Receptors & Clinical Investigation (E-Journal - Smart Science & Technology)
Not a member yet
168 research outputs found
Sort by
New mechanisms of neurite outgrowth and TrkA receptor activation/signaling
Get PDFThe paper we recently published in PNAS, entitled “Neurite outgrowth induced by NGF or L1CAM via activation of the TrkA receptor is sustained also by the exocytosis of enlargeosomes” (Colombo et al., 2014), reported studies carried out in clones isolated from the PC12 line, frequently employed as a neuronal model. Two original and integrated findings were obtained, concerning the vesicle traffic and fusion processes necessary for neurite outgrowth, and the activation of TrkA, the tyrosine kinase receptor of NGF, by the adhesion protein L1CAM. Both these findings provide an explanation to results previously obtained in our and other laboratories
The function of membrane-associated molecules in acquired resistance to antiestrogens in breast cancer
Get PDFLong-term clinical adjuvant antihormone therapy for breast cancer has significantly improved survival of estrogen receptor (ER)-positive breast cancer patients, but acquired resistance to antiestrogens is a major challenge in clinic. The evolution of acquired resistance to selective estrogen receptor modulators (SERMs) is unique because the growth of resistant tumors is dependent on SERMs. Thus, it appears that acquired resistance to SERMs is initially able to utilize either estrogen (E2) or a SERM as the growth stimulus in the ER-positive SERM-resistant breast tumors. However, no mechanism has been established to explain this paradox. Our newly established cell model MCF-7: PF, for the first time, replicates Phase I acquired resistance to SERMs in vitro. The cells are stimulated to grow robustly with E2 and SERMs through the ER which is confirmed by the evidence that pure antiestrogen ICI 182,780 (ICI) completely blocks the stimulation induced by E2 or SERMs. In contrast to E2 that activates classical ER-target genes, SERMs continue to function as effective antiestrogens to inhibit classical ER-target genes, even at the time of growth stimulation. A significant alteration of ER function observed in SERM-resistant cells is the enhancement of the non-genomic pathway of ER and the activation of multiple membrane function-associated molecules including focal adhesion molecules and adapter proteins to further increase phosphorylation of insulin-like growth factor-1 receptor (IGF-1R). Inhibition of membrane-associated signaling, IGF-1R and focal adhesion kinase (FAK), completely abolishes 4-OHT-stimulated cell growth. Overall, the constant nuclear pressure causes broad activation of membrane-associated signaling to aid breast cancer cell survival during the selection process required for acquired SERM resistance. The targeting of these membrane function-associated pathways and seeking new unanticipated combination therapies may have further clinical potential to decipher and treat endocrine-resistant breast cancer
Targeting receptor tyrosine kinases in malignant pleural mesothelioma: Focus on FGF-receptors
Get PDFFibroblast growth factor receptors (FGFRs) constitute a subfamily of receptor tyrosine kinases. Four different receptors, FGFR1-4, bind 18 different fibroblast growth factors (FGFs) and signal mainly along the mitogen-activated protein kinase (MAPK), the phosphatidylinositol 3 kinase (PI3K) and the phospholipase c gamma (PLC?) pathway. Physiologically, they are major regulators of embryonic development and metabolism. Deregulation of FGFR signals is increasingly recognized to play important roles in malignant diseases and may constitute a feasible therapeutic target. We recently investigated their role in malignant pleural mesothelioma (MPM), an aggressive malignancy mainly caused by asbestos exposure and with currently limited therapeutic options. We demonstrated high expression of several FGFs/FGFRs, especially FGFR1, FGF2 and FGF18 in cultured tumor cells and tissue specimens and identified FGFR-mediated signals as major driver of MPM cell growth, survival and migration. FGFR blockade by a tyrosine kinase inhibitor or by a dominant-negative receptor construct resulted in reduced MPM growth in vitro and in vivo and, furthermore, enhanced the efficacy of chemo- or radiotherapy. Several other receptor tyrosine kinases, including EGFR, MET and AXL were found to be overexpressed in MPM but translation into clinically successful therapeutic approaches has not yet been achieved. Inhibition of FGF-receptors may have the advantage of targeting both the tumor cells as well as the tumor vasculature and should be further evaluated
Mutual Inhibitory Mechanisms between PPAR? and Hif-1?: Implication in Pulmonary Hypertension
