Targeted delivery of a SNARE protease to sensory neurons using a single chain antibody (scFv) against the extracellular domain of P2X3 inhibits the release of a pain mediator

Abstract

P2X3 (P2X purinoceptor 3) is predominantly expressed on nociceptive sensory neurons and plays a crucial role in signalling leading to chronic inflammatory pain and some features of neuropathic pain. Thus it represents a potential target for pain therapeutics. BoNT/A (botulinum neurooxin type A) effectively relieves certain types of pain through inhibiting the neuronal release of pain peptides. A recombinant single-chain variable fragment (scFv) antibody designated MH7C was generated against the extracellular domain of P2X3 using phage display. The genes encoding the scFv and activated di-chain form of BoNT/A without the C-terminal-binding subdomain (LC–HN–HCN/A) were ligated and expressed in Escherichia coli cells as a composite fusion protein. The purified protein bound and entered P2X3-containing sensory neurons, cleaved synaptosomal-associated protein of 25 kDa and inhibited the release of a pain peptide. This novel fusion protein designated ‘LC–HN–HCN/A–MH7C’ has potential clinical applications in the treatment of chronic inflammatory and sympathetically maintained neuropathic pain.