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Papers of the Week

Papers: 25 May 2019 - 31 May 2019

Animal Studies

2019 Jul 24

J Neurosci



Editor's Pick

Growth factor signaling regulates mechanical nociception in flies and vertebrates.


Lopez-Bellido R, Puig S, Huang PJ, Tsai C-R, Turner HN, Galko MJ, Gutstein HB
J Neurosci. 2019 Jul 24; 39(30):6012-6030.
PMID: 31138657.


Mechanical sensitization is one of the most difficult clinical pain problems to treat. However, the molecular and genetic bases of mechanical nociception are unclear. Here we develop a model of mechanical nociception to investigate the ion channels and signaling pathways that regulate mechanical nociception. We fabricated Von Frey filaments that span the sub-threshold to high noxious range for larvae. Utilizing these, we discovered that pressure (force/area) rather than force per se is the main determinant of aversive rolling responses to noxious mechanical stimuli. We demonstrated that the RTK PDGF/VEGF receptor (Pvr) and its ligands (Pvfs 2 and 3) are required for mechanical nociception and normal dendritic branching. Pvr is expressed and functions in class IV sensory neurons, while Pvf2 and Pvf3 are produced by multiple tissues. Constitutive overexpression of Pvr and its ligands or inducible overexpression of Pvr led to mechanical hypersensitivity that could be partially separated from morphological effects. Genetic analyses revealed that the Piezo and Pain ion channels are required for mechanical hypersensitivity observed upon ectopic activation of Pvr signaling. Platelet-derived growth factor (PDGF), but not vascular endothelial growth factor (VEGF) peptides caused mechanical hypersensitivity in rats. Pharmacological inhibition of vascular endothelial growth factor receptor type 2 (VEGFR-2) signaling attenuated mechanical nociception in rats, suggesting a conserved role for PDGF and VEGFR-2 signaling in regulating mechanical nociception. VEGFR2 inhibition also attenuated morphine analgesic tolerance in rats. Our results reveal that a conserved RTK signaling pathway regulates baseline mechanical nociception in flies and rats.Hypersensitivity to touch is poorly understood and extremely difficult to treat. Using a refined model of mechanical nociception, we discovered a conserved VEGF-related receptor tyrosine kinase signaling pathway that regulates mechanical nociception in flies. Importantly, pharmacological inhibition of VEGFR-2 signaling in rats causes analgesia and blocks opioid tolerance. We have thus established a robust, genetically tractable system for the rapid identification and functional analysis of conserved genes underlying mechanical pain sensitivity.