Key points are not available for this paper at this time.
The transcriptional coactivator PPARγ coactivator-1α (PGC-1α) has been characterized as a broad regulator of cellular energy metabolism. Although PGC-1α functions through many transcription factors, the PGC-1α partners identified to date are unlikely to account for all of its biologic actions. The orphan nuclear receptor estrogen-related receptor α (ERRα) was identified in a yeast two-hybrid screen of a cardiac cDNA library as a novel PGC-1α-binding protein. ERRα was implicated previously in regulating the gene encoding medium-chain acyl-CoA dehydrogenase (MCAD), which catalyzes the initial step in mitochondrial fatty acid oxidation. The cardiac perinatal expression pattern of ERRα paralleled that of PGC-1α and MCAD. Adenoviral-mediated ERRα overexpression in primary neonatal cardiac mycoytes induced endogenous MCAD expression. Furthermore, PGC-1α enhanced the transactivation of reporter plasmids containing an estrogen response element or the MCAD gene promoter by ERRα and the related isoform ERRγ. In vitro binding experiments demonstrated that ERRα interacts with PGC-1α via its activation function-2 homology region. Mutagenesis studies revealed that the LXXLL motif at amino acid position 142–146 of PGC-1α (L2), necessary for PGC-1α interactions with other nuclear receptors, is not required for the PGC-1α·ERRα interaction. Rather, ERRα binds PGC-1α primarily through a Leu-rich motif at amino acids 209–213 (Leu-3) and utilizes additional LXXLL-containing domains as accessory binding sites. Thus, the PGC-1α·ERRα interaction is distinct from that of other nuclear receptor PGC-1α partners, including PPARα, hepatocyte nuclear factor-4α, and estrogen receptor α. These results identify ERRα and ERRγ as novel PGC-1α interacting proteins, implicate ERR isoforms in the of mitochondrial energy and a PGC-1α binds transcription The transcriptional coactivator PPARγ coactivator-1α (PGC-1α) has been characterized as a broad regulator of cellular energy metabolism. Although PGC-1α functions through many transcription factors, the PGC-1α partners identified to date are unlikely to account for all of its biologic actions. The orphan nuclear receptor estrogen-related receptor α (ERRα) was identified in a yeast two-hybrid screen of a cardiac cDNA library as a novel PGC-1α-binding protein. ERRα was implicated previously in regulating the gene encoding medium-chain acyl-CoA dehydrogenase (MCAD), which catalyzes the initial step in mitochondrial fatty acid oxidation. The cardiac perinatal expression pattern of ERRα paralleled that of PGC-1α and MCAD. Adenoviral-mediated ERRα overexpression in primary neonatal cardiac mycoytes induced endogenous MCAD expression. Furthermore, PGC-1α enhanced the transactivation of reporter plasmids containing an estrogen response element or the MCAD gene promoter by ERRα and the related isoform ERRγ. In vitro binding experiments demonstrated that ERRα interacts with PGC-1α via its activation function-2 homology region. Mutagenesis studies revealed that the LXXLL motif at amino acid position 142–146 of PGC-1α (L2), necessary for PGC-1α interactions with other nuclear receptors, is not required for the PGC-1α·ERRα interaction. Rather, ERRα binds PGC-1α primarily through a Leu-rich motif at amino acids 209–213 (Leu-3) and utilizes additional LXXLL-containing domains as accessory binding sites. Thus, the PGC-1α·ERRα interaction is distinct from that of other nuclear receptor PGC-1α partners, including PPARα, hepatocyte nuclear factor-4α, and estrogen receptor α. These results identify ERRα and ERRγ as novel PGC-1α interacting proteins, implicate ERR isoforms in the of mitochondrial energy and a PGC-1α binds transcription energy is to which in by and The for cellular is in by the expression of nuclear in mitochondrial metabolism. Thus, of cellular energy of related to cellular energy to the Although in the transcriptional of gene expression been the in the of cellular energy not been The of PPARγ coactivator-1α PPARγ fatty acid medium-chain acyl-CoA estrogen-related promoter transcription amino binding binding nuclear receptor response nuclear hepatocyte nuclear estrogen receptor α. PPARγ fatty acid medium-chain acyl-CoA estrogen-related promoter transcription amino binding binding nuclear receptor response nuclear hepatocyte nuclear estrogen receptor α. and the a of transcriptional to the and the of in energy metabolism. the of novel coactivator to was characterized as a regulator of in and via its of the nuclear PPARγ studies revealed a