Signaling proteins in HSC fate determination are unequally segregated during asymmetric cell division.

Hematopoietic stem cells (HSCs) continuously replenish mature blood cells with limited lifespans. To maintain the HSC compartment while ensuring output of differentiated cells, HSCs undergo asymmetric cell division (ACD), generating two daughter cells with different fates: one will proliferate and give rise to the differentiated cells' progeny, and one will return to quiescence to maintain the HSC compartment. A balance between MEK/ERK and mTORC1 pathways is needed to ensure HSC homeostasis.

Sequestration of translation initiation factors in p62 condensates.

Selective autophagy mediates the removal of harmful material from the cytoplasm. This cargo material is selected by cargo receptors, which orchestrate its sequestration within double-membrane autophagosomes and subsequent lysosomal degradation. The cargo receptor p62/SQSTM1 is present in cytoplasmic condensates, and a fraction of them are constantly delivered into lysosomes.

RAF1 contributes to cell proliferation and STAT3 activation in colorectal cancer independently of microsatellite and KRAS status.

More than 30% of all human cancers are driven by RAS mutations and activating KRAS mutations are present in 40% of colorectal cancer (CRC) in the two main CRC subgroups, MSS (Microsatellite Stable) and MSI (Microsatellite Instable). Studies in RAS-driven tumors have shown essential roles of the RAS effectors RAF and specifically of RAF1, which can be dependent or independent of RAF's ability to activate the MEK/ERK module. In this study, we demonstrate that RAF1, but not its kinase activity, plays a crucial role in the proliferation of both MSI and MSS CRC cell line-derived spheroids and patient-derived organoids, and independently of KRAS mutation status.

amica: an interactive and user-friendly web-platform for the analysis of proteomics data.

Background: Quantitative proteomics has become an increasingly prominent tool in the study of life sciences. A substantial hurdle for many biologists are, however, the intricacies involved in the associated high throughput data analysis.

Results: In order to facilitate this task for users with limited background knowledge, we have developed amica, a freely available open-source web-based software that accepts proteomic input files from different sources.

BRAF increases endothelial cell stiffness through reorganization of the actin cytoskeleton.

The dynamics of the actin cytoskeleton and its connection to endothelial cell-cell junctions determine the barrier function of endothelial cells. The proper regulation of barrier opening/closing is necessary for the normal function of vessels, and its dysregulation can result in chronic and acute inflammation leading to edema formation. By using atomic force microscopy, we show here that thrombin-induced permeability of human umbilical vein endothelial cells, associated with actin stress fiber formation, stiffens the cell center.

Impaired degradation of YAP1 and IL6ST by chaperone-mediated autophagy promotes proliferation and migration of normal and hepatocellular carcinoma cells.

Impaired degradation of the transcriptional coactivator YAP1 and IL6ST (interleukin 6 cytokine family signal transducer), two proteins deregulated in liver cancer, has been shown to promote tumor growth. Here, we demonstrate that YAP1 and IL6ST are novel substrates of chaperone-mediated autophagy (CMA) in human hepatocellular carcinoma (HCC) and hepatocyte cell lines. Knockdown of the lysosomal CMA receptor LAMP2A increases protein levels of YAP1 and IL6ST, without changes in mRNA expression.

Editor Profile: Manuela Baccarini.

In this special interview series, we profile members of The FEBS Journal editorial board to highlight their research focus, perspectives on the journal and future directions in their field. Manuela Baccarini is Professor of Cell Signaling at the University of Vienna, Coordinator of the International PhD Program 'Signaling Mechanisms in Cellular Homeostasis' and Director of the Vienna BioCenter PhD Program, a graduate school of the University and Medical University of Vienna in collaboration with the Institute of Molecular Pathology and the Austrian Academy of Sciences, Institute for Medical Biotechnology and Gregor Mendel Institute, as well as EMBO member and corresponding member of the Austrian Academy of Sciences. She has served as an editorial board member of The FEBS Journal since 2016.

Listeria monocytogenes infection rewires host metabolism with regulatory input from type I interferons.

Listeria monocytogenes (L. monocytogenes) is a food-borne bacterial pathogen. Innate immunity to L.

ERK phosphorylation is RAF independent in naïve and activated B cells but RAF dependent in plasma cell differentiation.

Members of the RAF family of serine-threonine kinases are intermediates in the mitogen-activated protein kinase and extracellular signal-regulated kinase (MAPK-ERK) signaling pathway, which controls key differentiation processes in B cells. By analyzing mice with B cell-specific deletion of , , or both, we showed that Raf-1 and B-Raf acted together in mediating the positive selection of pre-B and transitional B cells as well as in initiating plasma cell differentiation. However, genetic or chemical inactivation of RAFs led to increased ERK phosphorylation in mature B cells.

Combination of Hypoglycemia and Metformin Impairs Tumor Metabolic Plasticity and Growth by Modulating the PP2A-GSK3β-MCL-1 Axis.

Tumor cells may adapt to metabolic challenges by alternating between glycolysis and oxidative phosphorylation (OXPHOS). To target this metabolic plasticity, we combined intermittent fasting, a clinically feasible approach to reduce glucose availability, with the OXPHOS inhibitor metformin. In mice exposed to 24-h feeding/fasting cycles, metformin impaired tumor growth only when administered during fasting-induced hypoglycemia.

RAF dimers control vascular permeability and cytoskeletal rearrangements at endothelial cell-cell junctions.

The endothelium functions as a semipermeable barrier regulating fluid homeostasis, nutrient, and gas supply to the tissue. Endothelial permeability is increased in several pathological conditions including inflammation and tumors; despite its clinical relevance, however, there are no specific therapies preventing vascular leakage. Here, we show that endothelial cell-restricted ablation of BRAF, a kinase frequently activated in cancer, prevents vascular leaking as well metastatic spread.

Activating mutations in MEK1 enhance homodimerization and promote tumorigenesis.

RAS-RAF-MEK-ERK signaling has a well-defined role in cancer biology. Although aberrant pathway activation occurs mostly upstream of the kinase MEK, mutations in MEK are prevalent in some cancer subsets. Here, we found that cancer-related, activating mutations in MEK can be classified into two groups: those that relieve inhibitory interactions with the helix A region and those that are in-frame deletions of the β3-αC loop, which enhance MEK1 homodimerization.

The dimer-dependent catalytic activity of RAF family kinases is revealed through characterizing their oncogenic mutants.

Although extensively studied for three decades, the molecular mechanisms that regulate the RAF/MEK/ERK kinase cascade remain ambiguous. Recent studies identified the dimerization of RAF as a key event in the activation of this cascade. Here, we show that in-frame deletions in the β3-αC loop activate ARAF as well as BRAF and other oncogenic kinases by enforcing homodimerization.

An ERK-Dependent Feedback Mechanism Prevents Hematopoietic Stem Cell Exhaustion.

Hematopoietic stem cells (HSCs) sustain hematopoiesis throughout life. HSCs exit dormancy to restore hemostasis in response to stressful events, such as acute blood loss, and must return to a quiescent state to prevent their exhaustion and resulting bone marrow failure. HSC activation is driven in part through the phosphatidylinositol 3-kinase (PI3K)/AKT/mTORC1 signaling pathway, but less is known about the cell-intrinsic pathways that control HSC dormancy.

RAF proteins exert both specific and compensatory functions during tumour progression of NRAS-driven melanoma.

NRAS and its effector BRAF are frequently mutated in melanoma. Paradoxically, CRAF but not BRAF was shown to be critical for various RAS-driven cancers, raising the question of the role of RAF proteins in NRAS-induced melanoma. Here, using conditional ablation of Raf genes in NRAS-induced mouse melanoma models, we investigate their contribution in tumour progression, from the onset of benign tumours to malignant tumour maintenance.

RAF1/BRAF dimerization integrates the signal from RAS to ERK and ROKα.

