FRINK Linked Data Fragments server

Matches in SemOpenAlex for { <https://semopenalex.org/work/W2050318957> ?p ?o ?g. }

• W2050318957 endingPage "9647" @default.
• W2050318957 startingPage "9643" @default.
• W2050318957 abstract "Intensive study over the past 30 years has helped define the role of the GSK-3 (glycogen synthase kinase-3) family in a variety of physiological and pathophysiological processes. However, the majority of these studies have relied upon overexpression approaches or nonselective small molecule inhibitors. Herein, we examine recent data derived from studies in gene-targeted embryonic stem cells and knock-out mice in an attempt to define the role these protein kinases play in critical decisions made by stem/progenitor cells and by early lineage-committed cardiomyocytes during development. Intensive study over the past 30 years has helped define the role of the GSK-3 (glycogen synthase kinase-3) family in a variety of physiological and pathophysiological processes. However, the majority of these studies have relied upon overexpression approaches or nonselective small molecule inhibitors. Herein, we examine recent data derived from studies in gene-targeted embryonic stem cells and knock-out mice in an attempt to define the role these protein kinases play in critical decisions made by stem/progenitor cells and by early lineage-committed cardiomyocytes during development. The GSK-3 family of serine/threonine kinases was first identified as a negative regulator of glycogen synthase, the rate-limiting enzyme in glycogen synthesis (1Doble B.W. Woodgett J.R. J. Cell Sci. 2003; 116: 1175-1186Crossref PubMed Scopus (1744) Google Scholar, 2Frame S. Cohen P. Biochem. J. 2001; 359: 1-16Crossref PubMed Scopus (1266) Google Scholar). The family consists of two isoforms, α and β, which are 98% identical within their kinase domains but differ substantially in their N- and C-terminal sequences. Unlike most protein kinases, GSK-3 is typically active in unstimulated cells and is inhibited in response to a variety of inputs, including growth factors. Because GSK-3-mediated phosphorylation of substrates usually leads to inhibition of those substrates, the end result of growth factor-mediated inhibition of GSK-3 is typically functional activation of its downstream substrates.Traditionally, most attention has focused on the β-isoform of GSK-3. However, this bias appears to have arisen from two reports suggesting that mammalian GSK-3β was more effective than GSK-3α in rescuing Wnt/wingless pathway defects due to the Zeste-white 3 (GSK-3) mutation in Drosophila (3Ruel L. Bourouis M. Heitzler P. Pantesco V. Simpson P. Nature. 1993; 362: 557-560Crossref PubMed Scopus (164) Google Scholar, 4Siegfried E. Chou T.B. Perrimon N. Cell. 1992; 71: 1167-1179Abstract Full Text PDF PubMed Scopus (341) Google Scholar). However, in these studies, the level of expression of GSK-3α and GSK-3β was not equalized. Indeed, as we will discuss below, GSK-3α and GSK-3β appear to be entirely redundant in terms of regulating Wnt/β-catenin signaling.Based on studies in isoform-specific knock-outs, both isoforms appear to play key (but not entirely overlapping) roles in metabolism. GSK-3α KO 2The abbreviations used are: KO, knock-out; ES, embryonic stem; BIO, 6-bromoindirubin-3′-oxime; LIF, leukemia inhibitory factor; BMP, bone morphogenetic protein; ERK, extracellular signal-regulated kinase; EBs, embryoid bodies; DKO, double knock-out; WT, wild-type; PI3K, phosphatidylinositol 3-kinase; PKB, protein kinase B. mice demonstrate reduced fat mass with enhanced glucose tolerance and insulin sensitivity due, at least in part, to enhanced glycogen storage in the liver (5MacAulay K. Doble B.W. Patel S. Hansotia T. Sinclair E.M. Drucker D.J. Nagy A. Woodgett J.R. Cell Metab. 2007; 6: 329-337Abstract Full Text Full Text PDF PubMed Scopus (229) Google Scholar). Mice totally lacking GSK-3β die late in development (6Hoeflich K. Luo J. Rubie E.A. Tsao M.S. Jin O. Woodgett J.R. Nature. 2000; 406: 86-90Crossref PubMed Scopus (1208) Google Scholar, 7Kerkela R. Kockeritz L. MaCauly K. Zhou J. Doble B. Beahm C. Greytack S. Woulfe K. Trivedi C. Woodgett J.W. Epstein J.A. Force T. Huggins G.S. J. Clin. Investig. 