In this setting, PLSCR1 may serve as a transcription factor since it amplifies the expression of IFN/-stimulated genes [26] and promotes the transcription of the inositol 1, 4, 5-trisphosphate receptor gene [27]; iv) PLSCR1 potentiates granulopoiesis by prolonging growth of granulocyte precursors presumably through its role in transcriptional regulation [15]; v) Expression of PLSCR1 has been shown to be tumor suppressive, and its level of expression in bone marrow cells to correlate with long-term survival in acute myelogenous leukemia, whereas mutations affecting PLSCR1 appear to promote the leukemogenic potential of myeloid progenitors [28]C[31]; vi) PLSCR1 regulates compensatory endocytosis in neuroendocrine cells [32]; vii) PLSCR1 is usually capable of potentiating a select set of mast cell responses following FcRI aggregation [33]. in multiple ways. Conversely, the Fyn-dependent pathway negatively regulates it. This study reveals a complex regulation for PLSCR1 tyrosine phosphorylation in FcRI-activated mast cells and that PLSCR1 sits at a crossroads between Lyn and Fyn pathways. Introduction High-affinity receptors for IgE (FcRI) expressed on mast cells promote, after their aggregation by IgE and antigen, the release of preformed mediators stored in cytoplasmic granules and of newly synthesized lipid mediators and cytokines [1]. Engagement of FcRI prospects to the activation of at least two signaling pathways. One is initiated by the tyrosine kinase Lyn [2] and prospects to recruitment of another tyrosine kinase, Syk, to the receptor and to activation of the signaling complex recruited by the protein adaptor LAT [3], resulting in calcium mobilization [4]. The other pathway, initiated by the tyrosine kinase Fyn [4], prospects to phosphatidylinositol 3-kinase recruitment [4], [5]. Both pathways cooperate to determine the extent of degranulation and of cytokine and lipid inflammatory mediator production. It has been demonstrated that this Lyn-initiated pathway negatively regulates the Fyn-initiated pathway through recruitment of Bardoxolone (CDDO) the kinase Csk [6]. Since the FcRI-dependent cell Bardoxolone (CDDO) activation combines these pathways into one coherent transmission, mapping of their connections is an important task that remains to be completed to fully understand transmission integration. Recently, we reported that phospholipid scramblase 1 (PLSCR1) is usually phosphorylated on tyrosine after aggregation of FcRI on mast cells [7]. PLSCR1 is usually a multi-function protein. It was originally identified based on its capacity to accelerate transbilayer migration of phospholipids upon conversation with calcium, thereby collapsing the lipid asymmetry existing between inner and outer leaflets of plasma membranes [8], [9]. Activation of scrambling prospects to increased cell surface exposure of phosphatidylserine and other aminophospholipids. This has been implicated in the acknowledgement of apoptotic cells by phagocytes and in the cell surface expression of procoagulant activity by activated platelets and perturbed endothelium [10], [11]. Interestingly, activated mast cells also demonstrate transient exposure of phosphatidylserine [12], [13]. However, studies with knock-out mice questioned the involvement of PLSCR1 alone in phospholipid scrambling [14], [15]. Recently, several reports have implicated the Ca2+-activated ion channels belonging to the TMEM16 family in phospholipid scrambling induced by a calcium ionophore [16]C[18]. By contrast, phospholipid scrambling following caspase activation during apoptosis was shown to be promoted by Xkr8, a putative transporter [19]. Therefore, depending on the triggering transmission, phospholipid scrambling now appears to result from a variety of option mechanisms, in which the specific role of plasma membrane PLSCR1 remains to be resolved. In Bardoxolone (CDDO) addition to its putative role in mediating transbilayer movement of plasma membrane phospholipids that accompanies PS exposure at the cell surface, there is now also considerable evidence that: i) PLSCR1 serves as a signaling intermediate for the Epidermal Growth Factor (EGF) receptor promoting optimal activation of p60c-Src [20], [21]; ii) PLSCR1 contains Rabbit polyclonal to AQP9 a nuclear localisation signal domain name that mediates nuclear trafficking of the unpalmitoylated form of the protein [22], [23]; iii) synthesis of PLSCR1 is usually induced by interferon- (IFN) and results in its nuclear trafficking and binding to chromosomal DNA [23]C[25]. In this setting, PLSCR1 may serve as a transcription factor since it amplifies the expression of IFN/-stimulated genes [26] and promotes the transcription of the inositol 1, 4, 5-trisphosphate receptor gene [27]; iv) PLSCR1 potentiates granulopoiesis by prolonging growth of granulocyte precursors presumably through its role in transcriptional regulation [15]; v) Expression of PLSCR1 has Bardoxolone (CDDO) been shown to be tumor suppressive, and its level of expression in bone marrow cells to.