| Item type: | Article | ||||
|---|---|---|---|---|---|
| Journal or Publication Title: | Journal of Experimental Zoology Part A: Comparative Experimental Biology | ||||
| Publisher: | WILEY-LISS | ||||
| Place of Publication: | NEW YORK | ||||
| Volume: | 299A | ||||
| Number of Issue or Book Chapter: | 2 | ||||
| Page Range: | pp. 213-222 | ||||
| Date: | 2003 | ||||
| Institutions: | Biology, Preclinical Medicine > Institut für Anatomie | ||||
| Identification Number: |
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| Keywords: | MICROVILLAR MEMBRANE; ANGIOTENSINASE-A; BRUSH-BORDER; KIDNEY; RAT; PROTEINS; ENDOPEPTIDASE; GLUTAMYL; INVITRO; COMPLEX; | ||||
| Dewey Decimal Classification: | 500 Science > 570 Life sciences 500 Science > 590 Zoological sciences | ||||
| Status: | Published | ||||
| Refereed: | Yes, this version has been refereed | ||||
| Created at the University of Regensburg: | Yes | ||||
| Item ID: | 72047 |
Web of ScienceAbstract
Viviparity in goodeid teleosts is characterized by the elaboration of trophotaeniae, extraembryonic proctodaeal appendages facilitating maternal-embryonic nutrient transfer. The trophotaenial absorptive cells (TACs) express aminopeptidases (APs) such as APA, APN, gamma-glutamyltransferase (gamma-GT), dipeptidyl aminopeptidase (DAP) IV, and neutral endopeptidase (NEP) as inferred from the results ...
Abstract
Viviparity in goodeid teleosts is characterized by the elaboration of trophotaeniae, extraembryonic proctodaeal appendages facilitating maternal-embryonic nutrient transfer. The trophotaenial absorptive cells (TACs) express aminopeptidases (APs) such as APA, APN, gamma-glutamyltransferase (gamma-GT), dipeptidyl aminopeptidase (DAP) IV, and neutral endopeptidase (NEP) as inferred from the results of cleavage experiments with, respectively, Glu-gamma-(4MPNA), Ala(4MPNA), Glu-gamma-(4MbetaNA), Gly-Pro-(4MbetaNA), and Gl-(Ala)3-(4MPNA). Enzyme reaction product was localized to the apical and basolateral plasma membrane as well as to some intracellular compartments. In the accompanying report (Schindler, 2003) evidence is presented that the trophotaeniae of Ameca splendens embryos randomly, yet specifically, bind and ingest proteins as well as certain copolymers of amino acids. Present results demonstrate that endocytosis is significantly inhibitable by unspecific proteinase inhibitors, such as diisopropylphosphorofluoride, phenylmethanesulfonylfluoride, antipain, 1.10-phenanthroline, and dithiothreitol. The specific microbial AP inhibitors amastatin, bestatin, and phosphoramidon suppressed protein binding to TACs more effectively when added in combination than did either agent alone. Moreover, in the presence of 4MbetaNA assay substrates of APs the capability of TACs to bind proteins was significantly reduced. Conversely, the rate at which 4MPNA substrates were cleaved by trophotaenial APs was modified in the presence of proteins. Depending on protein concentrations the AP-catalyzed reactions either decreased or increased in velocity. Analysis of the enzyme kinetics by methods of linear transformation suggests that proteins bind to APs competitively, thereby adopting the role of enzyme inhibitors. On the other hand, protein binding to APs appears to be a signal to translocate enzymes from an internal pool to the surface membrane. In the presence of primaquine, the rate of AP-catalyzed cleavage of 4MbetaNA substrates was significantly reduced. That can be put down to the fact that weak bases disrupt the recycling of endocytosed membrane constituents. In conclusion, there is evidence that A-Ps in the trophotaenial placenta of A. splendens function as scavenger receptors mediating in the delivery of embryotrophic proteins for lysosomal degradation. J. Exp. Zool. 299A- 213-222, 2003. (C) 2003 Wiley-Liss, Inc.
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