title: Myocilin regulates cell proliferation and survival.
abstract: Myocilin, a causative gene for open angle glaucoma, encodes a secreted glycoprotein with poorly understood functions. To gain insight into its functions, we produced a stably transfected HEK293 cell line expressing myocilin under an inducible promoter and compared gene expression profiles between myocilin-expressing and vector control cell lines by a microarray analysis. A significant fraction of differentially expressed genes in myocilin-expressing cells was associated with cell growth and cell death, suggesting that myocilin may have a role in the regulation of cell growth and survival. Increased proliferation of myocilin-expressing cells was demonstrated by the WST-1 proliferation assay, direct cell counting, and immunostaining with antibodies against Ki-67, a cellular proliferation marker. Myocilin-containing conditioned medium also increased proliferation of unmodified HEK293 cells. Myocilin-expressing cells were more resistant to serum starvation-induced apoptosis than control cells. TUNEL-positive apoptotic cells were dramatically decreased, and two apoptotic marker proteins, cleaved caspase 7 and cleaved poly(ADP-ribose) polymerase, were significantly reduced in myocilin-expressing cells as compared with control cells under apoptotic conditions. In addition, myocilin-deficient mesenchymal stem cells exhibited reduced proliferation and enhanced susceptibility to serum starvation-induced apoptosis as compared with wild-type mesenchymal stem cells. Phosphorylation of ERK1/2 and its upstream kinases, c-Raf and MEK, was increased in myocilin-expressing cells compared with control cells. Elevated phosphorylation of ERK1/2 was also observed in the trabecular meshwork of transgenic mice expressing 6-fold higher levels of myocilin when compared with their wild-type littermates. These results suggest that myocilin promotes cell proliferation and resistance to apoptosis via the ERK1/2 MAPK signaling pathway.
authors.affiliation: From the Section of Retinal Ganglion Cell Biology, Laboratory of Retinal Cell and Molecular Biology, NEI, National Institutes of Health, Bethesda, Maryland 20892 and.
authors.forename: Myung Kuk
authors.initials: MK
authors.lastname: Joe
authors.forename: Heung Sun
authors.initials: HS
authors.lastname: Kwon
authors.forename: Radu
authors.initials: R
authors.lastname: Cojocaru
authors.forename: Stanislav I
authors.initials: SI
authors.lastname: Tomarev
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D053179:Caspase 7 / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation; D002470:Cell Survival / Q000502:physiology; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D000099179:Myocilin
chemical_list: D053179:Caspase 7; D003598:Cytoskeletal Proteins; D005136:Eye Proteins; D006023:Glycoproteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000099179:Myocilin; C535150:MAPK1 protein, human; C505520:CASP7 protein, human; C505524:Casp7 protein, mouse
keywords: Apoptosis; Cell Growth; Cell Proliferation; Cell Signaling; ERK; Mesenchymal Stem Cells