Comparative analysis of normal versus CLL B-lymphocytes reveals patient-specific variability in signaling mechanisms controlling LFA-1 activation by chemokines

L\u2019attivazione dell\u2019integrina LFA-1 (lymphocyte function-associated antigen-1) da parte di chemochine \ue8 finemente regolata dai meccanismi di signaling (definiti specificamente \u201cinside-out\u201d) responsabili dell\u2019adesione cellulare mediata dalle integrine. Nel presente studio abbiamo investigato la possibilit\ue0 di variazioni qualitative nei sistemi di signaling che controllano l\u2019attivazione di LFA-1 in cellule di pazienti affetti da leucemia linfocitica cronica (CLL). Abbiamo condotto un\u2019analisi 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\u2019attivazione di LFA-1, \ue8 funzionalmente conservato nei linfociti B normali. Nei linfociti B isolati da pazienti, invece, il ruolo del modulo rho-dipendente non \ue8 mantenuto, con notevoli differenze e forte variabilit\ue0. Nello specifico, RhoA e fosfolipasi D1 (PLD1) sono criticamente coinvolte nell\u2019aumento dell\u2019affinit\ue0 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\u2019affinit\ue0 di LFA-1 \ue8 completamente indipendente dall\u2019attivit\ue0 di signaling di Rac1 e Cdc42. Infine, abbiamo dimostrato che la fosfatidilinositolo-4-fosfato 5-chinasi isoforma 1\u3b3 (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\u2019attivazione integrinica tra linfociti normali e linfociti da pazienti con CLL, suggerendo che i pazienti con CLL possono essere valutati in modo ancor pi\uf9 accurato sulla base dell\u2019analisi dei meccanismi di signaling che controllano l\u2019attivazione 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 1\u3b3 (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

Chemokines and the Signaling Modules Regulating Integrin Affinity

Integrin-mediated adhesion is a general concept referring to a series of adhesive phenomena including tethering–rolling, affinity, valency, and binding stabilization altogether controlling cell avidity (adhesiveness) for the substrate. Arrest chemokines modulate each aspect of integrin activation, although integrin affinity regulation has been recognized as the prominent event in rapid leukocyte arrest induced by chemokines. A variety of inside-out and outside-in signaling mechanisms have been related to the process of integrin-mediated adhesion in different cellular models, but only few of them have been clearly contextualized to rapid integrin affinity modulation by arrest chemokines in primary leukocytes. Complex signaling processes triggered by arrest chemokines and controlling leukocyte integrin activation have been described for ras-related rap and for rho-related small GTPases. We summarize the role of rap and rho small GTPases in the regulation of rapid integrin affinity in primary leukocytes and provide a modular view of these pro-adhesive signaling events. A potential, albeit still speculative, mechanism of rho-mediated regulation of cytoskeletal proteins controlling the last step of integrin activation is also discussed. We also discuss data suggesting a functional integration between the rho- and rap-modules of integrin activation. Finally we examine the universality of signaling mechanisms regulating integrin triggering by arrest chemokines

Decreased apoptotic priming and loss of BCL-2 dependence are functional hallmarks of Richter's syndrome

Richter's syndrome (RS) is the transformation of chronic lymphocytic leukemia (CLL) into a high-grade B-cell malignancy. Molecular and functional studies have pointed out that CLL cells are close to the apoptotic threshold and dependent on BCL-2 for survival. However, it remains undefined how evasion from apoptosis evolves during disease transformation. Here, we employed functional and static approaches to compare the regulation of mitochondrial apoptosis in CLL and RS. BH3 profiling of 17 CLL and 9 RS samples demonstrated that RS cells had reduced apoptotic priming and lower BCL-2 dependence than CLL cells. While a subset of RS was dependent on alternative anti-apoptotic proteins and was sensitive to specific BH3 mimetics, other RS cases harbored no specific anti-apoptotic addiction. Transcriptomics of paired CLL/RS samples revealed downregulation of pro-apoptotic sensitizers during disease transformation. Albeit expressed, effector and activator members were less likely to colocalize with mitochondria in RS compared to CLL. Electron microscopy highlighted reduced cristae width in RS mitochondria, a condition further promoting apoptosis resistance. Collectively, our data suggest that RS cells evolve multiple mechanisms that lower the apoptotic priming and shift the anti-apoptotic dependencies away from BCL-2, making direct targeting of mitochondrial apoptosis more challenging after disease transformation

