Amino acid transport in chick embryo fibroblasts: Evidence for transcriptional regulation of transport following serum addition

✍ Scribed by Angelo F. Borghetti; Mariarosaria Tramacere; Giuseppe Piedimonte; Guido G. Guidotti

• Publisher: John Wiley and Sons
• Year: 1979
• Tongue: English
• Weight: 566 KB
• Volume: 98
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1040980207

✦ Synopsis

Abstract

Changes in amino acid transport activity by system A (a Na^+^‐dependent agency with affinity for a discrete group of neutral amino acids) caused by the addition of serum to serum‐deprived cultured chick embryo fibroblasts have been evaluated by measurements of ^14^C‐labeled L‐proline and α‐methylaminoisobutyric acid uptake under conditions approaching initial entry rates. Dialysed serum was as effective as undialysed serum in stimulating amino acid transport. This effect was inhibited by 7 μM cycloheximide, by 80 nM actinomycin D and by 40 μM cordycepin, but not by 0.3 mM cytosine arabinoside. Cultured avian fibroblasts previously incubated in a cycloheximide‐containing medium (phase of inhibited translation) in the presence of serum, subsequently exhibited a net increase of proline transport activity when transferred to a medium containing actinomycin D (phase of inhibited transcription). Omission of serum in the cycloheximide‐phase prevented the increase of transport activity during subsequent incubation in the actinomycin D‐phase; omission of serum in the actinomycin D‐phase allowed a shorter and less pronounced increase of transport activity than in the presence of serum. Additions of actinomycin D or cycloheximide slightly increased the rate of decay of amino acid transport caused by serum withdrawal. These observations suggest that in cultured avian fibroblasts, serum modulates the activity of transport system A by a mechanism acting at the transcription level.