Autoregulation of actin synthesis by physiological alterations of the G-actin level in hepatocytes.
Hypotonic treatment of cultured rat hepatocytes significantly decreased the monomeric G-actin level by 18% after 120 min while the level of filamentous F-actin remained essentially unchanged. Simultaneously the level of cellular actin mRNA was increased by 53%. Incubation of hepatocytes for 120 min with the F-actin stabilizing toxin phalloidin from Amanita phalloides led to a decrease of G-actin by 70% and an increase of F-actin by 55%. Although the toxin dependent decrease of G-actin was much more pronounced than the decrease after hypotonic treatment, the increase of actin mRNA was similar under both conditions. Simultaneous treatment with hypotonic medium did not result in a further decrease of the G-actin level. On the other hand, the G-actin elevating C2 toxin from Clostridium botulinum completely blocked the effects of osmotic stress on G-actin and actin-mRNA content. The results demonstrate that already an essentially physiological decrease of G-actin without alterations of F-actin results in a substantial enhancement of the actin mRNA level, indicating the physiological significance of this autoregulation.
Reuner
K H
KH
Institut für Klinische Chemie und Pathobiochemie, Universität Giessen, Germany.
Wiederhold
M
M
Schlegel
K
K
Just
I
I
Katz
N
N
D000199:Actins / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology; D002478:Cells, Cultured; D006706:Homeostasis / Q000502:physiology*; D007038:Hypotonic Solutions; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009997:Osmotic Pressure; D010590:Phalloidine / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar
D000199:Actins; D007038:Hypotonic Solutions; D012333:RNA, Messenger; D010590:Phalloidine; D001905:Botulinum Toxins