An isoform of the giant protein titin is a master regulator of human T lymphocyte trafficking

Response to multiple microenvironmental cues and resilience to mechanical stress are essential features of trafficking leukocytes. Here, we describe unexpected role of titin (TTN), the largest protein encoded by the human genome, in the regulation of mechanisms of lymphocyte trafficking. Human T and B lymphocytes express five TTN isoforms, exhibiting cell-specific expression, distinct localization to plasma membrane microdomains, and different distribution to cytosolic versus nuclear compartments. In T lymphocytes, the LTTN1 isoform governs the morphogenesis of plasma membrane microvilli independently of ERM protein phosphorylation status, thus allowing selectin-mediated capturing and rolling adhesions. Likewise, LTTN1 controls chemokine-triggered integrin activation. Accordingly, LTTN1 mediates rho and rap small GTPases activation, but not actin polymerization. In contrast, chemotaxis is facilitated by LTTN1 degradation. Finally, LTTN1 controls resilience to passive cell deformation and ensures T lymphocyte survival in the blood stream. LTTN1 is, thus, a critical and versatile housekeeping regulator of T lymphocyte trafficking

Exact Distributed Load Centrality Computation: Algorithms, Convergence, and Applications to Distance Vector Routing

Many optimization techniques for networking protocols take advantage of topological information to improve performance. Often, the topological information at the core of these techniques is a centrality metric such as the Betweenness Centrality (BC) index. BC is, in fact, a centrality metric with many well-known successful applications documented in the literature, from resource allocation to routing. To compute BC, however, each node must run a centralized algorithm and needs to have the global topological knowledge; such requirements limit the feasibility of optimization procedures based on BC. To overcome restrictions of this kind, we present a novel distributed algorithm that requires only local information to compute an alternative similar metric, called Load Centrality (LC). We present the new algorithm together with a proof of its convergence and the analysis of its time complexity. The proposed algorithm is general enough to be integrated with any distance vector (DV) routing protocol. In support of this claim, we provide an implementation on top of Babel, a real-world DV protocol. We use this implementation in an emulation framework to show how LC can be exploited to reduce Babel's convergence time upon node failure, without increasing control overhead. As a key step towards the adoption of centrality-based optimization for routing, we study how the algorithm can be incrementally introduced in a network running a DV routing protocol. We show that even when only a small fraction of nodes participate in the protocol, the algorithm accurately ranks nodes according to their centrality

Wikipedia pagecounts sorted by page (year 2014)

<div>This dataset contains the page view statistics for all the WikiMedia projects in the year 2014, ordered by (project, page, timestamp). It has been generated starting from the WikiMedia's pagecounts-raw[1] dataset.</div><br>The CSV uses *spaces* as delimiter, without any form of escaping because it is not needed. It has 5 columns:<br><br>* project: the project name<br>* page: the page requested, url-escaped<br>* timestamp: the timestamp of the hour (format: "%Y%m%d-%H%M%S")<br>* count: the number of times the page has been requested (in that hour)<br>* bytes: the number of bytes transferred (in that hour)<br><br>You can download the full dataset via torrent[2].<br><br>Further information about this dataset are available at:<br>http://disi.unitn.it/~consonni/datasets/wikipedia-pagecounts-sorted-by-page-year-2014/<div><br>[1] https://dumps.wikimedia.org/other/pagecounts-raw/</div><div>[2] http://disi.unitn.it/~consonni/datasets/wikipedia-pagecounts-sorted-by-page-year-2014/#download</div

Monocyte-to-macrophage switch reversibly impaired by Ibrutinib.

Ibrutinib 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