptors produce a depolarization in immature but nor in adult neurons?

Answer 10

Normally when GABA activated, Cl enters and hyperpolarizes.
KCC2: allows Cl out. NKCC1 lets Cl in.
- In immature neurons, KCC2 expression is lower, and NKCC1 expression is higher therefore more chloride comes in (higher Cl conc inside). When GABA binds to receptors, Cl leaves. Results in depolarization. Excitatory.

• In mature neurons, KCC2 expression is higher, maintains low Cl conc (transports Cl out), NKCC1 brings Cl in, but higher expression of KCC2 so low Cl concentration internally. When GABA Is activated, Cl enters, causes inhibitory/hyperpolarization.

Question 11

GABAa receptor endocytosis

Answer 11

• signal for receptor endocytosis is dephosphorylation of receptor
• recycling of receptor involves similar proteins: clathrin, AP2, dynamin
• involves endosomes, can be degraded or sent back to membrane

Question 12

Mechanism for epilepsy (dysregulation of GABAa receptor trafficking)?

Answer 12

Repeated activation of pathways leads to dephosphorylation of receptors, now large numbers of GABAergic receptors being recycled or internalized. Fewer GABA receptors, less inhibition, more excitation.. mechanism for epilepsy

Question 13

presynaptic GABAb receptors

Answer 13

• can activate alpha i subunit, inhibits adenylyl cyclase (less cAMP)
• beta gamma subunit can bind to voltage gated calcium channels (has inhibitory effect, less calcium coming in). or they can bind to snare proteins and have inhibitory effects. effects synaptic vesicle exocytosis
• can have number of effects on presynaptic side that affects nt release.
• on postsynaptic side, can have effects on signaling through adenylyl cyclase, and binds to ion channels.

Question 14

Define long term potentiation and depression

Answer 14

Long-term potentiation: a long-lasting (hours or days) increase in the synaptic response of the neurons to stimulation of their affronts following a brief patterned stimulus (for example, 1s stimulation at 100 Hz).

Long-term depression: a long-lasting decrease in the synaptic response of neurons to stimulation of their afferents following a long patterned stimulus (for example, 15 min stimulation at 15 Hz).

Question 15

Molecular mechanisms of LTP:

Answer 15

• glutamate binds to AMPA receptors.. depolarization.. removal of Mg block on NMDArs.
• phosphorylation of AMPA leads to more expressed on plasma membrane, leads to increase in AMPA on membrane.
• long lasting forms require new proteins, new gene transcription or local translation of existing transcripts.
• BDNF also plays role in synaptic plasticity
• structural change: bigger spine head and neck
• functional change: more AMPA receptors

Question 16

Molecular mechanisms of LTD:

Answer 16

• induction of LTD triggered by activation of NMDAr
• The Ca2+ transient determines the polarity of the induced plasticity, with low and prolonged Ca2+ transients inducing LTD and brief, steeper transients inducing LTP.
• results partly from dephosphorylation of AMPA receptors
• presynaptic mechanisms also contribute

Question 17

Glutamate excitotoxicity:

Answer 17

• Too much stimulation
• Leads to AMPA and NMDA being overactivated
• Leads to calcium imbalance
• Leads to increase in all those activities (ATPase, lipase, protease, DNAase), leads to neuronal cell death (PSD-95 and NOS might be mechanism)

Question 18

Short vs Long term memory

Answer 18

Short-term memory: protein synthesis independent, anesthesia sensitive

Long-term memory: protein synthesis dependent, anesthesia resistant

Question 19

What part of the brain does spatial learning and memory rely on

Answer 19

Hippocampus

Question 20

Mechanisms of short-term memory formation in Aplysia

Answer 20

1. Presynaptic PKA activated
2. Presynaptic Ca and CamKII
3. Presynaptic PKC
4. Postsynaptic Ca and CamKII
5. Recruitment of pre and possibly postsynaptic molecules to new sites.

Question 21

Mechanisms of long-term memory formation:

Answer 21

1. Nt release and short-term strengthening of synaptic connections
2. Involvement of kinases and phosphatases
3. Activation of nuclear transcription factors
4. Activity-dependent induction of gene expression
5. Chromatin alteration and epigenetic changes in gene expression
6. Synaptic growth and the formation of new synapses
7. Activation of pre-existing silent synapses

Question 22

Silent synapses definition?

Answer 22

structural specializations for neurotransmission that do not produce a physiological response in the receiving cell

Question 23

4 types of silent synapses:

Answer 23

1. Presynaptically silent synapse (missing smthn on presynaptic side)
2. Conditionally silent synapse (only have NMDA and not AMPA receptors, need AMPA to depolarize postsynaptic neuron to remove Mg block from NMDA)
3. Postsynaptically silent synapse (no NMDA or AMPA receptors)
4. Incompletely assembled synapse (can become active)

Question 24

Histone modification, heterochromatin vs euchromatin:

Answer 24

Heterochromatin: condensed chromatin and subsequent transcriptional repression. More methylation

Euchromatin: relaxed chromatin state that allows transcriptional machinery access to DNA for gene expression. Less methylation more acetylation and phosphorylation.

