title: A selective interaction between OS-9 and the carboxyl-terminal tail of meprin beta.
abstract: OS-9, a protein previously uncharacterized, was shown to interact specifically with the intracellular region of the membrane proteinase meprin beta found in brush border membranes of kidney and small intestine. We have shown previously that this cytoplasmic region is indispensable for the maturation of meprin beta, which included an endoplasmic reticulum (ER)-to-Golgi translocation. We characterized OS-9 and found that it is associated with ER membranes and that it is exposed to the cytoplasm. Consistent with the kinetics of maturation of meprin beta, OS-9 associates with meprin beta only transiently, coinciding with ER-to-Golgi transport of meprin beta. The OS-9-binding site in the cytoplasmic domain of meprin beta overlaps the region essential for this transport. We characterized alternatively spliced forms of rat and mouse OS-9, and we found that only the non-spliced form of OS-9 binds to meprin beta, implicating the spliced out segment in the binding, and suggesting the possible mechanism of the regulation of OS-9 function. Taken together, our results indicated that OS-9 may be involved in the ER-to-Golgi transport of meprin beta. Ubiquitous expression of OS-9 raises the possibility that it may interact with other membrane proteins that possess the cytoplasmic moiety homologous to that of meprin beta during their ER-to-Golgi transition.
authors.affiliation: Department of Adult Oncology, Dana-Farber Cancer Institute, 44 Binney Street, Mayer Building 444, Boston, MA 02115, USA. larisa_litovchick@dfci.harvard.edu
authors.forename: Larisa
authors.initials: L
authors.lastname: Litovchick
authors.forename: Elena
authors.initials: E
authors.lastname: Friedmann
authors.forename: Shmuel
authors.initials: S
authors.lastname: Shaltiel
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D007150:Immunohistochemistry; D037102:Lectins; D008099:Liver / Q000737:chemistry; D008666:Metalloendopeptidases / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D020033:Protein Isoforms; D021122:Protein Subunits; D051381:Rats; D016415:Sequence Alignment; D020798:Two-Hybrid System Techniques
chemical_list: D037102:Lectins; D009363:Neoplasm Proteins; C098898:OS9 protein, human; D020033:Protein Isoforms; D021122:Protein Subunits; D008666:Metalloendopeptidases; C053833:meprin A; C095663:meprin B