for PGC-1α in a of cellular energy including mitochondrial mitochondrial fatty acid and The of and to is from the and response of transcriptional in its expression its and its by PGC-1α is in for or is in and PGC-1α expression in with a from to mitochondrial as the energy in the PGC-1α expression is induced in and in response to that energy to a of PGC-1α gene expression in In and PGC-1α gene expression in and studies that PGC-1α is in response to of the in of the Furthermore, that activation of the PGC-1α of demonstrated activation of PGC-1α via of a results of studies demonstrated that PGC-1α as a regulator of mitochondrial and that overexpression of PGC-1α in the mitochondrial to an in mitochondrial and has that expression of PGC-1α in primary cardiac and in of to the transcriptional activation of encoding as medium-chain acyl-CoA dehydrogenase (MCAD), and a in mitochondrial cellular studies that PGC-1α to to to the transcriptional of mitochondrial of PGC-1α are to primarily by its to with and nuclear receptors, as as receptor transcription factors, in vitro and studies The of PGC-1α mitochondrial gene expression at in through its activation of the nuclear receptor The mitochondrial response the transcription nuclear and nuclear not all of the of PGC-1α cellular energy been to PGC-1α transcription The of PGC-1α as a regulator of cellular energy is by transcription factors, of which In the in by PGC-1α in the of transcription are an to identify PGC-1α interacting to the a two-hybrid screen of an cDNA library in yeast PGC-1α as the of its to mitochondrial energy with The orphan nuclear estrogen-related receptor α was identified as a novel PGC-1α interacting protein. PGC-1α enhanced the transcriptional of ERRα and the related isoform ERRγ. The PGC-1α·ERRα was to the MCAD a gene implicated previously as an ERRα and in vitro binding studies demonstrated that ERRα binds PGC-1α via a novel of domains with other characterized nuclear receptor PGC-1α These results identify a novel PGC-1α in In results that the of distinct binding PGC-1α coactivator in cellular and and and at and in experiments the in by the as plasmids with the gene by the to for expression for nuclear receptors, PGC-1α or the at the in the and and and as cardiac from as with or ERRα by a The from an of was by as by of from The was by from the by containing the ERRα cDNA encoding amino acids the and of ERRα was as MCAD plasmids been The containing of the estrogen element of the was by The was a from of The was by of the of the promoter of the reporter The is the response element in the gene promoter expression has been in PGC-1α by a Mutagenesis the as for The and the and The PGC-1α and been PGC-1α by an at the and a at or to a encoding a to of the PGC-1α The PGC-1α the of the for The and by the for PGC-1α to a at or The and by from the the from The has been The the and the expression from of and of the has been The was by the from the the cellular and was as with from the cDNA PPARα, and In and by and as of ERRα and or by and of MCAD was the vitro interaction been previously in the in In of a of to was with in of binding and for at The and with binding was to the for and the by The and and by the of that the PGC-1α·ERRα interaction a transcriptional in the of cardiac and metabolism. ERRα as PGC-1α interacting a two-hybrid The interaction of PGC-1α with ERRα and isoforms was in vitro binding binding domains the PGC-1α·ERRα binding ERRα and the of the interaction. the ERRα binding the PGC-1α is with other transcription binding sites. PGC-1α ERRα and ERRγ isoforms in of PGC-1α·ERRα in regulating cellular is by and expression of ERR and mitochondrial for the in mitochondrial is by the that PGC-1α is necessary for activation of the MCAD studies of the PGC-1α·ERRα binding revealed a novel nuclear receptor binding motif LXXLL coactivator been to interactions with nuclear The Leu-rich motif an that a binding by of the receptor PGC-1α LXXLL has been previously to a in binding nuclear studies demonstrated that the interaction of ERRα with PGC-1α the of an LXXLL motif as the ERRα binding is with the that the ERRα is required for the interaction with is the in which the motif of PGC-1α was to the interaction of PGC-1α with a nuclear receptor a as an accessory for interaction with PGC-1α results that the motif functions as the primary of interaction and that is to is distinct from other interactions with as demonstrated by the that the interaction of PGC-1α with and required the LXXLL the motif through which coactivator with nuclear receptors, studies