Active H+ Transport in Urinary Acidification

尿液酸化中的活性氢转运

• 批准号: 6786083
• 负责人: QAIS AL-AWQATI
• 金额: $ 36.79万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6786083
• 关键词: acid base balance; acidity /alkalinity; active transport; bicarbonates; biological signal transduction; cell differentiation; confocal scanning microscopy; extracellular matrix proteins; genetically modified animals; guinea pigs; hydrogen transport; immunocytochemistry; integrins; laboratory mouse; membrane transport proteins; polymerase chain reaction; renal tubular transport; renal tubule; scavenger receptor; tumor suppressor genes; urine acidity

DESCRIPTION (provided by applicant): Development of epithelia in organs like the kidney proceeds in two steps; stem cells are first converted to a proto-epithelium, which then undergo terminal differentiation into the 14 types of cells of the nephron. In the latter process, epithelia develop regulated exocytosis, apical endocytosis, and apical microvilli composed of newly induced actin binding proteins, a subapical network of actin and cytokeratins, as well as changes in cell shape. An identical phenomenon occurs in the HCO3 secreting beta-intercalated cell of the cortical collecting duct when it changes to an acid-secreting alpha-phenotype in response to an acid diet. This change is induced by the deposition of a new extracellular matrix protein, which we termed hensin. Hensin is secreted as a soluble monomer but gets polymerized by cyclophilin C, and later converted to fibers by galectin 3. Only the fiber form can bind and activate (by tyrosine phosphorylation) its receptor, which we recently identified as alpha-v beta-1 integrins. We generated a knockout of hensin and found that it is lethal at the time of implantation of the blastocyst. The trophectoderm, which is the first terminally differentiated epithelium of the embryo, expresses hensin. Hensin is expressed in all epithelia, and the recent findings that it is deleted in many human cancers suggest that it is a new tumor suppressor gene. We wish to pursue these studies by examining the locus of action of hensin in the blastocyst, in particular to examine whether its effect is due to a defect in the trophectoderm (the epithelium) or in the inner cell mass. In our second aim we will examine whether hensin induces terminal differentiation in the collecting tubule and other epithelia. We will generate tissue specific knockouts of hensin using the Cre/LoxP system deleting it from the intestine, the prostate, and the collecting duct in general and from the intercalated cell in particular. In a third aim, we will examine the signal transduction pathway induced by hensin by activation of integrin receptors with emphasis on discovering molecules that get activated by tyrosine phosphorylation during terminal differentiation. These studies should define the function of this critical new protein in differentiation of the kidney tubule, in acid base balance and in early embryonic development.

描述(申请人提供)：肾脏等器官中上皮细胞的发育分两步进行；干细胞首先转化为原始上皮细胞，然后经过终末分化为肾单位的14种细胞。在后一过程中，上皮细胞发生调节的胞吐作用、顶端内吞作用、由新诱导的肌动蛋白结合蛋白组成的顶端微绒毛、由肌动蛋白和细胞角蛋白组成的顶端网络，以及细胞形状的变化。同样的现象也发生在皮质集合管中分泌HCO3的β嵌入细胞中，当它在酸性饮食中改变为分泌酸性的α-表型时。这种变化是由一种新的细胞外基质蛋白的沉积引起的，我们称之为Hensin。Hensin以可溶性单体的形式分泌，但被亲环素C聚合，然后被Galectin 3转化为纤维。只有纤维形式才能结合并激活(通过酪氨酸磷酸化)其受体，我们最近确定该受体为α-vβ-1整合素。我们产生了Hensin的基因敲除，并发现它在胚泡植入时是致命的。滋养外胚层是胚胎第一个终末分化的上皮细胞，表达Hensin。Hensin在所有的上皮细胞中都有表达，最近的研究发现它在许多人类癌症中都是缺失的，这表明它是一个新的肿瘤抑制基因。 我们希望通过检查Hensin在胚泡中的作用轨迹来继续这些研究，特别是检查它的作用是由于滋养外胚层(上皮)还是内细胞团的缺陷。在我们的第二个目标中，我们将检查Hensin是否诱导集合管和其他上皮细胞的终末分化。我们将使用Cre/loxP系统产生组织特异性的Hensin基因敲除，将其从肠道、前列腺和集合管中删除，特别是从嵌入细胞中删除。在第三个目标中，我们将通过激活整合素受体来研究Hensin诱导的信号转导途径，重点是发现在终末分化过程中被酪氨酸磷酸化激活的分子。这些研究应该确定这种关键的新蛋白在肾小管分化、酸碱平衡和早期胚胎发育中的功能。