Differential Regulation of Immediate Early Gene Expression in Preadipocyte Cells through Multiple Signaling Pathways

Using digoxigenin (DIG)-based differential hybridization, a series of immediate early genes (IEG) was identified following the adipogenic stimulation in 3T3-L1 preadipocyte cells. Most of the known IEGs were identified as well as new members such as zf9 and Stra13. To delineate possible signaling pathways accounting for these gene expression, a subset of specific kinase inhibitors, SB203580, PD98059, rapamycin, LY294002, and Ro-32-0432, which inhibit p38 (HOG), MEK (MAPKK), S6 kinase, PI3 kinase, and protein kinase C (PKC), respectively, were employed. The IEGs were classified into three categories according to their susceptibility to the inhibitors. Expression of the first group (c-fos, jun-B, egr-1, tis11, tis21, thrombospondin-1, erp, thyroid hormone receptor [N-10], cyr61, and zf9) was mainly dependent on PKC and MEK pathways, while that of the second class (gene33 and tis10) exhibited an additional dependence on PI3 kinase pathways. The third one (Id-3, gly96, and Stra13) was characterized in that none of these inhibitors interfered with gene expression. Our results suggest that the induction of IEGs by the adipogenic stimuli is mediated by common as well as distinct signaling pathways.