the of the Leu-rich in receptor and binding distinct of LXXLL domains to the PGC-1α is a binding in by the of and of the of the LXXLL The through which ERRα primarily to an LXXLL not to studies with demonstrated that the coactivator binding of an motif an from the transcription coactivator the of a LXXLL motif in the transcription by to the motif the binding by the motif to The motif of PGC-1α in to an Furthermore, a of of the motif that to its by ERRα and ERRγ. with the motif not of and has not been identified as a binding in nuclear receptor interaction with PGC-1α for the interaction of ERRα with PGC-1α with other PGC-1α nuclear receptor partners is is related to the nuclear receptor The nuclear receptor with PGC-1α has not been coactivator binding been for a of receptors, including and receptor α interacts with transcription via the LXXLL and which and which of are in ERR that other the of ERRα and ERRγ account for binding with of the ERRα homology with that of in binding to are or in ERRα the distinct was to for the by the of ERRα the are distinct ERRα and ERRγ. These are not with coactivator the amino acid to in to the binding with a of studies of response the of that the of ERR isoforms for regulating of the of response or interactions has been to a of transcription in cellular The distinct binding PGC-1α with ERRα with other nuclear a by which PGC-1α of a nuclear receptor is by a of factors, including expression binding of and The of PGC-1α to distinct binding with partners an additional for receptor to a as the of nuclear receptor binding the PGC-1α the is the of the PGC-1α by PGC-1α is to partners, as a of activation of related gene of its ERR isoforms and a of nuclear receptor transcription in transcriptional activation or of Although ERRα was the orphan nuclear receptor the nuclear receptor is its the for ERRα of estrogen ERRα and and ERRα has been to transcriptional ERRα has been implicated in the of cellular and the of that ERRα to PGC-1α in mitochondrial metabolism. ERRα and ERRγ expression is in that mitochondrial as a primary for energy or as and that ERRα and expression and ERR isoforms and PGC-1α are in of with in which are the pattern of ERRα and PGC-1α expression a in ERRα and are in the in and and as the of ERRα expression is induced with for energy as as studies that the MCAD gene is a ERRα ERRα binds the MCAD gene promoter via a which is for the and expression of MCAD to of MCAD gene transcription was The results of the ERRα overexpression and studies that MCAD is an endogenous for ERRα and that in the of PGC-1α ERRα the MCAD studies that PGC-1α a in regulating cardiac mitochondrial and mitochondrial the that ERRα and ERRγ as of broad energy is to which in by and The for cellular is in by the expression of nuclear in mitochondrial metabolism. Thus, of cellular energy of related to cellular energy to the Although in the transcriptional of gene expression been the in the of cellular energy not been The of PPARγ coactivator-1α PPARγ fatty acid medium-chain acyl-CoA estrogen-related promoter transcription amino binding binding nuclear receptor response nuclear hepatocyte nuclear estrogen receptor α. PPARγ fatty acid medium-chain acyl-CoA estrogen-related promoter transcription amino binding binding nuclear receptor response nuclear hepatocyte nuclear estrogen receptor α. and the a of transcriptional to the and the of in energy metabolism. the of novel coactivator to was characterized as a regulator of in and via its of the nuclear PPARγ studies revealed a for PGC-1α in a of cellular energy including mitochondrial mitochondrial fatty acid and The of and to PGC-1α is from the and response of transcriptional in its expression its and its by PGC-1α is in for or is in and PGC-1α expression in with a from to mitochondrial as the energy in the PGC-1α expression is induced in and in response to that energy to a of PGC-1α gene expression in In and PGC-1α gene expression in and studies that PGC-1α is in response to of the in of the Furthermore, that activation of the PGC-1α of demonstrated activation of PGC-1α via of a The results of studies demonstrated that PGC-1α as a regulator of mitochondrial and that overexpression of PGC-1α in the mitochondrial to an in mitochondrial and has that expression of PGC-1α in primary cardiac and in of to the transcriptional activation of encoding as medium-chain acyl-CoA dehydrogenase (MCAD), and a in mitochondrial cellular studies that PGC-1α to to to the transcriptional of mitochondrial The of PGC-1α are to primarily by its to with and nuclear receptors, as