A Limited Spectrum of Mutations Causes Constitutive Activation of the Yeast -Factor Receptor

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• 作者：Christine M. Sommers ; Negin P. Martin ; Ayca Akal-Strader ; Jeffrey M. Becker ; Fred Naider ; and Mark E. Dumont
• 刊名：Biochemistry
• 出版年：2000
• 出版时间：June 13, 2000
• 年：2000
• 卷：39
• 期：23
• 页码：6898 - 6909
• 全文大小：205K
• 年卷期：v.39,no.23(June 13, 2000)
• ISSN：1520-4995

文摘

Activation of G protein coupled receptors (GPCRs) by binding of ligand is the initial event indiverse cellular signaling pathways. To examine the frequency and diversity of mutations that causeconstitutive activation of one particular GPCR, the yeast ages/gifchars/alpha.gif" BORDER=0>-factor receptor, we screened libraries of randommutations for constitutive alleles. In initial screens for mutant receptor alleles that exhibit signaling in theabsence of added ligand, 14 different point mutations were isolated. All of these 14 mutants could befurther activated by ages/gifchars/alpha.gif" BORDER=0>-factor. Ten of the mutants also acquired the ability to signal in response to bindingof desTrp¹[Ala³]ages/gifchars/alpha.gif" BORDER=0>-factor, a peptide that acts as an antagonist toward normal ages/gifchars/alpha.gif" BORDER=0>-factor receptors. Of these10 mutants, at least eight alleles residing in the third, fifth, sixth, and seventh transmembrane segmentsexhibit bona fide constitutive signaling. The remaining alleles are hypersensitive to ages/gifchars/alpha.gif" BORDER=0>-factor rather thanconstitutive. They can be activated by low concentrations of endogenous ages/gifchars/alpha.gif" BORDER=0>-factor present in MATa cells.The strongest constitutively active receptor alleles were recovered multiple times from the mutationallibraries, and extensive mutagenesis of certain regions of the ages/gifchars/alpha.gif" BORDER=0>-factor receptor did not lead to recoveryof any additional constitutive alleles. Thus, only a limited number of mutations is capable of causingconstitutive activation of this receptor. Constitutive and hypersensitive signaling by the mutant receptorsis partially suppressed by coexpression of normal receptors, consistent with preferential association ofthe G protein with unactivated receptors.