title: Insulin degrading enzyme is localized predominantly at the cell surface of polarized and unpolarized human cerebrovascular endothelial cell cultures.
abstract: Insulin degrading enzyme (IDE) is expressed in the brain and may play an important role there in the degradation of the amyloid beta peptide (Abeta). Our results show that cultured human cerebrovascular endothelial cells (HCECs), a primary component of the blood-brain barrier, express IDE and may respond to exposure to low levels of Abeta by upregulating its expression. When radiolabeled Abeta is introduced to the medium of cultured HCECs, it is rapidly degraded to smaller fragments. We believe that this degradation is largely the result of the action of IDE, as it can be substantially blocked by the presence of insulin in the medium, a competitive substrate of IDE. No inhibition is seen when an inhibitor of neprilysin, another protease that may degrade Abeta, is present in the medium. Our evidence suggests that the action of IDE occurs outside the cell, as inhibitors of internalization fail to affect the rate of the observed degradation. Further, our evidence suggests that degradation by IDE occurs on the plasma membrane, as much of the IDE present in HCECs was biotin-labeled by a plasma membrane impermeable reagent. This activity seems to be polarity dependent, as measurement of Abeta degradation by each surface of differentiated HCECs shows greater degradation on the basolateral (brain-facing) surface. Thus, IDE could be an important therapeutic target to decrease the amount of Abeta in the cerebrovasculature.
authors.affiliation: Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Lynch
authors.forename: Ana M
authors.initials: AM
authors.lastname: George
authors.forename: Patricia B
authors.initials: PB
authors.lastname: Eisenhauer
authors.forename: Kelly
authors.initials: K
authors.lastname: Conn
authors.forename: Wenwu
authors.initials: W
authors.lastname: Gao
authors.forename: Isabel
authors.initials: I
authors.lastname: Carreras
authors.forename: John M
authors.initials: JM
authors.lastname: Wells
authors.forename: Ann
authors.initials: A
authors.lastname: McKee
authors.forename: M David
authors.initials: MD
authors.lastname: Ullman
authors.forename: Richard E
authors.initials: RE
authors.lastname: Fine
mesh_terms: D000293:Adolescent; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D001667:Binding, Competitive / Q000187:drug effects / Q000502:physiology; D001812:Blood-Brain Barrier / Q000378:metabolism*; D002460:Cell Line; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D016764:Cell Polarity / Q000502:physiology*; D016657:Cerebral Amyloid Angiopathy / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D002536:Cerebral Arteries / Q000378:metabolism* / Q000648:ultrastructure; D042783:Endothelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D007339:Insulysin / Q000378:metabolism*; D008297:Male
chemical_list: D016229:Amyloid beta-Peptides; D004791:Enzyme Inhibitors; D007328:Insulin; D007339:Insulysin