Skeletal Muscle Fiber-type Switching, Exercise Intolerance, and Myopathy in PGC-1α Muscle-specific Knock-out Animals The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters Citation Handschin, Christoph, Sherry Chin, Ping Li, Fenfen Liu, Eleftheria Maratos-Flier, Nathan K. LeBrasseur, Zhen Yan, and Bruce M. Spiegelman. 2007. “Skeletal Muscle Fiber-Type Switching, Exercise Intolerance, and Myopathy in PGC-1α Muscle-Specific Knock-out Animals.” Journal of Biological Chemistry 282 (41): 30014–21. doi:10.1074/jbc.M704817200. Citable link http://nrs.harvard.edu/urn-3:HUL.InstRepos:41543093 Terms of Use This article was downloaded from Harvard University’s DASH repository, and is made available under the terms and conditions applicable to Other Posted Material, as set forth at http:// nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of- use#LAA THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 282, NO. 41, pp. 30014–30021, October 12, 2007 © 2007 by The American Society for Biochemistry and Molecular Biology, Inc. Printed in the U.S.A. Skeletal Muscle Fiber-type Switching, Exercise Intolerance, and Myopathy in PGC-1␣ Muscle-specific Knock-out Animals*□S Received for publication, June 12, 2007, and in revised form, July 5, 2007 Published, JBC Papers in Press, August 16, 2007, DOI 10.1074/jbc.M704817200 Christoph Handschin‡§1, Sherry Chin‡, Ping Li¶, Fenfen Liuʈ, Eleftheria Maratos-Flierʈ, Nathan K. LeBrasseur**, Zhen Yan¶, and Bruce M. Spiegelman‡2 From the ‡Dana-Farber Cancer Institute and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, §Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland, ¶Department of Medicine, Duke University Medical Center, Durham, North Carolina 27704, ʈDivision of Endocrinology, Diabetes, and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, and **Diabetes and Metabolism Unit, Boston University School of Medicine, Boston, Massachusetts 02118 The transcriptional coactivator peroxisome proliferator-acti- scription of myofibrillar genes typical of oxidative muscle fibers vated receptor ␥ coactivator 1␣ (PGC-1␣) is a key integrator of (6). Interestingly, MEF2 and PGC-1␣ also control PGC-1␣ gene neuromuscular activity in skeletal muscle. Ectopic expression of transcription in an autoregulatory loop (7, 8). Metabolic genes, PGC-1␣ in muscle results in increased mitochondrial number including those responsible for mitochondrial oxidative phos- Downloaded from and function as well as an increase in oxidative, fatigue-resistant phorylation, are induced by a transcriptional cascade with muscle fibers. Whole body PGC-1␣ knock-out mice have a very coactivation of the estrogen-related receptor ␣ (ERR␣, official complex phenotype but do not have a marked skeletal muscle nomenclature NR3B1), the nuclear respiratory factor 2 (NRF-2, phenotype. We thus analyzed skeletal muscle-specific PGC-1␣ alternatively called GA-binding protein, GABP), and the ␣ knock-out mice to identify a specific role for PGC-1 in skeletal nuclear respiratory factor 1 (NRF-1) by PGC-1␣ and subse- http://www.jbc.org/ muscle function. These mice exhibit a shift from oxidative type I quent increase in the levels of mitochondrial transcription fac- and IIa toward type IIx and IIb muscle fibers. Moreover, skeletal tor A (TFAM) and mitochondrial transcription specificity fac- muscle-specific PGC-1␣ knock-out animals have reduced tors TFB1M and TFB2M (9–13). Recently, we have found that endurance capacity and exhibit fiber damage and elevated activity-induced remodeling of the postsynaptic side of neuro- markers of inflammation following treadmill running. Our data ␣ muscular junctions involves a complex between PGC-1 , by guest on October 14, 2019 demonstrate a critical role for PGC-1␣ in maintenance of nor- GABP, and host cell factor that assembles upon phosphoryla- mal fiber type composition and of muscle fiber integrity follow- tion of PGC-1␣ and GABP in post-synaptic nuclei (14). ing exertion. Data obtained from muscle-specific PGC-1␣ transgenic ani- mals underline the importance of PGC-1␣ in skeletal muscle in vivo (6). These mice have increased number and function of Skeletal muscle has an enormous capacity to adapt to motor mitochondria accompanied by a higher number of type IIa and neuron activity. Many changes in gene expression are con- type I oxidative, slow twitch, high endurance muscle fibers (6). trolled by motor neuron-induced calcium signaling (1–3). The Furthermore, even in the absence of functional motor nerve transcriptional coactivator peroxisome proliferator-activated signaling following hind leg denervation, ectopically expressed ␥ ␣ ␣ 3 receptor coactivator 1 (PGC-1 ) is at the nexus of this PGC-1␣ maintains skeletal muscle function and blunts skeletal signaling and subsequently regulates the expression of gene muscle atrophy that normally occurs in the absence of motor programs needed for skeletal muscle adaptations to increased neuron signaling (15). Thus, PGC-1␣ apparently controls most work load (4, 5). By coactivating the myocyte enhancer factor 2 if not all of the transcriptional changes induced by motor neu- ␣ members MEF2C and MEF2D, PGC-1 potently drives tran- ron signaling in skeletal muscle. Surprisingly, whole body PGC-1␣ knock-out animals do not exhibit a marked skeletal * This work was supported in part by National Institutes of Health Grants muscle phenotype (16). Despite a significant reduction of tran- DK54477 and DK61562 (to B. M. S.) and AR050429 (to Z. Y.). The costs of publication of this article were defrayed in part by the payment of page scription of several mitochondrial genes, no difference in the charges. This article must therefore be hereby marked “advertisement”in relative numbers of the different fiber types is observed (17). accordance with 18 U.S.C. Section 1734 solely to indicate this fact. However, whole body PGC-1␣ knock-out animals have a dom- □S The on-line version of this article (available at http://www.jbc.org) contains inant central nervous system phenotype that might mask the supplemental Figs. S1–S4. 1 Supported by a Scientist Career Development grant from the Muscular Dys- effects of loss-of-function of PGC-1␣ in peripheral tissues (16). trophy Association, Swiss National Science Foundation Professorship These mice are hyperactive, show circadian abnormalities, and PP00A-110746, and the University Research Priority Program “Integrative have constitutively activated AMP-activated kinase in skeletal Human Physiology” of the University of Zurich. ␣ 2 To whom correspondence should be addressed: Dana-Farber Cancer Insti- muscle, all of which might compensate for the loss of PGC-1 tute, Smith Bldg., One Jimmy Fund Way, Boston, MA 02115. Tel.: 617-632- in this tissue (16, 18). In the liver, gluconeogenic and heme 3567; Fax: 617-632-4655; E-mail: [email protected]. 3 ␣ biosynthetic genes are constitutively elevated in whole body The abbreviations used are: PGC-1 , peroxisome proliferator-activated ␣ receptor ␥ coactivator 1␣; MKO, skeletal muscle-specific knock-out ani- PGC-1 knock-out animals even in the fed state (16). In con- mals; MyHC, myosin heavy chain; TNF␣, tumor necrosis factor ␣. trast, and as expected from previous studies, fasting induction 30014 JOURNAL OF BIOLOGICAL CHEMISTRY VOLUME 282•NUMBER 41•OCTOBER 12, 2007 PGC-1␣ and Skeletal Muscle Function of gluconeogenic and heme biosynthetic genes is severely blunted in the liver of liver-specific PGC-1␣ knock-out animals (19). To clarify the genetic requirement for PGC-1␣ in skeletal muscle function without the confounding variables seen in the whole body knockouts, skeletal muscle-specific PGC-1␣ knock-out animals (MKOs) were generated.4 Here, we report a moderate reduction in the number of oxidative type I and type IIa muscle fibers and exercise capacity in these mice. Strikingly, skeletal muscle of MKOs has a low level of damaged and regen- erating fibers. This compromised skeletal muscle integrity is dramatically exacerbated by physical exercise and accompa- nied by elevated markers of systemic inflammation. Our data thus highlight the importance of PGC-1␣ in maintaining proper function and integrity of skeletal muscle. FIGURE 1. Decreased metabolic gene expression in MKOs. Relative gene expression was measured from cDNA extracted from gastrocnemius and nor- malized to 18 S rRNA levels. Bars depict mean values, and error bars represent EXPERIMENTAL PROCEDURES standard error. *, p Ͻ 0.05 between control and MKO animals. PDH, pyruvate ␤ Animal Experimentation—Generation of MKOs has been dehydrogenase ; MCAD, medium chain acyl-CoA dehydrogenase; PGAM1, 4 phosphoglycerate mutase 1; PDC-E2, pyruvate dehydrogenase complex, E2 described elsewhere. Mice were held under standard condi- component; MDH1, malate dehydrogenase 1, NAD (soluble); OXCT1, tions. All experiments and protocols were performed in accord- 3-oxoacid CoA transferase; CKMT2, creatine kinase, mitochondrial 2 (sarcom- eric); LDHA, lactate dehydrogenase A. Downloaded from ance with the respective Animal Facility Institutional Animal Care and Use Committee regulations. animals were timed until release from the grid. A maximum Gene Expression Analysis—Total RNA was isolated from tis- score of 60 s was given if the animal did not fall. sues using the TRIzol reagent (Invitrogen) according