2008; 118: 3609-3618Crossref PubMed Scopus (182) Google Scholar), but tissue-specific knock-outs of GSK-3β have revealed metabolic phenotypes in muscle (but not liver), including enhanced insulin-stimulated glycogen synthase activation and glycogen deposition (8Patel S. Doble B.W. MacAulay K. Sinclair E.M. Drucker D.J. Woodgett J.R. Mol. Cell. Biol. 2008; 28: 6314-6328Crossref PubMed Scopus (194) Google Scholar). Moreover, inactivation of GSK-3β in just the β-cells of the pancreatic islets is sufficient to rescue insulin resistance and largely prevent the manifestations of diabetes in two different models of the disease in mice: haploinsufficiency of the insulin receptor and deletion of IRS2 (9Tanabe K. Liu Z. Patel S. Doble B.W. Li L. Cras-Meneur C. Martinez S.C. Welling C.M. White M.F. Bernal-Mizrachi E. Woodgett J.R. Permutt M.A. PLoS Biol. 2008; 6: e37Crossref PubMed Scopus (93) Google Scholar). The pancreatic β-cell knock-outs also demonstrate preservation of β-islet cells due to enhanced proliferation and reduced apoptosis of these critical insulin-secreting cells (9Tanabe K. Liu Z. Patel S. Doble B.W. Li L. Cras-Meneur C. Martinez S.C. Welling C.M. White M.F. Bernal-Mizrachi E. Woodgett J.R. Permutt M.A. PLoS Biol. 2008; 6: e37Crossref PubMed Scopus (93) Google Scholar). Although we will not be focusing on metabolism in this review, as we go forward to discuss ES cell and cardiomyocyte phenotypes secondary to deletion of the isoforms, it is important to bear in mind that some part of the phenotypes observed may be driven by alterations in metabolic status in ES cells, cardiomyocytes, or other tissues.Studies over the past few years have also implicated GSK-3 as a critical regulator of ES cell differentiation in vitro (10Cartwright P. McLean C. Sheppard A. Rivett D. Jones K. Dalton S. Development (Camb.). 2005; 132: 885-896Crossref PubMed Scopus (584) Google Scholar, 11Chou Y.F. Chen H.H. Eijpe M. Yabuuchi A. Chenoweth J.G. Tesar P. Lu J. McKay R.D. Geijsen N. Cell. 2008; 135: 449-461Abstract Full Text Full Text PDF PubMed Scopus (182) Google Scholar, 12Sato N. Meijer L. Skaltsounis L. Greengard P. Brivanlou A.H. Nat. Med. 2004; 10: 55-63Crossref PubMed Scopus (1714) Google Scholar, 13Silva J. Smith A. Cell. 2008; 132: 532-536Abstract Full Text Full Text PDF PubMed Scopus (359) Google Scholar, 14Ying Q.L. Wray J. Nichols J. Batlle-Morera L. Doble B. Woodgett J. Cohen P. Smith A. Nature. 2008; 453: 519-523Crossref PubMed Scopus (2490) Google Scholar). However, these studies typically have utilized the small molecule inhibitor BIO, which is not entirely selective for GSK-3 and cannot differentiate isoform-specific effects. More recently, three studies have employed ES cells deleted for GSK-3α, GSK-3β, or both, and findings from these studies clearly support a role for the GSK-3 isoforms in ES cell differentiation, including a central role for GSK-3β in regulating differentiation into the cardiomyocyte lineage (7Kerkela R. Kockeritz L. MaCauly K. Zhou J. Doble B. Beahm C. Greytack S. Woulfe K. Trivedi C. Woodgett J.W. Epstein J.A. Force T. Huggins G.S. J. Clin. Investig. 2008; 118: 3609-3618Crossref PubMed Scopus (182) Google Scholar, 14Ying Q.L. Wray J. Nichols J. Batlle-Morera L. Doble B. Woodgett J. Cohen P. Smith A. Nature. 2008; 453: 519-523Crossref PubMed Scopus (2490) Google Scholar, 15Doble B.W. Patel S. Wood G.A. Kockeritz L.K. Woodgett J.R. Dev. Cell. 2007; 12: 957-971Abstract Full Text Full Text PDF PubMed Scopus (372) Google Scholar). Indeed, the embryonic lethality seen with deletion of GSK-3β is due to unrestrained proliferation of early committed cardiomyocyte precursors or cardiomyoblasts, which, unlike more fully differentiated cells, retain the capacity to proliferate. Thus, the hyperproliferation is due, in part, to the failure of these cells to adequately differentiate. Herein, we will examine how findings in ES cells in vitro inform us as to mechanisms underlying the findings in the developing heart in vivo.GSK-3β Promotes ES Cell Differentiation into a Cardiomyocyte Lineage via Wnt/β-Catenin-independent MechanismsThe concept that GSK-3 isoforms might drive stem cell differentiation was first suggested by Sato et al. (12Sato N. Meijer L. Skaltsounis L. Greengard P. Brivanlou A.H. Nat. Med. 2004; 10: 55-63Crossref PubMed Scopus (1714) Google Scholar), who demonstrated that BIO maintained pluripotency of both human and mouse ES cells, leading the authors to propose a possible use for GSK-3 inhibition in regenerative medicine. Of note, the effects of BIO and other GSK-3 inhibitors on ES cells have generally been believed to be mediated by activation of the canonical Wnt/β-catenin pathway, rather than via effects on the activity of other GSK-3 targets. However, based on our studies in ES cells derived from embryos deleted for GSK-3α, GSK-3β, or both and on studies in the developing heart, it is clear that Wnt/β-catenin-independent effects are critically important as well (see below) (7Kerkela R. Kockeritz L. MaCauly K. Zhou J. Doble B. Beahm C. Greytack S. Woulfe K. Trivedi C. Woodgett J.W. Epstein J.A. Force T. Huggins G.S. J. Clin. Investig. 