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Membrane depolarization mediates phosphorylation and nuclear translocation of CREB in vascular smooth muscle cells

A S Stevenson1, L Cartin, T L Wellman

  • 1Department of Pharmacology, University of Vermont, Burlington, Vermont 05405, USA.

Experimental Cell Research
|February 13, 2001
PubMed

Insights

Ran GTPase differentially regulates signaling pathways to CREB in vascular smooth muscle cells (VSMCs). Nuclear import and export of activated CREB (P-CREB) are critical for signal transduction in VSMCs.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cardiovascular Research

Background:

  • Vascular smooth muscle cells (VSMCs) utilize Ca2+ and cAMP signaling pathways to modulate gene transcription via CREB.
  • Nuclear import is a critical step for signal transmission to CREB in VSMCs.
  • Ran GTPase plays a crucial role in regulating nuclear transport.

Purpose of the Study:

  • To investigate the role of Ran GTPase in regulating signaling pathways to CREB in VSMCs.
  • To determine how Ran GTPase influences the nuclear import and activation of CREB in response to different stimuli.
  • To elucidate the mechanisms by which PDGF-BB, Ca2+, and cAMP signaling affect CREB activity in VSMCs.

Main Methods:

  • Utilized PDGF-BB, membrane depolarization, and forskolin to stimulate CREB activation in VSMCs and intact aorta.
  • Employed calcium channel antagonist nimodipine to assess the role of Ca2+ influx.
  • Blocked Ran-mediated nuclear import using wheat germ agglutinin and T24N Ran mutant.
  • Inhibited nuclear export with leptomycin B.
  • Quantified levels of activated CREB (P-CREB) and c-fos.

Main Results:

  • PDGF-BB, membrane depolarization, and forskolin increased P-CREB and c-fos levels in VSMCs.
  • Nimodipine reduced P-CREB stimulated by depolarization but not by PDGF-BB or forskolin.
  • Inhibition of nuclear import reduced nuclear P-CREB for PDGF-BB and depolarization but enhanced it for forskolin.
  • Blocking nuclear import led to cytoplasmic P-CREB accumulation after depolarization.
  • Inhibition of nuclear export reduced P-CREB stimulation by depolarization and PDGF-BB.

Conclusions:

  • Ran GTPase differentially regulates PDGF-BB, Ca2+, and cAMP signaling to CREB in VSMCs.
  • Nuclear translocation of CREB is essential for its activation in response to various stimuli in VSMCs.
  • The interplay between nuclear import and export of P-CREB is a key determinant of CREB pathway activation in VSMCs.

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