title: RGS21, a regulator of taste and mucociliary clearance?
abstract: OBJECTIVE
  Motile cilia of airway epithelial cells help to expel harmful inhaled material. Activation of bitterant-responsive G protein-coupled receptors (GPCRs) is believed to potentiate cilia beat frequency and mucociliary clearance. In this study, we investigated whether regulator of G protein signaling-21 (RGS21) has the potential to modulate signaling pathways connected to airway mucociliary clearance, given that RGS proteins modulate GPCR signaling by acting as GTPase-accelerating proteins (GAPs) for the Gα subunits of heterotrimeric G proteins.
  
  
  METHODS
  This is a pilot investigation to determine if RGS21, a potential tastant specific RGS gene, is expressed in sinonasal mucosa, and to determine its specific Gα substrate using in vitro biochemical assays with purified proteins.
  
  
  METHODS
  Rgs21 expression in sinonasal mucosa was determined using quantitative, real-time PCR and a transgenic mouse expressing RFP from the Rgs21 promoter. Rgs21 was cloned, over-expressed, and purified using multistep protein chromatography. Biochemical and biophysical assays were used to determine if RGS21 could bind and accelerate the hydrolysis of GTP on heterotrimeric Gα subunits.
  
  
  RESULTS
  Rgs21 was expressed in sinonasal mucosa and lingual epithelium. Purified recombinant protein directly bound and accelerated GTP hydrolysis on Gα subunits.
  
  
  CONCLUSIONS
  Rgs21 is expressed in sinonasal mucosa, is amenable to purification as a recombinant protein, and can bind to Gα(i/o/q) subunits. Furthermore, RGS21 can accelerate the hydrolysis rate of GTP on Gαi subunits. This provides evidence that RGS21 may be a negative regulator of bitterant responses. Future studies will be needed to determine the physiological role of this protein in mucociliary clearance.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of North Carolina at Chapel Hill, North Carolina, U.S.A; Department of Pharmacology, University of North Carolina at Chapel Hill, North Carolina, U.S.A.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Kimple
authors.forename: Alaina L
authors.initials: AL
authors.lastname: Garland
authors.forename: Staci P
authors.initials: SP
authors.lastname: Cohen
authors.forename: Vincent
authors.initials: V
authors.lastname: Setola
authors.forename: Francis S
authors.initials: FS
authors.lastname: Willard
authors.forename: Thomas
authors.initials: T
authors.lastname: Zielinski
authors.forename: Robert G
authors.initials: RG
authors.lastname: Lowery
authors.forename: Robert
authors.initials: R
authors.lastname: Tarran
authors.forename: David P
authors.initials: DP
authors.lastname: Siderovski
mesh_terms: D000818:Animals; D005786:Gene Expression Regulation; D051379:Mice; D008822:Mice, Transgenic; D023421:Models, Animal; D009079:Mucociliary Clearance / Q000235:genetics*; D010865:Pilot Projects; D020710:RGS Proteins / Q000235:genetics*; D011897:Random Allocation; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity; D015398:Signal Transduction / Q000235:genetics; D013649:Taste / Q000235:genetics*
chemical_list: D020710:RGS Proteins
keywords: G proteins; Regulators of G protein signaling (RGS); gustation
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