Essential role of Ahnak in adipocyte differentiation leading to the transcriptional regulation of Bmpr1α expression

Cell Death Dis. 2018 Aug 28;9(9):864. doi: 10.1038/s41419-018-0873-6.

Abstract

The role of Ahnak in obesity has been reported previously. Loss of Ahnak leads to decreased Bmp4/Smad1 signaling, resulting in the downregulation of adipocyte differentiation. However, the biological significance of Ahnak remains largely unknown. In this study, we demonstrate that Ahnak-mediated impaired adipogenesis results in decreased Bmpr1α transcriptional expression. To confirm this, Ahnak siRNA was used to knock-down Ahnak in C3H10T1/2 and primary stromal vascular fraction cells. Ahnak siRNA transfected cells showed suppression of Bmpr1α expression and decreased BMP4/ Bmpr1α signaling. The differential adipogenesis was further confirmed by knock-down of Bmpr1α in C3H10T1/2 cells, which resulted in reduced adipogenesis. Moreover, stable Ahnak knock-out C3H10T1/2 cells stably transfected with Ahnak CRISPR/Cas9 plasmid suppressed expression of Bmpr1α and prevented differentiation into adipocytes. Furthermore, we developed immortalized pre-adipocytes from wild-type or Ahnak Knock-out mice's stromal vascular fraction (SVF) to confirm the function of Ahnak in pre-adipocyte transition. Immortalized Ahnak knock-out SVF cells showed lower level of Bmpr1α expression, evidence by their impaired BMP4/Bmpr1α signaling. Upon adipogenic induction, immortalized Ahnak knock-out SVF cells exhibited a marked decrease in adipocyte differentiation compared with immortalized wild-type pre-adipocytes. Furthermore, over-expression of Bmpr1α restored the adipogenic activity of Ahnak knock-out C3H10T1/2 cells and immortalized Ahnak knock-out SVF cells. Our data reveal the missing link in Ahnak-mediated adipose tissue remodeling and suggest that precise regulation of Ahnak in adipose tissue might have a therapeutic advantage for metabolic disease treatment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipocytes / physiology*
  • Adipogenesis / genetics
  • Adipose Tissue / physiology
  • Animals
  • Bone Morphogenetic Protein Receptors, Type I / genetics*
  • Cell Differentiation / genetics
  • Cell Line
  • Down-Regulation / genetics
  • Gene Expression Regulation / genetics
  • Male
  • Membrane Proteins / genetics*
  • Mice
  • Mice, Knockout
  • Neoplasm Proteins / genetics*
  • Obesity / genetics
  • Transcription, Genetic / genetics*

Substances

  • Ahnak protein, mouse
  • Membrane Proteins
  • Neoplasm Proteins
  • Bmpr1a protein, mouse
  • Bone Morphogenetic Protein Receptors, Type I