Endogenously activated mGlu5 metabotropic glutamate receptors sustain the increase in c‐Myc expression induced by leukaemia inhibitory factor in cultured mouse embryonic stem cells

We have shown that endogenous activation of type 5 metabotropic glutamate (mGlu5) receptors supports the maintenance of a pluripotent, undifferentiated state in D3 mouse embryonic stem cells cultured in the presence of leukaemia inhibitory factor (LIF). Here, we examined the interaction between LIF...

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Bibliographic Details
Published in:	Journal of neurochemistry 2006-10, Vol.99 (1), p.299-307
Main Authors:	Spinsanti, Paola, De Vita, Teresa, Di Castro, Sara, Storto, Marianna, Formisano, Pietro, Nicoletti, Ferdinando, Melchiorri, Daniela
Format:	Article
Language:	eng
Subjects:	Animals Antagonist drugs Biochemistry Biological and medical sciences Cell culture Cells, Cultured Central nervous system Central neurotransmission. Neuromudulation. Pathways and receptors c‐Myc Embryo, Mammalian embryonic stem cells Excitatory Amino Acid Antagonists - pharmacology Fundamental and applied biological sciences. Psychology Gene expression Gene Expression Regulation, Developmental Genes, myc Glycogen Synthase Kinase 3 - metabolism Glycogen Synthase Kinase 3 beta Hematologic and hematopoietic diseases Interleukin-6 - physiology leukaemia inhibitory factor Leukemia Inhibitory Factor Leukemias. Malignant lymphomas. Malignant reticulosis. Myelofibrosis Medical sciences Mice Phosphatidylinositol 3-Kinases - metabolism protein kinase C Proteins Pyridines - pharmacology Receptor, Metabotropic Glutamate 5 Receptors, Metabotropic Glutamate - physiology Rodents self‐renewal Stem cells Stem Cells - cytology Stem Cells - physiology type 5 metabotropic glutamate receptors Vertebrates: nervous system and sense organs
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Summary:	We have shown that endogenous activation of type 5 metabotropic glutamate (mGlu5) receptors supports the maintenance of a pluripotent, undifferentiated state in D3 mouse embryonic stem cells cultured in the presence of leukaemia inhibitory factor (LIF). Here, we examined the interaction between LIF and mGlu5 receptors using as a read‐out the immediate early gene, c‐Myc. The selective mGlu5 receptor antagonist, 2‐methyl‐6‐(phenylenthynyl)pyridine (MPEP; 1 μm), reduced the increase in c‐Myc protein levels induced by LIF by enhancing c‐Myc ubiquitination. A reduction in c‐Myc levels was also observed following small interfering RNA‐mediated mGlu5 receptor gene silencing. MPEP reduced glycogen synthase kinase‐3β phosphorylation on Ser9, but increased phosphorylation of the phosphatidylinositol‐3‐kinase (PI‐3‐K) substrate, AKT. In our hands, activated PI‐3‐K reduced the stability of c‐Myc, because (i) the PI‐3‐K inhibitor, LY294002, prevented the reduction in c‐Myc levels induced by MPEP; and (ii) over‐expression of AKT promoted c‐Myc ubiquitination. All effects of MPEP were mimicked by protein kinase C (PKC) inhibitors and reversed by the PKC activator, tetradecanoylphorbol‐13‐acetate. We conclude that endogenous activation of mGlu5 receptors sustains the increase in c‐Myc induced by LIF in embryonic stem cells by inhibiting both glycogen synthase kinase‐3β and PI‐3‐K, both effects resulting from the activation of PKC.
ISSN:	0022-3042 1471-4159