| Item type: | Article | ||||
|---|---|---|---|---|---|
| Journal or Publication Title: | Journal of Experimental Zoology Part A: Comparative Experimental Biology | ||||
| Publisher: | WILEY | ||||
| Place of Publication: | HOBOKEN | ||||
| Volume: | 299A | ||||
| Number of Issue or Book Chapter: | 2 | ||||
| Page Range: | pp. 197-212 | ||||
| Date: | 2003 | ||||
| Institutions: | Biology, Preclinical Medicine > Institut für Anatomie | ||||
| Identification Number: |
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| Keywords: | SAC CULTURED INVITRO; MATERNAL-EMBRYONIC RELATIONSHIPS; CUBILIN-MEDIATED ENDOCYTOSIS; INTERNAL OVARIAN EPITHELIUM; EPIDERMAL GROWTH-FACTOR; RENAL PROXIMAL TUBULE; AMINO-ACID SEQUENCE; CYPRINUS-CARPIO L; YOLK-SAC; ABSORPTIVE CELLS; | ||||
| 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: | 72048 |
Web of ScienceAbstract
in the goodeid placental analogue, trophotaeniae provide extraembryonic gut-derived exchange surfaces. Ameca splendens embryos possess endocytosing trophotaeniae that are capable of absorbing a dazzling array of proteinaceous substances. The iron core protein, native ferritin (NF), and several radioiodinated proteinaceous substances were used to study ligand and binding site pathways in the ...
Abstract
in the goodeid placental analogue, trophotaeniae provide extraembryonic gut-derived exchange surfaces. Ameca splendens embryos possess endocytosing trophotaeniae that are capable of absorbing a dazzling array of proteinaceous substances. The iron core protein, native ferritin (NF), and several radioiodinated proteinaceous substances were used to study ligand and binding site pathways in the trophotaenial absorptive cells (TACs). Time sequence analysis of NF trafficking indicated an exclusively lysosomal pathway. Binding to TACs of NF was completely inhibitable by proteins containing multiple lysine residues such as apoferritin, bovine serum albumin (BSA), human transferrin (HTf), fetuin, hemoglobin, myoglobin, cytochrome c, ubiquitin, parvalbumin as well as the random copolymers, poly(Glu,Lys,Tyr)6:3:1 and poly(D-Glu,D-Lys)6:4. Peptide hormones and pepsin that contains only one lysine residue did not produce inhibitory effects. Radiolabels such as I-125-BSA, I-125-HTf and I-125-poly (Glu,Lys,Tyr) bound to trophotaeniae in a specific saturable manner. Any two proteins were shown to hinder one another in getting hold of a binding site. Concentration-dependent I-125-BSA binding and Scatchard analysis of the data revealed both low- and medium-affinity binding with apparent dissociation constants, K(d)s, of 3.4 x 10(-5) M and 2 x 10(-7) M, respectively. Binding of NF and radioiodinated proteins was inhibited in the presence of a large excess of L-Lys, D-Lys, and several dipeptides containing Lys. Both Ca2+- depletion and low pH dramatically reduced the TACs' capacity to bind proteins. The effects of acidotropic agents included a reversible loss of surface protein binding sites, tremendous vacuolation, and the arrest of lysosomal degradation. Collectively, present results demonstrate that TACs bind and absorb multiple proteinaceous substances through a mechanism satisfying the criteria of receptor-mediated endocytosis. It is concluded that scavenger protein binding sites are used to ingest proteins for lysosomal degradation, helping to meet the embryos' amino acid requirement. (C) 2003 Wiley-Liss, Inc.
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