• Journal of Life Science
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• v.17 no.3 s.83
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• pp.350-355
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• 2007

The rat RBL-2H3 mast cells contain various Src-family kinases. Previous reports with this cell line indicated that Lyn activation is an important initial signaling for the activation of the cells. However, the role and location of other Src-family kinase isoforms which are expressed in the cells are not clear. In this study, we now show that isoforms of Src-family kinases, Lyn, fyn, Fgr, c-Src, and Yes are differentially expressed and located differently in the cells as indicated by RT-PCR, immunoblotting analysis, and confocal microscopy. Lyn and Fgr were located on plasma membrane but on the other hand c-Src and Yes were located on intracellular organelle. All of Src-family kinases were cloned and overexpressed for investigating the roles of the isoforms. Overexpression of Fyn and Fgr, not Lyn and c-Src, stimulated Ag-induced degranulation in the cells. Our findings strongly suggest for the first time that each of Src-family kinase isoform can regulate differentially $Fc{\varepsilon}RI$-mediated signaling in RBL-2H3 mast cells.

• Molecules and Cells
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• v.26 no.4
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• pp.329-337
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• 2008

Src-family kinases are critically involved in the control of cytoskeleton organization and in the generation of integrin-dependent signaling responses, inducing tyrosine phosphorylation of many signaling and cytoskeletal proteins. Activity of the Src family of tyrosine kinases is tightly controlled by inhibitory phosphorylation of a carboxy-terminal tyrosine residue, inducing an inactive conformation through binding with its SH2 domain. Dephosphorylation of C-ter tyrosine, as well as its deletion of substitution with phenylalanine in oncogenic Src kinases, leads to autophosphorylation at a tyrosine in the activation loop, thereby leading to enhanced Src activity. Beside this phophorylation/dephosphorylation circuitry, cysteine oxidation has been recently reported as a further mechanism of enzyme activation. Mounting evidence describes Src activation via its redox regulation as a key outcome in several circumstances, including growth factor and cytokines signaling, integrin-mediated cell adhesion and motility, membrane receptor cross-talk as well in cell transformation and tumor progression. Among the plethora of data involving Src kinase in physiological and pathophysiological processes, this review will give emphasis to the redox component of the regulation of this master kinase.

• Parasites, Hosts and Diseases
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• v.48 no.4
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• pp.285-290
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• 2010

Tyrosine kinases are one of the most important regulators for intracellular signal transduction related to inflammatory responses. However, there are no reports describing the effects of tyrosine kinases on neutrophil apoptosis induced by Entamoeba histolytica, In this study, isolated human neutrophils from peripheral blood were incubated with live trophozoites in the presence or absence of tyrosine kinase inhibitors. Entamoeba-induced receptor shedding of CD16 and PS externalization in neutrophils were inhibited by pre-incubation of neutrophils with the broad-spectrum tyrosine kinase inhibitor genistein or the Src family kinase inhibitor PP2. Entamoeba-induced ROS production was also inhibited by genistein or PP2, Moreover, genistein and PP2 blocked the phosphorylation of ERK and p38 MAPK in neutrophils induced by E. histolytica. These results suggest that Src tyrosine kinases may participate in the signaling event for ROS-dependent activation of MAPKs during neutrophil apoptosis induced by E. histolytica.

• BMB Reports
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• v.43 no.2
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• pp.91-96
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• 2010

The function of macrophage inhibitory cytokine-1 (MIC-1) in cancer remains controversial, and its signaling pathways remain poorly understood. In this study, we demonstrate that MIC-1 induces the transactivation of EGFR, ErbB2, and ErbB3 through the activation of c-Src in SK-BR-3 breast cells. MIC-1 induced significant phosphorylation of EGFR at Tyr845, ErbB2 at Tyr877, and ErbB3 at Tyr1289 as well as Akt and p38, Erk1/2, and JNK mitogen-activated protein kinases (MAPKs). Treatment of SK-BR-3 cells with MIC-1 increased the phosphorylation level of Src at Tyr416, and induced invasiveness of those cells. Inhibition of c-Src activity resulted in the complete abolition of MIC-1-induced phosphorylation of the EGFR, ErbB2, and ErbB3, as well as invasiveness and matrix metalloproteinase (MMP)-9 expression in SK-BR-3 cells. Collectively, these results show that MIC-1 may participate in the malignant progression of certain cancer cells through the activation of c-Src, which in turn may transactivate ErbB-family receptors.

