title: Human cataract mutations in EPHA2 SAM domain alter receptor stability and function.
abstract: The cellular and molecular mechanisms underlying the pathogenesis of cataracts leading to visual impairment remain poorly understood. In recent studies, several mutations in the cytoplasmic sterile-α-motif (SAM) domain of human EPHA2 on chromosome 1p36 have been associated with hereditary cataracts in several families. Here, we have investigated how these SAM domain mutations affect EPHA2 activity. We showed that the SAM domain mutations dramatically destabilized the EPHA2 protein in a proteasome-dependent pathway, as evidenced by the increase of EPHA2 receptor levels in the presence of the proteasome inhibitor MG132. In addition, the expression of wild-type EPHA2 promoted the migration of the mouse lens epithelial αTN4-1 cells in the absence of ligand stimulation, whereas the mutants exhibited significantly reduced activity. In contrast, stimulation of EPHA2 with its ligand ephrin-A5 eradicates the enhancement of cell migration accompanied by Akt activation. Taken together, our studies suggest that the SAM domain of the EPHA2 protein plays critical roles in enhancing the stability of EPHA2 by modulating the proteasome-dependent process. Furthermore, activation of Akt switches EPHA2 from promoting to inhibiting cell migration upon ephrin-A5 binding. Our results provide the first report of multiple EPHA2 cataract mutations contributing to the destabilization of the receptor and causing the loss of cell migration activity.
authors.affiliation: Susan Lehman-Cullman Laboratory for Cancer Research, Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, New Jersey, USA.
authors.forename: Jeong Eun
authors.initials: JE
authors.lastname: Park
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Son
authors.forename: Rui
authors.initials: R
authors.lastname: Hua
authors.forename: Lianqing
authors.initials: L
authors.lastname: Wang
authors.forename: Xue
authors.initials: X
authors.lastname: Zhang
authors.forename: Renping
authors.initials: R
authors.lastname: Zhou
mesh_terms: D000818:Animals; D002386:Cataract / Q000235:genetics* / Q000378:metabolism*; D002460:Cell Line; D002465:Cell Movement / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D036386:Ephrin-A5 / Q000494:pharmacology; D023061:Gene Order; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D010766:Phosphorylation / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs / Q000235:genetics*; D055550:Protein Stability; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D036104:Receptor, EphA2 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D036386:Ephrin-A5; D025801:Ubiquitin; D014443:Tyrosine; D036104:Receptor, EphA2; D051057:Proto-Oncogene Proteins c-akt; D046988:Proteasome Endopeptidase Complex