Identification of human zonulin, a physiological modulator of tight junctions, as prehaptoglobin-2
Identification of human zonulin, a physiological modulator of tight junctions, as prehaptoglobin-2
复制标题
DOI：
10.1073/pnas.0906773106
复制
发表时间：
2009-09-29
影响因子：
11.1
通讯作者：
Fasano, Alessio
中科院分区：
文献类型：
--
作者：
Tripathi, Amit;Lammers, Karen M.;Fasano, Alessio
肠通透性增加（IP）最近被认为是过敏性、炎症性和自身免疫性疾病发病的共同潜在机制。zonulin是唯一已知的可逆调节IP的生理介质，其特性仍然难以捉摸。通过对人类血清的蛋白质组学分析，我们现在已经确定人类带蛋白是接触珠蛋白-2的前体（pre-HP2）。虽然已知成熟的HP清除游离血红蛋白（Hb）以抑制其氧化活性，但没有功能归因于其未裂解的前体形式。我们发现单链zonulin含有一个EGF样基序，该基序通过蛋白酶激活受体2 （PAR(2)）激活导致EGF受体（EGFR）的反激活。这两种受体的激活与增加的IP相结合。sirna诱导的PAR(2)沉默或使用PAR(2)（-/-）小鼠可防止屏障完整性的丧失。zonulin的蛋白水解裂解使其α(2)-和β -亚基中和了其激活EGFR和增加IP的能力。定量基因表达显示zonulin在乳糜泻患者肠黏膜中过表达。据我们所知，这是分子在其前体形式中发挥生物活性的最初例子，这种活性与成熟形式的功能不同。因此，我们的研究结果将zonulin描述为一种以前描述过的配体，它参与了人类免疫介导疾病发病机制的关键信号体，可以作为治疗干预的目标。
Increased intestinal permeability (IP) has emerged recently as a common underlying mechanism in the pathogenesis of allergic, inflammatory, and autoimmune diseases. The characterization of zonulin, the only physiological mediator known to regulate IP reversibly, has remained elusive. Through proteomic analysis of human sera, we have now identified human zonulin as the precursor for haptoglobin-2 (pre-HP2). Although mature HP is known to scavenge free hemoglobin (Hb) to inhibit its oxidative activity, no function has ever been ascribed to its uncleaved precursor form. We found that the single-chain zonulin contains an EGF-like motif that leads to transactivation of EGF receptor (EGFR) via proteinase-activated receptor 2 (PAR(2)) activation. Activation of these 2 receptors was coupled to increased IP. The siRNA-induced silencing of PAR(2) or the use of PAR(2)(-/-) mice prevented loss of barrier integrity. Proteolytic cleavage of zonulin into its alpha(2)- and beta-subunits neutralized its ability to both activate EGFR and increase IP. Quantitative gene expression revealed that zonulin is overexpressed in the intestinal mucosa of subjects with celiac disease. To our knowledge, this is the initial example of a molecule that exerts a biological activity in its precursor form that is distinct from the function of its mature form. Our results therefore characterize zonulin as a previously undescribed ligand that engages a key signalosome involved in the pathogenesis of human immune-mediated diseases that can be targeted for therapeutic interventions.