The Aging Gut: Regulation of Cell Proliferation

描述（由申请人提供）：在Fischer-344大鼠的胃肠道（GI）的几种组织（如胃和结肠）中，已充分记录了老化期间粘膜增殖增加和细胞凋亡减少。尽管这些与年龄相关的增殖和凋亡变化的调节机制尚未确定，但我们观察到这些事件与EGFR/ErbB-1及其一些受体家族成员，特别是HER-2/ErbB-2的表达和活化增加有关，表明EGFR和ErbB-2在衰老中调节粘膜生长中的作用。然而，迄今为止，还没有努力描绘EGFR及其家族成员（EGFR）在衰老期间GI粘膜生长中的个体作用。在当前的资助期内，我们分离出一种新的生长信号调节剂，CARP-1（细胞周期凋亡调节蛋白），一种130 kDa的核周蛋白，参与EGFR依赖性信号传导。我们已经观察到，尽管EGFR的活化随着GI粘膜中的老化而增加，但CARP-1表达及其酪氨酸磷酸化（Tyr 192）降低，表明EGFR和CARP-1可能具有相互关系。因此，我们假设增强的EGFR，特别是EGFR和ErbB-2，信号通路的激活，与减少的CARP-1表达/激活相关，使衰老的肠道易于增殖增加和/或凋亡减少。为了验证我们的假设，我们将首先确定EGFR和ErbB-2在调节Fischer-344大鼠年龄增长过程中胃和结肠粘膜增殖和凋亡中的各自作用。然后，我们将研究不同的细胞内途径，特别是PI 3-K，MAPK和Src-K，可能介导EGFR和/或ErbB-2的增殖和凋亡作用。最后，我们将通过最初定量CARP-1表达和磷酸化，然后研究这些变化是否可能是由于CARP-1启动子和/或DNA序列的甲基化状态的EGFR依赖性改变，来确定CARP-1参与EGFR和/或ErbB-2依赖性GI粘膜生长的程度。我们预计，不同的以及重叠的途径是利用EGFRs调节粘膜生长在老化过程中。从这项研究中获得的知识应该提供对这些途径以及CARP-1在GI粘膜中年龄相关的增殖和凋亡过程中的作用的更清楚的理解。

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.