The Aquaporin-3/Phospholipase D2 Signaling Pathway in Corneal Wound Healing

项目总结/摘要 我们实验室以前的数据表明，脂质代谢酶磷脂酶D2（PLD 2） 和甘油转运蛋白水通道蛋白-3（AQP 3）在表皮角质形成细胞中物理和功能上相互作用。 AQP 3将甘油转运到细胞中，使其可用于相关的PLD 2，后者将其转化为 磷脂酰甘油（PG）。我们的研究结果进一步表明，PG作为脂质第二信使， 促进表皮伤口愈合。Verkman及其同事已经建立了一个AQP 3敲除小鼠模型， 其显示出包括延迟的皮肤伤口愈合的显著的表皮表型。有趣的是， 对于该应用直接重要的是，这些AQP 3敲除小鼠也表现出受损的角膜伤口愈合。 对文献的研究表明，表皮角质形成细胞和角膜上皮细胞显示出许多与细胞增殖有关的特征。 它们有相似之处，可以通过共同的机制进行调节。在令人兴奋的初步数据中，我们发现， PLD 2和AQP 3也在角膜上皮细胞中结合，并且这种相互作用的产物PG增强了角膜上皮细胞的增殖。 培养物中角膜上皮细胞的划痕伤口闭合以及野生型和 体内AQP 3敲除小鼠。这些发现使我们推测，PLD 2/AQP 3/PG信号传导模块 对角膜很重要。因为PG的这些作用让人联想到表皮生长的作用 角膜上皮细胞上的表皮生长因子受体（EGFR）配体，我们特别假设PLD 2和AQP 3 在角膜上皮细胞中结合产生PG以响应EGFR配体，并且这种PG充当 信号分子，以通过增加上皮细胞迁移来加速角膜中的伤口愈合，和/或 增殖在这项研究中，我们将测试这一假设，并确定PLD 2/AQP 3的作用， 角膜细胞生物学和伤口愈合中的信号模块。文献中的数据和我们自己的初步结果 表皮角质形成细胞表明PG可激活蛋白激酶CβII（PKCβII）。根据这些数据，作为 以及PKCβ抑制或沉默可以抑制角膜增殖和增殖信号的报道，我们 进一步假设PLD 2/AQP 3模型的功能机制是通过PG激活 PKCβII激活。我们将使用基因敲除动物，以及过表达，RNA干扰， 药理学抑制方法可提高或降低PLD 2、AQP 3和PKCβII的水平; 然后我们将监测角膜上皮细胞迁移和增殖、PG水平、PKCβII自磷酸化 （活化）和角膜伤口愈合。如果我们的假设被证明是正确的，这项研究将导致 更好地了解角膜上皮伤口愈合过程，并可能导致识别新的 目标是开发治疗方法，以促进创伤、感染、 或眼科手术。

Project Summary/Abstract Previous data from our laboratory indicate that the lipid-metabolizing enzyme phospholipase D2 (PLD2) and the glycerol transporter aquaporin-3 (AQP3) physically and functionally interact in epidermal keratinocytes. AQP3 transports glycerol into the cell, making it available to the associated PLD2, which converts it to phosphatidylglycerol (PG). Our results further demonstrate that PG acts as a lipid second messenger to promote epidermal wound healing. Verkman and colleagues have generated an AQP3 knockout mouse model, which shows a profound epidermal phenotype including delayed skin wound healing. Interestingly, and of direct significance to this application, these AQP3 knockout mice also exhibit impaired corneal wound healing. Inspection of the literature suggests that epidermal keratinocytes and corneal epithelial cells show a number of similarities and may be regulated by common mechanisms. In exciting preliminary data we have found that PLD2 and AQP3 also associate in corneal epithelial cells and that the product of this interaction, PG, enhances scratch wound closure of corneal epithelial cells in culture as well as corneal wound healing in wild-type and AQP3 knockout mice in vivo. These findings lead us to hypothesize that the PLD2/AQP3/PG signaling module is important in the cornea. Because these effects of PG are reminiscent of the actions of epidermal growth factor receptor (EGFR) ligands on corneal epithelium, we specifically hypothesize that PLD2 and AQP3 associate in corneal epithelial cells to produce PG in response to EGFR ligands and that this PG acts as a signaling molecule to accelerate wound healing in the cornea by increasing epithelial cell migration and/or proliferation. In the research proposed, we will test this hypothesis and define the role of the PLD2/AQP3 signaling module in corneal cell biology and wound healing. Data in the literature and our own initial results in epidermal keratinocytes indicate that PG can activate protein kinase CβII (PKCβII). Based on these data, as well as reports that PKCβ inhibition or silencing can inhibit corneal proliferation and proliferative signaling, we further hypothesize that the mechanism by which the PLD2/AQP3 model functions is through PG-activated PKCβII activation. We will test this idea using knockout animals, as well as overexpression, RNA interference, and pharmacological inhibition approaches to increase and decrease the levels of PLD2, AQP3 and PKCβII; we will then monitor corneal epithelial cell migration and proliferation, PG levels, PKCβII autophosphorylation (activation) and corneal wound healing in vivo. If our hypothesis proves correct, the research will lead to a better understanding of the corneal epithelial wound healing process and may lead to the identification of novel targets for the development of treatments to promote corneal would healing in patients after trauma, infection or ophthalmic surgery.