An adipocyte-specific lncRAP2 – Igf2bp2 complex enhances adipogenesis and energy expenditure by stabilizing target mRNAs

lncRAP2 is a conserved cytoplasmic adipocyte-specific lncRNA required for adipogenesis. Using hybridization-based purification combined with in vivo interactome analyses, we show that lncRAP2 forms ribonucleoprotein complexes with several mRNA stability and translation modulators, among them Igf2bp2. Transcriptome-wide identification of Igf2bp2 client mRNAs in white adipocytes reveals selective binding to mRNAs encoding adipogenic effectors and regulators. Depleting either lncRAP2 or Igf2bp coordinately downregulates these same target proteins. Ribosome profiling and quantitative proteomics show that this occurs predominantly at the level of mRNA, as binding of the lncRAP2-Igf2bp complex does not affect mRNA translation. Suppressing lncRAP2 or Igf2bp2 selectively destabilizes many mRNAs encoding proteins essential for energy expenditure, including Adiponectin, reducing adipocyte lipolytic capacity. Genome-wide association studies reveal specific association of genetic variants within both lncRAP2 and Igf2bp2 with body mass and type 2 diabetes, and we find that adipose lncRAP2 and Igf2bp2 are suppressed during obesity and diabetes progression. Thus, the lncRAP2-Igf2bp complex potentiates adipose development and energy expenditure and is associated with susceptibility to obesity-linked diabetes.