Downstream of growth factor receptors and of the guanine triphosphatase (GTPase) RAS, heterodimers of the serine/threonine kinases BRAF and RAF1 are critical upstream kinases and activators of the mitogen-activated protein kinase (MAPK) module containing the mitogen-activated and extracellular signal-regulated kinase kinase (MEK) and their targets, the extracellular signal-regulated kinase (ERK) family. Either direct or scaffold protein-mediated interactions among the components of the ERK module (the MAPKKKs BRAF and RAF1, MEK, and ERK) facilitate signal transmission. RAF1 also has essential functions in the control of tumorigenesis and migration that are mediated through its interaction with the kinase ROKα, an effector of the GTPase RHO and regulator of cytoskeletal rearrangements.

Deciphering the RAS/ERK pathway .

The RAS/ERK pathway has been intensely studied for about three decades, not least because of its role in human pathologies. ERK activation is observed in the majority of human cancers; in about one-third of them, it is driven by mutational activation of pathway components. The pathway is arguably one of the best targets for molecule-based pharmacological intervention, and several small-molecule inhibitors are in clinical use.

Raf Kinases Are Essential for Phosphate Induction of ERK1/2 Phosphorylation in Hypertrophic Chondrocytes and Normal Endochondral Bone Development.

Hypophosphatemia causes rickets by impairing hypertrophic chondrocyte apoptosis. Phosphate induction of MEK1/2-ERK1/2 phosphorylation in hypertrophic chondrocytes is required for phosphate-mediated apoptosis and growth plate maturation. MEK1/2 can be activated by numerous molecules including Raf isoforms.

A cell-autonomous tumour suppressor role of RAF1 in hepatocarcinogenesis.

Hepatocellular carcinoma (HCC) is a leading cause of cancer deaths, but its molecular heterogeneity hampers the design of targeted therapies. Currently, the only therapeutic option for advanced HCC is Sorafenib, an inhibitor whose targets include RAF. Unexpectedly, RAF1 expression is reduced in human HCC samples.

MEK1 is required for the development of NRAS-driven leukemia.

The dual-specificity kinases MEK1 and MEK2 act downstream of RAS/RAF to induce ERK activation, which is generally considered protumorigenic. Activating MEK mutations have not been discovered in leukemia, in which pathway activation is caused by mutations in upstream components such as RAS or Flt3. The anti-leukemic potential of MEK inhibitors is being tested in clinical trials; however, downregulation of MEK1 promotes Eμ-Myc-driven lymphomagenesis and MEK1 ablation induces myeloproliferative disease in mice, raising the concern that MEK inhibitors may be inefficient or counterproductive in this context.

Epidermal RAF prevents allergic skin disease.

The RAS pathway is central to epidermal homeostasis, and its activation in tumors or in Rasopathies correlates with hyperproliferation. Downstream of RAS, RAF kinases are actionable targets regulating keratinocyte turnover; however, chemical RAF inhibitors paradoxically activate the pathway, promoting epidermal proliferation. We generated mice with compound epidermis-restricted BRAF/RAF1 ablation.

Knock-in(g) RAF for a loop.

Phosphorylation of the activation loop in RAF kinases has been suggested to be critical for changes in activity. The extent to which the activation segment is phosphorylated, the specific structural consequences, and the relevance have however remained elusive. In this issue of the , Köhler (2015) addressed these questions by generating a mouse expressing a B‐Raf mutant with a non‐phosphorylatable activation loop.

c-Raf promotes angiogenesis during normal growth plate maturation.

Extracellular phosphate plays a key role in growth plate maturation by inducing Erk1/2 (Mapk3/1) phosphorylation, leading to hypertrophic chondrocyte apoptosis. The Raf kinases induce Mek1/2 (Map2k1/2) and Erk1/2 phosphorylation; however, a role for Raf kinases in endochondral bone formation has not been identified. Ablation of both A-Raf (Araf) and B-Raf (Braf) in chondrocytes does not alter growth plate maturation.

Alike but Different: RAF Paralogs and Their Signaling Outputs.

RAF links RAS, one of the most potent human oncogenes, to its effector ERK and to proliferation. This role is evolutionarily conserved, but while simpler multicellular organisms express one RAF, mammals have three. This Minireview highlights common and divergent features of RAF paralogs, their signaling outputs, and roles in tumorigenesis.