Sci. Signal., 22 January 2013
Making a Bigger HeartPathological cardiac hypertrophy can be fatal because it can cause congestive heart failure and arrhythmias. Glycogen synthase kinase-3 (GSK-3), which inhibits cardiac hypertrophy, is active when dephosphorylated by the protein phosphatase PP2A, the activity of which is stimulated by methylation mediated by the methyltransferase PPMT-1. Mohan et al. found that mice lacking the isoform of phosphoinositide 3-kinase (PI3K) had smaller hearts than wild-type mice and showed decreased phosphorylation of GSK-3. In addition, these mice showed increased activity of PP2A and PPMT-1. Biochemical experiments indicated that PI3K inhibited the interaction between PP2A and PPMT-1. Heart size and phosphorylation of GSK-3 were increased, and the association of PP2A with PPMT-1 was decreased in PI3K knockout mice by expression of a catalytically inactive form of PI3K. Thus, PI3K promotes cardiac hypertrophy by attenuating the PP2A–PPMT-1 interaction and the inactivation of GSK-3 in a kinase-independent manner.
Citation: M. L. Mohan, B. K. Jha, M. K. Gupta, N. T. Vasudevan, E. E. Martelli, J. D. Mosinski, S. V. Naga Prasad, Phosphoinositide 3-Kinase Inhibits Cardiac GSK-3 Independently of Akt. Sci. Signal. 6, ra4 (2013).
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