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Microinjection of ADP-ribosylated actin inhibits actin synthesis in hepatocyte-hepatoma hybrid cells.

Abstract
Treatment of hepatocyte-hepatoma hybrid cells with Clostridium botulinum C2 toxin led to a 167% increase in monomeric globular actin (G-actin) and to a 57% decrease in filamentous actin (F-actin) within 2 h. Simultaneously, the level of actin mRNA was specifically decreased to 49% and actin synthesis was significantly diminished. In contrast, treatment of hybrid cells with phalloidin led to a decrease in G-actin to 55% and to a reciprocal increase in actin mRNA to 244% and an increase in actin synthesis. These alterations of actin synthesis depending on the G-actin/F-actin ratio corresponded to the autoregulation of actin synthesis observed in primary cultures of rat hepatocytes. Microinjection of C2 toxin or of phalloidin into hepatocyte-hepatoma hybrid cells had the same effects on actin synthesis as incubation with either toxin in the culture medium. Microinjection of nonpolymerizable ADP-ribosylated G-actin into hepatocyte-hepatoma hybrid cells specifically decreased the incorporation of [35S]methionine into newly synthesized actin within 1 h. This decrease continued for at least 19 h. Microinjection of ADP-ribosylated actin led to rounding of cells and obvious disaggregation of actin filaments, which might be due to capping of actin filaments by the ADP-ribosylated actin. Because stabilization of actin filaments by phalloidin before microinjection of ADP-ribosylated actin also resulted in decreased actin synthesis, the concentration of monomeric G-actin seems to be responsible for the regulation of actin synthesis in hepatocyte-hepatoma hybrid cells, which can be regarded as immortalized hepatocytes.
AuthorsK H Reuner, A van der Does, P Dunker, I Just, K Aktories, N Katz
JournalThe Biochemical journal (Biochem J) Vol. 319 ( Pt 3) Pg. 843-9 (Nov 01 1996) ISSN: 0264-6021 [Print] England
PMID8920989 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Actins
  • RNA, Messenger
  • Serum Albumin
  • Phalloidine
  • Adenosine Diphosphate Ribose
  • Botulinum Toxins
  • botulinum toxin type C
Topics
  • Actins (biosynthesis, isolation & purification, pharmacology)
  • Adenosine Diphosphate Ribose (metabolism)
  • Animals
  • Botulinum Toxins (pharmacology)
  • Cells, Cultured
  • Homeostasis
  • Hybrid Cells (drug effects, metabolism)
  • Liver (metabolism)
  • Liver Neoplasms, Experimental (metabolism)
  • Phalloidine (pharmacology)
  • RNA, Messenger (analysis, biosynthesis)
  • Rats
  • Rats, Wistar
  • Serum Albumin (biosynthesis)
  • Transcription, Genetic

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