title: The interaction of Bex and OMP reveals a dimer of OMP with a short half-life.
abstract: Olfactory marker protein (OMP) participates in the olfactory signal transduction pathway. This is evident from the behavioral and electrophysiological deficits of OMP-null mice, which can be reversed by intranasal infection of olfactory sensory neurons with an OMP-expressing adenovirus. Bex, brain expressed X-linked protein, has been identified as a protein that interacts with OMP. We have now further characterized the interaction of OMP and Bex1/2 by in vitro binding assays and by immuno-coprecipitation experiments. OMP is a 19 kDa protein but these immunoprecipitation studies have revealed the unexpected presence of a 38 kDa band in addition to the expected 19 kDa band. Furthermore, the 38 kDa form was preferentially co-immunoprecipitated with Bex from cell extracts. In-gel tryptic digestion, mass spectrometry, and two-dimensional gel electrophoresis indicate that the 38 kDa protein behaves as a covalently cross-linked OMP-homodimer. The 38 kDa band was also identified in western blots of olfactory epithelium demonstrating its presence in vivo. The stabilities and subcellular localizations of the OMP-monomer and -dimer were studied in transfected cells. These results demonstrated that the OMP-dimer is much less stable than the monomer, and that while the monomer is present both in the nuclear and cytosolic compartments, the dimer is preferentially located in a Triton X-100 insoluble cytoskeletal fraction. These novel observations led us to hypothesize that regulation of the level of the rapidly turning-over OMP-dimer and its interaction with Bex1/2 is critical for OMP function in sensory transduction.
authors.affiliation: Department of Anatomy & Neurobiology, University of Maryland, School of Medicine, Baltimore, Maryland, USA.
authors.forename: Jae Hyung
authors.initials: JH
authors.lastname: Koo
authors.forename: Stephanie
authors.initials: S
authors.lastname: Gill
authors.forename: Lewis K
authors.initials: LK
authors.lastname: Pannell
authors.forename: Bert Ph M
authors.initials: BP
authors.lastname: Menco
authors.forename: Joyce W
authors.initials: JW
authors.lastname: Margolis
authors.forename: Frank L
authors.initials: FL
authors.lastname: Margolis
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D006224:Cricetinae; D003546:Cysteine Endopeptidases; D019281:Dimerization; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005982:Glutathione Transferase / Q000235:genetics; D006801:Humans; D008297:Male; D051379:Mice; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051842:Olfactory Marker Protein; D009928:Organ Specificity; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding / Q000187:drug effects; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000737:chemistry / Q000378:metabolism; D014162:Transfection
chemical_list: C118512:Bex1 protein, mouse; D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D009419:Nerve Tissue Proteins; C497597:OMP protein, human; D051842:Olfactory Marker Protein; C497598:Omp protein, mouse; C497599:Omp protein, rat; D011500:Protein Synthesis Inhibitors; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex