Active H+ Transport in Urinary Acidification

尿液酸化中的活性氢转运

• 批准号: 6933011
• 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/6933011
• 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（由申请人提供）：肾等器官上皮的发育分两步进行；干细胞首先转化为原上皮细胞，然后经过终末分化为14种肾元细胞。在后一过程中，上皮细胞发生受调节的胞吐、顶端内吞和由新诱导的肌动蛋白结合蛋白、肌动蛋白和细胞角蛋白组成的顶端微绒毛，以及细胞形状的变化。同样的现象也发生在皮质集管分泌HCO3的β插层细胞中，当它在酸性饮食的作用下转变为分泌酸的α表现型时。这种变化是由一种新的细胞外基质蛋白的沉积引起的，我们称之为母鸡素。母鸡素作为可溶性单体分泌，但被亲环蛋白C聚合，然后被凝集素3转化为纤维。只有纤维形式可以结合并激活（通过酪氨酸磷酸化）其受体，我们最近确定为α -v β -1整合素。我们对母鸡素进行了基因敲除，发现它在囊胚植入时是致命的。滋养外胚层是胚胎的第一个终末分化上皮，表达母鸡素。Hensin在所有上皮细胞中表达，最近发现它在许多人类癌症中被删除，这表明它是一种新的肿瘤抑制基因。