2008; 118: 3609-3618Crossref PubMed Scopus (182) Google Scholar, 15Doble B.W. Patel S. Wood G.A. Kockeritz L.K. Woodgett J.R. Dev. Cell. 2007; 12: 957-971Abstract Full Text Full Text PDF PubMed Scopus (372) Google Scholar).Studies on the factors regulating ES cell self-renewal and pluripotency have typically employed empiric formulations of growth media. For example, mouse ES cell self-renewal is sustained by culturing cells in medium containing LIF (a cytokine of the interleukin-6 family that acts via JAK/STAT3 and probably c-Myc) and BMP, acting via Smad proteins and Id (inhibitors of differentiation) proteins (Fig. 1) (Ref. 10Cartwright P. McLean C. Sheppard A. Rivett D. Jones K. Dalton S. Development (Camb.). 2005; 132: 885-896Crossref PubMed Scopus (584) Google Scholar and reviewed in Refs. 13Silva J. Smith A. Cell. 2008; 132: 532-536Abstract Full Text Full Text PDF PubMed Scopus (359) Google Scholar and 16Niwa H. Development (Camb.). 2007; 134: 635-646Crossref PubMed Scopus (653) Google Scholar). Recently, the inductive signal in mouse ES cells leading to lineage commitment that is inhibited by LIF and BMP has been reported to be triggered by FGF4/fibroblast growth factor receptor-mediated activation of the ERK pathway (17Kunath T. Saba-El-Leil M.K. Almousailleakh M. Wray J. Meloche S. Smith A. Development (Camb.). 2007; 134: 2895-2902Crossref PubMed Scopus (586) Google Scholar, 18Stavridis M.P. Lunn J.S. Collins B.J. Storey K.G. Development (Camb.). 2007; 134: 2889-2894Crossref PubMed Scopus (229) Google Scholar).Not surprisingly, there has been intense interest in defining the components of the so-called “ground state” of ES cell self-renewal, including the signaling pathways that can maintain self-renewal in the absence of exogenous factors such as LIF and BMP (11Chou Y.F. Chen H.H. Eijpe M. Yabuuchi A. Chenoweth J.G. Tesar P. Lu J. McKay R.D. Geijsen N. Cell. 2008; 135: 449-461Abstract Full Text Full Text PDF PubMed Scopus (182) Google Scholar, 13Silva J. Smith A. Cell. 2008; 132: 532-536Abstract Full Text Full Text PDF PubMed Scopus (359) Google Scholar, 14Ying Q.L. Wray J. Nichols J. Batlle-Morera L. Doble B. Woodgett J. Cohen P. Smith A. Nature. 2008; 453: 519-523Crossref PubMed Scopus (2490) Google Scholar). Ying et al. (14Ying Q.L. Wray J. Nichols J. Batlle-Morera L. Doble B. Woodgett J. Cohen P. Smith A. Nature. 2008; 453: 519-523Crossref PubMed Scopus (2490) Google Scholar) recently employed small molecule ATP-competitive kinase inhibitors to define this ground state in mouse ES cells. They utilized inhibitors of the fibroblast growth factor receptor (SU5402), ERKs (PD184352), and a more selective inhibitor of GSK-3 than BIO (CHIR99021) to demonstrate maintenance of self-renewal and pluripotency in the absence of exogenous factors. The contribution of inhibition of GSK-3 activity to maintaining self-renewal was felt to be important when ERK signaling was suppressed by signals transduced by LIF or BMP or by the small molecule inhibitors. Thus, Ying et al. (14Ying Q.L. Wray J. Nichols J. Batlle-Morera L. Doble B. Woodgett J. Cohen P. Smith A. Nature. 