Cystic fibrosis（CF） is a severe genetic disease caused by the gene mutation of the cystic fibrosis transmembrane conductance regulator（CFTR） chloride channel. The most common point mutation AF508, which leads to impaired intracellular processing and channel gating of CFTR, appears in about 90% CF patients. The natural compound curcumin was reported to correct the processing defect of AF508-CFTR and proposed as a potential therapeutic drug to cure CF. In the present study, we analyzed the effect of curcumin on AF508-CFTR and demonstrated that curcumin can restore the impaired chloride conductance of AF508 mutant CFTR. The activity is rapid, reversible and cAMP-dependent. However, we couldn＇t reproduce the previously reported correction of the defective membrane trafficking of AF508-CFTR by curcumin. Therefore, curcumin may not be a superior lead compound for developing anti-CF drugs.
LIU XinGUAN LiHE Cheng-yanZHANG Xiao-jingXU Li-naSHANG De-jingMA Tong-huiYANG Hong
Migration of tumor cells is a crucial step in tumor invasion and metastasis. Here we provide evidence that aquaporin expression is involved in tumor cell migration. RT-PCR, immunofluorescence and Western blot analysis demonstrated the AQP1 protein expression on the plasma membrane of SMMC-7221 human hepatoma cells. SMMC-7221 cell clones with high (SMMC-7221hPf) and low (SMMC-7221lPf) water permeability were identified by functional assays with corresponding high and low AQP1 expression. Cell migration rate was remarka- bly higher in SMMC-7221hPf cells than SMMC-7221l Pf cells, assessed by Boyden chamber and wound healing assays, whereas cell growth and adhesion were not different. Adenovirus-mediated AQP1 ex- pression in SMMC-7221lPf cells increased their water permeability and migration rate. These results pro- vide the first evidence that aquaporin-mediated membrane water permeability enhances tumor cell migration and may be associated with tumor invasion and metastasis.
Aquaporins（AQPs） are molecular water channels that play important physiological roles in fluid trans-porting organs. The expression and function of AQPs in the immune system are largely unknown. CD 11 （a-d）/CD18 integrins are adhesion molecules expressed on leukocytes, which play a critical role in leukocyte adhesion, migration and host defense. In the present study, we discovered the expression of aquaporin-3（AQP3） on spleen CD1 lb positive cells, and the content of CDllb positive splenocytes in aquaporin 3-null mice is significantly decreased. Further analysis suggested remarkably decreased monocyte/macrophage subpopulation and significantly decreased granulocyte subpopulation. It is the first report suggesting an important role of AQP in the development and maturation of imrnunocytes.
In the present study, we identified the natural compound curcumin to be an effective G551D-CFTR activator by cell-based fluorescent assay and electrophysiological measurement. We demonstrated that curcumin can restore the impaired chloride conductance of G551D mutant CFTR. The activity is rapid, reversible, and cAMP-dependent. Our study identified a new natural lead compound for the pharmacological therapy of cystic fibrosis caused by G551D mutation of CFTR.
The asparagine-proline-alanine sequences (NPA motifs) are highly conserved in aquaporin water channel family. Crystallographic studies of AQP1 structure demonstrated that the two NPA motifs are in the narrow central constriction of the channel, serving to bind water molecules for selective and effi-cient water passage. To investigate the importance of the two NPA motifs in the structure, function and biogenesis of aquaporin water channels, we generated AQP1 mutations with NPA1 deletion, NPA2 de-letion and NPA1,2 double deletion. The coding sequences of the three mutated cDNAs were subcloned into the mammalian expression vector pcDNA3.1 to form expression plasmids. We established stably transfected CHO cell lines expressing these AQP1 mutants. Immunofluorescence indicated that all the three mutated AQP1 proteins are expressed normally on the plasma membrane of stably transfected CHO cells, suggesting that deletion of NPA motifs does not influence the expression and intracellular processing of AQP1. Functional analysis demonstrated that NPA1 or NPA2 deletion reduced AQP1 water permeability by 49.6% and 46.7%, respectively, while NPA1,2 double deletion had little effect on AQP1 water permeability. These results provide evidence that NPA motifs are important for water per-meation but not essential for the expression, intracellular processing and the basic structure of AQP1 water channel.
