PURPOSE: 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). METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
PURPOSE: 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). METHODS: 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. RESULTS: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. CONCLUSIONS: 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.
Authors: Marjan Farid; Anshu Agrawal; Daniel Fremgen; Jeremiah Tao; He Chuyi; Anthony B Nesburn; Lbachir BenMohamed Journal: Ocul Immunol Inflamm Date: 2014-12-23 Impact factor: 3.070