2008; 453: 519-523Crossref PubMed Scopus (2490) Google Scholar) proposed that the primary consequence of reduced GSK-3 activity is to maintain ES cell viability and growth capacity in the setting of persistent inhibition of the cytoprotective ERK pathway by SU5402 and PD184352 (or LIF/BMP) by what they termed “global modulation of the ES cell metabolomic and biosynthetic capacity” (Fig. 1).Upon examining pluripotent stem cells derived from blastocysts, Chou et al. (11Chou Y.F. Chen H.H. Eijpe M. Yabuuchi A. Chenoweth J.G. Tesar P. Lu J. McKay R.D. Geijsen N. Cell. 2008; 135: 449-461Abstract Full Text Full Text PDF PubMed Scopus (182) Google Scholar) have challenged the concept of a common ground state. Rather, they proposed that both developmental and environmental (i.e. growth factors) inputs remain central to pluripotency. However, inhibition of GSK-3 (via BIO) is still required.Because these studies have predominantly employed pharmacologic inhibitors of GSK-3, isoform-specific effects, if any, could not be discerned. To address this limitation, we examined the role of individual GSK-3 isoforms in regulating differentiation of ES cells, specifically focusing on differentiation of ES cells into the cardiomyocyte lineage, an obvious critical step in heart formation during embryogenesis. We studied EBs derived from ES cells deleted for both alleles of either GSK-3α or GSK-3β or all four GSK-3 alleles (DKO) (7Kerkela R. Kockeritz L. MaCauly K. Zhou J. Doble B. Beahm C. Greytack S. Woulfe K. Trivedi C. Woodgett J.W. Epstein J.A. Force T. Huggins G.S. J. Clin. Investig. 2008; 118: 3609-3618Crossref PubMed Scopus (182) Google Scholar, 15Doble B.W. Patel S. Wood G.A. Kockeritz L.K. Woodgett J.R. Dev. Cell. 2007; 12: 957-971Abstract Full Text Full Text PDF PubMed Scopus (372) Google Scholar).DKO EBs were markedly impaired in their ability to differentiate and retained large numbers of cells that were Oct4- and Nanog-positive (markers of pluripotency in mouse ES cells) even in the absence of LIF in the culture medium. In contrast, Oct4 and Nanog levels in WT EBs were an order of magnitude lower than in DKO EBs. Furthermore, teratomas derived from DKO ES cells were highly undifferentiated with a carcinomatous appearance. Neuronal tissue was completely absent. DKO EBs also failed to produce any contracting cardiomyocytes, whereas >80% of WT EBs developed regions of spontaneously contracting cardiomyocytes. This failure of DKO EBs to differentiate into cardiomyocytes was partially rescued by lentivirus-mediated gene transfer of wild-type GSK-3α or GSK-3β but not by kinase-inactive mutants of GSK-3.The failure of DKO ES cells to differentiate into the cardiomyocyte lineage is consistent with the previously proposed concept of the role of Wnt/β-catenin signaling in cardiomyocyte differentiation, i.e. inhibition of Wnt/β-catenin signaling is necessary for cardiomyocyte specification (19Eisenberg L.M. Eisenberg C.A. Dev. Biol. 2006; 293: 305-315Crossref PubMed Scopus (91) Google Scholar, 20Naito A.T. Shiojima I. Akazawa H. Hidaka K. Morisaki T. Kikuchi A. Komuro I. Proc. Natl. Acad. Sci. U. S. A. 2006; 103: 19812-19817Crossref PubMed Scopus (372) Google Scholar, 21Ueno S. Weidinger G. Osugi T. Kohn A.D. Golob J.L. Pabon L. Reinecke H. Moon R.T. Murry C.E. Proc. Natl. Acad. Sci. U. S. A. 2007; 104: 9685-9690Crossref PubMed Scopus (463) Google Scholar). In the DKO, β-catenin levels were markedly increased, as was activation of a reporter construct (TOP-Flash) regulated by β-catenin (15Doble B.W. Patel S. Wood G.A. Kockeritz L.K. Woodgett J.R. Dev. Cell. 2007; 12: 957-971Abstract Full Text Full Text PDF PubMed Scopus (372) Google Scholar). Indeed, based on the lack of neuronal and cardiomyocyte tissue and on the maintenance of pluripotency markers under differentiation conditions, it seems likely that the dominant effect in the DKO cells is dysregulation of Wnt signaling.Strikingly, in ES cells engineered to lack GSK-3α or GSK-3β but not both, no stabilization of β-catenin occurred, and induction of β-catenin/Tcf-responsive genes was not observed. There was only a minor increase in β-catenin in ES cells lacking both alleles of GSK-3α and one of GSK-3β (15Doble B.W. Patel S. Wood G.A. Kockeritz L.K. Woodgett J.R. Dev. Cell. 2007; 12: 957-971Abstract Full Text Full Text PDF PubMed Scopus (372) Google Scholar). These data indicate that the two isoforms are not independently rate-limiting in the Wnt pathway and are entirely redundant. Indeed, the limiting factor in this pathway is likely Axin, which does not discriminate between binding of the two isoforms and is present at significantly lower concentrations than either. Deletion of all four GSK-3 alleles in either ES cells or mouse embryo fibroblasts results in massive up-regulation of β-catenin, as is found in tumor cells that either lack adenomatous polyposis coli or harbor phosphorylation site mutations in β-catenin (reviewed in Ref. 22Polakis P. Curr. Opin. Genet. Dev. 