Increased proteasome activity in human embryonic stem cells is regulated by PSMD11


Embryonic stem cells can replicate continuously in the absence of senescence and, therefore, are immortal in culture1,2. Although genome stability is essential for the survival of stem cells, proteome stability may have an equally important role in stem-cell identity and function. Furthermore, with the asymmetric divisions invoked by stem cells, the passage of damaged proteins to daughter cells could potentially destroy the resulting lineage of cells. Therefore, a firm understanding of how stem cells maintain their proteome is of central importance. Here we show that human embryonic stem cells (hESCs) exhibit high proteasome activity that is correlated with increased levels of the 19S proteasome subunit PSMD11 (known as RPN-6 in Caenorhabditis elegans)3,4,5 and a corresponding increased assembly of the 26S/30S proteasome. Ectopic expression of PSMD11 is sufficient to increase proteasome assembly and activity. FOXO4, an insulin/insulin-like growth factor-I (IGF-I) responsive transcription factor associated with long lifespan in invertebrates6,7, regulates proteasome activity by modulating the expression of PSMD11 in hESCs. Proteasome inhibition in hESCs affects the expression of pluripotency markers and the levels of specific markers of the distinct germ layers. Our results suggest a new regulation of proteostasis in hESCs that links longevity and stress resistance in invertebrates to hESC function and identity.

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Figure 1: Increased proteasome activity in hESCs.
Figure 2: Increased proteasome assembly in hESCs depends on PSMD11 expression.
Figure 3: FOXO4 regulates proteasome activity in hESCs.
Figure 4: Acute proteasome inhibition affects pluripotency of hESCs.


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We thank W. E. Balch for critical comments on this work. We thank A. Stauffer and V. Modesto for their help with BrdU assays and cell culture, respectively. We thank S. Ruiz for advice on hESC culture and lentiviral infection. This work was supported by the Howard Hughes Medical Institute. D.V. was a recipient of the F.M. Kirby, Inc. Foundation Postdoctoral Scholar Award and Beatriu de Pinós (AGAUR) fellowship. F.H.G. acknowledges the Helmsley Foundation, JPB Foundation, Mathers Foundation, Lookout Fund and California Institute for Regenerative Medicine.

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D.V. and A.D. planned and supervised the project. D.V. performed the experiments, data analysis and interpretation. L.B. performed neural differentiation assays and contributed to other assays. I.M. performed biochemistry experiments and contributed to other assays. M.L. performed cell culturing and trophoblast/fibroblast differentiation. C.M. performed biochemistry experiments and contributed to other assays. D.J. performed proteasome assembly experiments. B.S., L.P. and E.M. generated lentiviral constructs. W.T.B. and F.H.G. contributed with their knowledge of stem-cell biology and neural differentiation, and helped to supervise the project. The manuscript was written by D.V. and A.D. and edited by L.B., I.M., C.M., W.T.B. and F.H.G. All authors discussed the results and commented on the manuscript.

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Correspondence to Andrew Dillin.

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Vilchez, D., Boyer, L., Morantte, I. et al. Increased proteasome activity in human embryonic stem cells is regulated by PSMD11. Nature 489, 304–308 (2012).

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