Differentiation of 3T3‐L1 pre‐adipocytes induced by inhibitors of poly(ADP‐ribose) polymerase and by related noninhibitory acids

Abstract

To analyze a possible involvement of ADP-ribosylation reactions in 3T3-LI pre-adipocyte differentiation, ADP-ribosyltransferase activities is permeabilized cells as well as endogenous amounts of protein-bound monoand poly(ADP-ribose) residues were determined. Also, in vivo labeling with [3H]adenosine of ADP-ribose residues linked to high-mobility-group (HMG) proteins was performed. As an additional probe, the effects of ADPribosylation inhibitors and non-inhibitory analogs were studied. Basal and total poly(ADP-ribose) polymerase activities markedly increased prior to the appearance of the differentiation marker glycerol-3-phosphate dehydrogenase. Despite these apparent changes in activity, however, neither protein-bound poly(ADP-ribose) residue nor mono(ADP-ribosyl) groups in histones, nor the NAD content, changed significantly under these conditions. Furthermore, although HMG protein-associated [3H]ADP-ribose was reduced in differentiating [3H]adenosinelabeled cells, the data suggest altered precursor pool labeling rather than a specific decrease in ADP-ribosylated HMG proteins. Non-participation of ADP-ribosylation reactions in 3T3-LI differentiation is further supported by experiments with inhibitors and non-inhibitory analogs. Benzamide at 0.3 -3 mM per SP without effect on differentiation, was able to induce specific gene expression when combined with insulin (10-l 2 -M). Similar effects were seen with benzoate as well as with nicotinamide, 3-aminobenzamide and their corresponding acids. The data indicate that benzaiiiide and analogs have profound effects on chromatin functions that are not mediated by ADP-ribosylation reactions Eukaryotic cells contain an enzyme, poly(ADP-ribose) polymerase, which uses NAD to modify nuclear proteins by homopolymeric ADP-ribose. In addition, modification of acceptor polypeptides by single ADP-ribosyl groups [mono-(ADP-ribosyl)ation] has been found. Nuclear poly(ADPribosy1)ation appears to be linked to processes like DNA excision repair and carcinogenesis (for reviews see [l -31). The reaction has also been implicated in various differentiation processes [3,4], although opposite changes in different systems have been reported. Thus, in some differentiating cell lines, a rise of poly(ADP-ribose) as a prerequisite for differentiation was deduced mainly from experiments with inhibitors [5 -81, while in others a transient decrease of poly(ADP-ribose) polymerase activity as a regulatory signal was postulated [9 -121. Conflicting data were presented even for one and the same system: reports on an apparent decrease in poly(ADPribose) polymerase activity during 3T3-LI pre-adipocyte differentiation [13] and an inducing action of polymerase inhibitors [14] contrast with observations of a prevention of differentiation by nicotinamide or benzamide [15]. This led us to analyze the ADP-ribosylation status in vivo during 3T3-Ll

PARP-1 Controls the Adipogenic Transcriptional Program by PARylating C/EBPβ and Modulating Its Transcriptional Activity

“…Consistent with previous studies (Janssen and Hilz, 1989; Pekala et al, 1981), we observed a reduction in nuclear PAR levels (as detected by Western blotting for PAR) during the first two days of adipogenesis (i.e., post-differentiation with MDI), followed by an increase in PAR levels when the cells undergo terminal differentiation (Fig. 3, A and B).…”

Peroxisome Proliferator-activated Receptor (PPAR)-2 Controls Adipocyte Differentiation and Adipose Tissue Function through the Regulation of the Activity of the Retinoid X Receptor/PPARγ Heterodimer

“…Poly-(ADP-ribosyl)ation is reported to increase throughout the differentiation process of 3T3-L1 cells (46). Interestingly, this poly(ADP-ribosyl)ation activity is not completely inhibited by PARP-1 depletion (47), suggesting the involvement of other member(s) of the PARP family, such as PARP-2.…”

PARPs and ADP-ribosylation: recent advances linking molecular functions to biological outcomes

“…Although NAD + has historically been thought to pass freely from one cellular compartment to another, the results from recent studies (e.g., Zhang et al 2012;Cambronne et al 2016) and the fact that the three NMNATs have discreet and distinct subcellular localizations have challenged this view. Moreover, NAD + and PAR levels fluctuate during key biological processes, exemplified by a precipitous drop in both during the transition from mitotic cell growth to cellular differentiation during adipogenesis studies (Pekala et al 1981;Janssen and Hilz 1989;Luo et al 2017). As such, the dynamic NAD + synthesis and its subcellular localization are important considerations for PARP function.…”