Membrane depolarization mediates phosphorylation and nuclear translocation of CREB in vascular smooth muscle cells.
Diverse signals have the potential to modulate gene transcription through the Ca2+ and cAMP response element binding protein (CREB) in vascular smooth muscle cells (VSMCs). A key step in the transmission of these signals is import into the nucleus. Here, we provide evidence that the Ran GTPase, which regulates nuclear import, exerts different regulation over PDGF-BB, Ca2+, and cAMP signaling to CREB in VSMCs. PDGF-BB, membrane depolarization, and forskolin increased levels of activated CREB (P-CREB) and c-fos in VSMCs and intact aorta. The calcium channel antagonist nimodipine reduced the level of P-CREB stimulated by membrane depolarization, but not by PDGF-BB or forskolin. Block of Ran-mediated nuclear import, by wheat germ agglutinin or an inactivating Ran mutant (T24N Ran), significantly reduced nuclear P-CREB in response to PDGF-BB or membrane depolarization, but enhanced levels of P-CREB in response to forskolin. Contrary to expectation, block of nuclear import led to the appearance of P-CREB in the cytoplasm after depolarization. Furthermore, blocking nuclear export with leptomycin B reduced P-CREB stimulation by both depolarization and PDGF-BB. These results suggest that translocation of CREB between the nucleus and the cytoplasm provides an important role in CREB activating pathways in VSMCs.
Stevenson
A S
AS
Department of Pharmacology, University of Vermont, Burlington, Vermont 05405, USA.
Cartin
L
L
Wellman
T L
TL
Dick
M H
MH
Nelson
M T
MT
Lounsbury
K M
KM
D000199:Actins / Q000378:metabolism; D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000494:pharmacology; D005260:Female; D005434:Flow Cytometry; D016762:Genes, fos / Q000235:genetics; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000502:physiology*; D008845:Microinjections; D008954:Models, Biological; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009553:Nimodipine / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D051381:Rats; D015398:Signal Transduction; D014162:Transfection; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
D000199:Actins; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D017362:Cyclic AMP Response Element-Binding Protein; D010982:Platelet-Derived Growth Factor; D005576:Colforsin; D009553:Nimodipine; D017868:Cyclic AMP-Dependent Protein Kinases; D020931:ran GTP-Binding Protein; D002118:Calcium