2007; 17: 45-51Crossref PubMed Scopus (746) Google Scholar). In these situations, resulting phenotypes are likely dominated by the deregulation of β-catenin, although the Hedgehog, Notch, and other pathways are similarly derepressed.Studies in the GSK-3α KO and GSK-3β KO ES cells provided the first opportunity to date to identify Wnt/β-catenin-independent effects of GSK-3 isoforms in the regulation of differentiation of ES cells, including differentiation into the cardiomyocyte lineage. Notably, whereas the percent of GSK-3α KO EBs with regions of actively contracting cardiomyocytes was comparable with that of WT EBs, the percent of GSK-3β KO EBs with contracting regions was markedly reduced (7Kerkela R. Kockeritz L. MaCauly K. Zhou J. Doble B. Beahm C. Greytack S. Woulfe K. Trivedi C. Woodgett J.W. Epstein J.A. Force T. Huggins G.S. J. Clin. Investig. 2008; 118: 3609-3618Crossref PubMed Scopus (182) Google Scholar). These findings indicate that GSK-3β promotes cardiomyocyte differentiation via Wnt/β-catenin-independent mechanisms. These results, which were supported by studies examining expression of markers of “stemness” and of cardiomyocyte differentiation, suggest a critical role for GSK-3β, particularly in the later stages of differentiation of cardiomyocytes when they begin to express contractile proteins, natriuretic peptides, and calcium-handling proteins (7Kerkela R. Kockeritz L. MaCauly K. Zhou J. Doble B. Beahm C. Greytack S. Woulfe K. Trivedi C. Woodgett J.W. Epstein J.A. Force T. Huggins G.S. J. Clin. Investig. 2008; 118: 3609-3618Crossref PubMed Scopus (182) Google Scholar).How might the KO of GSK-3β block differentiation if not via effects on Wnt signaling? Although GSK-3β has a host of targets, one candidate regulator of proliferation versus differentiation is c-Myc, which is up-regulated in response to LIF-mediated induction of STAT3 (10Cartwright P. McLean C. Sheppard A. Rivett D. Jones K. Dalton S. Development (Camb.). 2005; 132: 885-896Crossref PubMed Scopus (584) Google Scholar). Phosphorylation of Myc at Thr58 by GSK-3β destabilizes c-Myc, leading to its degradation (23Gregory M.A. Qi Y. Hann S.R. J. Biol. Chem. 2003; 278: 51606-51612Abstract Full Text Full Text PDF PubMed Scopus (324) Google Scholar). This phosphorylation event has been reported to promote ES cell differentiation, and a T58A mutation, preventing phosphorylation and degradation, maintained pluripotency, even in the absence of LIF (10Cartwright P. McLean C. Sheppard A. Rivett D. Jones K. Dalton S. Development (Camb.). 2005; 132: 885-896Crossref PubMed Scopus (584) Google Scholar, 16Niwa H. Development (Camb.). 2007; 134: 635-646Crossref PubMed Scopus (653) Google Scholar). In WT ES cells, PI3K likely mediates inhibition of GSK-3 (and stabilization of c-Myc) via activation of PKB/Akt and inhibitory phosphorylation of Ser9 (GSK-3β) and Ser21 (GSK-3α), thereby maintaining self-renewal and pluripotency (10Cartwright P. McLean C. Sheppard A. Rivett D. Jones K. Dalton S. Development (Camb.). 2005; 132: 885-896Crossref PubMed Scopus (584) Google Scholar, 24Watanabe S. Umehara H. Murayama K. Okabe M. Kimura T. Nakano T. Oncogene. 2006; 25: 2697-2707Crossref PubMed Scopus (272) Google Scholar, 25Paling N.R. Wheadon H. Bone H.K. Welham M.J. J. Biol. Chem. 2004; 279: 48063-48070Abstract Full Text Full Text PDF PubMed Scopus (340) Google Scholar, 26Storm M.P. Bone H.K. Beck C.G. Bourillot P.Y. Schreiber V. Damiano T. Nelson A. Savatier P. Welham M.J. J. Biol. Chem. 2007; 282: 6265-6273Abstract Full Text Full Text PDF PubMed Scopus (108) Google Scholar). More recently, virus- or plasmid-mediated transduction of c-Myc was reported to be a key component of a “mixture” of genes encoding the transcription factors Oct4, Sox2, and Klf4 that allowed the creation of induced pluripotent stem cells derived from fibroblasts (27Okita K. Nakagawa M. Hyenjong H. Ichisaka T. Yamanaka S. Science. 2008; 322: 949-953Crossref PubMed Scopus (1587) Google Scholar, 28Stadtfeld M. Nagaya M. Utikal J. Weir G. Hochedlinger K. Science. 