From Quiescence to Activation: The Reciprocal Regulation of Ras and Rho Signaling in Hepatic Stellate Cells.

Chronic liver diseases are marked by persistent inflammation and can evolve into liver fibrosis, cirrhosis, and hepatocellular carcinoma. In an affected liver, hepatic stellate cells (HSCs) transition from a quiescent to an activated state and adopt a myofibroblast-like cell phenotype. While these activated cells play a role in supporting liver regeneration, they can also have detrimental effects on liver function as the disease progresses to fibrosis and cirrhosis.

Structural Insights Into the Impact of the Glycine-Rich Loop Mutation in Noonan Syndrome on the ATP Binding Pocket of CRAF Kinase.

The pathogenic G361A variant of CRAF, associated with increased intrinsic kinase activity in Noonan syndrome (NS), remains poorly understood in terms of its molecular and structural impact on kinase activity. To elucidate the mechanistic implications of the glycine to alanine substitution at residue 361 in CRAF, we employed molecular dynamics simulations. Our findings reveal that this mutation predominantly affects the ATP binding pocket and critical intermolecular interactions within the active cleft that favors the phosphate transfer reaction.

SIRT4 as a novel interactor and candidate suppressor of C-RAF kinase in MAPK signaling.

Cellular responses leading to development, proliferation, and differentiation depend on RAF/MEK/ERK signaling, which integrates and amplifies signals from various stimuli for downstream cellular responses. C-RAF activation has been reported in many types of tumor cell proliferation and developmental disorders, necessitating the discovery of potential C-RAF protein regulators. Here, we identify a novel and specific protein interaction between C-RAF among the RAF kinase paralogs, and SIRT4 among the mitochondrial sirtuin family members SIRT3, SIRT4, and SIRT5.

The Microenvironment of the Pathogenesis of Cardiac Hypertrophy.

Pathological cardiac hypertrophy is a key risk factor for the development of heart failure and predisposes individuals to cardiac arrhythmia and sudden death. While physiological cardiac hypertrophy is adaptive, hypertrophy resulting from conditions comprising hypertension, aortic stenosis, or genetic mutations, such as hypertrophic cardiomyopathy, is maladaptive. Here, we highlight the essential role and reciprocal interactions involving both cardiomyocytes and non-myocardial cells in response to pathological conditions.

Molecular analyses of the C-terminal CRAF variants associated with cardiomyopathy reveal their opposing impacts on the active conformation of the kinase domain.

The germline mutations in the C-terminus of CRAF kinase, particularly L603, and S612T/L613V, are associated with congenital heart disorders, for example, dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). The experimental data suggest that genetic alternation at position 603 impairs, while those at positions 612/613 enhance the CRAF kinase activity. However, the underlying mechanistic details by which these mutations increase or decrease kinase activity remain elusive.

Testicular germ cell tumors: Genomic alternations and RAS-dependent signaling.

Testicular germ cell tumors (TGCTs) are a common malignancy occurring in young adult men. The various genetic risk factors have been suggested to contribute to TGCT pathogenesis, however, they have a distinct mutational profile with a low rate of somatic point mutations, more frequent chromosomal gains, and aneuploidy. The most frequently mutated oncogenes in human cancers are RAS oncogenes, while their impact on testicular carcinogenesis and refractory disease is still poorly understood.

New mechanistic insights into the RAS-SIN1 interaction at the membrane.

Stress-activated MAP kinase-interacting protein 1 (SIN1) is a central member of the mTORC2 complex that contains an N-terminal domain (NTD), a conserved region in the middle (CRIM), a RAS-binding domain (RBD), and a pleckstrin homology domain. Recent studies provided valuable structural and functional insights into the interactions of SIN1 and the RAS-binding domain of RAS proteins. However, the mechanism for a reciprocal interaction of the RBD-PH tandem with RAS proteins and the membrane as an upstream event to spatiotemporal mTORC2 regulation is not clear.

Physical Interaction between Embryonic Stem Cell-Expressed Ras (ERas) and Arginase-1 in Quiescent Hepatic Stellate Cells.

Embryonic stem cell-expressed Ras (ERas) is an atypical constitutively active member of the Ras family and controls distinct signaling pathways, which are critical, for instance, for the maintenance of quiescent hepatic stellate cells (HSCs). Unlike classical Ras paralogs, ERas has a unique N-terminal extension (Nex) with as yet unknown function. In this study, we employed affinity pull-down and quantitative liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses and identified 76 novel binding proteins for human and rat ERas Nex peptides, localized in different subcellular compartments and involved in various cellular processes.

Novel FMRP interaction networks linked to cellular stress.

Silencing of the fragile X mental retardation 1 (FMR1) gene and consequently lack of synthesis of FMR protein (FMRP) are associated with fragile X syndrome, which is one of the most prevalent inherited intellectual disabilities, with additional roles in increased viral infection, liver disease, and reduced cancer risk. FMRP plays critical roles in chromatin dynamics, RNA binding, mRNA transport, and mRNA translation. However, the underlying molecular mechanisms, including the (sub)cellular FMRP protein networks, remain elusive.

Coadministration of auraptene and radiotherapy; a novel modality against colon carcinoma cells and .

