Aminopeptidase N/CD13 is associated with raft membrane microdomains in monocytes.
Ectopeptidases play important roles in cell activation, proliferation, and communication. Human monocytic cells express considerable amounts of aminopeptidase N/CD13, a transmembrane protein previously proposed to play a role in the regulation of neuropeptides and chemotactic mediators as well as in adhesion and cell-cell interactions. Here, we report for the first time that aminopeptidase N/CD13 in monocytes is partially localized in detergent-insoluble membrane microdomains enriched in cholesterol, glycolipids, and glycosylphosphoinositol-anchored proteins, referred to as "rafts." Raft fractions of monocytes were characterized by the presence of GM1 ganglioside as raft marker molecule and by the high level of tyrosine-phosphorylated proteins. Furthermore, similar to polarized cells, rafts in monocytic cells lack Na(+), K(+)-ATPase. Cholesterol depletion of monocytes by methyl-beta-cyclodextrin greatly reduces raft localization of aminopeptidase N/CD13 without affecting ala-p-nitroanilide cleaving activity of cells.
Navarrete Santos
A
A
Institute of Medical Immunology, Martin Luther University Halle-Wittenberg, Strasse der OdF 6, Halle, D-06097, Germany. alexander.navarrete@medizin.uni-halle.de
Roentsch
J
J
Danielsen
E M
EM
Langner
J
J
Riemann
D
D
D018826:CD13 Antigens / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism; D003505:Cyclodextrins / Q000494:pharmacology; D003902:Detergents; D005677:G(M1) Ganglioside / Q000378:metabolism; D006801:Humans; D008563:Membrane Lipids / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D009000:Monocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D015398:Signal Transduction; D012995:Solubility; D020298:U937 Cells; D047392:beta-Cyclodextrins
D003505:Cyclodextrins; D003902:Detergents; D008563:Membrane Lipids; D008565:Membrane Proteins; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D005677:G(M1) Ganglioside; D002784:Cholesterol; D018826:CD13 Antigens