• Animal cells and systems
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• v.6 no.1
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• pp.1-12
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• 2002

A role of Src family protein Tyrosine kinases (SFK) as mediators of receptor-ligand initiated responses is well established. Well documented, but less well understood is the role of SFK in cellular reaction to stresses. Evidence from the wide variety of experimental systems indicates that SFK mediate responses to all major classes of stress, including oxidation, DNA damage, mechanical impacts, and protein denaturing. SFK may be activated by stresses directly or via regulatory circuits whose identity is not yet fully understood. Depending on the cell type and the nature of activating stimulus, SFK may activate known downstream signaling cascades leading to cell survival, proliferation, cytoskeletal rearrangement, and apoptosis; the identity of these cascades is discussed. As in the case of receptor-initiated signaling, roles of individual SFK in various stress response may be redundant or non-redundant. Although signals generated by different stresses are generally transduced via distinct SFK pathways, these pathways may overlap or exhibit crosstalk. In some cell types stress-induced activation of SFK promotes survival and inhibits apoptosis, whereas the opposite may be true for other cell types. Stress responses constitute a new and rapidly developing area of SFK-mediated signaling.

• Biomolecules & Therapeutics
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• v.29 no.1
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• pp.41-51
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• 2021

Src family kinases (SFKs), an important group of non-receptor tyrosine kinases, are suggested to be excessively activated during various types of tissue fibrosis. The present study investigated the effect of KF-1607, an orally active and a newly synthesized Src kinase inhibitor (SKI) with proposed low toxicity, in preventing the progression of renal interstitial fibrosis. Unilateral ureteral obstruction (UUO) surgery was performed in 6-week-old male C57BL/6 mice to induce renal interstitial fibrosis. Either KF-1607 (30 mg/kg, oral gavage) or PP2 (2 mg/kg, intraperitoneal injection), a common experimental SKI, was administered to mice for seven days, started one day prior to surgery. UUO injury-induced SFK expression, including Src, Fyn, and Lyn kinase. SFK inhibition by KF-1607 prevented the progression of tubular injury in UUO mice, as indicated by decreases in albuminuria, urinary KIM-1 excretion, and kidney NGAL protein expression. Renal tubulointerstitial fibrosis was attenuated in response to KF-1607, as shown by decreases in α-SMA, collagen I and IV protein expression, along with reduced Masson's trichrome and collagen-I staining in kidneys. KF-1607 also inhibited inflammation in the UUO kidney, as exhibited by reductions in F4/80 positive-staining and protein expression of p-NFκB and ICAM. Importantly, the observed effects of KF-1607 were similar to those of PP2. A new pan Src kinase inhibitor, KF-1607, is a potential pharmaceutical agent to prevent the progression of renal interstitial fibrosis.

• Biomolecules & Therapeutics
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• v.28 no.5
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• pp.456-464
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• 2020