as receptor transcription factors, in vitro and studies The of PGC-1α mitochondrial gene expression at in through its activation of the nuclear receptor The mitochondrial response the transcription nuclear and nuclear not all of the of PGC-1α cellular energy been to PGC-1α transcription The of PGC-1α as a regulator of cellular energy is by transcription factors, of which In the in by PGC-1α in the of transcription are In an to identify PGC-1α interacting to the a two-hybrid screen of an cDNA library in yeast PGC-1α as the of its to mitochondrial energy with The orphan nuclear estrogen-related receptor α was identified as a novel PGC-1α interacting protein. PGC-1α enhanced the transcriptional of ERRα and the related isoform ERRγ. The PGC-1α·ERRα was to the MCAD a gene implicated previously as an ERRα and in vitro binding studies demonstrated that ERRα binds PGC-1α via a novel of domains with other characterized nuclear receptor PGC-1α These results identify a novel PGC-1α in In results that the of distinct binding PGC-1α coactivator in cellular and and and at and in experiments the in by the as plasmids with the gene by the to for expression for nuclear receptors, PGC-1α or the at the in the and and and as cardiac from as with or ERRα by a The from an of was by as by of from The was by from the by containing the ERRα cDNA encoding amino acids the and of ERRα was as MCAD plasmids been The containing of the estrogen element of the was by The was a from of The was by of the of the promoter of the reporter The is the response element in the gene promoter expression has been in PGC-1α by a Mutagenesis the as for The and the and The PGC-1α and been PGC-1α by an at the and a at or to a encoding a to of the PGC-1α The PGC-1α the of the for The and by the for PGC-1α to a at or The and by from the the from The has been The the and the expression from of and of the has been The was by the from the the cellular and was as with from the cDNA PPARα, and In and by and as of ERRα and or by and of MCAD was the vitro interaction been previously in the in In of a of to was with in of binding and for at The and with binding was to the for and the by The and and by the and and at and in experiments the in by the as plasmids with the gene by the to for expression for nuclear receptors, PGC-1α or the at the in the and and and as cardiac from as with or ERRα by a The from an of was by as by of from The was by from the by containing the ERRα cDNA encoding amino acids the and of ERRα was as and at and in experiments the in by the as plasmids with the gene by the to for expression for nuclear receptors, PGC-1α or the at the in the and and and as cardiac from as with or ERRα by a The from an of was by as by of from The was by from the by containing the ERRα cDNA encoding amino acids the and of ERRα was as MCAD plasmids been The containing of the estrogen element of the was by The was a from of The was by of the of the promoter of the reporter The is the response element in the gene promoter expression has been in PGC-1α by a Mutagenesis the as for The and the and The PGC-1α and been PGC-1α by an at the and a at or to a encoding a to of the PGC-1α The PGC-1α the of the for The and by the for PGC-1α to a at or The and by from the the from The has been The the and the expression from of and of the has been The was by the from the the MCAD plasmids been The containing of the estrogen element of the was by The was a from of The was by of the of the promoter of the reporter The is the response element in the gene promoter expression has been in PGC-1α by a Mutagenesis the as for The and the and The PGC-1α and been PGC-1α by an at the and a at or to a encoding a to of the PGC-1α The PGC-1α the of the for The and by the for PGC-1α to a at or The and by from the the from The has been The the and the expression from of and of the has been The was by the from the the MCAD plasmids been The containing of the estrogen element of the was by The was a from of The was by of the of the promoter of the reporter The is the response element in the gene promoter The MCAD plasmids been The containing of the estrogen element of the was by The was a from of The was by of the of the promoter of the reporter The is the response element in the gene promoter expression has been in PGC-1α by a Mutagenesis the as for The and the and The PGC-1α and been PGC-1α by an at the and a at or to a encoding a to of the PGC-1α The PGC-1α the of the for The and by the for PGC-1α to a at or The and by from the the from The has been The the and the expression from