2008; 322: 945-949Crossref PubMed Scopus (1321) Google Scholar). All of these findings are consistent with the concept of c-Myc being a key driver of proliferation of ES cells that, as a result, restricts the ability of the ES cells to differentiate (13Silva J. Smith A. Cell. 2008; 132: 532-536Abstract Full Text Full Text PDF PubMed Scopus (359) Google Scholar).GSK-3β Regulates Cardiomyoblast Proliferation and Differentiation in VivoDo findings in KO EBs translate into cardiac developmental abnormalities in vivo? GSK-3α KO mice develop normally with no cardiac abnormalities noted at up to 8 weeks of age. In contrast, Hoeflich et al. (6Hoeflich K. Luo J. Rubie E.A. Tsao M.S. Jin O. Woodgett J.R. Nature. 2000; 406: 86-90Crossref PubMed Scopus (1208) Google Scholar) previously reported that targeted deletion of GSK-3β leads to embryonic lethality in a substantial number of embryos secondary to marked hepatic apoptosis. This is due to the failure to recruit cytoprotective NF-κB signaling in response to tumor necrosis factor-α. However, this phenotype appears to require exposure of the mothers to pathogens that trigger production of tumor necrosis factor-α, which then leads to the death of the embryos. In the absence of pathogen exposure, the great majority of GSK-3β KO embryos survive to late gestation and then die just before or at birth. Examination of the hearts of these embryos revealed normal valve development, endocardial cushion morphology, and neural crest function, suggesting complete or near-complete compensation by GSK-3α for loss of GSK-3β as regards these critical functions. Strikingly, however, both the left and right ventricles were packed with myocytes, with little or no apparent cavity, a phenotype that can be expected to lead to inadequate output of blood from the heart, resulting in heart failure and death (7Kerkela R. Kockeritz L. MaCauly K. Zhou J. Doble B. Beahm C. Greytack S. Woulfe K. Trivedi C. Woodgett J.W. Epstein J.A. Force T. Huggins G.S. J. Clin. Investig. 2008; 118: 3609-3618Crossref PubMed Scopus (182) Google Scholar).This phenotype was traced to hyperproliferation of cardiomyoblasts in GSK-3β KO embryos. Thus, the inability of GSK-3β KO cardiomyoblasts to fully differentiate appears to allow continued proliferation, leading to a hypertrophic myopathy. This conclusion is consistent with the finding that GSK-3β KO EBs appear to be markedly larger than WT or GSK-3α EBs and have significantly greater mRNA content.However, the hyperproliferation does not seem to be due solely to a failure to differentiate because GSK-3 also has multiple targets that are regulators of cell cycle progression. Indeed, further analysis implicated dysregulation of at least three of these targets (GATA4, D-type cyclins, and Myc family members) as responsible, at least in part, for the hyperproliferative phenotype (Fig. 2). All of these had previously been implicated in regulating cardiomyocyte proliferation during development because deletion of these was associated with thin-walled hearts, which was believed to be secondary to hypoproliferation (29Kozar K. Ciemerych M.A. Rebel V.I. Shigematsu H. Zagozdzon A. Sicinska E. Geng Y. Yu Q. Bhattacharya S. Bronson R.T. Akashi K. Sicinski P. Cell. 2004; 118: 477-491Abstract Full Text Full Text PDF PubMed Scopus (539) Google Scholar, 30Moens C.B. Stanton B.R. Parada L.F. Rossant J. Development (Camb.). 1993; 119: 485-499PubMed Google Scholar, 31Zeisberg E.M. Ma Q. Jurasek A.L. Moses K. Schwartz R.J. Izumo S. Pu W.T. J. Clin. Investig. 2005; 115: 1522-1531Crossref PubMed Scopus (203) Google Scholar). Furthermore, although debate remains (32Yang K. Guo Y. Stacey W.C. Harwalkar J. Fretthold J. Hitomi M. Stacey D.W. BMC Cell Biol. 2006; 7: 33Crossref PubMed Scopus (45) Google Scholar), all had also been proposed to be regulated by GSK-3 based on studies in various types of cultured cells (33Diehl J.A. Cheng M. Roussel M.F. Sherr C.J. Genes Dev. 1998; 12: 3499-3511Crossref PubMed Scopus (1851) Google Scholar, 34Guo Y. Yang K. Harwalkar J. Nye J.M. Mason D.R. Garrett M.D. Hitomi M. Stacey D.W. Oncogene. 