Molecular Determinants of TRP Channel Gating

<p>Transient Receptor Potential (TRP) ion channels are a family of proteins that contribute to a myriad of physiological functions. They have been extensively studied since their discovery 35 years ago; however, there are still many questions regarding the mechanisms by which they function. This family of proteins is characterized by a generally shared structure: an intracellular N terminus featuring ankyrin repeats, six transmembrane helices including the pore domain, a re-entrant loop and TRP helix, and an intracellular C terminus with varying structure. Each of these regions has been implicated in the regular function of TRPs, while mutations that alter trafficking or function have been found throughout these domains. Here, I describe my contribution to uncovering the mechanisms by which several of these channels are governed in various pathophysiological conditions, including hyperalgesia, gut barrier dysfunction, and ataxia. Thermal hyperalgesia is a condition in which previously innocuous stimuli become painful as a result of inflammatory responses. TRP Vanilloid member 1 (TRPV1) is a contributor to this process due to its involvement in temperature sensing. Phosphoinositides, a component of the plasma membrane that modulate the activity of various ion channels (including TRPV1), are cleaved in response to inflammatory signals. Their role in regulating TRPV1 activity is controversial. To address this role in TRPV1 function in vivo, we leveraged dietary supplementation, genetic dissection, and functional assays. We found that phosphoinositides are a negative regulator of channel activity in vivo and influence channel activity through a putative interaction site on the distal C terminus. These findings are discussed in further detail in Chapter 2. Chronic alcohol use is associated with many symptoms, including dysbiosis and organ damage, which are a consequence of alterations to the gut barrier. The specific events leading to the development of a leaky gut due to chronic alcohol intake require further study. An initial step in this process is a rise in intracellular Ca2+ at the gut epithelium. Hence, we explored the role of TRPV6, a Ca2+-selective channel expressed in the intestinal epithelium. Using in vitro and in vivo models of the gut barrier, as well as biochemical and functional assays, we found that TRPV6 is essential for the development of alcohol-associated changes in gut barrier function, likely through a site within the channel’s N-terminal ankyrin repeat domain. Additional information regarding this topic can be found in Chapter 3. Ataxia is a condition characterized by a loss in coordination, which can result from damage or degeneration of the body’s central motor axis. The Canonical TRP member 3 (TRPC3) is highly expressed in the cerebellum, where it modulates neuronal activity. Mutation of this channel results in neurodegeneration and ataxia. However, the mechanism by which this occurs is unclear. Accordingly, we utilized functional, behavioral, and structural techniques to reveal that mutant-associated enhancement in channel activity results in neurodegenerative phenotypes through a combination of molecular determinants. Chapter 4 includes a detailed discussion of these results. Taken together, these findings provide new insight into the mechanisms underlying TRP channel function, as well as reveal potential targets for modulating the activity of these proteins. This is an important step in developing strategies against pathophysiological changes associated with dysfunction of these channels.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biomedical Sciences

Year dc:date.available

2024

Author dc:creator

• Bell, Briar J.

Contributors dc:contributor

• Julio Cordero-Morales, PhD

• Alcohol
• Ataxia
• Phosphoinositides
• TRP channels
• Amino Acids, Peptides, and Proteins
• Chemicals and Drugs
• Diseases
• Medical Cell Biology
• Medical Physiology
• Medical Sciences
• Medicine and Health Sciences
• Nervous System Diseases

Repository record dc:identifier

https://dc.uthsc.edu/dissertations/693

OAI identifier oai:identifier

oai:dc.uthsc.edu:dissertations-1693