# Defining the mechanism of PTCHD1 and membrane cholesterol in the regulation of the mu-opioid receptor

> **NIH NIH F32** · UNIVERSITY OF FLORIDA · 2024 · $44,935

## Abstract

Project Summary
G protein coupled receptors (GPCRs) are family of receptors that translate extracellular cues into intracellular
responses by activating heterotrimeric G proteins. GPCRs are involved in many aspects of biology and play
critical roles as receptors for neuromodulators, neurotransmitters, and hormones. GPCRs are characterized by
their seven transmembrane domains. Despite having so much of their structure embedded in the membrane,
most of the known GPCR regulators are cytosolic proteins. Thus, an unanswered question remains does the
membrane shape GPCR signaling and is the cell able to control the local membrane landscape to modulate
GPCR function. The mu-opioid receptor (µOR) is a prototypical class A GPCR with clinical relevance as it is the
molecular target of opioids and drives the analgesic effect of these drugs, as well as the undesirable side effects
that make the ongoing opioid abuse epidemic so devastating. In a screen for µOR regulators, we identified the
cholesterol binding protein patched domain containing-1 (PTCHD1) as a negative regulator of opioid action.
PTCHD1 is a critical regulator of opioid action and its knockout in mice results in elevated opioid efficacy without
the development of tolerance. Our data suggests that PTCHD1 acts to shape the local membrane environment
reducing the accessibility of cholesterol. Here we explore how PTCHD1 and membrane cholesterol regulate the
µOR which will lead to a better understanding of how GPCRs are regulated by the membrane. We hypothesize
that PTCHD1 acts in a localized manner to reduce cholesterol accessibility preventing membrane cholesterol
from acting as a positive allosteric modulator of the µOR and altering the postendocytic trafficking of the receptor.
We will test this hypothesis using a combination of cellular signaling and protein trafficking assays in cell lines
as well as in primary neurons. This line of research is predicted to provide novel insights into the mechanisms
that shape the action of opioids and underlie the development of tolerance, a major obstacle in the use of opioids
in pain management that contributes to the opioid abuse crisis. Further, this research is poised to reveal a novel
avenue of GPCR regulation through shaping the membrane lipid composition.

## Key facts

- **NIH application ID:** 10996216
- **Project number:** 1F32GM155989-01
- **Recipient organization:** UNIVERSITY OF FLORIDA
- **Principal Investigator:** Colten Keith Lankford
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $44,935
- **Award type:** 1
- **Project period:** 2025-03-01 → 2025-10-16

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10996216

## Citation

> US National Institutes of Health, RePORTER application 10996216, Defining the mechanism of PTCHD1 and membrane cholesterol in the regulation of the mu-opioid receptor (1F32GM155989-01). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/10996216. Licensed CC0.

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