Journal
STEM CELLS
Volume 32, Issue 5, Pages 1267-1277Publisher
WILEY
DOI: 10.1002/stem.1646
Keywords
Hematopoietic stem/progenitor cells; Hypoxic adaptation; Neuroglobin; Redox signaling; Myoglobin
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Funding
- Italian Ministry of University and Research [PRIN-2008FJJHKM_001]
- Italian Association against Leukemia-Lymphoma and Myeloma (AIL-Foggia)
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Oxidative metabolism and redox signaling prove to play a decisional role in controlling adult hematopoietic stem/progenitor cells (HSPCs) biology. However, HSPCs reside in a hypoxic bone marrow microenvironment raising the question of how oxygen metabolism might be ensued. In this study, we provide for the first time novel functional and molecular evidences that human HSPCs express myoglobin (Mb) at level comparable with that of a muscle-derived cell line. Optical spectroscopy and oxymetry enabled to estimate an O-2-sensitive heme-containing protein content of approximately 180 ng globin per 10(6) HSPC and a P-50 of approximately 3 mu M O-2. Noticeably, expression of Mb mainly occurs through a HIF-1-induced alternative transcript (Mb-V/Mb-N = 35 +/- 15, p < .01). A search for other Mb-related globins unveiled significant expression of neuroglobin (Ngb) but not of cytoglobin. Confocal microscopy immune detection of Mb in HSPCs strikingly revealed nuclear localization in cell subsets expressing high level of CD34 (nuclear/cytoplasmic Mb ratios 1.40 +/- 0.02 vs. 0.85 +/- 0.05, p < .01) whereas Ngb was homogeneously distributed in all the HSPC population. Dual-color fluorescence flow cytometry indicated that while the Mb content was homogeneously distributed in all the HSPC subsets that of Ngb was twofold higher in more immature HSPC. Moreover, we show that HSPCs exhibit a hypoxic nitrite reductase activity releasing NO consistent with described noncanonical functions of globins. Our finding extends the notion that Mb and Ngb can be expressed in nonmuscle and non-neural contexts, respectively, and is suggestive of a differential role of Mb in HSPC in controlling oxidative metabolism at different stages of commitment. Stem Cells 2014;32:1267-1277
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