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Principal Investigator: NIGEL W BUNNETT
Organization: NEW YORK UNIVERSITY
Fiscal Year: 2019
Award: $282,990
Funding agency: National Institute of Neurological Disorders and Stroke
PROJECT SUMMARY
This proposal examines the mechanisms by which G protein-coupled receptors (GPCRs) signal pain. Chronic
pain is a hallmark of disease, a side effect of therapy, and a major cause of suffering. Although GPCRs
mediate all aspects of nociception and are major therapeutic targets, the mechanisms by which GPCRs signal
sustained pain are poorly understood, and clinical trials of GPCR antagonists in chronic pain often fail for
unexplained reasons. The proposal challenges three dogmas that contribute to this lack of understanding: 1.
GPCRs signal only from the cell-surface. 2. Endosomes are merely a conduit for GPCR recycling or
degradation. 3. Cell-surface GPCRs are the optimal therapeutic target. The proposal hypothesizes that: 1.
Endosomal GPCRs generate sustained signals that mediate persistent excitation of spinal neurons and
nociception. 2. Targeting endosomal rather than cell-surface GPCRs is the ideal therapeutic strategy, and the
clinical failure of conventional antagonists relates to their inability to inhibit endosomal receptors. Experiments
will focus on substance P and calcitonin gene-related peptide receptors, which mediate central pain
transmission and are internalized after painful stimuli. The contribution of receptor endocytosis to nociception
will be evaluated using pharmacological and genetic approaches to disrupt clathrin, dynamin and β-arrestin,
and by studying transgenic mice expressing non-internalizing receptors. Lipid-conjugation and nanoparticle-
encapsulation will be used to deliver antagonists to endosomal GPCRs. Aim 1 will determine the contribution of
endocytosis to somatic and colonic nociception in conscious mice. Aim 2 will define the importance of
endocytosis for excitation of spinal neurons, which will be analyzed in intact tissues using electrophysiology.
Aim 3 will determine the requirement of endocytosis for the generation of signals in subcellular compartments
that underlie neuronal excitation and nociception, which will be studied in isolated neurons using biophysical,
imaging and proteomic approaches. The results will provide fundamental information about pain signaling
and therapy. Since GPCRs are the largest class of signaling proteins and the target of one half of
therapeutic drugs, the outcomes will be broadly significant.