title: Lens major intrinsic protein (MIP)/aquaporin 0 expression in rat lens epithelia explants requires fibroblast growth factor-induced ERK and JNK signaling.
abstract: Lens major intrinsic protein (MIP), exclusive to the vertebrate lens, otherwise known as MIP26 and Aquaporin 0, is abundantly expressed as a lens fiber membrane protein. Although relatively less efficient compared with other aquaporins, MIP is suggested to function as a water channel, as an adhesion molecule, and is required for lens transparency. Because MIP is specifically expressed in lens fiber cells, we investigated in this study the activation of Mip expression after triggering differentiation of rat lens epithelia explants by fibroblast growth factor (FGF)-2. Here, we show that Mip expression in the lens cells is regulated by FGF-2. Using Real time PCR we demonstrate that endogenous Mip levels in the explants were up-regulated upon FGF-2 stimulation, in a concentration-dependent manner. Up-regulation of Mip at the transcriptional level was simultaneous with the activation of the FGF down-stream signaling components, ERK1/2 and JNK. Specific inhibitors, UO126 for ERK1/2 and SP600125 for JNK, abrogated Mip expression in response to FGF-2 in the explants. This inhibition pattern was recapitulated in reporter assays for transfection of the rat lens epithelia explants, driven by the Mip promoter (-1648/+44). Our studies show that ERK1/2 and JNK signaling pathways are required for Mip expression in lens epithelia explants induced to differentiate by FGF-2.
authors.affiliation: Laboratory of Molecular and Developmental Biology, NEI, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Nady
authors.initials: N
authors.lastname: Golestaneh
authors.forename: Jianguo
authors.initials: J
authors.lastname: Fan
authors.forename: Robert N
authors.initials: RN
authors.lastname: Fariss
authors.forename: Woo-Kuen
authors.initials: WK
authors.lastname: Lo
authors.forename: Peggy S
authors.initials: PS
authors.lastname: Zelenka
authors.forename: Ana B
authors.initials: AB
authors.lastname: Chepelinsky
mesh_terms: D000818:Animals; D020346:Aquaporins; D001483:Base Sequence; D002454:Cell Differentiation / Q000187:drug effects; D046508:Culture Techniques; D017931:DNA Primers / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D004848:Epithelium / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D048031:JNK Mitogen-Activated Protein Kinases; D007903:Lens Capsule, Crystalline / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats
chemical_list: D020346:Aquaporins; D017931:DNA Primers; D005136:Eye Proteins; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; C030328:aquaporin 0; D016222:Fibroblast Growth Factor 2; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases