title: Megalin binds and internalizes angiotensin-(1-7).
abstract: Megalin is a multiligand receptor heavily involved in protein endocytosis. We recently demonstrated that megalin binds and mediates internalization of ANG II. Although there is a strong structural resemblance between ANG II and ANG-(1-7), their physiological actions and their affinity for the angiotensin type 1 receptor (AT(1)R) are dissimilar. Therefore, the hypothesis of the present work was to test whether megalin binds and internalizes ANG-(1-7). The uptake of ANG-(1-7) was determined by exposure of confluent monolayers of BN/MSV cells (a model representative of the yolk sac epithelium) to fluorescently labeled ANG-(1-7) (100 nM) and measurement of the amount of cell-associated fluorescence after 4 h by flow cytometry. Anti-megalin antisera and an AT(1)R blocker (olmesartan) were used to interfere with uptake via megalin and the AT(1)R, respectively. ANG-(1-7) uptake was prevented by anti-megalin antisera (63%) to a higher degree than olmesartan (13%) (P < 0.001). In analysis by flow cytometry of binding experiments performed in brush-border membrane vesicles isolated from kidneys of CD-1 mice, anti-megalin antisera interfered with ANG-(1-7) binding more strongly than olmesartan (P < 0.05 against positive control). Interactions of megalin with ANG-(1-7) at a molecular level were studied by surface plasmon resonance, demonstrating that ANG-(1-7) binds megalin dose and time dependently and with an affinity similar to ANG II. These results show that the scavenger receptor megalin binds and internalizes ANG-(1-7).
authors.affiliation: Dept. of Medicine/Section of Nephrology SL-45, Tulane Univ. Health Sciences Ctr., 1430 Tulane Ave., New Orleans, LA 70112, USA.
authors.forename: Romer
authors.initials: R
authors.lastname: Gonzalez-Villalobos
authors.forename: R Bryan
authors.initials: RB
authors.lastname: Klassen
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Allen
authors.forename: Kelly
authors.initials: K
authors.lastname: Johanson
authors.forename: Chasity B
authors.initials: CB
authors.lastname: Baker
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kobori
authors.forename: L G
authors.initials: LG
authors.lastname: Navar
authors.forename: Timothy G
authors.initials: TG
authors.lastname: Hammond
mesh_terms: D000803:Angiotensin I / Q000378:metabolism*; D000959:Antihypertensive Agents / Q000378:metabolism*; D018929:Cell Culture Techniques; D004848:Epithelium; D005434:Flow Cytometry; D006801:Humans; D007668:Kidney / Q000502:physiology; D026561:Low Density Lipoprotein Receptor-Related Protein-2 / Q000502:physiology*; D010446:Peptide Fragments / Q000378:metabolism*; D012084:Renin-Angiotensin System / Q000502:physiology; D015017:Yolk Sac / Q000166:cytology
chemical_list: D000959:Antihypertensive Agents; D026561:Low Density Lipoprotein Receptor-Related Protein-2; D010446:Peptide Fragments; D000803:Angiotensin I; C118790:angiotensin I (1-7)