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Lithium activates the Wnt and phosphatidylinositol 3-kinase Akt signaling pathways to promote cell survival in the absence of soluble survival factors.
Am J Physiol Renal Physiol. 2005 Apr; 288(4):F703-13.AJ

Abstract

Mouse proximal tubular cells (BUMPT), when cultured in the absence of growth factors, activate a default apoptotic pathway. Although Wnt signaling antagonizes the effect of proapoptotic triggers, its role in regulating the default pathway of apoptosis is less well defined. The present study examines the hypothesis that lithium (Li(+)) and (2'Z,3'E)-6-bromoindirubin-3'-oxime (BIO), two glycogen synthase kinase-3beta (GSK3beta) inhibitors, promote survival of growth factor-deprived renal epithelial cells by activating the Wnt pathway. These studies demonstrate that Li(+) and BIO activate Wnt signaling as indicated by the following changes: phosphorylation (inhibition) of GSK3beta; decreased phosphorylation of beta-catenin (a GSK3beta substrate); nuclear translocation of beta-catenin; specific transcriptional activation of Tcf/catenin-responsive pTopflash constructs; and an increase in the expression of cyclin D1 (indicative of a promitogenic cell response). In addition, Li(+) or BIO significantly increases the phosphorylation (activation) of Akt, an anti-apoptotic protein, and inhibits apoptosis (decreases both annexin-V staining and caspase-3 activation), during serum deprivation. Inhibition of phosphatidylinositol 3-kinase (responsible for Akt activation) either by wortmanin or LY-294002 prevented Li(+)- or BIO-induced Akt phosphorylation and reduces cell survival without altering the phosphorylation state of GSK3beta. Li(+) or BIO also increases the expression of insulin-like growth factor-II (IGF-II), a potent proliferative signaling protein. Li(+) or BIO-free conditioned medium harvested from Li(+)- or BIO-exposed cells also induced Akt phosphorylation, mimicking the protective effect of the two GSK3beta inhibitors on serum-starved cells. Furthermore, the effect of conditioned medium on Akt phosphorylation could be inhibited by either LY-294002 or IGF-binding protein. BIO, a specific GSK3beta inhibitor, replicated the protective effect of Li(+) on cell viability, suggesting that GSK3beta activation is important for initiating the apoptotic pathway. Taken together, these data suggest that Li(+) or BIO promotes renal epithelial cell survival by inhibiting apoptosis through GSK3beta-dependent activation of the Wnt pathway and subsequent release of IGF-II. Extracellular IGF-II serves as an autocrine survival factor that is responsible, in part, for activating the anti-apoptotic phosphatidylinositol-3-kinase-Akt pathway during serum deprivation.

Authors+Show Affiliations

Renal Section, Evans Biomedical Research Center, Rm. 546, 650 Albany St., Boston, MA 02118, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

15572521

Citation

Sinha, Diviya, et al. "Lithium Activates the Wnt and Phosphatidylinositol 3-kinase Akt Signaling Pathways to Promote Cell Survival in the Absence of Soluble Survival Factors." American Journal of Physiology. Renal Physiology, vol. 288, no. 4, 2005, pp. F703-13.
Sinha D, Wang Z, Ruchalski KL, et al. Lithium activates the Wnt and phosphatidylinositol 3-kinase Akt signaling pathways to promote cell survival in the absence of soluble survival factors. Am J Physiol Renal Physiol. 2005;288(4):F703-13.
Sinha, D., Wang, Z., Ruchalski, K. L., Levine, J. S., Krishnan, S., Lieberthal, W., Schwartz, J. H., & Borkan, S. C. (2005). Lithium activates the Wnt and phosphatidylinositol 3-kinase Akt signaling pathways to promote cell survival in the absence of soluble survival factors. American Journal of Physiology. Renal Physiology, 288(4), F703-13.
Sinha D, et al. Lithium Activates the Wnt and Phosphatidylinositol 3-kinase Akt Signaling Pathways to Promote Cell Survival in the Absence of Soluble Survival Factors. Am J Physiol Renal Physiol. 2005;288(4):F703-13. PubMed PMID: 15572521.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Lithium activates the Wnt and phosphatidylinositol 3-kinase Akt signaling pathways to promote cell survival in the absence of soluble survival factors. AU - Sinha,Diviya, AU - Wang,Zhiyong, AU - Ruchalski,Kathleen L, AU - Levine,Jerrold S, AU - Krishnan,Selvi, AU - Lieberthal,Wilfred, AU - Schwartz,John H, AU - Borkan,Steven C, Y1 - 2004/11/30/ PY - 2004/12/2/pubmed PY - 2005/4/19/medline PY - 2004/12/2/entrez SP - F703 EP - 13 JF - American journal of physiology. Renal physiology JO - Am J Physiol Renal Physiol VL - 288 IS - 4 N2 - Mouse proximal tubular cells (BUMPT), when cultured in the absence of growth factors, activate a default apoptotic pathway. Although Wnt signaling antagonizes the effect of proapoptotic triggers, its role in regulating the default pathway of apoptosis is less well defined. The present study examines the hypothesis that lithium (Li(+)) and (2'Z,3'E)-6-bromoindirubin-3'-oxime (BIO), two glycogen synthase kinase-3beta (GSK3beta) inhibitors, promote survival of growth factor-deprived renal epithelial cells by activating the Wnt pathway. These studies demonstrate that Li(+) and BIO activate Wnt signaling as indicated by the following changes: phosphorylation (inhibition) of GSK3beta; decreased phosphorylation of beta-catenin (a GSK3beta substrate); nuclear translocation of beta-catenin; specific transcriptional activation of Tcf/catenin-responsive pTopflash constructs; and an increase in the expression of cyclin D1 (indicative of a promitogenic cell response). In addition, Li(+) or BIO significantly increases the phosphorylation (activation) of Akt, an anti-apoptotic protein, and inhibits apoptosis (decreases both annexin-V staining and caspase-3 activation), during serum deprivation. Inhibition of phosphatidylinositol 3-kinase (responsible for Akt activation) either by wortmanin or LY-294002 prevented Li(+)- or BIO-induced Akt phosphorylation and reduces cell survival without altering the phosphorylation state of GSK3beta. Li(+) or BIO also increases the expression of insulin-like growth factor-II (IGF-II), a potent proliferative signaling protein. Li(+) or BIO-free conditioned medium harvested from Li(+)- or BIO-exposed cells also induced Akt phosphorylation, mimicking the protective effect of the two GSK3beta inhibitors on serum-starved cells. Furthermore, the effect of conditioned medium on Akt phosphorylation could be inhibited by either LY-294002 or IGF-binding protein. BIO, a specific GSK3beta inhibitor, replicated the protective effect of Li(+) on cell viability, suggesting that GSK3beta activation is important for initiating the apoptotic pathway. Taken together, these data suggest that Li(+) or BIO promotes renal epithelial cell survival by inhibiting apoptosis through GSK3beta-dependent activation of the Wnt pathway and subsequent release of IGF-II. Extracellular IGF-II serves as an autocrine survival factor that is responsible, in part, for activating the anti-apoptotic phosphatidylinositol-3-kinase-Akt pathway during serum deprivation. SN - 1931-857X UR - https://www.unboundmedicine.com/medline/citation/15572521/Lithium_activates_the_Wnt_and_phosphatidylinositol_3_kinase_Akt_signaling_pathways_to_promote_cell_survival_in_the_absence_of_soluble_survival_factors_ L2 - https://journals.physiology.org/doi/10.1152/ajprenal.00189.2004?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -