The secretion of tropoelastin by chick-embryo artery cells.
Chymotryptic fingerprint analyses of tropoelastin a and tropoelastin b demonstrated a very close relationship between these two polypeptides synthesized in a cell-free system under the direction of chick-embryo polyribosomal mRNA. A similar study on tropoelastin polypeptides extracted in their hydroxylated and under-hydroxylated forms from artery cells incubated with [3H]valine in the absence and presence of alpha alpha'-bipyridine or 3,4-dehydroproline confirmed this close relationship and suggested that tropoelastins a and b are likely to be the products of a single gene. Pulse-chase experiments in which the synthesis and secretion of tropoelastin by artery cells were monitored demonstrated that, after a pulse with [3H]proline, the polypeptides rapidly appeared in the medium and the half-time of tropoelastin secretion was approx. 30 min. Further pulse-chase studies, in which [3H]tropoelastin contents of subcellular fractions were determined, showed that rough and smooth microsomal fractions contained maximal amounts of tropoelastin at different times. The quantity of tropoelastin in the smooth-microsomal fraction was always only a small proportion of that in the rough-microsomal fraction, suggesting rapid translocation of the polypeptides to the plasma membrane. Incubation of the cells with 0.1 mM-colchicine did not markedly alter the rate of secretion or the distribution of tropoelastin between the subcellular fractions, whereas when 1 microM-monensin was included in the incubations the polypeptides were retained in the rough microsomal fraction. The results are consistent with the proposal that tropoelastin may follow a pathway of secretion from rough endoplasmic reticulum to the plasma membrane via secretory vesicles.
D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D002642:Chick Embryo; D003078:Colchicine / Q000494:pharmacology; D004549:Elastin / Q000031:analogs & derivatives*; D004591:Electrophoresis, Polyacrylamide Gel; D008985:Monensin / Q000494:pharmacology; D010446:Peptide Fragments / Q000032:analysis; D013347:Subcellular Fractions / Q000378:metabolism; D014333:Tropoelastin / Q000096:biosynthesis*
D010446:Peptide Fragments; D014333:Tropoelastin; D004549:Elastin; D008985:Monensin; D003078:Colchicine