Mast cells (MCs) are systemically distributed and secrete several allergic mediators such as histamine and leukotrienes to cause type I hypersensitivity. Dasatinib is a type of anti-cancer agent and it has also been reported to inhibit human basophils. However, dasatinib has not been reported for its inhibitory effects on MCs or type I hypersensitivity in mice. In this study, we examined the inhibitory effect of dasatinib on MCs and MC-mediated allergic response in vitro and in vivo. In vitro, dasatinib inhibited the degranulation of MCs by antigen stimulation in a dose-dependent manner (IC₅₀, ~34 nM for RBL-2H3 cells; ~52 nM for BMMCs) without any cytotoxicity. It also suppressed the secretion of inflammatory cytokines IL-4 and TNF-α by antigen stimulation. Furthermore, dasatinib inhibited MC-mediated passive cutaneous anaphylaxis (PCA) in mice (ED₅₀, ~29 mg/kg). Notably, dasatinib significantly suppressed the degranulation of MCs in the ear tissue. As the mechanism of its effect, dasatinib inhibited the activation of Syk and Syk-mediated downstream signaling proteins, LAT, PLCγ1, and three typical MAP kinases (Erk1/2, JNK, and p38), which are essential for the activation of MCs. Interestingly, in vitro tyrosine kinase assay, dasatinib directly inhibited the activities of Lyn and Fyn, the upstream tyrosine kinases of Syk in MCs. Taken together, dasatinib suppresses MCs and PCA in vitro and in vivo through the inhibition of Lyn and Fyn Src-family kinases. Therefore, we suggest the possibility of repositioning the anti-cancer drug dasatinib as a treatment for various MC-mediated type I hypersensitive diseases.

• International Journal of Oral Biology
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• v.39 no.3
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• pp.131-136
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• 2014

Porphyromonas gingivalis is one of the most important periodontal pathogens and has been to known to invade various types of cells, including endothelial cells. The present study investigated the mechanisms involved in the internalization of P. gingivalis in human umbilical vein endothelial cells (HUVEC). P. gingivalis internalization was reduced by clathrin and lipid raft inhibitors, as well as a siRNA knockdown of caveolin-1, a principal molecule of lipid raft-related caveolae. The internalization was also reduced by perturbation of actin rearrangement, while microtubule polymerization was not required. Furthermore, we found that Src kinases are critical for the internalization of P. gingivalis into HUVEC, while neither Rho family GTPases nor phosphatidylinositol 3-kinase are required. Taken together, this study indicated that P. gingivalis internalization into endothelial cells involves clathrin and lipid rafts and requires actin rearrangement associated with Src kinase activation.

• BMB Reports
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• v.48 no.2
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• pp.97-102
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• 2015

Neurons in the developing brain form the cortical plate (CP) in an inside-out manner, in which the late-born neurons are located more superficially than the early-born neurons. Fyn, a member of the Src family kinases, plays an important role in neuronal migration by binding to many substrates. However, the role of the Src-homology 2 (SH2) domain in function of Fyn in neuronal migration remains poorly understood. Here, we demonstrate that the SH2 domain is essential for the action of Fyn in neuronal migration and cortical lamination. A point mutation in the Fyn SH2 domain ($Fyn^{R176A}$) impaired neuronal migration and their final location in the cerebral cortex, by inducing neuronal aggregation and branching. Thus, we provide the first evidence of the Fyn SH2 domain contributing to neuronal migration and neuronal morphogenesis.

• YAKHAK HOEJI
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• v.56 no.1
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• pp.26-34
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• 2012

Mast cells play an important role in early and late phase allergic reactions through allergen and IgE-dependent release of histamine, proteases, prostaglandins, and several multifunctional cytokines. In this study, we investigated whether Cudrania tricuspidata extract (CTE) suppresses IgE-mediated allergic responses in mast cells, an allergic animal model, and its mechanism of action in mast cells. We found that CTE inhibited IgE-mediated degranulation and cytokine production in rat basophilic leukemia (RBL)-2H3 mast cells and bone marrow-derived mast cells (BMMC), as well as passive cutaneous anaphylaxis (PCA) in mice. With regard to its mechanism of action, CTE suppressed the activating phosphorylation of spleen tyrosine kinase (Syk), a key enzyme in mast cell signaling processes and that of LAT, a downstream adaptor molecule of Syk in $Fc{\varepsilon}RI$-mediated signal pathways. CTE also suppressed the activating phosphorylation of mitogen-activated protein (MAP) kinases and Akt. The present results strongly suggest that the anti-allergic activity of CTE is mediated through inhibiting degranulation and allergic cytokine secretion by inhibition of Syk kinase in mast cells. Therefore, CTE may be useful for the treatment of allergic diseases.