Inhibition of nuclear import of calcineurin prevents myocardial hypertrophy.
The time that transcription factors remain nuclear is a major determinant for transcriptional activity. It has recently been demonstrated that the phosphatase calcineurin is translocated to the nucleus with the transcription factor nuclear factor of activated T cells (NF-AT). This study identifies a nuclear localization sequence (NLS) and a nuclear export signal (NES) in the sequence of calcineurin. Furthermore we identified the nuclear cargo protein importinbeta(1) to be responsible for nuclear translocation of calcineurin. Inhibition of the calcineurin/importin interaction by a competitive peptide (KQECKIKYSERV), which mimicked the calcineurin NLS, prevented nuclear entry of calcineurin. A noninhibitory control peptide did not interfere with the calcineurin/importin binding. Using this approach, we were able to prevent the development of myocardial hypertrophy. In angiotensin II-stimulated cardiomyocytes, [(3)H]-leucine incorporation (159%+/-9 versus 111%+/-11; P<0.01) and cell size were suppressed significantly by the NLS peptide compared with a control peptide. The NLS peptide inhibited calcineurin/NF-AT transcriptional activity (227%+/-11 versus 133%+/-8; P<0.01), whereas calcineurin phosphatase activity was unaffected (298%+/-9 versus 270%+/-11; P=NS). We conclude that calcineurin is not only capable of dephosphorylating NF-AT, thus enabling its nuclear import, but the presence of calcineurin in the nucleus is also important for full NF-AT transcriptional activity.
Hallhuber
Matthias
M
Department of Medicine I, DFG-Research Center for Experimental Biomedicine, University of Wuerzburg, Germany.
Burkard
Natalie
N
Wu
Rongxue
R
Buch
Mamta H
MH
Engelhardt
Stefan
S
Hein
Lutz
L
Neyses
Ludwig
L
Schuh
Kai
K
Ritter
Oliver
O
D021581:Active Transport, Cell Nucleus / Q000187:drug effects*; D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D019703:Calcineurin / Q000378:metabolism*; D006332:Cardiomegaly / Q000517:prevention & control*; D049108:Cell Enlargement / Q000187:drug effects; D002478:Cells, Cultured; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000473:pathology*; D050778:NFATC Transcription Factors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D049790:Nuclear Export Signals; D019913:Nuclear Localization Signals / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D028961:beta Karyopherins / Q000378:metabolism / Q000502:physiology
D050778:NFATC Transcription Factors; D049790:Nuclear Export Signals; D019913:Nuclear Localization Signals; D010446:Peptide Fragments; D028961:beta Karyopherins; D019703:Calcineurin