CPPS 325 VERGE 2025 Signalling #17 #18 to upload (1)

Question 1

What is pain?

Answer 1

A complex sensation interpreted through anatomical pathways in response to tissue injury or inflammation.

Pain involves sensory neurons signaling to the spinal cord and brain about harmful stimuli.

Question 2

What happens to regions of the body when tissue is injured or inflamed?

Answer 2

They rapidly sensitize to sensory input.

This sensitization is part of the body’s response to pain and injury.

Question 3

What are inflammatory agents that regulate TRPV1?

Answer 3

They can act through direct and indirect mechanisms, including pathway crosstalk in inflammatory pain.

TRPV1 is a receptor sensitive to heat and protons that plays a significant role in pain perception.

Question 4

What initiates action potentials in sensory neurons?

Answer 4

Generator potentials resulting from the inward flow of cations.

This process is crucial for signaling pain to the central nervous system.

Question 5

What do neurotrophins do in sensory neurons?

Answer 5

They regulate the properties of sensory modalities.

Neurotrophins like NGF and BDNF are essential for the health and function of sensory neurons.

Question 6

Define proprioception.

Answer 6

The capacity to sense the position of joints, direction, and velocity of movement.

Proprioception is crucial for coordination and balance.

Question 7

What is mechanoception?

Answer 7

The ability to convey information about touch.

This sensory modality is critical for interacting with the environment.

Question 8

What is nociception?

Answer 8

The detection of painful and thermal stimuli.

Nociception is a protective mechanism that alerts the body to potential harm.

Question 9

What is the role of inflammation in pain transmission?

Answer 9

It leads to increased production of molecules involved in pain transmission and sensitization of primary afferent fibers.

Inflammatory responses can heighten sensitivity to pain.

Question 10

What effect does NGF have on sensory neurons?

Answer 10

Increased NGF leads to increased expression of trkA, SubP, CGRP, TRPV1, and other channels.

These proteins are involved in pain signaling and sensory neuron function.

Question 11

What ion channels do sensory neurons have that respond to pain stimuli?

Answer 11

They have a variety of ion channels that allow cations to enter the neuron.

This entry leads to increased generator potentials, contributing to pain sensation.

Question 12

How do protons affect TRPV1 channels?

Answer 12

They can activate TRPV1 channels at sites of tissue injury during the inflammatory response.

Protons lower pH and contribute to pain signaling.

Question 13

What is the significance of pH in mobilizing trkA to the membrane?

Answer 13

Decreases in pH induce trkA mobilization to the neuronal membrane, increasing sensitivity to NGF.

This mechanism is linked to inflammation-associated nociceptor sensitization.

Question 14

What was the hypothesis regarding decreases in pH and trkA mobilization?

Answer 14

Decreases in pH induce trkA mobilization to the neuronal membrane and increase the cell’s sensitivity to NGF.

This hypothesis was explored in the context of inflammation and pain.

Question 15

What experimental conditions were used to study trkA mobilization?

Answer 15

Sensory neurons were exposed to an acidic environment (pH 6.5) for 30 minutes.

This exposure was designed to observe changes in trkA levels on the neuronal membrane.

Question 16

What method was used to assess changes in trkA levels?

Answer 16

Biotinylation of cell-surface proteins was employed to quantify trkA on sensory neurons.

This method helps distinguish between membrane-associated and cytoplasmic proteins.

Question 17

What did the findings reveal about trkA after exposure to acidic conditions?

Answer 17

There was a significant increase in the amount of cell surface trkA protein detected following exposure to acidic conditions.

This indicates that acidic environments can enhance the sensitivity of sensory neurons.

Question 18

What is the outcome of biotinylation experiments under acidic conditions?

Answer 18

Significant increase in the amount of cell surface trkA protein detected

This indicates that acidic conditions enhance the mobilization of trkA to the cell surface.

Question 19

What does neutravidin gel capture?

Answer 19

Proteins on the cell surface

It washes off cytoplasmic proteins, allowing for the study of surface proteins.

Question 20

What is the role of Brefeldin A (BFA)?

