1,720,977 research outputs found
Comparative analysis of normal versus CLL B-lymphocytes reveals patient-specific variability in signaling mechanisms controlling LFA-1 activation by chemokines
Full text linkL’attivazione dell’integrina LFA-1 (lymphocyte function-associated antigen-1) da parte di chemochine è finemente regolata dai meccanismi di signaling (definiti specificamente “inside-out”) responsabili dell’adesione cellulare mediata dalle integrine. Nel presente studio abbiamo investigato la possibilità di variazioni qualitative nei sistemi di signaling che controllano l’attivazione di LFA-1 in cellule di pazienti affetti da leucemia linfocitica cronica (CLL). Abbiamo condotto un’analisi comparativa multipla del ruolo del modulo di signaling rho-dipendente, recentemente descritto nel nostro laboratorio, in linfociti B da donatori sani e da soggetti affetti da CLL. Abbiamo scoperto che il modulo rho-dipendente, che regola l’attivazione di LFA-1, è funzionalmente conservato nei linfociti B normali. Nei linfociti B isolati da pazienti, invece, il ruolo del modulo rho-dipendente non è mantenuto, con notevoli differenze e forte variabilità. Nello specifico, RhoA e fosfolipasi D1 (PLD1) sono criticamente coinvolte nell’aumento dell’affinità di LFA-1 indotta da chemochina CXCL12 in tutti i campioni studiati. Le funzioni di Rac1 e Cdc42, invece, sono variabili da paziente a paziente, con un gruppo di pazienti in cui la regolazione dell’affinità di LFA-1 è completamente indipendente dall’attività di signaling di Rac1 e Cdc42. Infine, abbiamo dimostrato che la fosfatidilinositolo-4-fosfato 5-chinasi isoforma 1γ (PIP5KC) non esercita alcuna funzione regolatoria in tutti i campioni analizzati. I nostri dati implicano che la progressione neoplastica potrebbe completamente annullare la funzione regolatoria di Rac1, Cdc42 e PIP5KC e mostrano quindi una profonda divergenza nei meccanismi di signaling che modulano l’attivazione integrinica tra linfociti normali e linfociti da pazienti con CLL, suggerendo che i pazienti con CLL possono essere valutati in modo ancor più accurato sulla base dell’analisi dei meccanismi di signaling che controllano l’attivazione di LFA-1. I nostri dai possono, quindi, potenzialmente avere effetti sui protocolli di diagnosi, prognosi e terapia della leucemia linfocitica cronica.Activation of lymphocyte function-associated antigen-1 (LFA-1) by chemokines is fine-tuned by inside-out signaling mechanisms responsible for integrin-mediated adhesion modulation. In the present study we investigated the possibility of qualitative variability of signaling mechanisms controlling LFA-1 activation in chronic lymphocytic leukemia (CLL) cells. We pursued a multiplexed comparative analysis of the role of the recently described chemokine-triggered rho-signaling module in human normal versus CLL B-lymphocytes. We found that the rho module of LFA-1 affinity triggering is functionally conserved in normal B-lymphocytes. In contrast, in malignant B-lymphocytes isolated from B-CLL patients the role of the rho module was not maintained, showing remarkable differences and variability. Specifically, RhoA and phospholipase D1 (PLD1) were crucially involved in LFA-1 affinity triggering by CXCL12 in all analyzed patients. In contrast, Rac1 and CDC42 involvement displayed a consistent patient-by-patient variability, with a group of patients showing LFA-1 affinity modulation totally independent of Rac1 and CDC42 signaling activity. Finally, phosphatidylinositol-4-phosphate 5-kinase isoform 1γ (PIP5KC) was found without any regulatory role in all patients. The data imply that the neoplastic progression may completely bypass the regulatory role of Rac1, CDC42 and PIP5KC and show a profound divergence in the signaling mechanisms controlling integrin activation in normal versus neoplastic lymphocytes, suggesting that CLL patients can be more accurately evaluated on the basis of the analysis of signaling mechanisms controlling integrin activation. Our findings may potentially impact diagnosis, prognosis and therapy of CLL disorders
Monocyte-to-macrophage switch reversibly impaired by Ibrutinib.
