NAMPT_SIRT2-mediated inhibition of thep53-p21 signaling pathway is indispensablefor maintenance and hematopoieticdifferentiation of human iPS cells

Abstract

NAMPT modulates cellular functions by means of the protein deacetylation activity of NAD+-dependent sirtuins which determines functions of histones and none-histone proteins via deacetylation. The role of NAMPT and SIRT2 in maintenance and hematopoietic differentiation of iPS cells is poorly investigated. We assessed the effect of NAMPT and SIRT2 on the pluripotency, proliferation, survival, and granulocytic differentiation of human iPS cells. We applied two approaches to inhibit NAMPT or SIRT2, the addition of specific chemical inhibitors of NAMPT or SIRT2 (FK866 and AC93253, respectively) to the culture medium, shRNA mediated NAMPT/SIRT2 knockdown in iPS cells. The molecular mechanism downstream of NAMPT/SIRT2 functions in iPS cells is also investigated. We provide that evidence that NAMPT is essential for the maintenance, survival and myeloid differentiation of iPS cells. We found that of the NAMPT or SIRT2 blockage in iPS cells induces p53 upregulation by enhancing its lysine acetylation. This results in activation of p21, the target of p53, consequently, the cell cycle arrested in G1 phase and apoptosis was induced in iPS cells. NAMPT and SIRT2 inhibition also abolished iPS cells’ granulocytic differentiation in an embryoid body (EB)-based differentiation. Taken together, our data shows that the NAMPT/SIRT2/p53/p21 signaling axis plays an essential role in the iPS cells maintenance and hematopoietic differentiation.