CPPS 325 VERGE 2025 Signalling #17 #18 to upload (1) Flashcards
What is pain?
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.
What happens to regions of the body when tissue is injured or inflamed?
They rapidly sensitize to sensory input.
This sensitization is part of the body’s response to pain and injury.
What are inflammatory agents that regulate TRPV1?
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.
What initiates action potentials in sensory neurons?
Generator potentials resulting from the inward flow of cations.
This process is crucial for signaling pain to the central nervous system.
What do neurotrophins do in sensory neurons?
They regulate the properties of sensory modalities.
Neurotrophins like NGF and BDNF are essential for the health and function of sensory neurons.
Define proprioception.
The capacity to sense the position of joints, direction, and velocity of movement.
Proprioception is crucial for coordination and balance.
What is mechanoception?
The ability to convey information about touch.
This sensory modality is critical for interacting with the environment.
What is nociception?
The detection of painful and thermal stimuli.
Nociception is a protective mechanism that alerts the body to potential harm.
What is the role of inflammation in pain transmission?
It leads to increased production of molecules involved in pain transmission and sensitization of primary afferent fibers.
Inflammatory responses can heighten sensitivity to pain.
What effect does NGF have on sensory neurons?
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.
What ion channels do sensory neurons have that respond to pain stimuli?
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.
How do protons affect TRPV1 channels?
They can activate TRPV1 channels at sites of tissue injury during the inflammatory response.
Protons lower pH and contribute to pain signaling.
What is the significance of pH in mobilizing trkA to the membrane?
Decreases in pH induce trkA mobilization to the neuronal membrane, increasing sensitivity to NGF.
This mechanism is linked to inflammation-associated nociceptor sensitization.
What was the hypothesis regarding decreases in pH and trkA mobilization?
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.
What experimental conditions were used to study trkA mobilization?
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.
What method was used to assess changes in trkA levels?
Biotinylation of cell-surface proteins was employed to quantify trkA on sensory neurons.
This method helps distinguish between membrane-associated and cytoplasmic proteins.
What did the findings reveal about trkA after exposure to acidic conditions?
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.
What is the outcome of biotinylation experiments under acidic conditions?
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.
What does neutravidin gel capture?
Proteins on the cell surface
It washes off cytoplasmic proteins, allowing for the study of surface proteins.
What is the role of Brefeldin A (BFA)?
Inhibits protein transport from the endoplasmic reticulum to the Golgi complex
BFA prevents the association of COP-I coat to the Golgi membrane.
How does BFA affect export from the Golgi?
Blocks export via both the constitutive and regulated pathways
This indicates that BFA disrupts multiple pathways of protein transport.
What experimental approach did Geoff Bray use to study trkA mobilization?
Nonpermeabilizing immunofluorescence with an antibody against an epitope in the extracellular portion of trkA
This method allows for analysis of only surface proteins.
What effect does a slight drop in pH have on trkA detection?
Results in ~150% levels of trkA being detected
This suggests that lower pH enhances trkA surface expression.
What does biotinylation of surface proteins allow researchers to do?
Separate membrane proteins from cytoplasmic proteins
This separation facilitates analysis via Western blot.
What was observed when using BFA in conjunction with pH6.5?
Prevented the mobilization of additional trkA to the membrane
This indicates that BFA disrupts the response to acidic conditions.
What does the fixable membrane stain FM 1-43FX measure?
Endocytosis
It fluoresces when trapped in endocytotic vesicles.
What was the conclusion regarding internalization levels with BFA treatment?
No discernible levels of internalization beyond that observed at neutral pH
This indicates that BFA does not affect endocytosis under the conditions tested.
What happens when neurons are challenged with NGF?
Significant increase in internalized membrane observed
This suggests NGF induces internalization of trkA.
Does increased presentation of trkA on the cell surface make cells more responsive to NGF?
Yes
This implies a functional relationship between surface receptor levels and responsiveness.
What is the effect of acidosis and NGF challenge on phospho-trkA levels?
Increased detection of phospho-trkA levels and activation of downstream signaling
This highlights the role of these factors in sensory neuron signaling.
What is the significance of blocking BDNF activation of trkB?
Ensures that phosphorylated tyrosine 490 is only due to NGF activation of trkA
This is crucial for isolating the effects of NGF on trkA.
What is the downstream effect of trkA activation by NGF?
Phosphorylation of p38 MAPK
This indicates a pathway of signaling initiated by trkA activation.
What triggers mobilization of more trkA receptors to the membrane in response to reduced pH?
Greater proton drive
This suggests that protons may act as a depolarizing stimulus.
What type of channels might protons activate during neuronal activity?
Proton-sensitive ion channels
These channels could play a role in the mobilization of trkA.
What is the relationship between neuronal activity and trkA mobilization?
Neuronal activity is linked to mobilization of trkA to the membrane
This connection underscores the importance of neuronal signaling in maintaining receptor levels.
What does the Rhod-2 AM indicator measure?
Ca2+ fluxes
This is important for understanding calcium dynamics in neurons.
What does BAPTA-AM do in the context of calcium measurement?
Acts as a cell-permeable Ca2+ chelator
This helps to analyze the role of calcium in neuronal responses.
How does acidosis affect trkA receptor protein localization?
Increases localization to membranes of sensory neurons
This may enhance receptor activation in response to NGF.
What happens to trkA receptor phosphorylation in the absence of exogenous NGF challenge during acidosis?
Increases level of trkA receptor phosphorylation/activation
The mechanism remains to be determined.
What could the rapid mobilization of trkA in response to acidosis signify?
An adaptive response contributing to rapid sensitization of sensory neurons under inflammatory conditions
This highlights the potential for heightened sensitivity in pain pathways.
