Reciprocal roles of SIRT1 and SKIP in the regulation of RAR activity: implication in the retinoic acid-induced neuronal differentiation of P19 cells

Abstract

Human sirtuin 1 (SIRT1) is a NAD+-dependent deacetylase that participates in cell death/survival, senescence and metabolism. Although its substrates are well characterized, no direct regulators have been defined. Here, we show that SIRT1 associates with SKI-interacting protein (SKIP) and modulates its activity as a coactivator of retinoic acid receptor (RAR). Binding assays indicated that SKIP interacts with RAR in a RA-dependent manner, through a region that overlaps the binding site for SIRT1. SKIP augmented the transcriptional activation activity of RAR by cooperating with SRC-1, and SIRT1 suppressed SKIP/SRC-1-enhanced RAR transactivation activity. The suppression was dependent on the deacetylase activity of SIRT1 and was enhanced by a SIRT1 activator, resveratrol. In contrast, the suppression was relieved by SIRT1 knockdown, overexpression of SKIP and treatment with a SIRT1 inhibitor, splitomicin. Upon SKIP overexpression, the recruitment of SIRT1 to the endogenous RARβ2 promoter was severely impaired, and SKIP was recruited to the promoter instead. Finally, resveratrol treatment inhibited RA-induced neuronal differentiation of P19 cells, accompanied by reductions in the neuronal marker nestin and a RAR target gene, RARβ2. This inhibition was relieved by either knockdown of SIRT1 or overexpression of SKIP. These data suggest that SIRT1 and SKIP play reciprocal roles in the regulation of RAR activity, which is implicated in the regulation of RA-induced neuronal differentiation of P19 cells.

Retinoic Acid Induces Neurogenesis by Activating Both Retinoic Acid Receptors (RARs) and Peroxisome Proliferator-activated Receptor β/δ (PPARβ/δ)

“…The data indicate that early steps in RA-induced neurogenesis, entailing differentiation of stem cells into neuronal progenitors, are driven by CRABP-II and RAR and can be inhibited by the FABP5/PPAR␤/␦ path. The data further show that inhibition of the commitment of stem cells to the neuronal lineage by the FABP5/PPAR␤/␦ path is mediated by the direct PPAR␤/␦ target genes Ajuba and SIRT1, known to suppress the transcriptional activity of RAR (25,26). In contrast with their inhibitory activity in this early stage, FABP5 and PPAR␤/␦ promote the completion of neurogenesis by supporting differentiation of neuronal progenitor cells to mature neurons.…”

“…One of these is SIRT1, an NAD ϩ -dependent class III histone deacetylase that was shown to inhibit RA-induced differentiation of P19 cells by competing with RAR for the coactivator SKI-interacting protein (25). The other is Ajuba, a member of the Ajuba/Zyxin family of LIM proteins (26), which was shown to inhibit RAinduced P19 cell differentiation by interacting with RAR␣ to repress its transcriptional activity (27).…”

SIRT1-Mediated Deacetylation of CRABPII Regulates Cellular Retinoic Acid Signaling and Modulates Embryonic Stem Cell Differentiation

“…For instance, the developmental defects observed in SIRT1 KO mice (Figure S5A, (Cheng et al, 2003; McBurney et al, 2003)) closely resemble the developmental defects caused by altered vitamin A metabolism and RA signaling (Ghyselinck et al, 1998; Grondona et al, 1996; Kastner et al, 1996; MacLean et al, 2007; Sucov et al, 1994). SIRT1 has also been shown to function as a co-repressor in inhibition of the RAR-mediated neuronal differentiation of P19 cells (Kang et al, 2009; Yu et al, 2012). Here we showed that by direct deacetylation of CRABPII, SIRT1 limits nuclear RAs that are available to their receptors and represses RA-induced ESC differentiation.…”

“…In particular, the survival rate of SIRT1 whole body KO mice on a 129SvEv/FVB background is about 1% (Wang et al, 2008). Specifically, SIRT1 has been shown to modulate the neural and glial specification of neural precursors (Kang et al, 2009; Prozorovski et al, 2008), control differentiation of skeletal myoblasts (Fulco et al, 2008; Fulco et al, 2003), and influence spermatogenesis (Coussens et al, 2008). Despite the studies above, however, the molecular mechanisms underlying the important function of SIRT1 in development and stem cell biology are still unclear.…”

SIRT1 and Neural Cell Fate Determination

“…This inhibition was relieved by either knockdown of sirt1 or overexpression of SKIP. These results suggest that SIRT1 and SKIP play reciprocal roles in the regulation of RA-induced neuronal differentiation of P19 cells through RAR activity [90]. Furthermore, Yu et al found that RA-induced neuronal differentiation of P19 stem cells is mediated by the CRABP-II/RAR pathway in the early stages and through the PPARβ/δ/FABP5 pathway in the late stages of the process.…”