title: Post-transcriptional regulation of IGF1R by key microRNAs in long-lived mutant mice.
abstract: Long-lived mutant mice, both Ames dwarf and growth hormone receptor gene-disrupted or knockout strains, exhibit heightened cognitive robustness and altered IGF1 signaling in the brain. Here, we report, in both these long-lived mice, that three up-regulated lead microRNAs, miR-470, miR-669b, and miR-681, are involved in posttranscriptional regulation of genes pertinent to growth hormone/IGF1 signaling. All three are most prominently localized in the hippocampus and correspond to reduced expression of key IGF1 signaling genes: IGF1, IGF1R, and PI3 kinase. The decline in these genes' expression translates into decreased phosphorylation of downstream molecules AKT and FoxO3a. Cultures transfected with either miR-470, miR-669b, or miR-681 show repressed endogenous expression of all three genes of the IGF1 signaling axis, most significantly IGF1R, while other similarly up-regulated microRNAs, including let-7g and miR-509, do not induce the same levels of repression. Transduction study in IGF1-responsive cell cultures shows significantly reduced IGF1R expression, and AKT to some extent, most notably by miR-681. This is accompanied by decreased levels of downstream phosphorylated forms of AKT and FoxO3a upon IGF1 stimulation. Suppression of IGF1R by the three microRNAs is further validated by IGF1R 3'UTR reporter assays. Taken together, our results suggest that miR-470, miR-669b, and miR-681 are all functionally able to suppress IGF1R and AKT, two upstream genes controlling FoxO3a phosphorylation status. Their up-regulation in growth hormone signaling-deficient mutant mouse brain suggests reduced IGF1 signaling at the posttranscriptional level, for numerous gains of neuronal function in these long-lived mice.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, 580 South Preston Street, Louisville, KY 40202, USA.
authors.forename: Ruqiang
authors.initials: R
authors.lastname: Liang
authors.forename: Amit
authors.initials: A
authors.lastname: Khanna
authors.forename: Senthilkumar
authors.initials: S
authors.lastname: Muthusamy
authors.forename: Na
authors.initials: N
authors.lastname: Li
authors.forename: Harshini
authors.initials: H
authors.lastname: Sarojini
authors.forename: John J
authors.initials: JJ
authors.lastname: Kopchick
authors.forename: Michal M
authors.initials: MM
authors.lastname: Masternak
authors.forename: Andrzej
authors.initials: A
authors.lastname: Bartke
authors.forename: Eugenia
authors.initials: E
authors.lastname: Wang
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000172:deficiency* / Q000235:genetics; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D008136:Longevity; D051379:Mice; D008822:Mice, Transgenic; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D017526:Receptor, IGF Type 1 / Q000172:deficiency* / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics*; D014162:Transfection
chemical_list: D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; C474033:FoxO3 protein, mouse; D035683:MicroRNAs; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D019869:Phosphatidylinositol 3-Kinases; D017526:Receptor, IGF Type 1; D051057:Proto-Oncogene Proteins c-akt