Hematopoietic Stem Cell Activity Is Regulated by Pten Phosphorylation Through a Niche-Dependent Mechanism

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• 作者：Jing Li ; Jun Zhang ; Minghui Tang ; Junping Xin ; Yan Xu ; Andrew Volk ; Caiqin Hao ; Chenglong Hu ; Jiewen Sun ; Wei Wei ; Quichan Cao ; Peter Breslin and Jiwang Zhang
• 刊名：STEM CELLS
• 出版年：2016
• 出版时间：August 2016
• 年：2016
• 卷：34
• 期：8
• 页码：2130-2144
• 全文大小：1210K
• ISSN：1549-4918

文摘

The phosphorylated form of Pten (p-Pten) is highly expressed in >70% of acute myeloid leukemia samples. However, the role of p-Pten in normal and abnormal hematopoiesis has not been studied. We found that Pten protein levels are comparable among long-term (LT) hematopoietic stem cells (HSCs), short-term (ST) HSCs, and multipotent progenitors (MPPs); however, the levels of p-Pten are elevated during the HSC-to-MPP transition. To study whether p-Pten is involved in regulating self-renewal and differentiation in HSCs, we compared the effects of overexpression of p-Pten and nonphosphorylated Pten (non-p-Pten) on the hematopoietic reconstitutive capacity (HRC) of HSCs. We found that overexpression of non-p-Pten enhances the LT-HRC of HSCs, whereas overexpression of p-Pten promotes myeloid differentiation and compromises the LT-HRC of HSCs. Such phosphorylation-regulated Pten functioning is mediated by repressing the cell:cell contact-induced activation of Fak/p38 signaling independent of Pten's lipid phosphatase activity because both p-Pten and non-p-Pten have comparable activity in repressing PI3K/Akt signaling. Our studies suggest that, in addition to repressing PI3K/Akt/mTor signaling, non-p-Pten maintains HSCs in bone marrow niches via a cell-contact inhibitory mechanism by inhibiting Fak/p38 signaling-mediated proliferation and differentiation. In contrast, p-Pten promotes the proliferation and differentiation of HSCs by enhancing the cell contact-dependent activation of Src/Fak/p38 signaling. Stem Cells 2016;34:2130–2144