Distinct expression of Mas1-related G-protein-coupled receptor B4 in dorsal root and trigeminal ganglia--implications for altered behaviors in acid-sensing ion channel 3-deficient mice.

Mas1-related G-protein-coupled receptors (Mrgprs), comprising more than 50 distinct members, are specifically expressed in primary sensory neurons. Reflecting the diversity and specificity of stimuli they detect, Mrgprs are involved in pain, touch, and itch-related behaviors. Sensory-neuron-specific acid-sensing ion channel 3 (ASIC3) is essential for touch and inflammatory pain, but mice lacking ASIC3 have complex behavioral alterations in various modalities of pain and touch. To understand whether Mrgprs are involved in complex behavioral alterations found in ASIC3-deficient mice, we examined Mrgpr gene expression in ASIC3(-/-) mice. Only MrgprB4 expression has shown significant change. MrgprB4 expression was increased in ASIC3(-/-) dorsal root ganglia (DRG) but decreased in ASIC3(-/-) trigeminal ganglia. The distinct alterations in DRG and trigeminal ganglia imply that MrgprB4 could have multiple functions. Given that MrgprB4 is expressed in neurons that may detect gentle touch and that ASIC3(-/-) mice have altered sensitivity of mechanoreceptors for light touch, the expression change of MrgprB4 is more likely related to the altered touch behaviors of ASIC3(-/-) mice.