Sodium/(calcium + potassium) exchanger NCKX4 optimizes KLK4 activity in the enamel matrix microenvironment to regulate ECM modeling.
Sodium/(calcium + potassium) exchanger NCKX4 optimizes KLK4 activity in the enamel matrix microenvironment to regulate ECM modeling.
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DOI：
10.3389/fphys.2023.1116091
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发表时间：
2023
影响因子：
4
通讯作者：
中科院分区：
文献类型：
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釉质发育是一个细胞外基质从柔软的蛋白质基质转变为脊椎动物中矿化程度最高的组织的过程。编码一种依赖钾离子的钠/钙交换体的NCKX4基因发生突变的患者会出现矿化不足和成熟不全的釉质。NCKX4如何调节釉质蛋白的去除以形成几乎无蛋白的釉质尚不清楚。我们通过定量聚合酶链反应（qPCR）描述了在逐渐分化的成釉细胞中Nckx4的上调模式，并且通过对持续生长的小鼠门齿进行免疫染色，证实NCKX4蛋白主要定位于野生型皱褶末端成熟成釉细胞的顶端表面，从而呈现出釉质的整个发育轨迹。与细胞外基质（ECM）蛋白被水解和去除的正常成熟釉质不同，我们发现Nckx4 -/-小鼠釉质在成熟阶段存在明显的蛋白滞留。通过能谱分析（EDX）测量，与Nckx4 +/+釉质相比，Nckx4 -/-釉质含有较少的钙离子和钾离子，但钠离子较多。在矿化的Nckx4 +/+釉质表面交替出现的酸性和中性pH区域在Nckx4 -/-釉质中被一个基本呈中性pH的基质所取代。原位酶谱分析显示Nckx4 -/-釉质中激肽释放酶相关肽酶4（KLK4）的活性降低。我们发现KLK4在正常釉质成熟阶段承担了90%的蛋白酶活性，并且重组KLK4以及天然小鼠釉质KLK4在钠离子浓度增加和pH升高的缓冲液中（Nckx4 -/-发育中的釉质所处的条件）活性均降低。据我们所知，这项研究首次提供了证据，证明Nckx4 -/-釉质中KLK4的原位活性受损，并表明NCKX4在促进KLK4介导的细胞外基质蛋白水解和去除方面具有新的功能，这对于釉质基质的塑形完成是必要的。
Enamel development is a process in which extracellular matrix models from a soft proteinaceous matrix to the most mineralized tissue in vertebrates. Patients with mutant NCKX4, a gene encoding a K+-dependent Na+/Ca2+—exchanger, develop a hypomineralized and hypomature enamel. How NCKX4 regulates enamel protein removal to achieve an almost protein-free enamel is unknown. We characterized the upregulation pattern of Nckx4 in the progressively differentiating enamel-forming ameloblasts by qPCR, and as well as confirmed NCKX4 protein to primarily localize at the apical surface of wild-type ruffle-ended maturation ameloblasts by immunostaining of the continuously growing mouse incisors, posing the entire developmental trajectory of enamel. In contrast to the normal mature enamel, where ECM proteins are hydrolyzed and removed, we found significant protein retention in the maturation stage of Nckx4 −/− mouse enamel. The Nckx4 −/− enamel held less Ca2+ and K+ but more Na+ than the Nckx4 +/+ enamel did, as measured by EDX. The alternating acidic and neutral pH zones at the surface of mineralizing Nckx4 +/+ enamel were replaced by a largely neutral pH matrix in the Nckx4 −/− enamel. In situ zymography revealed a reduced kallikrein-related peptidase 4 (KLK4) activity in the Nckx4 −/− enamel. We showed that KLK4 took on 90% of proteinase activity in the maturation stage of normal enamel, and that recombinant KLK4 as well as native mouse enamel KLK4 both performed less effectively in a buffer with increased [Na+] and pH, conditions found in the Nckx4 −/− developing enamel. This study, for the first time to our knowledge, provides evidence demonstrating the impaired in situ KLK4 activity in Nckx4 −/− enamel and suggests a novel function of NCKX4 in facilitating KLK4-mediated hydrolysis and removal of ECM proteins, warranting the completion of enamel matrix modeling.
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DOI：
10.1155/2013/684607
发表时间：
2013-09-16
期刊：
ISRN dentistry
影响因子：
--
作者：
Bartlett JD
通讯作者：
Bartlett JD
影响因子：
4.2
作者：
Bronckers, A. L. J. J.;Jalali, R.;Lytton, J.
通讯作者：
Lytton, J.
影响因子：
2.9
作者：
Buchko, Garry W.;Tarasevich, Barbara J.;Bekhazi, Jacky;Snead, Malcolm L.;Shaw, Wendy J.
通讯作者：
Shaw, Wendy J.
影响因子：
2.7
作者：
Hu, Jan C. -C.;Chun, Yong-Hee P.;Simmer, James P.
通讯作者：
Simmer, James P.
影响因子：
11.2
作者：
Doe MR;Ascano JM;Kaur M;Cole MD
通讯作者：
Cole MD