Quantitative Transcriptional Control of ErbB Receptor Signaling Undergoes Graded to Biphasic Response for Cell Differentiation

Abstract

The different kinetics displayed by extracellular signal-regulated kinase (ERK) 3 activation often results in distinct cellular phenotypes of mammalian cells. In PC12 cells, the epidermal growth factor (EGF)-stimulated transient activation of ERK induces cell proliferation, whereas a nerve growth factor-stimulated sustained activation of ERK induces differentiation (1, 2). Similarly, different growth factor ligands cause distinct kinetics of ERK activation in human breast cancer cells (3, 4). ERK and Akt/protein kinase B are deterministic kinases that control the activation of nuclear transcription factors (5-7); therefore, it is expected that the activation kinetics of these kinases might affect the following gene expression profiles. However, the question concerning gene expression dynamics induced by kinetically different kinase activities and its effect on cell determination mechanisms remains unsolved.In this study we focused on the dose-dependent time course analysis of early transcription induced by two ligands of the ErbB family receptor, EGF and heregulin (HRG), which induce distinct kinase activity patterns and phenotypes of MCF-7 cells. Although many studies attempted to delineate the biochemical characteristics of ErbB ligands and receptors, no systematic study has been reported concerning the analysis of ErbB receptor-mediated cell fate control.MCF-7 cells endogenously express all family members of the ErbB protein-tyrosine kinase receptors (EGFR/ErbB1, ErbB2, ErbB3, and ErbB4 receptors). EGF preferably binds to an EGFR, whereas HRG first binds to either the ErbB3 or ErbB4 receptor and then induces trans-activation of ErbB2 (8). ErbB receptors tend to form heterodimers in response to ligand binding when different ErbB receptors are co-expressed in the same cell. In particular, ErbB2 is the preferred heterodimerization partner among the receptor family (9), and it functions as an oncogenic unit through heterodimer formation with ErbB3 (10). EGFR activation induces selfdown-regulation of the receptor by recruitment of the Cbl ubiquitin ligase (11,12), and the activation of ErbB3 strongly evokes phosphatidylinositol 3Ј-kinase (PI3K) activation (13,14). Activation of ErbB receptor is often accompanied by activation of Shc-ERK and PI3K-Akt pathways. These two pathways often cross-talk or inhibit each other (15, 16) thereby resulting in distinct activity patterns pertaining to intracellular signaling that activate various types of transcription factors (17-19). In addition, many studies attempted to identify specific gene expression induced by different ErbB ligands that show signaling diversities and distinct biological outcomes (20, 21); however, earlier results using platelet-derived growth factor (PDGF)-␤ receptor mutants indicated that diverse signaling pathways induce broadly overlapping transcription (22).

Dynamically varying interactions between heregulin and ErbB proteins detected by single-molecule analysis in living cells

“…This feature increases the probability of forming doubly liganded ErbB dimers, thereby facilitating cell signaling (33). MCF-7 induces prolonged or transient signals in response to HRG or EGF, respectively (5,34), and these distinct signal kinetics ultimately lead to different cell fates. This study indicates that the kinetic schema and parameters that describe ligand binding to the EGF and HRG receptors are similar, suggesting that their distinct biochemical characteristics may not originate from the ligand-receptor association itself.…”

“…The dysregulation of ErbB3 and B4 (referred to hereafter as "HRG receptors") is often related to malignancy in human cancers (2). The long-term exposure of MCF-7 cells, a cultured cell line derived from a human breast carcinoma, to HRG induces the production of differentiation markers, such as milk proteins or lipid droplets, whereas similar exposure to epidermal growth factor induces proliferation (5).…”

Differential localization of A-Raf regulates MST2-mediated apoptosis during epithelial differentiation

“…MCF7 cells, derived from breast adenocarcinoma, can undergo phenotypic changes including lipid accumulation, which can be quantified as a measure of differentiation ( Figure 4a). [57][58][59][60][61][62] We therefore stably overexpressed A-Raf fused to EGFP in MCF7 cells and induced differentiation by serum starvation and Figure S4C).…”

Remarks on feedforward circuits, adaptation, and pulse memory

“…Other references on feedforward circuits include [22] (showing their over-representation at the interface of genetic and metabolic networks), [28] (classification of different subtypes of such circuits), and [10] (clas-sification into "time-dependent" versus "dose-dependent" biphasic responses, which are in a sense the opposite of adaptated responses). The latter reference provides a large number of additional incoherent feedforward input-to-response circuits, including: EGF to ERK activation [21,18], glucose to insulin release [17,19], ATP to intracellular calcium release [14,16], nitric oxide to NF-κB activation [20], microRNA regulation [25], and many others. Dealing specifically with adaptation properties of feedforward circuits, and in addition to the papers [26,30], are the paper [29] on microRNA-mediated loops, and [11], which deals with the role of feedforward structures in the robust behavior in E.coli carbohydrate uptake via the carbohydrate phosphotransferase system (an analogous metabolic mechanism is also discussed in [27]).…”