Nuclear targeting of Akt antagonizes aspects of cardiomyocyte hypertrophy.
The serine/threonine kinase Akt regulates cellular survival, proliferation, gene transcription, protein translation, metabolism, and differentiation. Although Akt substrates are found throughout the cell, activated Akt normally accumulates in the nucleus, suggesting that biologically relevant targets are located there. Consequences of nuclear Akt signaling in cardiomyocytes were explored by using nuclear-targeted Akt (Akt-nuc). Accumulation of Akt-nuc did not provoke hypertrophy, unlike constitutively activated Akt. Instead, Akt-nuc inhibited hypertrophy concurrent with increased atrial natriuretic peptide (ANP) expression that depended upon phosphatidylinositol-3 kinase activity. Akt-nuc antihypertrophic effects were blocked by inhibition of either guanylyl cyclase A receptor or cyclic guanosine monophosphate-dependent protein kinase in cultured cardiomyocytes. Corroborating evidence showed blunted acute hypertrophic remodeling in Akt-nuc transgenic mice after transverse aortic constriction coincident with higher ANP expression and smaller myocyte volume. In addition, Akt-nuc expression improved systolic function and survival in the chronic phase of transverse aortic constriction-induced hypertrophy. Thus, Akt-nuc antagonizes certain aspects of hypertrophy through autocrine/paracrine stimulation of a phosphatidylinositol-3 kinase-dependent signaling cascade that promotes ANP expression, resulting in a unique combination of prosurvival coupled with antihypertrophic signaling.
Tsujita
Yasuyuki
Y
San Diego State University Heart Institute, Department of Biology, CA 92182, USA.
Muraski
John
J
Shiraishi
Isao
I
Kato
Takahiro
T
Kajstura
Jan
J
Anversa
Piero
P
Sussman
Mark A
MA
D021581:Active Transport, Cell Nucleus; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D005786:Gene Expression Regulation; D006984:Hypertrophy / Q000473:pathology*; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D009206:Myocardium / Q000473:pathology; D032383:Myocytes, Cardiac / Q000473:pathology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics* / Q000378:metabolism*; D013599:Systole
D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt