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T-cell-dependent antigenic stimulation drives the differentiation of B cells into antibody-secreting plasma cells and memory B cells, but how B cells regulate this process is unclear. We show that LKB1 expression in B cells maintains B-cell quiescence and prevents the premature formation of germinal centers (GCs).
Germline mutations in the gene encoding tumor suppressor kinase LKB1 lead to gastrointestinal tumorigenesis in Peutz-Jeghers syndrome (PJS) patients and mouse models; however, the cell types and signaling pathways underlying tumor formation are unknown. Here, we demonstrated that mesenchymal progenitor- or stromal fibroblast–specific deletion of Lkb1 results in fully penetrant polyposis in mice.
Linking AMPK to organelle biogenesis
The kinase AMPK is a key sensor that helps to control energy homeostasis. Malik et al. reveal the mechanism by which AMPK controls the transcription factor TFEB to increase gene transcription and to support mitochondrial and lysosomal biogenesis. AMPK appears to act by direct phosphorylation of folliculin-interacting protein 1 (FNIP1). FNIP is part of a complex that acts as a GTP-activating protein for the GTPases RagC and RagD, which regulate the mechanistic target of rapamycin complex 1 protein kinase signaling complex on the lysosomal surface. This results in release of TFEB from the lysosome, allowing it to act at the nucleus.