MITOGENIC SIGNAL TRANSDUCTION IN PANCREATIC BETA CELLS

描述（取自应用程序） 虽然某些营养素和生长因子已被证明增加 β-细胞增殖，β-细胞增殖调节背后的信号通路， 细胞有丝分裂发生没有很好地定义。这项建议的用意是 为了更好地表征细胞中促有丝分裂信号转导途径， 胰腺β细胞的详细信息，以确定关键的信号传导元件 是诱发β细胞生长所必需的然后检查是否有腺病毒 在原代β细胞中介导关键信号传导元件表达 可以在体外引起β细胞的显著扩增。超出 研究所有潜在促有丝分裂 β细胞中的途径。因此，从初步报告中可以看出， 研究，将集中在葡萄糖，IGF-1，和生长激素（GH） 通过胰岛素受体底物（IRS）介导的诱导β细胞生长 信号转导途径已经发现，葡萄糖诱导β- 细胞仅在生理相关范围（5- 20 mM）内增殖， IGF-1和生长激素（GH）诱导的β细胞生长是葡萄糖- 依赖。这再次证实了β细胞中的大多数信号通路是 与糖酵解代谢密切相关因此， 阐明葡萄糖代谢产生的次级信号 提供IGF-1/GH促有丝分裂反应所需的平台。一个 对信号转导途径的初步研究表明，葡萄糖和 IGF-1可以激活β细胞中IRS介导的信号通路， 仅通过激活磷脂酰肌醇-3-激酶（PI 3 '-K）进行信号传导 而p70 S6 K与葡萄糖/IGF-1诱导的β细胞生长相关。 葡萄糖依赖性GH诱导的β细胞增殖也需要IRS-1。 介导的P13 '-K的激活，但独立于IGF-1的因子， 需要，因为IGF-1和GH的组合协同增加 β细胞增殖（高于基础3 mM葡萄糖80倍以上）。它 因此，β细胞中的IRS-促有丝分裂信号通路可能是 复杂的，强调的观察，IRS-1，-2，-3，和-4都是 在β细胞中表达。因此，需要进行更详细的研究， 定义葡萄糖和葡萄糖依赖性IGF-1/GH诱导的β细胞生长。 最近，我们已经产生了表达IRS-1的重组腺病毒， -2，正在生成IRS-3和-4， 通过腺病毒合作获得，以表达组成型活性 PI3'-K。这些实验工具将有利于拟议的研究， IRS介导的β细胞有丝分裂的深度表征。而且 目的是检测IRS-1，-2，-3，-4， 和/或PI 3 '-K在原代大鼠胰岛β细胞中可诱导显著的β- 细胞生长如果实现这一点，那么重要的是， 在以下方面表征这种扩增的β细胞群体： （pro）胰岛素产生和骨调节胰岛素分泌。是 预计这些研究最终可能会导致一种诱导 显著的β-细胞生长将提供有意义的来源β- 适合用于糖尿病的新型β-细胞替代疗法的细胞。

DESCRIPTION (taken from the application) Although certain nutrients and growth factors have been shown to increase Beta-cell proliferation, the signaling pathways behind regulation of Beta- cell mitogenesis are not well defined. The intention of this proposal is to better characterize mitogenic signal transduction pathways in pancreatic Beta-cells in detail, to pin point a key signaling element(s) required to evoke Beta-cell growth. Then it will be examined if adenoviral mediated expression of that key signaling element(s) in primary Beta-cells can instigate a significant expansion of Beta-cells in vitro. It is beyond the scope of a single proposal to investigate all potential mitogenic pathways in Beta-cells. Thus, the focus as indicated from preliminary studies, will be centered on glucose, IGF-1, and growth hormone (GH) induced Beta-cell growth as mediated via insulin-receptor substrate (IRS) signal transduction pathways. It has been found that glucose induces Beta- cells proliferation only in the physiologically relevant range (5-20mM), and IGF-1 and growth hormone (GH) induced Beta-cell growth are glucose- dependent. This reaffirms that most signaling pathways in Beta-cells are uniquely linked to glycolytic metabolism. As such, it will be important to elucidate what secondary signal(s) emanating from glucose metabolism provide a platform necessary for an IGF-1/GH mitogenic response. An initial study of signal transduction pathways has shown that glucose and IGF-1 can activate IRS-mediated signaling pathways in Beta-cells, but only signaling via activation of phosphatidylinositol-3-kinase (PI3'-K) and p70S6K correlated with glucose/IGF-1 induced Beta-cell growth. Glucose-dependent GH-induced Beta-cell proliferation also requires IRS- mediated activation of P13'-K, but factors independent of IGF-1 are required, since the combination of IGF-1 and GH synergistically increased Beta-cell proliferation (more than 80-fold above basal 3mM glucose). It follows that IRS-mitogenic signaling pathways in Beta-cells are likely complex, underscored by the observation that IRS-1, -2, -3, and -4 are all expressed in Beta-cells. Thus, a more detailed study is required to better define glucose-, and glucose-dependent IGF-1/GH-induced Beta-cell growth. Recently, we have generated recombinant adenoviruses to express IRS-1 and -2, are in the process of generating those to IRS-3 and -4 and have obtained via collaboration adenoviruses to express constitutively active PI3'-K. Such experimental tools will benefit the proposed studies for a in depth characterization of IRS-mediated Beta-cell mitogenesis. Moreover, it is intended to examine whether over-expression of IRS-1, -2, -3, -4, and/or PI3'-K in primary rat islet Beta-cells can induce significant Beta- cell growth. If this is achieved, then it will be important to characterize such an expanded Beta-cell population in terms of (pro)insulin production and bone fide regulated insulin secretion. It is anticipated that these studies may eventually lead to a means of inducing significant Beta-cell growth that will provide a meaningful source Beta- cell suitable for a novel Beta-cell replacement therapy for diabetes.