Novel mechanistic role of Kif26b in adipogenic differentiation of murine multipotent stromal cells

Emerging evidence delineates that obesity, a complex metabolic disorder, impairs the structure and function of stromal cells residing in various tissues. The exuberant adipose tissue mass observed in obesity is, in part, associated with hyperplasia of adipocytes resulting from recruitment of multipotent stromal cells within the stromal vascular fraction of adipose tissues. However, a clear understanding of the causal role of stromal cells and biological factors in obesity is lacking. In our quest to understanding the role of kinesin family member 26B (KIF26B), we found that KIF26B regulates osteogenic and chondrogenic differentiation of stromal/progenitor cells. In this study, we sought to examine the effects of Kif26b loss-of-function on adipogenic differentiation of murine C3H10T1/2 multipotent stromal cells. In vitro loss-of-function studies demonstrated that Kif26b knockdown by lentivirus mediated shRNA markedly dampened the differentiation potential of C3H10T1/2 cells to adipocytes and suppressed the expression of adipogenesis-related genes e.g., Pparg, C/ebpα, Fabp4 and Adipoq. Analysis of cell cycle revealed that Kif26b knockdown resulted in elevated expression of cyclins (Ccnd1, Ccnb1, Ccna2) along with rapid cell cycle progression from G0/G1 to S and G2 phases. Mechanistically, reduced adipogenic differentiation of Kif26b-deficient cells was partly dependent on PPARγ, a key transcription factor implicated in adipogenesis. This observation was experimentally supported as loss of adipogenesis was partially rescued by the addition of PPARγ agonist, rosiglitazone in Kif26b-deficient cells. We further found that silencing of Kif26b lessened the protein levels of phospho-AKT(Ser473), phospho-S6(Ser235/236), and phospho-mTOR(Ser2448), the major component of AKT/mTOR complex 1 (mTORC1) signaling at the basal level. Together, these data define a novel role of Kif26b in regulating the commitment of C3H10T1/2 multipotent stromal cells to the adipocyte lineage and provide a practical framework for further experiments to establish its therapeutic potential for the treatment of problems associated with adipogenesis such as obesity at the cellular and molecular level.