Familial hemiplegic migraine Ca_V2.1 channel mutation R192Q enhances ATP-gated P2X₃receptor activity of mouse sensory ganglion neurons mediating trigeminal pain

• Main Authors: Nair Asha (Author), Simonetti Manuela (Author), Birsa Nicol (Author), Ferrari Michel D (Author), van den Maagdenberg Arn MJM (Author), Giniatullin Rashid (Author), Nistri Andrea (Author), Fabbretti Elsa (Author)
• Format: Book
• Published: SAGE Publishing, 2010-08-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.
• Notes: 10.1186/1744-8069-6-48; 1744-8069
• Keywords: Pathology; RB1-214
• Source: Molecular Pain, Vol 6, Iss 1, p 48 (2010)

<p>Abstract</p> <p>Background</p> <p>The R192Q mutation of the CACNA1A gene, encoding for the α1 subunit of voltage-gated P/Q Ca²⁺channels (Ca_v2.1), is associated with familial hemiplegic migraine-1. We investigated whether this gain-of-function mutation changed the structure and function of trigeminal neuron P2X₃receptors that are thought to be important contributors to migraine pain.</p> <p>Results</p> <p>Using in vitro trigeminal sensory neurons of a mouse genetic model knockin for the CACNA1A R192Q mutation, we performed patch clamp recording and intracellular Ca²⁺imaging that showed how these knockin ganglion neurons generated P2X₃receptor-mediated responses significantly larger than wt neurons. These enhanced effects were reversed by the Ca_v2.1 blocker ω-agatoxin. We, thus, explored intracellular signalling dependent on kinases and phosphatases to understand the molecular regulation of P2X₃receptors of knockin neurons. In such cells we observed strong activation of CaMKII reversed by ω-agatoxin treatment. The CaMKII inhibitor KN-93 blocked CaMKII phosphorylation and the hyperesponsive P2X₃phenotype. Although no significant difference in membrane expression of knockin receptors was found, serine phosphorylation of knockin P2X₃receptors was constitutively decreased and restored by KN-93. No change in threonine or tyrosine phosphorylation was detected. Finally, pharmacological inhibitors of the phosphatase calcineurin normalized the enhanced P2X₃receptor responses of knockin neurons and increased their serine phosphorylation.</p> <p>Conclusions</p> <p>The present results suggest that the CACNA1A mutation conferred a novel molecular phenotype to P2X₃receptors of trigeminal ganglion neurons via CaMKII-dependent activation of calcineurin that selectively impaired the serine phosphorylation state of such receptors, thus potentiating their effects in transducing trigeminal nociception.</p>