Binding and uptake of Col 1(I), a peptide capable of inhibiting collagen synthesis in fibroblasts.
Col 1(I), a collagenase-resistant segment of the amino-terminal propeptide of pro alpha 1(I) chains, is known to inhibit collagen synthesis in cultured skin fibroblasts and also in a cell-free protein synthesizing system by reducing the translation of procollagen mRNA. These findings prompted us to explore the fate of exogenous Col 1(I) in the cellular processing of human skin fibroblasts using colloidal gold labeled protein (Col 1(I)-Au). Distribution of Col 1(I)-Au on the cell surface was studied by the platinum-carbon replication technique. Three different types of binding pattern could be observed: 1) Binding sites in the form of a fibrillar network, 2) those in the form of clusters, and 3) solitary bound gold conjugates. The latter two cases were determined to be specific. The intracellular routing of Col 1(I)-Au was studied by thin sections. Specifically bound gold conjugates were found in coated pits and after the initiation of the internalization process in coated vesicles and endosomes. Acid phosphatase cytochemistry revealed that only a small amount of Col 1(I)-Au is delivered to lysosomes. The bulk of gold conjugates is present even after prolonged incubation at 37 degrees C in acid phosphatase-negative compartments of the cell. Our data suggest a mechanism in which Col 1(I) initially is bound to the cell surface and subsequently internalized via the coated pit-coated vesicle pathway.
Schlumberger
W
W
Medizinische Fakultät der Universität, Arbeitsgruppe Zellbiologie, Münster/Bundesrepublik Deutschland.
Thie
M
M
Volmer
H
H
Rauterberg
J
J
Robenek
H
H
D000135:Acid Phosphatase / Q000032:analysis; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis*; D004705:Endocytosis; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D006046:Gold; D006651:Histocytochemistry; D006801:Humans; D008247:Lysosomes / Q000201:enzymology; D008854:Microscopy, Electron; D010446:Peptide Fragments / Q000378:metabolism*; D011347:Procollagen / Q000378:metabolism*
D010446:Peptide Fragments; D011347:Procollagen; C041876:procollagen Type III-N-terminal peptide; D006046:Gold; D003094:Collagen; D000135:Acid Phosphatase