Get PDFTranscription factor hypoxia-inducible factor 1? (Hif-1?) is known for its crucial role in promoting the pathogenesis of pulmonary hypertension (PH). Previous studies have indicated the in-depth mechanisms that Hif-1? increases the distal pulmonary arterial (PA) pressure and vascular remodeling by triggering the intracellular calcium homeostasis, especially the store-operated calcium entry (SOCE) process. In our recent research paper published in the Journal of Molecular Medicine, we found that the transcription factor peroxisome proliferator-activated receptor ? (PPAR?) activation could attenuate the PH pathogenesis by suppressing the elevated distal PA pressure and vascular remodeling. Moreover, these effects are likely mediated through the inhibition of SOCE by suppressing Hif-1?. These results provided convincing evidence and novel mechanisms in supporting the protective roles of PPAR? on PH treatment. Then, by using comprehensive loss-of-function and gain-of-function strategies, we further identified the presence of a mutual inhibitory mechanism between PPAR? and Hif-1?. Basically, under chronic hypoxic stress, accumulated Hif-1? leads to abolished expression of PPAR? and progressive imbalance between PPAR? and Hif-1?, which promotes the PH progression; however, targeted PPAR? restoration approach reversely inhibits Hif-1? level and Hif-1? mediated signaling transduction, which subsequently attenuates the elevated pulmonary arterial pressure and vascular remodeling under PH pathogenesis
Estrogen receptor-dependent modulation of dendritic cell biology of mice and women
Get PDFAutoimmune and infectious diseases differentially affect women from men. Women tend to develop stronger immune responses and thus in general men are more susceptible to infectious diseases whereas women are more likely to develop autoimmune diseases. These differences could be in part attributable to the pro-inflammatory role of the female sex hormone estrogen on immunity and particularly on dendritic cells (DCs), a key subset of innate immune cells. For several years now, we have undertaken studies to understand how estrogens influence the biology of murine and human DCs. We and others have demonstrated that estradiol (E2) was required for the optimal in vitro differentiation of murine DCs and acquisition of their effector functions. These effects on DC biology were dependent on the activation of the estrogen receptor a (ERa). More recently, we focused our interest on plasmacytoid dendritic cells (pDCs). Indeed, this subset that produces large amounts of IFN-a/b in response to viral or endogenous nucleic acids through activation of their TLR-7 and TLR-9 show gender differences with enhanced IFN-a production by pDCs from women, compared to men. We could establish, in Human and in mice, that in vivo treatment with E2 enhanced the TLR-dependent production of IFNa by pDCs. In mice, we demonstrated that the amplifying effect of endogenous and exogenous estrogens is dependent on the intrinsic activation of ER? by hormone in the pDCs. To further characterize the mechanisms underlying this sex-based difference in pDC innate functions, we investigated the respective contribution of X chromosome dosage versus sex hormones using a humanized mouse model in which male or female NOD-SCID-ß2m-/- mice were transplanted with human progenitor cells (HPCs) purified from either male (XY) or female (XX) donors. We could show that cell-intrinsic ER-signaling and X chromosome complement both independently contribute to the enhanced TLR-7-mediated response of pDCs in women, which may account for the sex-based differences in autoimmune and infectious diseases. Altogether, our work demonstrates that estrogen-mediated activation of ER signaling is a key regulator of DC biology both in Human and in mouse
Unraveling the mechanism of cholesterol-mediated regulation of receptor dimerization in plasma membranes in vivo
Get PDFMembrane cholesterol can alter the signaling pathways of living cells. However, the process that modulates the interaction of receptor proteins is still unclear. We performed single-molecule optical tracking of ligand-induced dimerization of epidermal growth factor receptors (EGFRs) in two cancerous cell lines (HeLa and A431) and one normal endothelial cell line (MCF12A). We discovered that unliganded EGFRs typically reside in non-raft regions of the plasma membrane and can move into raft domains upon ligand binding. This ligand-induced motion could be a common behavior in live cells. We found that the amount of membrane cholesterol significantly affects the stability of EGFR dimers by manipulating the total amount of membrane cholesterol with methyl-?-cyclodextrin and the local concentration of cholesterol with nystatin. The EGFR dimers in the plasma membrane of normal cells are more sensitive to changes in the local concentration of cholesterol compared with the cancer cells. Our methodology can yield useful information for understanding cholesterol-mediated protein-protein interactions in live cells
Rictor beyond the TORC: linking the proliferation, migration and Fc?RI-mediated degranulation of human mast cells
Get PDFRictor is a cytosolic protein that was originally recognized as a specific component of the mammalian target of rapamycin (mTOR) complex 2 (mTORC2). This complex integrates nutrient- and growth factor-induced signaling cascades to regulate cell proliferation and metabolism. An increasing body of evidence however shows that rictor may also function independently of mTORC2 through association with other proteins and complexes. Recent studies on mast cells demonstrated that in the context of mTORC2 rictor positively regulates proliferation of immature and migration of mature mast cells whereas by itself rictor independently functions as a molecular relay that sets the sensitivity of high affinity receptor for IgE (FceRI) for activating mast cell degranulation. These novel findings suggest that rictor is a multifunctional protein that plays a role in synchronization of multiple cellular functions in mast cells
