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Multiple signalling pathways maintain human embryonic stem cells (hESC) in an undifferentiated state. Here we sought to define the significance of G protein signal transduction in the preservation of this state distinct from other cellular processes. Continuous treatment with drugs targeting G(αs)-, G(α-i/o)- and G(α-q/11)-subunit signalling mediators were assessed in independent hESC lines after 7days to discern effects on normalised alkaline phosphatase positive colony frequency vs total cell content. This identified PLCβ, intracellular free calcium and CAMKII kinase activity downstream of G(α-q/11) as of particular importance to the former. To confirm the significance of this finding we generated an agonist-responsive hESC line transgenic for a G(α-q/11) subunit-coupled receptor and demonstrated that an undifferentiated state could be promoted in the presence of an agonist without exogenously supplied bFGF and that this correlated with elevated intracellular calcium. Similarly, treatment of unmodified hESCs with a range of intracellular free calcium-modulating drugs in biologically defined mTESR culture system lacking exogenous bFGF promoted an hESC phenotype after 1week of continuous culture as defined by co-expression of OCT4 and NANOG. At least one of these drugs, lysophosphatidic acid significantly elevates phosphorylation of calmodulin and STAT3 in this culture system (p<0.05). These findings substantiate a role for G-protein and calcium signalling in undifferentiated hESC culture., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Abstract: Ca2+‐mediated signaling is widely spread in nature and plays critical role in the individual development of various organisms ranging from microorganisms to mammals. In vertebrates, Ca2+ is involved in important developmental events: fertilization, body plan establishment, and organogenesis. The two later events are defined by embryonic stem cells (ESCs). ESCs are capable of self‐renewal and are pluripotent by nature, that is, can give rise to all types of cells that make up the body. Given the paramount importance of Ca2+ signalization in the development, it is therefore not surprising this process also plays role in the biology of stem cells. In this review, we scrutinize the published experimental data on the role of Ca2+ ions in embryonic stem cells self‐renewal and pluripotency. In line with this, we also discuss possible mechanisms of p53 inhibition as a major hindrance to self‐renewal of ESCs. Finally, we argue about the role of G‐protein‐coupled receptors (GPCRs), the largest family of heteromeric transmembrane receptors, and GPCR‐mediated signalization in stem cells, and propose the role for the GPCR‐G‐protein‐PLC‐Ca2+‐downstream signaling pathway in the regulation of pluripotency of both mouse and human ESCs. [ABSTRACT FROM AUTHOR]