Epidermal growth factor-mediated activation of the ETS domain transcription factor Elk-1 requires nuclear calcium.
Cytosolic and nuclear Ca(2+) have been shown to differentially regulate transcription. However, the impact of spatially distinct Ca(2+) signals on mitogen-activated protein kinase-mediated gene expression remains unknown. Here we investigated the role of nuclear and cytosolic Ca(2+) signals in epidermal growth factor (EGF)-induced transactivation of the ternary complex factor Elk-1 using a GAL4-Elk-1 construct. EGF increased Ca(2+) in both the nucleus and cytosol of HepG2 or 293 cells. Pretreatment with the intracellular Ca(2+) chelator bis(2-aminophenyl)ethyleneglycol-N,N,N',N'-tetraacetic acid significantly reduced EGF-induced transactivation of Elk-1, indicating that EGF-stimulated Elk-1 transcriptional activity is dependent on intracellular Ca(2+). To determine the relative contribution of nuclear and cytosolic Ca(2+) signals during EGF-mediated Elk-1 transactivation, Ca(2+) signals in either compartment were selectively impaired by targeted expression of the Ca(2+)-binding protein parvalbumin to either the nucleus or cytosol. Suppression of nuclear but not cytosolic Ca(2+) signals inhibited EGF-induced transactivation of Elk-1. However, suppression of nuclear Ca(2+) signals did not affect the ability of ERK either to become phosphorylated or to undergo translocation to the nucleus in response to EGF. Elk-1 phosphorylation and nuclear localization following EGF stimulation were also unaffected by suppressing nuclear Ca(2+) signals. These results suggest that nuclear Ca(2+) is required for EGF-mediated transcriptional activation of Elk-1 and that phosphorylation of Elk-1 alone is not sufficient to induce its transcriptional activation in response to EGF. Thus, subcellular targeting of parvalbumin reveals a distinct role for nuclear Ca(2+) signals in mitogen-activated protein kinase-mediated gene transcription.
Pusl
Thomas
T
Department of Medicine, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
Wu
Julie J
JJ
Zimmerman
Tracy L
TL
Zhang
Lei
L
Ehrlich
Barbara E
BE
Berchtold
Martin W
MW
Hoek
Joannes B
JB
Karpen
Saul J
SJ
Nathanson
Michael H
MH
Bennett
Anton M
AM
D021581:Active Transport, Cell Nucleus; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004268:DNA-Binding Proteins; D004815:Epidermal Growth Factor / Q000378:metabolism*; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D016297:Mutagenesis, Site-Directed; D010320:Parvalbumins / Q000378:metabolism; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D050807:ets-Domain Protein Elk-1
D004268:DNA-Binding Proteins; C494112:ELK1 protein, human; C494114:Elk1 protein, rat; D010320:Parvalbumins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D004815:Epidermal Growth Factor; D000255:Adenosine Triphosphate; D005982:Glutathione Transferase; D002118:Calcium