en
Scientific article
English

The specific NH2-terminal sequence Ac-EEED of alpha-smooth muscle actin plays a role in polymerization in vitro and in vivo

Published inThe Journal of cell biology, vol. 130, no. 4, p. 887-895
Publication date1995
Abstract

The blocking effect of the NH2-terminal decapeptide of alpha-smooth muscle (SM) actin AcEEED-STALVC on the binding of the specific monoclonal antibody anti-alpha SM-1 (Skalli, O., P. Ropraz, A. Trzeviak, G. Benzonana, D. Gillessen, and G. Gabbiani. 1986. J. Cell Biol. 103:2787-2796) was compared with that of synthetic peptides modified by changing the acetyl group or by substituting an amino acid in positions 1 to 5. Using immunofluorescence and immunoblotting techniques, anti-alpha SM-1 binding was abolished by the native peptide and by peptides with a substitution in position 5, indicating that AcEEED is the epitope for anti-alpha SM-1. Incubation of anti-alpha SM-1 (or of its Fab fragment) with arterial SM actin increased polymerization in physiological salt conditions; the antibody binding did not hinder the incorporation of the actin antibody complex into the filaments. This action was not exerted on skeletal muscle actin. After microinjection of the alpha-SM actin NH2-terminal decapeptide or of the epitopic peptide into cultured aortic smooth muscle cells, double immunofluorescence for alpha-SM actin and total actin showed a selective disappearance of alpha-SM actin staining, detectable at approximately 30 min. When a control peptide (e.g. alpha-skeletal [SK] actin NH2-terminal peptide) was microinjected, this was not seen. This effect is compatible with the possibility that the epitopic peptide traps a protein involved in alpha-SM actin polymerization during the dynamic filament turnover in stress fibers. Whatever the mechanism, this is the first evidence that the NH2 terminus of an actin isoform plays a role in the regulation of polymerization in vitro and in vivo.

Keywords
  • Actins/immunology/ metabolism/ultrastructure
  • Amino Acid Sequence
  • Animals
  • Antibody Specificity
  • Aorta/cytology
  • Binding, Competitive
  • Centrifugation
  • Epitopes
  • Immunoblotting
  • Microinjections
  • Microscopy, Electron
  • Microscopy, Fluorescence
  • Molecular Sequence Data
  • Muscle, Smooth, Vascular/ metabolism
  • Oligopeptides/immunology/ metabolism
  • Peptide Fragments/immunology
  • Polymers/metabolism
  • Protein Binding
  • Rats
  • Rats, Wistar
Citation (ISO format)
CHAPONNIER, Christine et al. The specific NH2-terminal sequence Ac-EEED of alpha-smooth muscle actin plays a role in polymerization in vitro and in vivo. In: The Journal of cell biology, 1995, vol. 130, n° 4, p. 887–895.
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ISSN of the journal0021-9525
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