Ohashi Yoshiki, Tsuzaka Kensei, Takeuchi Tsutomu, Sasaki Yasumasa, Tsubota Kazuo
Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan.
Curr Eye Res. 2008 Aug;33(8):621-9. doi: 10.1080/02713680802262819.
To investigate the distribution and expression of aquaporin 5 (AQP5) and its C-terminal binding protein in the apical membrane of the lacrimal glands (LGs) in a mouse model for Sjogren's syndrome (SS).
The LGs of NOD mice (mouse model for SS) and ICR mice (normal control) were homogenized and delivered into the affinity columns bound to synthetic AQP5 C-terminal peptide. The eluates were analyzed by electrophoresis and liquid chromatography mass spectrometry/mass spectrometry (LC-MS/MS) techniques.
AQP5 from the NOD mice exhibited the capacity to bind a 21-kDa protein that was lacking in the ICR mice. Instead, ICR mouse expressed a 17-kDa AQP5 binding protein that was absent in LGs of SS. LC-MS/MS analysis revealed these respective proteins to be major urinary protein 4 (MUP4) and prolactin-inducible protein (PIP). The treatment of ICR mice with antisense PIP oligonucleotides decreased immunostaining of AQP5 in the apical membrane.
These observations suggest that the binding of PIP to the C-terminal portion of AQP5 may cause AQP5 to be transported to the apical membrane of LGs. Correction of the aberrant binding of PIP to the AQP5 C-terminus could normalize AQP5 trafficking to the apical membrane, leading to a treatment for patients with SS.
在干燥综合征（SS）小鼠模型中，研究水通道蛋白5（AQP5）及其C末端结合蛋白在泪腺（LGs）顶膜中的分布与表达。
将非肥胖糖尿病（NOD）小鼠（SS小鼠模型）和ICR小鼠（正常对照）的泪腺匀浆，然后加入与合成的AQP5 C末端肽结合的亲和柱中。通过电泳和液相色谱串联质谱（LC-MS/MS）技术对洗脱液进行分析。
NOD小鼠的AQP5表现出与一种21 kDa蛋白结合的能力，而ICR小鼠缺乏这种蛋白。相反，ICR小鼠表达一种17 kDa的AQP5结合蛋白，而SS的泪腺中不存在这种蛋白。LC-MS/MS分析显示，这些蛋白分别是主要尿蛋白4（MUP4）和催乳素诱导蛋白（PIP）。用反义PIP寡核苷酸处理ICR小鼠可降低AQP5在顶膜中的免疫染色。
这些观察结果表明，PIP与AQP5 C末端部分的结合可能导致AQP5转运至泪腺顶膜。纠正PIP与AQP5 C末端的异常结合可使AQP5向顶膜的转运正常化，从而为SS患者提供一种治疗方法。
