c-Myb-dependent cell cycle progression and Ca2+ storage in cultured vascular smooth muscle cells.
Considerable controversy surrounds the role of the c-myb proto-oncogene in vascular smooth muscle cells (VSMCs). Previous investigations using antisense approaches have suggested a relationship between c-myb expression, cell cycle progression, and cytoplasmic Ca2+ concentration ([Ca2+]cyt). However, the ability of certain antisense oligonucleotides to bind and inactivate growth factors allows alternative explanations. To define more specifically the role of c-Myb in cultured VSMCs (SVE and A10 cell lines), we have generated stable cell clones expressing a dominant-negative c-Myb lacking critical elements of the DNA binding domain (delta5-SVE) and transiently transfected cell populations (GRE-MEn-SVE and GRE-MEn-A10) expressing a glucocorticoid-inducible chimeric protein that targets the Drosophila Engrailed repressor domain to c-Myb-responsive promoters. The delta5-SVE clones and GRE-MEn cell populations exhibit a 60% reduction in mean intracellular c-Myb activity, as measured by cotransfection assays with a c-Myb-responsive reporter, a 42% decrease in the mean S phase entry of growth-arrested (G[0]) cells after serum stimulation, and a 36% inhibition of mean cell proliferation over 4 days. These cells also display 28% (34-nmol/L) and 30% (42-nmol/L) reductions in mean [Ca2+]cyt at G(0) and at the G1/S interface, respectively, as well as significant reductions in the peak [Ca2+]cyt responses to thapsigargin (5 micromol/L) and caffeine (10 mmol/L). These latter reductions in operationally defined Ca2+ pools were observed both at different stages of the cell cycle and after transient induction of the dominant-interfering construct, suggesting that c-Myb regulates these releasable Ca2+ stores independent of its effects on cell cycle progression.
Husain
M
M
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
Bein
K
K
Jiang
L
L
Alper
S L
SL
Simons
M
M
Rosenberg
R D
RD
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002453:Cell Cycle; D002455:Cell Division; D002460:Cell Line; D003587:Cytomegalovirus / Q000235:genetics; D003593:Cytoplasm / Q000378:metabolism; D003627:Data Interpretation, Statistical; D004330:Drosophila / Q000235:genetics; D016257:Fura-2 / Q000494:pharmacology; D005786:Gene Expression Regulation; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011519:Proto-Oncogenes / Q000235:genetics / Q000502:physiology*; D051381:Rats; D013997:Time Factors; D014162:Transfection
D002118:Calcium; D016257:Fura-2