Nociceptor-specific signaling of the receptor guanylyl cyclase Npr2 contributes to acute and persistent pain

Natriuretic peptide receptor 2 (Npr2; also termed guanylyl cyclase B) is a transmembrane guanylyl cyclase that is highly abundant in nociceptors. Here, we investigated the role of production of cyclic GMP (cGMP) by Npr2 in pain processing. Adult mice with a deletion of Npr2 specifically in nociceptive sensory neurons exhibited deficits in noxious heat sensing, which can activate the nonselective cation channels TRPV1 and TRPA1. In parallel, Npr2-deficient mice showed a reduction in TRPV1-mediated nocifensive behavior and Ca 2+ influx into sensory neurons. Furthermore, Npr2-deficient mice had considerably reduced hypersensitivity after hindpaw injection of TRPA1 and TRPV1 activators or after hindpaw injection of complete Freund adjuvant, a model of persistent inflammatory pain. These results indicate that Npr2 contributes to the pain sensitization that can lead to chronic pain. Patch-clamp recordings revealed that the endogenous Npr2 ligand, C-type natriuretic peptide (CNP), enhanced the excitability of nociceptive sensory neurons through Npr2. CNP/Npr2 signaling led to the phosphorylation of cysteine-rich LIM-only protein 4 (CRP4), a substrate of cGMP-dependent protein kinase I. Behavioral and electrophysiological analyses using CRP4-deficient mice revealed that CRP4 limited CNP/Npr2-mediated pain sensitization. Our findings reveal a role for CNP/Npr2 signaling in sensory neurons in acute nociceptive and chronic pain and suggest that CRP4 is a downstream target that attenuates pain sensitization.