2005; 24: 2599-2612Crossref PubMed Scopus (71) Google Scholar, 35Sears R. Nuckolls F. Haura E. Taya Y. Tamai K. Nevins J.R. Genes Dev. 2000; 14: 2502-2514Crossref Scopus (939) Google Scholar). Our studies support the contention that these are bona fide targets in the heart in vivo. Indeed, it appears that reduced signaling through GSK-3β may connect the several growth factors and their receptors at the cell membrane that are known to drive cardiomyoblast proliferation in the developing heart to the transcription factors and cell cycle regulators that transduce the proliferative signals in the nucleus (Fig. 2).FIGURE 2Regulation of cardiomyoblast proliferation/differentiation in the developing heart. Several growth factors, including Nrg1, insulin-like growth factor 1 (IGF-1), retinoic acid, fibroblast growth factors (FGFs), and BMP10, acting through their cognate receptors, regulate cardiomyoblast proliferation in the developing heart (reviewed in Ref. 42Smith T.K. Bader D.M. Semin. Cell Dev. Biol. 2007; 18: 84-89Crossref PubMed Scopus (50) Google Scholar). Inhibition of GSK-3β, likely mediated via activation of PI3K and PKB/Akt, appears to be critical to the proliferative response. GSK-3β negatively regulates a number of factors, including transcription factors and cell cycle regulators, via ubiquitination and degradation (Ub/Deg) and/or or nuclear (Nuc) export. Thus, inhibition of GSK-3β appears to connect signaling at the cardiomyoblast membrane to nuclear events driving proliferation. Loss of the negative input contributed by GSK-3β leads to the near obliteration of the left and right ventricle cavities, heart failure, and embryonic death. GSK-3α appears to be able to compensate in the developing heart for loss of GSK-3β as regards regulation of NF-AT (nuclear factor of activated T cells) family members and β-catenin, as evidenced by the normal valve development in the GSK-3β KO (7Kerkela R. Kockeritz L. MaCauly K. Zhou J. Doble B. Beahm C. Greytack S. Woulfe K. Trivedi C. Woodgett J.W. Epstein J.A. Force T. Huggins G.S. J. Clin. Investig. 2008; 118: 3609-3618Crossref PubMed Scopus (182) Google Scholar). It is not clear why GSK-3α and GSK-3β can compensate for loss of the other isoform in some cells and tissues but not in others. This tissue-specific dominant effect is not simply due to relative levels of expression because, as noted above, GSK-3α primarily regulates glycogen storage in the liver, whereas GSK-3β primarily regulates this in skeletal muscle, yet expression levels of the isoforms are comparable in the two tissues. Other possibilities include tissue-specific scaffolds that facilitate binding of one versus the other isoform to specific targets.View Large Image Figure ViewerDownload Hi-res image Download (PPT)These studies thus confirmed a central role for GSK-3β in the negative regulation of cardiomyocyte proliferation in vivo and demonstrated that GSK-3α cannot compensate for loss of GSK-3β with regard to this function. That this role of GSK-3β in regulating cell proliferation is not restricted to cardiomyocytes is illustrated by the fact that pharmacologic inhibition of GSK-3 has been reported to enhance repopulation of the bone marrow by hematopoietic stem cells (36Trowbridge J.J. Xenocostas A. Moon R.T. Bhatia M. Nat. Med. 2006; 12: 89-98Crossref PubMed Scopus (224) Google Scholar), although Wnt signaling was believed to be primarily responsible for this. In contrast and consistent with the studies in KO EBs, we saw no evidence of increased activation of canonical Wnt signaling in the developing heart (6Hoeflich K. Luo J. Rubie E.A. Tsao M.S. Jin O. Woodgett J.R. Nature. 2000; 406: 86-90Crossref PubMed Scopus (1208) Google Scholar, 7Kerkela R. Kockeritz L. MaCauly K. Zhou J. Doble B. Beahm C. Greytack S. Woulfe K. Trivedi C. Woodgett J.W. Epstein J.A. Force T. Huggins G.S. J. Clin. Investig. 2008; 118: 3609-3618Crossref PubMed Scopus (182) Google Scholar), again suggesting a specific role of GSK-3β in regulating proliferation that is independent of Wnt/β-catenin signaling. Thus, KO of GSK-3β inhibits differentiation, thereby allowing continued proliferation, but proliferation also appears to be directly driven by dysregulation of cell cycle regulators and transcription factors due to the lack of GSK-3β inhibitory inputs. In summary, GSK-3β is necessary for maintaini" @default.
• W2050318957 created "2016-06-24" @default.
• W2050318957 creator A5017332459 @default.
• W2050318957 creator A5043927370 @default.
• W2050318957 date "2009-04-01" @default.
• W2050318957 modified "2023-09-30" @default.
• W2050318957 title "Unique and Overlapping Functions of GSK-3 Isoforms in Cell Differentiation and Proliferation and Cardiovascular Development" @default.
• W2050318957 cites W1841872780 @default.
• W2050318957 cites W1972343960 @default.
• W2050318957 cites W1974986171 @default.
• W2050318957 cites W1980220309 @default.
• W2050318957 cites W1986876732 @default.