No full textIbrutinib is increasingly adopted for treating lymphoid malignancies. While growing amounts of data pile up about Ibrutinib mechanism of action on neoplastic B cells, little is known about its impact on other immune cells. Here we investigated the effect of Ibrutinib on monocyte/macrophage functions. (1) Ibrutinib treatment of purified human monocytes affected both chemoattractant-triggered inside-out as well as integrin-mediated outside-in signaling events, thus provoking defective adhesion and spreading on purified integrin ligands, respectively. (2) In in vitro cell-culture experiments, Ibrutinib promoted a differentiation shift of monocytes to fibrocyte-like cells, characterized by the acquisition of a typical elongated cell morphology. Importantly, this clear-cut shape transition also occurred upon culturing monocytes with sera derived from Ibrutinib-treated patients, thus clearly suggesting that the drug concentrations achievable in vivo can generate the phenotypic shift. (3) Ibrutinib-induced fibrocyte-like cells showed adhesion deficiency, altered phagocytic properties, and, with respect to macrophages, they acquired the capability of generating larger amounts of reactive oxygen species, possibly displaying different metabolic activities. Taken together, our results indicate that Ibrutinib has profound effects on the monocyte/macrophage immunobiology. They may finally shed some light about the biological ground of several Ibrutinib-related toxicities
Activation of Protein Tyrosine Phosphatase Receptor Type γ Suppresses Mechanisms of Adhesion and Survival in Chronic Lymphocytic Leukemia Cells
No full textThe regulatory role of protein tyrosine kinases in β1- and β2-integrin activation and in the survival of chronic lymphocytic leukemia (CLL) cells is well established. In contrast, the involvement of protein tyrosine phosphatases in CLL biology was less investigated. We show that selective activation of the protein tyrosine phosphatase receptor type γ (PTPRG) strongly suppresses integrin activation and survival in leukemic B cells isolated from patients with CLL. Activation of PTPRG specifically inhibits CXCR4- as well as BCR-induced triggering of LFA-1 and VLA-4 integrins and mediated rapid adhesion. Triggering of LFA-1 affinity is also prevented by PTPRG activity. Analysis of signaling mechanisms shows that activation of PTPRG blocks chemokine-induced triggering of JAK2 and Bruton's tyrosine kinase protein tyrosine kinases and of the small GTP-binding protein RhoA. Furthermore, activated PTPRG triggers rapid and robust caspase-3/7-mediated apoptosis in CLL cells in a manner quantitatively comparable to the Bruton's tyrosine kinase inhibitor ibrutinib. However, in contrast to ibrutinib, PTPRG-triggered apoptosis is insensitive to prosurvival signals generated by CXCR4 and BCR signaling. Importantly, PTPRG activation does not trigger apoptosis in healthy B lymphocytes. The data show that activated PTPRG inhibits, at once, the signaling pathways controlling adhesion and survival of CLL cells, thus emerging as a negative regulator of CLL pathogenesis. These findings suggest that pharmacological potentiation of PTPRG tyrosine-phosphatase enzymatic activity could represent a novel approach to CLL treatment
Protein Tyrosine Phosphatase Receptor Type γ Is a JAK Phosphatase and Negatively Regulates Leukocyte Integrin Activation
No full textRegulation of signal transduction networks depends on protein kinase and phosphatase activities. Protein tyrosine kinases of the JAK family have been shown to regulate integrin affinity modulation by chemokines and mediated homing to secondary lymphoid organs of human T lymphocytes. However, the role of s in leukocyte recruitment is still elusive. In this study, we address this issue by focusing on protein tyrosine phosphatase receptor type γ (PTPRG), a tyrosine phosphatase highly expressed in human primary monocytes. We developed a novel methodology to study the signaling role of receptor type tyrosine phosphatases and found that activated PTPRG blocks chemoattractant-induced β2 integrin activation. Specifically, triggering of LFA-1 to high-affinity state is prevented by PTPRG activation. High-throughput phosphoproteomics and computational analyses show that PTPRG activation affects the phosphorylation state of at least 31 signaling proteins. Deeper examination shows that JAKs are critically involved in integrin-mediated monocyte adhesion and that PTPRG activation leads to JAK2 dephosphorylation on the critical 1007-1008 phosphotyrosine residues, implying JAK2 inhibition and thus explaining the antiadhesive role of PTPRG. Overall, the data validate a new approach to study receptor tyrosine phosphatases and show that, by targeting JAKs, PTPRG downmodulates the rapid activation of integrin affinity in human monocytes, thus emerging as a potential novel critical regulator of leukocyte trafficking
JAK2 tyrosine kinase mediates integrin activation induced by CXCL12 in B-cell chronic lymphocytic leukemia
No full textChemokines participate to B-cell chronic lymphocytic leukemia (B-CLL) pathogenesis by promoting cell adhesion and survival in bone marrow stromal niches and mediating cell dissemination to secondary lymphoid organs. In this study we investigated the role of JAK protein tyrosine kinases (PTK) in adhesion triggering by the CXC chemokine CXCL12 in normal versus CLL B-lymphocytes. We demonstrate that CXCL12 activates JAK2 in normal as well as CLL B-lymphocytes, with kinetics consistent with rapid adhesion triggering. By using complementary methodologies of signal transduction interference, we found that JAK2 mediates CXCL12-triggered activation of lymphocyte function-associated antigen-1 (LFA-1) and very late antigen-4 (VLA-4) integrins. We also show that JAK2 mediates the activation of the small GTP-binding protein RhoA, in turn controlling LFA-1 affinity triggering by CXCL12. Importantly, comparative analysis of 41 B-CLL patients did not evidence JAK2 functional variability between subjects, thus suggesting that JAK2, differently from other signaling events involved in adhesion regulation in B-CLL, is a signaling molecule downstream to CXCR4 characterized by a conserved regulatory role. Our results reveal JAK2 as critical component of chemokine signaling in CLL B-lymphocytes and indicate JAK inhibition as a potentially useful new pharmacological approach to B-CLL treatment
The expression of p75 neurotrophin receptor protects against the neurotoxicity of soluble oligomers of beta-amyloid.