Use of ionizing radiation (IR) is a common therapeutic modality for patients with colon carcinoma, although resistance of cancer cells and unintended toxicity reduce clinical outcomes. To enhance radioresponse of colon cancer cells, we designed a novel approach using auraptene (AUR) in combination with ionizing radiation (IR). For in vitro studies, CT26 cells were pretreated with AUR and irradiated at different doses.

bFGF-mediated pluripotency maintenance in human induced pluripotent stem cells is associated with NRAS-MAPK signaling.

Background: Human pluripotent stem cells (PSCs) open new windows for basic research and regenerative medicine due to their remarkable properties, i.e. their ability to self-renew indefinitely and being pluripotent.

Structural snapshots of RAF kinase interactions.

RAF (rapidly accelerated fibrosarcoma) Ser/Thr kinases (ARAF, BRAF, and CRAF) link the RAS (rat sarcoma) protein family with the MAPK (mitogen-activated protein kinase) pathway and control cell growth, differentiation, development, aging, and tumorigenesis. Their activity is specifically modulated by protein-protein interactions, post-translational modifications, and conformational changes in specific spatiotemporal patterns via various upstream regulators, including the kinases, phosphatase, GTPases, and scaffold and modulator proteins. Dephosphorylation of Ser-259 (CRAF numbering) and dissociation of 14-3-3 release the RAF regulatory domains RAS-binding domain and cysteine-rich domain for interaction with RAS-GTP and membrane lipids.

Suppression of dsRNA response genes and innate immunity following Oct4, Stella, and Nanos2 overexpression in mouse embryonic fibroblasts.

The self-renewal capacity of germline derived stem cells (GSCs) makes them an ideal source for research and use in clinics. Despite the presence of active gene network similarities between embryonic stem cells (ESCs) and GSCs, there are unanswered questions regarding the roles of evolutionary conserved genes in GSCs. To determine the reprogramming potential of germ cell- specific genes, we designed a polycistronic gene cassette expressing Stella, Oct4 and Nanos2 in a lentiviral-based vector.

IL-2 Inducible Kinase ITK is Critical for HIV-1 Infection of Jurkat T-cells.

Successful replication of Human immunodeficiency virus (HIV)-1 depends on the expression of various cellular host factors, such as the interleukin-2 inducible T-cell kinase (ITK), a member of the protein family of TEC-tyrosine kinases. ITK is selectively expressed in T-cells and coordinates signaling pathways downstream of the T-cell receptor and chemokine receptors, including PLC-1 activation, Ca-release, transcription factor mobilization, and actin rearrangements. The exact role of ITK during HIV-1 infection is still unknown.

Correction: Aberrant neuronal activity-induced signaling and gene expression in a mouse model of RASopathy.

[This corrects the article DOI: 10.1371/journal.pgen.

Aberrant neuronal activity-induced signaling and gene expression in a mouse model of RASopathy.

Noonan syndrome (NS) is characterized by reduced growth, craniofacial abnormalities, congenital heart defects, and variable cognitive deficits. NS belongs to the RASopathies, genetic conditions linked to mutations in components and regulators of the Ras signaling pathway. Approximately 50% of NS cases are caused by mutations in PTPN11.

The RAS-Effector Interface: Isoform-Specific Differences in the Effector Binding Regions.

RAS effectors specifically interact with the GTP-bound form of RAS in response to extracellular signals and link them to downstream signaling pathways. The molecular nature of effector interaction by RAS is well-studied but yet still incompletely understood in a comprehensive and systematic way. Here, structure-function relationships in the interaction between different RAS proteins and various effectors were investigated in detail by combining our in vitro data with in silico data.

Dedifferentiation Effects of Rabbit Regenerating Tissue on Partially Differentiated Cells.

Cell Stemness can be achieved by various reprogramming techniques namely, somatic cell nuclear transfer, cell fusion, cell extracts, and introduction of transcription factors from which induced pluripotent stem cells (iPSCs) are obtained. iPSCs are valuable cell sources for drug screening and human disease modeling. Alternatives to virus-based introduction of transcription factors include application of DNA-free methods and introduction of chemically defined culturing conditions.

The Role of Embryonic Stem Cell-expressed RAS (ERAS) in the Maintenance of Quiescent Hepatic Stellate Cells.

Hepatic stellate cells (HSCs) were recently identified as liver-resident mesenchymal stem cells. HSCs are activated after liver injury and involved in pivotal processes, such as liver development, immunoregulation, regeneration, and also fibrogenesis. To date, several studies have reported candidate pathways that regulate the plasticity of HSCs during physiological and pathophysiological processes.

The Function of Embryonic Stem Cell-expressed RAS (E-RAS), a Unique RAS Family Member, Correlates with Its Additional Motifs and Its Structural Properties.

E-RAS is a member of the RAS family specifically expressed in embryonic stem cells, gastric tumors, and hepatic stellate cells. Unlike classical RAS isoforms (H-, N-, and K-RAS4B), E-RAS has, in addition to striking and remarkable sequence deviations, an extended 38-amino acid-long unique N-terminal region with still unknown functions. We investigated the molecular mechanism of E-RAS regulation and function with respect to its sequence and structural features.