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Myopalladin, a novel 145-kilodalton sarcomeric protein with multiple roles in Z-disc and I-band protein assemblies

M L Bang1, R E Mudry, A S McElhinny

  • 1European Molecular Biology Laboratory, Heidelberg 69117, Germany.

The Journal of Cell Biology
|April 20, 2001
PubMed

Insights

We discovered myopalladin, a novel sarcomeric protein that links Z-line structure proteins like alpha-actinin and nebulin to CARP, a nuclear protein regulating muscle gene expression, maintaining sarcomeric integrity.

Area of Science:

  • Muscle biology
  • Cellular structure
  • Protein interactions

Background:

  • The Z-line is a critical structure in sarcomeres, composed of various proteins that anchor the thin filaments.
  • Nebulin and alpha-actinin are key components of the Z-line, involved in sarcomere assembly and stability.
  • Palladin is known to be essential for actin cytoskeletal assembly.

Purpose of the Study:

  • To identify and characterize a novel sarcomeric protein involved in Z-line structure and function.
  • To elucidate the binding partners and functional role of this new protein within the sarcomere.
  • To investigate the potential link between Z-line integrity and muscle gene expression.

Main Methods:

  • Protein purification and characterization to identify the novel 145-kD protein, myopalladin.
  • Analysis of protein domains and homology to known proteins like palladin.
  • Immunofluorescence and immunoelectron microscopy to determine myopalladin localization within sarcomeres.
  • Functional studies involving overexpression of myopalladin domains in cardiac myocytes.

Main Results:

  • A novel sarcomeric protein, myopalladin, was identified, binding to nebulin/nebulette and alpha-actinin in the Z-lines.
  • Myopalladin shares homology with palladin, suggesting conserved roles in cytoskeletal assembly.
  • Myopalladin's N-terminal region binds to CARP, a nuclear protein involved in muscle gene expression.
  • Myopalladin and CARP colocalize in the central I-band of striated muscle sarcomeres.
  • Overexpression of the myopalladin-CARP binding region disrupted sarcomeric structure.

Conclusions:

  • Myopalladin acts as a molecular bridge, connecting Z-line structural components (nebulin, nebulette, alpha-actinin) with nuclear regulatory factors (CARP).
  • The myopalladin-CARP complex in the I-band plays a crucial role in maintaining sarcomeric integrity.
  • Myopalladin may link sarcomeric structure regulation to muscle gene expression control.

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