• W2050318957 cites W1990568577 @default.
• W2050318957 cites W1991323262 @default.
• W2050318957 cites W2000246164 @default.
• W2050318957 cites W2006743934 @default.
• W2050318957 cites W2014222652 @default.
• W2050318957 cites W2018765068 @default.
• W2050318957 cites W2020330574 @default.
• W2050318957 cites W2020965347 @default.
• W2050318957 cites W2027304196 @default.
• W2050318957 cites W2032570745 @default.
• W2050318957 cites W2039873727 @default.
• W2050318957 cites W2043474049 @default.
• W2050318957 cites W2050689355 @default.
• W2050318957 cites W2058106363 @default.
• W2050318957 cites W2058521801 @default.
• W2050318957 cites W2059772934 @default.
• W2050318957 cites W2065746091 @default.
• W2050318957 cites W2073304650 @default.
• W2050318957 cites W2075469935 @default.
• W2050318957 cites W2077517942 @default.
• W2050318957 cites W2078368358 @default.
• W2050318957 cites W2083308747 @default.
• W2050318957 cites W2085897342 @default.
• W2050318957 cites W2089426706 @default.
• W2050318957 cites W2099140108 @default.
• W2050318957 cites W2102908737 @default.
• W2050318957 cites W2106119346 @default.
• W2050318957 cites W2108958930 @default.
• W2050318957 cites W2117793740 @default.
• W2050318957 cites W2119584760 @default.
• W2050318957 cites W2128282944 @default.
• W2050318957 cites W2145808065 @default.
• W2050318957 cites W2146812359 @default.
• W2050318957 cites W2161594343 @default.
• W2050318957 cites W2189058568 @default.
• W2050318957 cites W4236316592 @default.
• W2050318957 cites W4256264762 @default.
• W2050318957 doi "https://doi.org/10.1074/jbc.r800077200" @default.
• W2050318957 hasPubMedCentralId "https://www.ncbi.nlm.nih.gov/pmc/articles/2665084" @default.
• W2050318957 hasPubMedId "https://pubmed.ncbi.nlm.nih.gov/19064989" @default.
• W2050318957 hasPublicationYear "2009" @default.
• W2050318957 type Work @default.
• W2050318957 sameAs 2050318957 @default.
• W2050318957 citedByCount "121" @default.
• W2050318957 countsByYear W20503189572012 @default.
• W2050318957 countsByYear W20503189572013 @default.
• W2050318957 countsByYear W20503189572014 @default.
• W2050318957 countsByYear W20503189572015 @default.
• W2050318957 countsByYear W20503189572016 @default.
• W2050318957 countsByYear W20503189572017 @default.
• W2050318957 countsByYear W20503189572018 @default.
• W2050318957 countsByYear W20503189572019 @default.
• W2050318957 countsByYear W20503189572020 @default.
• W2050318957 countsByYear W20503189572021 @default.
• W2050318957 countsByYear W20503189572022 @default.
• W2050318957 countsByYear W20503189572023 @default.
• W2050318957 crossrefType "journal-article" @default.
• W2050318957 hasAuthorship W2050318957A5017332459 @default.
• W2050318957 hasAuthorship W2050318957A5043927370 @default.
• W2050318957 hasBestOaLocation W20503189571 @default.
• W2050318957 hasConcept C104317684 @default.
• W2050318957 hasConcept C120665830 @default.
• W2050318957 hasConcept C121332964 @default.
• W2050318957 hasConcept C148738053 @default.
• W2050318957 hasConcept C185592680 @default.
• W2050318957 hasConcept C192209626 @default.
• W2050318957 hasConcept C53345823 @default.
• W2050318957 hasConcept C55493867 @default.
• W2050318957 hasConcept C62112901 @default.
• W2050318957 hasConcept C70721500 @default.
• W2050318957 hasConcept C86803240 @default.
• W2050318957 hasConcept C95444343 @default.
• W2050318957 hasConceptScore W2050318957C104317684 @default.
• W2050318957 hasConceptScore W2050318957C120665830 @default.
• W2050318957 hasConceptScore W2050318957C121332964 @default.
• W2050318957 hasConceptScore W2050318957C148738053 @default.
• W2050318957 hasConceptScore W2050318957C185592680 @default.
• W2050318957 hasConceptScore W2050318957C192209626 @default.
• W2050318957 hasConceptScore W2050318957C53345823 @default.
• W2050318957 hasConceptScore W2050318957C55493867 @default.
• W2050318957 hasConceptScore W2050318957C62112901 @default.
• W2050318957 hasConceptScore W2050318957C70721500 @default.
• W2050318957 hasConceptScore W2050318957C86803240 @default.
• W2050318957 hasConceptScore W2050318957C95444343 @default.
• W2050318957 hasIssue "15" @default.
• W2050318957 hasLocation W20503189571 @default.

• next