Question 25

5 neurological diseases:

Answer 25

Alzheimers, Fragile X, Huntingtons, Parkinsons, Amyotrophic later sclerosis

Question 26

What is Alzheimers characterized by:

Answer 26

Accumulation of plaques (amyloid beta peptides, cleaved from APP.. cleaved by complex family of enzymes.. gamma and beta secretases including presenilin) and tangles (insoluble filaments of tau protein)

Question 27

APP processing and formation of amyloid beta peptide

Answer 27

Has number of cleavage sites (beta, alpha and gamma sites) Depending on what's cleaved, can be pro (beta/gamma secretases) or anti amyloidogenic (alpha secretases) (anti=less plaques)

Question 28

Effects of presenilin:

Answer 28

Takeaway: presenilin is involved in a number of effects both presynaptically and postaynaptically. In some presynapse there was reduction in CICR, which leads to reduction in nt release, paired pulse facilitation, and facilitation. Postsynaptically, can effect amount of NMDAR and LTP (reduces). Presenilin can have number of effects presynaptically and postsynaptically.

Question 29

mGluR theory for Fragile X syndrome:

Answer 29

- mGluR receptor on postsynaptic stimulated by glutamate, induces local mRNA translation - protein synthesis stimulates internalization of AMPA receptors - FMRP negatively regulates that translation and reduces the internalization of AMPA receptors - So in fmr1 KO mice, neurons from patients with FXS have increased internalization of AMPA receptors in the absence of FMRP. This therefore weakens the synapse.

Question 30

Characterization of FXS

Answer 30

FXS usually caused by a 50 untranslated region (UTR) trinucleotide repeat expansion in the FMR1 gene, resulting in loss of FMRP

Question 31

Cellular mechanisms of huntingtons

Answer 31

huntington fragments forming due to CAG repeats, important effect they have: mitochondrial toxicity/energy imbalance effects, axonal transport impairment, synaptic dysfunction

Question 32

6 hypotheses for AD:

Answer 32

AB-amyloid hypothesis, AB-oligomer hypothesis, presenilin hypothesis, calcium dysregulation hypothesis, lysosome hypothesis, Tau hypothesis.

Question 33

Parkinson Disease- inherited mutations

Answer 33

- alpha-synuclein - Leucin-rich repeat kinase 2 (LRRK2) - Parkin - DJ1 - PREN-induced kinase 1 (PINK1) 5 proteins linked to PD, mutations in genes can have effects at synapses/effect synaptic function, can lead to tangles and aggregation, effects on ubiquitin and proteasome, effect on mitochondria, all effects collectively can lead to neuronal death.

Question 34

Take away for ALS

Answer 34

ALS is disease of motor neurons, characterized by degeneration of motor neurons, which leads to muscle weakness and paralysis, can affect number of things, can be involved in oxidative stress, mitochondrial dysfunction, affects on DNA, RNA.

Question 35

Short term plasticity in pain (facilitation and depression)

Answer 35

Short term facilitation> Paired Pulse Facilitation: two stimuli occur in short interval, second stimulus induces larger response Stf>Wind up: repeated low freq stimulation, you get larger response. Short term depression>Paired Pulse Depression: two stimuli occurring in short interval, second stimuli results in smaller response. Std>Steady state depression: repeated stimulation results in smaller response

Question 36

Presynaptic mechanisms of synaptic plasticity

Answer 36

Nt release, binds to AMPA and NMDAR, leads to pathways on postsynaptic cell. Ca entering activates NO synthase, NO diffuses through membrane, goes into presynaptic terminal, activates Guanyl cyclase enzyme, makes cGMP, activates PKG, lead to phosphorylation of various targets, leads to increase in NT release. Glia can contribute by releasing NO

Question 37

Microglia-neuron interactions crucial for pain hypersensitivity induced by peripheral nerve injury

Answer 37

EXP: in mice how injury induces increase in pain sensitivity. There's nociceptor innervating neurons. You have nerve injury During nerve injury, you get increased expression of p2X4 receptor on microglia They are purinergic receptors, can bind ATP. Following nerve injury, increase in p2X4 receptor expressed on microglia, leads to more of their activation, leads to more calcium entering microglia Leads to increase in neurotrophic factor release (BDNF) BDNF can bind to TrkB receptors on postsynaptic neuron. TrkB receptors are tyrosine kinase receptors, can phosphorylate other targets TrkB has few effects: activates another kinase known as Fin Fin phosphorylates NMDA receptors, increase in their activity TrkB can have inhibitory effect on KCC2 (pumps Cl and K out of neurons, keep Cl concentration low) when GABA neurons enter neuron, hyperpolarizes But since KCC2 is inhibited, there will be increase in Cl conc in neuron More excitation bc activating NMDA receptors, and less inhibition bc inhibiting KCC2 Essentially, u have mechanism of pain hypersensitivity induced by nerve injury.