of and The expression has been in PGC-1α by a Mutagenesis the as for The and the and The PGC-1α and been PGC-1α by an at the and a at or to a encoding a to of the PGC-1α The PGC-1α the of the for The and by the for PGC-1α to a at or The and by from the the from The has been The the and the expression from of and of the has been The was by the from the the of the has been The was by the from the the cellular and was as with from the cDNA PPARα, and In and cellular and was as with from the cDNA PPARα, and In and by and as of ERRα and or by and of MCAD was the by and as of ERRα and or by and of MCAD was the vitro interaction been previously in the in In of a of to was with in of binding and for at The and with binding was to the for and the by The and and by the In vitro interaction been previously in the in In of a of to was with in of binding and for at The and with binding was to the for and the by The and and by the of that the PGC-1α·ERRα interaction a transcriptional in the of cardiac and metabolism. ERRα as PGC-1α interacting a two-hybrid The interaction of PGC-1α with ERRα and isoforms was in vitro binding binding domains the PGC-1α·ERRα binding ERRα and the of the interaction. the ERRα binding the PGC-1α is with other transcription binding sites. PGC-1α ERRα and ERRγ isoforms in of PGC-1α·ERRα in regulating cellular is by and expression of ERR and mitochondrial for the in mitochondrial is by the that PGC-1α is necessary for activation of the MCAD studies of the PGC-1α·ERRα binding revealed a novel nuclear receptor binding motif LXXLL coactivator been to interactions with nuclear The Leu-rich motif an that a binding by of the receptor PGC-1α LXXLL has been previously to a in binding nuclear studies demonstrated that the interaction of ERRα with PGC-1α the of an LXXLL motif as the ERRα binding is with the that the ERRα is required for the interaction with is the in which the motif of PGC-1α was to the interaction of PGC-1α with a nuclear receptor a as an accessory for interaction with PGC-1α results that the motif functions as the primary of interaction and that is to is distinct from other interactions with as demonstrated by the that the interaction of PGC-1α with and required the LXXLL the motif through which coactivator with nuclear receptors, studies the of the Leu-rich in receptor and binding distinct of LXXLL domains to the PGC-1α is a binding in by the of and of the of the LXXLL The through which ERRα primarily to an LXXLL not to studies with demonstrated that the coactivator binding of an motif an from the transcription coactivator the of a LXXLL motif in the transcription by to the motif the binding by the motif to The motif of PGC-1α in to an Furthermore, a of of the motif that to its by ERRα and ERRγ. with the motif not of and has not been identified as a binding in nuclear receptor interaction with PGC-1α for the interaction of ERRα with PGC-1α with other PGC-1α nuclear receptor partners is is related to the nuclear receptor The nuclear receptor with PGC-1α has not been coactivator binding been for a of receptors, including and receptor α interacts with transcription via the LXXLL and which and which of are in ERR that other the of ERRα and ERRγ account for binding with of the ERRα homology with that of in binding to are or in ERRα the distinct was to for the by the of ERRα the are distinct ERRα and ERRγ. These are not with coactivator the amino acid to in to the binding with a of studies of response the of that the of ERR isoforms for regulating of the of response or interactions has been to a of transcription in cellular The distinct binding PGC-1α with ERRα with other nuclear a by which PGC-1α of a nuclear receptor is by a of factors, including expression binding of and The of PGC-1α to distinct binding with partners an additional for receptor to a as the of nuclear receptor binding the PGC-1α the is the of the PGC-1α by PGC-1α is to partners, as a of activation of related gene of its ERR isoforms and a of nuclear receptor transcription in transcriptional activation or of Although ERRα was the orphan nuclear receptor the nuclear receptor is its the for ERRα of estrogen ERRα and and ERRα has been to transcriptional ERRα has been implicated in the of cellular and the of that ERRα to PGC-1α in mitochondrial metabolism. ERRα and ERRγ expression is in that mitochondrial as a primary for energy or as and that ERRα and expression and ERR isoforms and PGC-1α are in of with in which are the pattern of ERRα and PGC-1α expression a in ERRα and are in the in and and as the of ERRα expression