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

• Published in: The Journal of clinical investigation Vol. 122; no. 6; pp. 2079 - 2091
• Main Authors: Jiang, Jing, Balcerek, Joanna, Rozenova, Krasimira, Cheng, Ying, Bersenev, Alexey, Wu, Chao, Song, Yiwen, Tong, Wei
• Format: Journal Article
• Language: English
• Published: United States American Society for Clinical Investigation 01.06.2012
• Subjects: 14-3-3 Proteins - genetics; 14-3-3 Proteins - metabolism; Animals; Antibodies; Apoptosis; Biomedical research; Blood; Bone Marrow Transplantation; Cell cycle; Cell growth; Cell Proliferation; Cyclic AMP-Dependent Protein Kinases - genetics; Cyclic AMP-Dependent Protein Kinases - metabolism; Cytokines; Genetic aspects; Genetic regulation; Glycogen Synthase Kinase 3 - genetics; Glycogen Synthase Kinase 3 - metabolism; Hematopoietic stem cells; Hematopoietic Stem Cells - metabolism; Humans; Intracellular Signaling Peptides and Proteins - genetics; Intracellular Signaling Peptides and Proteins - metabolism; Janus Kinase 2 - genetics; Janus Kinase 2 - metabolism; Kinases; Mice; Mice, Knockout; Mutation; Myeloproliferative Disorders - genetics; Myeloproliferative Disorders - metabolism; Phosphorylation; Phosphorylation - genetics; Proteins; Regulation; Signal Transduction; Transplantation, Homologous; United States
• ISSN: 0021-9738; 1558-8238
• DOI: 10.1172/jci59719

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.