JNK activation decreases PP2A regulatory subunit B56alpha expression and mRNA stability and increases AUF1 expression in cardiomyocytes.
A central feature of heart disease is a molecular remodeling of signaling pathways in cardiac myocytes. This study focused on novel molecular elements of MAPK-mediated alterations in the pattern of gene expression of the protein phosphatase 2A (PP2A). In an established model of sustained JNK activation, a 70% decrease in expression of the targeting subunit of PP2A, B56alpha, was observed in either neonatal or adult cardiomyocytes. This loss in protein abundance was accompanied by a decrease of 69% in B56alpha mRNA steady-state levels. Given that the 3'-untranslated region of this transcript contains adenylate-uridylate-rich elements known to regulate mRNA degradation, experiments explored the notion that instability of B56alpha mRNA accounts for the response. mRNA time-course analyses with real-time PCR methods showed that B56alpha transcript was transformed from a stable (no significant decay over 1 h) to a labile form that rapidly degraded within minutes. These results were supported by complementary experiments that revealed that the RNA-binding protein AUF1, known to destabilize target mRNA, was increased fourfold in JNK-activated cells. A variety of other stress-related stimuli, such as p38 MAPK activation and phorbol ester, upregulated AUF1 expression in cultured cardiac cells as well. In addition, gel mobility shift assays demonstrated that p37AUF1 binds with nanomolar affinity to segments of the B56alpha 3'-untranslated region. Thus these studies provide new evidence that signaling-induced mRNA instability is an important mechanism that underlies the changes in the pattern of gene expression evoked by stress-activated pathways in cardiac cells.
Glaser
Nicole D
ND
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108 N. Greene St., Baltimore, MD 21201, USA.
Lukyanenko
Yevgeniya O
YO
Wang
Yibin
Y
Wilson
Gerald M
GM
Rogers
Terry B
TB
D020413:3' Untranslated Regions / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D / Q000235:genetics / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D048688:MAP Kinase Kinase 7 / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D054648:Protein Phosphatase 2; D020871:RNA Stability / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
D020413:3' Untranslated Regions; C000630986:HNRNPD protein, human; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D; C000630988:Hnrnpd protein, rat; C000630987:Hnrpd protein, mouse; C432785:PPP2R1B protein, human; C086766:Ppp2r1b protein, mouse; D012333:RNA, Messenger; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048688:MAP Kinase Kinase 7; C482569:MAP2K7 protein, human; C513662:B56alpha protein, rat; D010749:Phosphoprotein Phosphatases; C522189:Ppp2r1b protein, rat; D054648:Protein Phosphatase 2