Melendez Romero,Alirio Jose
Email Address
phsmraj@nus.edu.sg
Organizational Units
PHYSIOLOGY
dept
YONG LOO LIN SCH OF MEDICINE
faculty
22 results
Publication Search Results
Now showing 1 - 10 of 22
Publication Sphingosine kinase signalling in immune cells(2005) Kee, T.H.; Vit, P.; Melendez, A.J.; PHYSIOLOGYPublication Peritoneal CD5 + B-1 cells have signaling properties similar to tolerant B cells(2002-08-23) Wong, S.-C.; Chew, W.-K.; Tan, J.E.-L.; Melendez, A.J.; Francis, F.; Lam, K.-P.; PHYSIOLOGY; PAEDIATRICSCD5 + B (or B-1) cells are the normal precursors of B cell chronic lymphocytic leukemia. They differ from conventional B (B-2) cells with respect to their phenotype and mitogenic responses and are often secretors of the natural polyreactive antibodies in the serum. The origin of B-1 cells remains controversial, and the relationship between B-1 cells and autoreactive B cells is unclear. Here, we compare the signaling pathways that are activated by the engagement of the B cell antigen receptor (BCR) in B-1 and B-2 cells. Stimulation of the BCR leads to the induced activation of the three major classes of mitogen-activated protein kinases (MAPKs), ERK, JNK, and p38 MAPK, as well as the Akt kinase and the transcription factors nuclear factor of activated T cells (NF-AT) and NF-κB in B-2 cells. In contrast, B-1 cells have constitutive activation of ERK and NF-AT but exhibit delayed JNK and lack p38 MAPK and NF-κB induction upon BCR cross-linking. The lack of NF-κB activation in B-1 cells may be due to a lack of Akt activation in these cells. Furthermore, our study using specific inhibitors reveals that the extended survival of B-1 cells in culture is not due to the constitutive activation of ERK; nor is it due to Akt signaling or Bcl-X L regulation, since these are not induced in B-1 cells. The current findings of altered MAPK and NF-AT activation and lack of NF-κB induction in B-1 cells indicate that these cells have signaling properties similar to tolerant B cells that are chronically exposed to self-antigens. Indeed, BCR stimulation of B-1 cells does not lead to their full activation as indicated by their lack of maximal up-regulation of specific markers such as CD25, CD69, and CD86.Publication Proteasome inhibition by lactacystin in primary neuronal cells induces both potentially neuroprotective and pro-apoptotic transcriptional responses: A microarray analysis(2005) Yew, E.H.J.; Cheung, N.S.; Choy, M.S.; Qi, R.Z.; Lee, A.Y.-W.; Peng, Z.F.; Melendez, A.J.; Manikandan, J.; Koay, E.S.-C.; Chiu, L.-L.; Ng, W.L.; Whiteman, M.; Kandiah, J.; Halliwell, B.; PHARMACOLOGY; PHYSIOLOGY; BIOCHEMISTRYPublication Phagocytosis: A repertoire of receptors and Ca2+ as a key second messenger(2008-10) Melendez, A.J.; Tay, H.K.; PHYSIOLOGYReceptor-mediated phagocytosis is a complex process that mediates the internalization, by a cell, of other cells and large particles; this is an important physiological event not only in mammals, but in a wide diversity of organisms. Of simple unicellular organisms that use phagocytosis to extract nutrients, to complex metazoans in which phagocytosis is essential for the innate defence system, as a first line of defence against invading pathogens, as well as for the clearance of damaged, dying or dead cells. Evolution has armed multicellular organisms with a range of receptors expressed on many cells that serve as the molecular basis to bring about phagocytosis, regardless of the organism or the specific physiological event concerned. Key to all phagocytic processes is the finely controlled rearrangement of the actin cytoskeleton, in which Ca2+ signals play a major role. Ca2+ is involved in cytoskeletal changes by affecting the actions of a number of contractile proteins, as well as being a cofactor for the activation of a number of intracellular signalling molecules, which are known to play important roles during the initiation, progression and resolution of the phagocytic process. In mammals, the requirement of Ca2+ for the initial steps in phagocytosis, and the subsequent phagosome maturation, can be quite different depending on the type of cell and on the type of receptor that is driving phagocytosis. In this review we discuss the different receptors that mediate professional and non-professional phagocytosis, and discuss the role of Ca2+ in the different steps of this complex process.Publication Anaphylatoxin signaling in human neutrophils: A key role for sphingosine kinase(2004) Ibrahim, F.B.M.; Pang, S.J.; Melendez, A.J.; PHYSIOLOGYPublication A critical role for sphingosine kinase in anaphylatoxin-induced neutropenia, peritonitis, and cytokine production in vivo(2005) Vlasenko, L.P.; Melendez, A.J.; PHYSIOLOGYPublication Anti-inflammatory effects of sphingosine kinase modulation in inflammatory arthritis(2009) Lai, W.-Q.; Irwan, A.W.; Goh, H.H.; Melendez, A.J.; Leung, B.P.; Howe, H.S.; Yu, D.T.; Valle-Onate, R.; McInnes, I.B.; PHYSIOLOGYPublication Differential signal transduction, membrane trafficking, and immune effector functions mediated by FcγRI versus FcγRIIa(2009) Dai, X.; Lin, G.; Chien, T.T.; Yan, T.L.; Soh, H.C.; Kemeny, D.M.; MacAry, P.A.; Jayapal, M.; Hwee, K.T.; Reghunathan, R.; Melendez, A.J.; Floto, R.A.; Smith, K.G.C.; MEDICINE; PHYSIOLOGY; MICROBIOLOGYPublication Distinct roles of sphingosine kinase 1 and 2 in murine collagen-induced arthritis(2009) Lai, W.-Q.; Irwan, A.W.; Goh, H.H.; Melendez, A.J.; Leung, B.P.; McInnes, I.B.; PHYSIOLOGYPublication Expression profile of immune response genes in patients with severe acute respiratory syndrome(2005) Reghunathan, R.; Jayapal, M.; Leung, B.P.; Melendez, A.J.; Hsu, L.-Y.; Chng, H.-H.; Tai, D.; PHYSIOLOGY
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