No full textIn this paper, evidence is provided that p75 neurotrophin receptor (p75NTR) exerts an opposite role on the cytotoxic function of hamyloid
(Ah) depending on the different state of the peptide, fibrillar or oligomeric soluble form. Previous work in our laboratory has shown
that the expression of p75NTR is required for cell death in vitro by Ah peptides in fibrillar form (G. Perini, V. Della-Bianca, V. Politi, G.
Della Valle, I. Dal-Pra, F. Rossi, U. Armato. Role of p75 neurotrophin receptor in the neurotoxicity by beta-amyloid peptides and synergistic
effect of inflammatory cytokines. J. Exp. Med. 195 (2002) 907-918). In the present study, performed by using the same cell clones and
procedures as in previous paper, we show that: (a) soluble oligomers of Ah(1–42) exert a cytotoxic activity independent of p75NTR, (b) the
expression of p75NTR exerts a protective role against the toxic activity of soluble oligomers, (c) this role is due to an active function of the
juxtamembrane sequence of the cytoplasmic region of p75NTR and (d) the protective function is mediated by phosphatidylinositide 3-kinase
(PI3K) activity
Soluble factors released from astrocytes modulate the insulin-like growth factor receptor (IGF1-R) expression in cortical neurons during in vitro senescence.
No full textLate-onset Alzheimer’s disease (AD) is the World’s most prevalent form of dementia and one of most common age-releated diseases. The abnormal accumulation of amyloid β-peptides (Aβ) is considered the main pathogenetic event responsible for the loss of synapses and neurons and the consequent cognitive decline. Although aging represents the single most important risk factor for Alzheimer’s disease, the molecular events that connect normal aging to AD are unkown. Recently it has been shown that during normal aging, Aβ generation in the brain is induced by a switch from the TrkA to p75NTR neurotrophin receptor, that leads to the activation of neutral sphingomyelinase and liberation of the lipid second messenger ceramide, which in turn is responsible for the molecular stabilization of BACE1 and the production of Aβ. An increased expression of insulin-like growth factor receptor (IGF1-R) during aging is responsible for the switch of the two neurotrophin receptors (Costantini et al. EMBO J. 2006), thus representing an interesting target for prevention. However, the molecular mechanism(s) that regulate the IGF1-R expression in brain during aging are not known.
Here, by using long-term neuronal cultures as a model of aging (Lesuisse et al J. Neurobiol. 2002), we report data showing that soluble factors released from glial cells modulate IGF1-R expression in neurons during senescence. In fact: i) IGF1-R expression does not increase in neuronal cell cultures where the proliferation of glial cells was prevented by cytosine β-D-arabinofuranoside hydrochloride (Ara-C) treatment; ii) the addition of conditioned medium from a 24-days-old neuronal culture (high percentage of glial cells and high expression of IGF1R) to a 3-days-old neuronal culture (low percentage of glial cells and low expression of IGF1R) induces an increase of IGF1-R expression; iii) co-culturing Ara-C-treated neurons with primary astrocytes in the presence of a transwell that physically separates the two cell populations, but allows the passage of soluble factors, increases the expression of IGF1-R in neurons. Studies are now under investigation in order to identify the glial-derived soluble factors responsible for the modulation of IGF1-R expression
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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