14-3-3 regulates the LNK/JAK2 pathway in mouse hematopoietic stem and progenitor cells
Jing Jiang, … , Yiwen Song, Wei Tong
Jing Jiang, … , Yiwen Song, Wei Tong
Published May 1, 2012
Citation Information: J Clin Invest. 2012;122(6):2079-2091. https://doi.org/10.1172/JCI59719.
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Research Article Hematology

14-3-3 regulates the LNK/JAK2 pathway in mouse hematopoietic stem and progenitor cells

Abstract

Hematopoietic stem and progenitor cell (HSPC) functions are governed by intricate signaling networks. The tyrosine kinase JAK2 plays an essential role in cytokine signaling during hematopoiesis. The adaptor protein LNK is a critical determinant of this process through its inhibitory interaction with JAK2, thereby limiting HSPC self-renewal. LNK deficiency promotes myeloproliferative neoplasm (MPN) development in mice, and LNK loss-of-function mutations are found in human MPNs, emphasizing its pivotal role in normal and malignant HSPCs. Here, we report the identification of 14-3-3 proteins as LNK binding partners. 14-3-3 interfered with the LNK-JAK2 interaction, thereby alleviating LNK inhibition of JAK2 signaling and cell proliferation. Binding of 14-3-3 required 2 previously unappreciated serine phosphorylation sites in LNK, and we found that their phosphorylation is mediated by glycogen synthase kinase 3 and PKA kinases. Mutations of these residues abrogated the interaction and augmented the growth inhibitory function of LNK. Conversely, forced 14-3-3 binding constrained LNK function. Furthermore, interaction with 14-3-3 sequestered LNK in the cytoplasm away from the plasma membrane-proximal JAK2. Importantly, bone marrow transplantation studies revealed an essential role for 14-3-3 in HSPC reconstitution that can be partially mitigated by LNK deficiency. We believe that, together, this work implicates 14-3-3 proteins as novel and positive HSPC regulators by impinging on the LNK/JAK2 pathway.

Authors

Jing Jiang, Joanna Balcerek, Krasimira Rozenova, Ying Cheng, Alexey Bersenev, Chao Wu, Yiwen Song, Wei Tong

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Figure 10

14-3-3s regulate HSPC reconstitution in mice partially through the LNK/JAK2/Stat5 pathway.

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14-3-3s regulate HSPC reconstitution in mice partially through the LNK/J...
(A and B) Lin– BM cells from WT and Lnk–/– mice were infected with lentiviruses expressing shRNA to either Luc or (A) pan 14-3-3 no. 1 or (B) no. 2 and subsequently transplanted. The percentages of GFP+ cells before transplant and in host PB after transplant are shown (n = 5–7). Average ± SEM. (C) Lin– BM cells were infected with pLKO-Luc or pan 14-3-3 no. 2, and subsequently purified GFP+Lin–Sca1+ progenitors were stimulated with or without IL-3 for 10 minutes and subjected to phospho-flow analysis using anti-pStat5 antibodies. Histograms of unstimulated and stimulated cells are overlaid and shown. shLuc-infected cells are labeled in red, while the sh14-3-3 cells are labeled in blue. Dashed lines indicate unstimulated cells, while solid lines indicate stimulated cells. Shaded areas represent secondary antibody-only controls.