Which ARB drug is better for heart failure therapy? Aldosterone suppression holds the answer
Get PDFThe known physiological effect of angiotensin II (AngII) type I receptors (AT1Rs), synthesis and secretion of the cardiotoxic hormone aldosterone, whose elevation accompanies and aggravates heart failure (HF), is mediated by both G proteins and barrestins (barrs). We recently examined the relative potencies of all the currently used in the clinic AT1R antagonist drugs (angiotensin receptor blockers, ARBs, or sartans) at preventing activation of either of these two signaling mediators at the AngII-bound AT1R and, consequently, at suppression of aldosterone in vitro and in vivo. We also tested the impact of the aldosterone suppression they produce in vivo on the cardiac function of post-myocardial infarction (MI) animals progressing to HF. By using a variety of techniques in cultured cells in vitro, we found that all ARBs are potent inhibitors of G protein activation at the AT1R but display striking differences in their potency at blocking the second signaling component of aldosterone production in the adrenal cortex, i.e. barrs. Candesartan and valsartan in particular were found the most potent at blocking AngII-induced barr activation at this receptor, translating into excellent efficacies at aldosterone suppression in vitro and in vivo and at post-MI cardiac function and remodeling amelioration. Conversely, irbesartan appears to be largely G protein- inhibitory, as it exhibits very low potency towards barr inhibition. As a result, it is a very weak aldosterone suppressor in vitro and in vivo, and fails to improve cardiac function or adverse remodeling post-MI. These findings will aid pharmacotherapeutic decisions for therapy of post-MI HF and they will also help develop novel and better ARB drugs, with greater efficacy for HF therapy
P2X7 is an archaic scavenger receptor recognizing apoptotic neuroblasts in early human neurogenesis
Get PDFThe expression and function of P2X7 receptors in adult CNS have been widely studied, however, the roles of these purinergic receptors in human neural development has largely focused on the effects of receptor activation. Previous studies of embryonic and adult rodent neural precursors suggest adenosine triphosphate (ATP), the physiological agonist for P2X receptors, can act as a potent modifier of proliferation, migration and differentiation, mediated via intracellular calcium ([Ca2+]i) signaling. The P2X7 receptor has a ubiquitous distribution in the body but is most abundant on macrophages and microglia where its activation by ATP leads to secretion of proinflammatory cytokines. However, extracellular ATP concentrations in the CNS are usually at sub-micromolar levels suggesting that ATP-induced activation of the P2X7 receptor will not occur under physiological circumstances in the CNS. Another possible role for P2X7 receptors has been suggested by recent work on macrophages and neural precursor cells. In these studies the P2X7 receptor was shown to act as a scavenger receptor i.e. a receptor present on a phagocytotic cell which detects molecules present on the surface of apoptotic cells and facilitates phagocytosis of the apoptotic cell. In a recent study of human neural precursor cells (hNPCs) and neuroblasts isolated from human fetal telencephalons at 16-19 WG, our group showed that both P2X7Rhigh/DCXlow hNPCs and P2X7Rhigh/DCXhigh neuroblasts were capable of phagocytic engulfment of a range of targets including latex beads, apoptotic ReN cells and apoptotic neuroblasts. We found that these neuroblasts and their precursor cells expressed functional P2X7 receptors on their cell surface. Although expression of P2X7 is widespread in the cells of the neuroblast, it is those DCX+ neuroblasts with the highest expression of P2X7 which are actively phagocytic towards an autologous apoptotic neighbour or other phagocytic targets, including latex beads and apoptotic ReNcells. Pre-incubation of P2X7high neuroblasts with ATP or oxidized ATP inhibited phagocytosis of targets by these cells. Moreover siRNA knockdown of P2X7R also inhibited phagocytosis of the apoptotic targets. This review considers this major new role for the P2X7 receptor in early human neurogenesis
Enhancement of osteoblastogenesis and suppression of osteoclastogenesis by inhibition of de-phosphorylation of eukaryotic translation initiation factor 2 alpha
Get PDFThe phosphorylation of eukaryotic translation initiation factor 2 alpha (eIF2a) is activated in response to various stresses such as viral infection, nutrient deprivation, and stress to the endoplasmic reticulum. Severe stress to the endoplasmic reticulum, for instance, induces an apoptotic pathway, while mild stress, on the contrary, leads to a pro-survival pathway. Little has been known about the elaborate role of eIF2a phosphorylation in the development of bone-forming osteoblasts and bone-resorbing osteoclasts. Using salubrinal and guanabenz as inhibitors of the de-phosphorylation of eIF2a, we have recently reported that the phosphorylation of eIF2a significantly alters fates of both osteoblasts and osteoclasts. Based on our recent findings, we review in this research highlight the potential mechanisms of the enhancement of osteoblastogenesis and the suppression of osteoclastogenesis through the elevated level of phosphorylated eIF2a