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The pro-apoptotic protein Par-4 facilitates vascular contractility by cytoskeletal targeting of ZIPK

Susanne Vetterkind1, Kathleen G Morgan

  • 1Boston Biomedical Research Institute, Watertown, MA, USA.

Journal of Cellular and Molecular Medicine
|May 29, 2008
PubMed

Insights

Prostate apoptosis response 4 (Par-4) protein regulates vascular smooth muscle contraction. Par-4 targets ZIPK to actin filaments, impacting myosin light chain phosphorylation and smooth muscle contractility.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Physiology

Background:

  • Prostate apoptosis response 4 (Par-4) is a known pro-apoptotic protein and tumor suppressor.
  • Par-4 was initially identified for its role in prostate cancer apoptosis.
  • Its function in non-cancerous differentiated vascular smooth muscle cells was previously unknown.

Purpose of the Study:

  • To investigate the expression and function of Par-4 in vascular smooth muscle.
  • To determine Par-4's role in regulating smooth muscle contraction and associated signaling pathways.

Main Methods:

  • Immunofluorescence to assess Par-4 localization with actin filaments in vascular smooth muscle.
  • Use of a cell-permeant Par-4 decoy peptide to inhibit protein interactions.
  • Assessment of smooth muscle tissue contractility.
  • Knockdown of Par-4 using antisense morpholino nucleotides.
  • Measurement of myosin light chain (MLC) and myosin phosphatase target subunit (MYPT) phosphorylation.

Main Results:

  • Par-4 is expressed in vascular smooth muscle and co-localizes with actin filaments.
  • A Par-4 decoy peptide inhibited ZIPK targeting to actin filaments and PGF-2alpha-induced smooth muscle contraction.
  • Par-4 knockdown reduced contractility and phosphorylation of MLC and MYPT.

Conclusions:

  • Par-4 plays a critical role in regulating vascular smooth muscle contraction.
  • Par-4 facilitates contraction by targeting ZIPK to its substrates, MLC and MYPT, on actin filaments.
  • Par-4 is identified as a novel regulator of myosin light chain phosphorylation in contractile vascular smooth muscle.

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