title: Outside or inside: role of the subcellular localization of DP4-like enzymes for substrate conversion and inhibitor effects.
abstract: The discovery of the DP4-related enzymes DP8 and DP9 raised controversial discussion regarding the physiological and pathophysiological function of distinct members of the DP4 family. Particularly with regard to their potential relevance in regulating immune functions, it is of interest to know which role the subcellular distribution of the enzymes play. Synthetic substrates as well as low molecular weight inhibitors are widely used as tools, but little is yet known regarding their features in cell experiments, such as their plasma membrane penetration capacity. The fluorogenic substrates Gly-Pro-AMC or (Ala-Pro)₂-R110 predominantly detect plasma membrane-bound activities of viable cells (less than 0.1% of fluorochromes R110 or AMC inside viable cells after 1 h incubation). Additionally, the selective and non-selective DP8/9 inhibitors allo-Ile-isoindoline and Lys[Z(NO₂)]-pyrrolidide were found to be incapable of passing the plasma membrane easily. This suggests that previously reported cellular effects are not due to inhibition of the cytosolic enzymes DP8 or DP9. Moreover, our enzymatic studies with viable cells provided evidence that DP8 and/or DP9 are also present on the surface of immune cells under certain circumstances and could gain relevance particularly in the absence of DP4 expression. In summary, in cells which do express DP4 on the surface, this archetypical member of the DP4 family is the most relevant peptidase in the regulation of cellular functions.
authors.affiliation: IMTM GmbH, Department Immunopharm, D-39120 Magdeburg, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Bank
authors.forename: Anke
authors.initials: A
authors.lastname: Heimburg
authors.forename: Astrid
authors.initials: A
authors.lastname: Wohlfarth
authors.forename: Gudrun
authors.initials: G
authors.lastname: Koch
authors.forename: Karsten
authors.initials: K
authors.lastname: Nordhoff
authors.forename: Heiko
authors.initials: H
authors.lastname: Julius
authors.forename: Martin
authors.initials: M
authors.lastname: Helmuth
authors.forename: Doreen
authors.initials: D
authors.lastname: Breyer
authors.forename: Dirk
authors.initials: D
authors.lastname: Reinhold
authors.forename: Michael
authors.initials: M
authors.lastname: Täger
authors.forename: Siegfried
authors.initials: S
authors.lastname: Ansorge
mesh_terms: D000818:Animals; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis; D004150:Dipeptidases / Q000378:metabolism*; D018819:Dipeptidyl Peptidase 4 / Q000235:genetics / Q000378:metabolism*; D054873:Dipeptidyl-Peptidase IV Inhibitors / Q000494:pharmacology; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000378:metabolism; D042541:Intracellular Space / Q000378:metabolism*; D007532:Isoleucine / Q000031:analogs & derivatives / Q000378:metabolism; D008239:Lysine / Q000031:analogs & derivatives / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009478:Neuropeptide Y / Q000378:metabolism; D011759:Pyrrolidines / Q000378:metabolism; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000201:enzymology
chemical_list: D054873:Dipeptidyl-Peptidase IV Inhibitors; D005456:Fluorescent Dyes; D007211:Indoles; D009478:Neuropeptide Y; D011759:Pyrrolidines; C524159:UAMC00132; C110164:lysyl-(Z(nitro))pyrrolidide; D007532:Isoleucine; D004247:DNA; D004150:Dipeptidases; C471241:DPP9 protein, human; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; C487997:DPP8 protein, human; D018819:Dipeptidyl Peptidase 4; D008239:Lysine