Smooth muscle caldesmon modulates peristalsis in the wild type and non-innervated zebrafish intestine

Neurogastroenterol Motil. 2012 Mar;24(3):288-99. doi: 10.1111/j.1365-2982.2011.01844.x.

Abstract

Background: The high molecular weight isoform of the actin-binding protein Caldesmon (h-CaD) regulates smooth muscle contractile function by modulating cross-bridge cycling of myosin heads. The normal inhibitory activity of h-CaD is regulated by the enteric nervous system; however, the role of h-CaD during intestinal peristalsis has never been studied.

Methods: We identified a zebrafish paralog of the human CALD1 gene that encodes an h-CaD isoform expressed in intestinal smooth muscle. We examined the role of h-CaD during intestinal peristalsis in zebrafish larvae by knocking down the h-CaD protein using an antisense morpholino oligonucleotide. We also developed transgenic zebrafish that express inhibitory peptides derived from the h-CaD myosin and actin-binding domains, and examined their effect on peristalsis in wild-type zebrafish larvae and sox10 (colourless) mutant larvae that lack enteric nerves.

Key results: Genomic analyses identified two zebrafish Caldesmon paralogs. The cald1a ortholog encoded a high molecular weight isoform generated by alternative splicing whose intestinal expression was restricted to smooth muscle. Propulsive intestinal peristalsis was increased in wild-type zebrafish larvae by h-CaD knockdown and by expression of transgenes encoding inhibitory myosin and actin-binding domain peptides. Peristalsis in the non-innervated intestine of sox10 (colourless) larvae was partially restored by h-CaD knockdown and expression of the myosin-binding peptide.

Conclusions & inferences: Disruption of the normal inhibitory function of h-CaD enhances intestinal peristalsis in both wild-type zebrafish larvae and mutant larvae that lack enteric nerves, thus confirming a physiologic role for regulation of smooth muscle contraction at the actin filament.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Actins / metabolism
  • Alternative Splicing
  • Animals
  • Animals, Genetically Modified
  • Calmodulin-Binding Proteins / genetics
  • Calmodulin-Binding Proteins / metabolism*
  • Humans
  • Intestines / innervation*
  • Intestines / physiology*
  • Muscle Contraction / physiology
  • Muscle, Smooth / innervation
  • Muscle, Smooth / physiology*
  • Myosins / metabolism
  • Peristalsis / physiology*
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Zebrafish / anatomy & histology*
  • Zebrafish / physiology*

Substances

  • Actins
  • Calmodulin-Binding Proteins
  • Protein Isoforms
  • Myosins