title: The cathepsin L gene is a direct target of FOXO1 in skeletal muscle.
abstract: FOXO1 (forkhead box O1), a forkhead-type transcription factor whose gene expression is up-regulated in the skeletal muscle during starvation, appears to be a key molecule of energy metabolism and skeletal muscle atrophy. Cathepsin L, a lysosomal proteinase whose expression is also up-regulated in the skeletal muscle during starvation, is induced in transgenic mice overexpressing FOXO1 relative to wild-type littermates. In the present study, we conducted in vivo and in vitro experiments focusing on FOXO1 regulation of Ctsl (cathepsin L gene; CTSL1 in humans) expression in the skeletal muscle. During fasting and refeeding of C57BL/6 mice, Ctsl was regulated in parallel with FOXO1 in the skeletal muscle. Fasting-induced Ctsl expression was attenuated in transgenic mice overexpressing a dominant-negative form of FOXO1 or in skeletal-muscle-specific Foxo1-knockout mice relative to respective wild-type controls. Using C2C12 mouse myoblasts overexpressing a constitutively active form of FOXO1, we showed that FOXO1 induces Ctsl expression. Moreover, we found FOXO1-binding sites in both the mouse Ctsl and human CTSL1 promoters. The luciferase reporter analysis revealed that the mouse Ctsl and human CTSL1 promoters are activated by FOXO1, which is abolished by mutations in the consensus FOXO1-binding sites. Gel mobility-shift and chromatin immunoprecipiation assays showed that FOXO1 is recruited and binds to the Ctsl promoter. The present study provides in vivo and in vitro evidence that Ctsl is a direct target of FOXO1 in the skeletal muscle, thereby suggesting a role for the FOXO1/cathepsin L pathway in fasting-induced skeletal muscle metabolic change and atrophy.
authors.affiliation: Department of Molecular Medicine and Metabolism, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Yamazaki
authors.forename: Yasutomi
authors.initials: Y
authors.lastname: Kamei
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sugita
authors.forename: Fumiko
authors.initials: F
authors.lastname: Akaike
authors.forename: Sayaka
authors.initials: S
authors.lastname: Kanai
authors.forename: Shinji
authors.initials: S
authors.lastname: Miura
authors.forename: Yukio
authors.initials: Y
authors.lastname: Hirata
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Troen
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Kitamura
authors.forename: Ichizo
authors.initials: I
authors.lastname: Nishino
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Suganami
authors.forename: Osamu
authors.initials: O
authors.lastname: Ezaki
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Ogawa
mesh_terms: D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D056668:Cathepsin L / Q000502:physiology*; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D032446:Myoblasts / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; C467200:Foxo1 protein, mouse; D012333:RNA, Messenger; D008156:Luciferases; C534281:CTSL protein, human; D056668:Cathepsin L; C534278:Ctsl protein, mouse