Answer 20

Inhibits protein transport from the endoplasmic reticulum to the Golgi complex

BFA prevents the association of COP-I coat to the Golgi membrane.

Question 21

How does BFA affect export from the Golgi?

Answer 21

Blocks export via both the constitutive and regulated pathways

This indicates that BFA disrupts multiple pathways of protein transport.

Question 22

What experimental approach did Geoff Bray use to study trkA mobilization?

Answer 22

Nonpermeabilizing immunofluorescence with an antibody against an epitope in the extracellular portion of trkA

This method allows for analysis of only surface proteins.

Question 23

What effect does a slight drop in pH have on trkA detection?

Answer 23

Results in ~150% levels of trkA being detected

This suggests that lower pH enhances trkA surface expression.

Question 24

What does biotinylation of surface proteins allow researchers to do?

Answer 24

Separate membrane proteins from cytoplasmic proteins

This separation facilitates analysis via Western blot.

Question 25

What was observed when using BFA in conjunction with pH6.5?

Answer 25

Prevented the mobilization of additional trkA to the membrane ## Footnote This indicates that BFA disrupts the response to acidic conditions.

Question 26

What does the fixable membrane stain FM 1-43FX measure?

Answer 26

Endocytosis ## Footnote It fluoresces when trapped in endocytotic vesicles.

Question 27

What was the conclusion regarding internalization levels with BFA treatment?

Answer 27

No discernible levels of internalization beyond that observed at neutral pH ## Footnote This indicates that BFA does not affect endocytosis under the conditions tested.

Question 28

What happens when neurons are challenged with NGF?

Answer 28

Significant increase in internalized membrane observed ## Footnote This suggests NGF induces internalization of trkA.

Question 29

Does increased presentation of trkA on the cell surface make cells more responsive to NGF?

Answer 29

Yes ## Footnote This implies a functional relationship between surface receptor levels and responsiveness.

Question 30

What is the effect of acidosis and NGF challenge on phospho-trkA levels?

Answer 30

Increased detection of phospho-trkA levels and activation of downstream signaling ## Footnote This highlights the role of these factors in sensory neuron signaling.

Question 31

What is the significance of blocking BDNF activation of trkB?

Answer 31

Ensures that phosphorylated tyrosine 490 is only due to NGF activation of trkA ## Footnote This is crucial for isolating the effects of NGF on trkA.

Question 32

What is the downstream effect of trkA activation by NGF?

Answer 32

Phosphorylation of p38 MAPK ## Footnote This indicates a pathway of signaling initiated by trkA activation.

Question 33

What triggers mobilization of more trkA receptors to the membrane in response to reduced pH?

Answer 33

Greater proton drive ## Footnote This suggests that protons may act as a depolarizing stimulus.

Question 34

What type of channels might protons activate during neuronal activity?

Answer 34

Proton-sensitive ion channels ## Footnote These channels could play a role in the mobilization of trkA.

Question 35

What is the relationship between neuronal activity and trkA mobilization?

Answer 35

Neuronal activity is linked to mobilization of trkA to the membrane ## Footnote This connection underscores the importance of neuronal signaling in maintaining receptor levels.

Question 36

What does the Rhod-2 AM indicator measure?

Answer 36

Ca2+ fluxes ## Footnote This is important for understanding calcium dynamics in neurons.

Question 37

What does BAPTA-AM do in the context of calcium measurement?

Answer 37

Acts as a cell-permeable Ca2+ chelator ## Footnote This helps to analyze the role of calcium in neuronal responses.

Question 38

How does acidosis affect trkA receptor protein localization?

Answer 38

Increases localization to membranes of sensory neurons ## Footnote This may enhance receptor activation in response to NGF.

Question 39

What happens to trkA receptor phosphorylation in the absence of exogenous NGF challenge during acidosis?

Answer 39

Increases level of trkA receptor phosphorylation/activation ## Footnote The mechanism remains to be determined.

Question 40

What could the rapid mobilization of trkA in response to acidosis signify?

Answer 40

An adaptive response contributing to rapid sensitization of sensory neurons under inflammatory conditions ## Footnote This highlights the potential for heightened sensitivity in pain pathways.