is induced with for energy as as studies that the MCAD gene is a ERRα ERRα binds the MCAD gene promoter via a which is for the and expression of MCAD to of MCAD gene transcription was The results of the ERRα overexpression and studies that MCAD is an endogenous for ERRα and that in the of PGC-1α ERRα the MCAD studies that PGC-1α a in regulating cardiac mitochondrial and mitochondrial the that ERRα and ERRγ as of broad The of that the PGC-1α·ERRα interaction a transcriptional in the of cardiac and metabolism. ERRα as PGC-1α interacting a two-hybrid The interaction of PGC-1α with ERRα and isoforms was in vitro binding binding domains the PGC-1α·ERRα binding ERRα and the of the interaction. the ERRα binding the PGC-1α is with other transcription binding sites. PGC-1α ERRα and ERRγ isoforms in of PGC-1α·ERRα in regulating cellular is by and expression of ERR and mitochondrial for the in mitochondrial is by the that PGC-1α is necessary for activation of the MCAD studies of the PGC-1α·ERRα binding revealed a novel nuclear receptor binding motif LXXLL coactivator been to interactions with nuclear The Leu-rich motif an that a binding by of the receptor PGC-1α LXXLL has been previously to a in binding nuclear studies demonstrated that the interaction of ERRα with PGC-1α the of an LXXLL motif as the ERRα binding is with the that the ERRα is required for the interaction with is the in which the motif of PGC-1α was to the interaction of PGC-1α with a nuclear receptor a as an accessory for interaction with PGC-1α results that the motif functions as the primary of interaction and that is to is distinct from other interactions with as demonstrated by the that the interaction of PGC-1α with and required the Although LXXLL the motif through which coactivator with nuclear receptors, studies the of the Leu-rich in receptor and binding distinct of LXXLL domains to the PGC-1α is a binding in by the of and of the of the LXXLL The through which ERRα primarily to an LXXLL not to studies with demonstrated that the coactivator binding of an motif an from the transcription coactivator the of a LXXLL motif in the transcription by to the motif the binding by the motif to The motif of PGC-1α in to an Furthermore, a of of the motif that to its by ERRα and ERRγ. with the motif not of and has not been identified as a binding in nuclear receptor interaction with PGC-1α The for the interaction of ERRα with PGC-1α with other PGC-1α nuclear receptor partners is is related to the nuclear receptor The nuclear receptor with PGC-1α has not been coactivator binding been for a of receptors, including and receptor α interacts with transcription via the LXXLL and which and which of are in ERR that other the of ERRα and ERRγ account for binding with of the ERRα homology with that of in binding to are or in ERRα the distinct was to for the by the of ERRα the are distinct ERRα and ERRγ. These are not with coactivator the amino acid to in to the binding with a of studies of response the of that the of ERR isoforms for regulating of the of response or interactions PGC-1α has been to a of transcription in cellular The distinct binding PGC-1α with ERRα with other nuclear a by which PGC-1α of a nuclear receptor is by a of factors, including expression binding of and The of PGC-1α to distinct binding with partners an additional for receptor to a as the of nuclear receptor binding the PGC-1α the is the of the PGC-1α by PGC-1α is to partners, as a of activation of related gene of its The ERR isoforms and a of nuclear receptor transcription in transcriptional activation or of Although ERRα was the orphan nuclear receptor the nuclear receptor is its the for ERRα of estrogen ERRα and and ERRα has been to transcriptional ERRα has been implicated in the of cellular and the of that ERRα to PGC-1α in mitochondrial metabolism. ERRα and ERRγ expression is in that mitochondrial as a primary for energy or as and that ERRα and expression and ERR isoforms and PGC-1α are in of with in which are the pattern of ERRα and PGC-1α expression a in ERRα and are in the in and and as the of ERRα expression is induced with for energy as as studies that the MCAD gene is a ERRα ERRα binds the MCAD gene promoter via a which is for the and expression of MCAD to of MCAD gene transcription was The results of the ERRα overexpression and studies that MCAD is an endogenous for ERRα and that in the of PGC-1α ERRα the MCAD studies that PGC-1α a in regulating cardiac mitochondrial and mitochondrial the that ERRα and ERRγ as of broad to for with of the
Huss et al. (Tue,) studied this question.