The Aging Gut: Regulation of Cell Proliferation

描述(由申请人提供)：在Fischer-344大鼠的胃肠道(Gl)的几个组织中，如胃和结肠，在衰老过程中粘膜增殖增加和细胞凋亡减少已被很好地记录下来。尽管这些与年龄相关的增殖和凋亡变化的调控机制尚未明确，但我们观察到这些事件与EGFR/ErbB-1及其受体家族成员，特别是HER-2/ErbB-2的表达和激活有关，提示EGFR和ErbB-2在衰老过程中对粘膜生长的调节作用。然而，到目前为止，还没有人试图描述EGFR及其家族成员(EGFR)在衰老过程中G1粘膜生长中的个体作用。在当前的资助期间，我们分离到了一种新的生长信号调节蛋白CARP-1(细胞周期凋亡调节蛋白)，它是一种130 kDa的核周蛋白，参与EGFR依赖的信号转导。我们观察到，尽管Gl粘膜中EGFR的活性随着年龄的增长而增加，但CARP-1的表达及其酪氨酸磷酸化(Tyr192)减少，提示EGFR与CARP-1可能具有相互作用的关系。因此，我们假设，EGFR，特别是EGFR和ErbB-2信号通路的激活，与CARP-1表达/激活的减少相关，使衰老的肠道易于增加增殖和/或减少凋亡。为了验证我们的假设，我们将首先确定EGFR和ErbB-2在Fischer-344大鼠增龄期间胃和结肠粘膜增殖和凋亡调节中的单独作用。然后我们将研究不同的细胞内通路，特别是PI3-K、MAPKs和Src-K，它们可能介导EGFR和/或ErbB-2的增殖和凋亡效应。最后，我们将通过最初定量CARP-1的表达和磷酸化，然后研究这些变化是否可能是由于依赖于EGFR的CARP-1启动子和/或DNA序列的甲基化状态的改变，来确定CARP-1在依赖EGFR和/或ErbB-2的Gl粘膜生长中的参与程度。我们预计EGFR利用不同的和重叠的途径来调节衰老过程中的粘膜生长。从这项研究中获得的知识应该可以更清楚地了解这些途径，以及CARP-1在与年龄相关的G1粘膜增殖和凋亡过程中的作用。

DESCRIPTION (provided by applicant): Increased mucosal proliferation and decreased apoptosis during aging have been well-documented in several tissues of the gastrointestinal (Gl) tract, such as the stomach and colon, of Fischer-344 rats. Although the regulatory mechanisms for these age-related proliferative and apoptotic changes are yet to be defined, we have observed that these events are associated with increased expression and activation of EGFR/ErbB-1 and some of its receptor family members, particularly, HER-2/ErbB-2, suggesting roles for EGFR and ErbB-2 in the regulation of mucosal growth in aging. However, to date, no effort has been made to delineate the individual roles of EGFR and its family members (EGFRs) in Gl mucosal growth during aging. In the current funding period, we isolated a novel growth signaling regulator, CARP-1 (Cell Cycle Apoptosis Regulatory Protein), a 130 kDa perinuclear protein that participates in EGFR-dependent signaling. We have observed that, although activation of EGFRs increases with aging in the Gl mucosa, CARP-1 expression and its tyrosine phosphorylation (Tyr192) are decreased, suggesting that EGFRs and CARP-1 may have a reciprocal relationship. We, therefore, hypothesize that enhanced activation of EGFRs, specifically EGFR and ErbB-2, signaling pathways, in association with diminished CARP-1 expression/activation, predispose the aging gut to increased proliferation and/or decreased apoptosis. To test our hypothesis, we will first determine the individual roles of EGFR and ErbB-2 in the regulation of proliferation and apoptosis in gastric and colonic mucosa during advancing age in Fischer-344 rats. We will then examine the different intracellular pathways, specifically PI3-K, MAPKs and Src-K that may mediate the proliferative and apoptotic effects of EGFR and/or ErbB-2. Finally, we will determine the extent to which CARP-1 participates in EGFR-and/or ErbB-2-dependent Gl mucosal growth by initially quantitating CARP-1 expression and phosphorylation then investigating whether these changes may be due to EGFRs-dependent alterations in the methylation status of the CARP-1 promoter and/or DNA sequences. We anticipate that distinct as well as overlapping pathways are utilized by EGFRs to regulate mucosal growth during aging. The knowledge gained from this study should provide a clearer understanding of these pathways, and the role of CARP-1, in age-related proliferative and apoptotic processes in Gl mucosa.