Constitutive Gγi coupling activity of VLGR1 and its regulation by PDZD7

【作者】 孙金鹏； 屈昌秀； 胡巧霞； 董俊红； 徐志刚；

【机构】 山东大学；

【摘要】 The very large G protein-coupled receptor 1(VLGR1)is a core component in inner ear haircell development.Mutations in the vlgr1 gene cause Usher syndrome,the symptoms ofwhich include congenital hearing loss and progressive retinitis pigmentosa.However,themechanism of VLGR1-regulated intracellular signaling and its role in Usher syndrome remainelusive.Here,we show that VLGR1 is processed into two fragments after autocleavageat the G-protein-coupled receptor proteolytic site(GPS).The cleaved VLGR1β-subunitconstitutively inhibited adenylate cyclase(AC)activity through Gαi coupling.Co-expressionof the Gαiq chimera with the VLGR1β-subunit changes its activity to the PLC/NFAT signalingpathway,which demonstrates the Gαi protein-coupling specificity of this subunit.AR6002A mutation in intracellular loop 2(ICL2)of VLGR1 abolished Gαi coupling,but thepathogenic VLGR1 Y6236fsx1 mutant showed increased AC inhibition.Furthermore,overexpressionof another Usher syndrome protein,PDZD7,decreased the AC inhibition of theVLGR1β-subunit but showed no effect on the VLGR1 Y6236fsx1 mutant.Taken together,we identified an independent Gαi signaling of the VLGR1β-subunit and its regulatorymechanisms,which may have a role in the development of Usher syndrome.更多还原

【Abstract】 The very large G protein-coupled receptor 1(VLGR1)is a core component in inner ear haircell development.Mutations in the vlgr1 gene cause Usher syndrome,the symptoms ofwhich include congenital hearing loss and progressive retinitis pigmentosa.However,themechanism of VLGR1-regulated intracellular signaling and its role in Usher syndrome remainelusive.Here,we show that VLGR1 is processed into two fragments after autocleavageat the G-protein-coupled receptor proteolytic site(GPS).The cleaved VLGR1β-subunitconstitutively inhibited adenylate cyclase(AC)activity through Gαi coupling.Co-expressionof the Gαiq chimera with the VLGR1β-subunit changes its activity to the PLC/NFAT signalingpathway,which demonstrates the Gαi protein-coupling specificity of this subunit.AR6002A mutation in intracellular loop 2(ICL2)of VLGR1 abolished Gαi coupling,but thepathogenic VLGR1 Y6236fsx1 mutant showed increased AC inhibition.Furthermore,overexpressionof another Usher syndrome protein,PDZD7,decreased the AC inhibition of theVLGR1β-subunit but showed no effect on the VLGR1 Y6236fsx1 mutant.Taken together,we identified an independent Gαi signaling of the VLGR1β-subunit and its regulatorymechanisms,which may have a role in the development of Usher syndrome.更多还原