Lithium regulates keratinocyte proliferation via glycogen synthase kinase 3 and NFAT2 (nuclear factor of activated T cells 2).
Bottom Line: Inhibition of GSK-3 in keratinocytes by retroviral transduction of GSK-binding protein (an endogenous inhibitory protein) or through a highly selective pharmacological inhibitor also resulted in increased keratinocyte proliferation.Both lithium and genetic/pharmacological inhibition of GSK-3 resulted in increased nuclear localization of NFAT2 (NFATc1) and increased NFAT transcriptional activation.Finally, retroviral transduction of NFAT2 increased keratinocyte proliferation whereas siRNA-mediated knockdown of NFAT2 reduced keratinocyte proliferation and decreased epidermal thickness in an organotypic skin equivalent model.
Affiliation: Dermatological Sciences, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK.Show MeSH
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Mentions: Having demonstrated that inhibition of GSK-3 induced keratinocyte proliferation, we next investigated the role of the GSK substrate NFAT in keratinocyte proliferation. Since NFAT is a negatively regulated substrate of GSK-3, we investigated the effect of inhibition of GSK-3 on NFAT nuclear localization and transcriptional activity. Primary keratinocytes were transiently transfected with an NFAT-luciferase reporter and either the GSKBP or empty vector. As expected, GSKBP induced significantly greater activation of the NFAT-luciferase reporter than empty vector (Fig. 3A, P < 0.005). A similar effect on the NFAT-luciferase reporter was seen following retroviral transduction with the fusion protein pLEGFP-GSKBP compared to empty vector, further validating that this construct was functionally active in this system (data not shown). Consistent with the effect of GSKBP, overexpression of a constitutively active GSK mutant (CaGSK-3β-S9A), reduced activation of the NFAT-luciferase reporter (Fig. 3B, P = 0.002). Retroviral transduction of pLEGFP GSKBP induced increased nuclear NFAT2 compared with transduction of pLEGFP empty (Fig. 3C).
Affiliation: Dermatological Sciences, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK.