Role Of Src Family Tyrosine Kinases Research Articles

C-Src but Not Fyn Promotes Proper Spindle Orientation in Early Prometaphase

Src family tyrosine kinases (SFKs) participate in mitotic signal transduction events, including mitotic entry, cleavage furrow ingression, and cytokinesis abscission. Although SFKs have been shown to associate with the mitotic spindle, the role of SFKs in mitotic spindle formation remains unclear. Here, we show that c-Src promotes proper spindle orientation in early prometaphase. Src localizes close to spindle poles in a manner independent of Src kinase activity. Three-dimensional analyses showed that Src inhibition induced spindle misorientation, exhibiting a tilting spindle in early prometaphase. Spindle misorientation is frequently seen in SYF cells, which harbor triple knock-out mutations of c-Src, c-Yes, and Fyn, and reintroduction of c-Src but not Fyn into SYF cells rescued spindle misorientation. Spindle misorientation was also observed upon Src inhibition under conditions in which Aurora B was inhibited. Inducible expression of c-Src promoted a properly oriented bipolar spindle, which was suppressed by Src inhibition. Aster formation was severely inhibited in SYF cells upon Aurora B inhibition, which was rescued by reintroduction of c-Src into SYF cells. Furthermore, reintroduction of c-Src facilitated microtubule regrowth from cold-induced depolymerization and accelerated M phase progression. These results suggest that c-Src is involved in spindle orientation through centrosome-mediated aster formation.

Src family tyrosine kinase regulates acrosome reaction but not motility in porcine spermatozoa

During the capacitation process, spermatozoa acquire the ability to fertilize an oocyte, and upregulation of cAMP-dependent protein tyrosine phosphorylation occurs. Recently, Src family tyrosine kinase (SFK) has been involved in spermatozoa capacitation as a key PKA-dependent tyrosine kinase in several species. This work investigates the expression and role of SFK in porcine spermatozoa. SFK members Lyn and Yes are identified in porcine spermatozoa by western blotting as well as two proteins named SFK1 and SFK2 were also detected by their tyrosine 416 phosphorylation, a key residue for SFK activation. Spermatozoa with SFK1 and SFK2 increase their Y416 phosphorylation time-dependently under capacitating conditions compared with noncapacitating conditions. The specific SFK inhibitor SU6656 unaffected porcine spermatozoa motility or viability. Moreover, SFK inhibition in spermatozoa under capacitating conditions leads to a twofold increase in both nonstimulated and calcium-induced acrosome reaction. Our data show that capacitating conditions lead to a time-dependent increase in actin polymerization in boar spermatozoa and that long-term incubation with SFK inhibitor causes a reduction in the F-actin content. In summary, this work shows that the SFK members Lyn and Yes are expressed in porcine spermatozoa and that SFK1 and SFK2 are phosphorylated (activated) during capacitation. Our results point out the important role exerted by SFK in the acrosome reaction, likely mediated in part by its involvement in the actin polymerization process that accompanies capacitation, and rule out its involvement in porcine spermatozoa motility.

SFK Inhibition with Dasatinib Results In Selective Targeting of Primitive Human Acute Myeloid Leukemia Stem and Progenitor Cells.

AbstractAbstract 1053The Src family tyrosine kinases (SFKs) are abnormally activated in AML compared to normal CD34+ hematopoietic progenitors. Studies using pharmacological and siRNA approaches indicate an important role for the SFK Lyn in AML progenitor cell growth and survival (Dos Santos et al., 2008). However the role of SFKs in AML leukemic stem cell (LSC) growth and survival is not clear. SFK activity in Lin- CD34+ CD38- primitive stem/progenitor cells, Lin- CD34+ CD38+ committed progenitors, and Lin-CD34- cells from primary human AML (n=14) and cord blood (CB) (n=6) samples was measured by analyzing SFK phosphorylation using flow cytometry. We observed significant increase of SFK phosphorylation in AML compared to CB Lin- CD34+CD38- cells (3.8±1.9 versus 1.9±0.7, p=0.006), Lin- CD34+ CD38+ (3.9±1.7 versus 1.9±0.6, p=0.013) and Lin- CD34- cells (3.4±1.8 versus 1.1±0.5, p=0.0005). Dasatinib, a potent SFK and ABL kinase inhibitor, is approved for clinical use in chronic myeloid leukemia. We evaluated the effect of SFK inhibition using Dasatinib on the growth and viability of AML stem and progenitor cells. Dasatinib exposure resulted in dose-dependent inhibition of SFK phosphorylation in each subpopulation (in CD34+ CD38-, 3.0 for the control versus 1.9 with 100nM and 1.6 with 500nM, in CD34+ CD38+, 2.8 for the control versus 1.9 with 100nM and 1.6 with 500nM) after 30 minutes of drug treatment). The addition of Dasatinib (10-500nM) to methylcellulose progenitor assays resulted in dose-dependent inhibition of AML colony forming cell (CFC) growth (83.9±16.1% inhibition with 500nM, and 48.1±6.8% inhibition with 10nM Dasatinib, n=8), to a greater extent than CB CFC to (CFU-GM inhibition 62.6±1.5% with 500nM, and 1.1±16.3% with 10nM Dasatinib, n=4). Short-term exposure to Dasatinib (10-500nM) for 48 hours also resulted in significantly greater inhibition of AML CFC (73.6±13% with 500nM, and 41.7±10.8% with 10nM Dasatinib, n=8) compared to CB CFC (CFU-GM inhibition 23±9.1% with 500nM, and 1.3±11.3% with 10nM Dasatinib, n=4). Importantly Dasatinib treatment (200nM) also resulted in reduction of AML stem/primitive progenitor growth in long term culture-initiating cells (LTC-IC) assays (56±23, 8 % inhibition, p=0.003, n=4), suggesting that SFK inhibition may inhibit AML stem cell maintenance. The effect of Dasatinib on apoptosis was evaluated by labeling cells with Annexin V and DAPI. Treatment with Dasatinib resulted in significant increase in apoptosis of Lin- AML cells (41.5% ±10.7 of apoptosis with 200nM Dasatinib versus 25%±10.8 for the control, p=0,004, n=5) We studied the effects of Dasatinib on differentiation of Lin- CB (n=3) and AML cells (N=5) cultured with SCF, IL-3, GM-CSF, G-CSF and EPO. In normal CD34+, Dasatinib (100 nM) treatment resulted in increased CD33+ and CD14+ cells and reduced CD34+, CD11b+, CD15+, GPA+ and CD71+ cell numbers, indicating that SFK increased monocytic but reduced granulocytic and erythroid differentiation. Treatment of AML cells with Dasatinib resulted in markedly reduced numbers of CD34+, CD33+ and CD71+ cells, but increased numbers of CD11b cells, in 3 of 5 samples, indicating a trend towards increased granulocytic differentiation in contrast to normal progenitors. Our results indicate that SFK activity is increased in primary human AML stem and progenitor cells and suggest that SFK blockade with Dasatinib may reduce maintenance of AML LSC/ primitive progenitors, through inhibition of progenitor proliferation, induction of apoptosis and enhancement of differentiation. These results support further evaluation of SFK blockade with Dasatinib for targeting of AML stem and progenitor cells in preclinical and clinical studies. Disclosures:Bhatia:Novartis: Consultancy, Honoraria.

Abstract A67: An LC-MRM method to simultaneously measure abundance and activation of Src family tyrosine kinases in a B cell line model of IL-6 signaling

Abstract Introduction: Interleukin-6 (IL-6) is a pleiotropic cytokine important to tumor biology in epithelial and hematopoietic malignancies. IL-6 signaling through gp130 mediates cell survival, proliferation, and migration via multiple downstream signaling pathways. Preliminary data has demonstrated that point mutations within a discrete acidic region of the cytoplasmic domain of gp130 attenuate both IL-6-mediated Src family tyrosine kinase (SFK) activation and cell migration in a pro-B cell line. These data suggest that SFK activation via this domain is integral in modulating the adherent potential and migratory properties of IL-6 stimulated B cells. Importantly, the role of SFKs in IL-6-mediated cell migration has not been described previously. Nine SFKs are differentially expressed in various tissues; seven are specific to hematopoietic cells (Src, Fyn, Lyn, Hck, Lck, Blk, and Fgr). Identification of the relevant SFKs in this model will enable us to fully characterize the role of these effectors in relevant biological endpoints. Methods: Currently, the measurement of specific SFK member expression and activation is limited by the ability of available antibodies to distinguish between highly homologous family members. Therefore, we are developing a mass spectrometry-based method that utilizes Liquid Chromatography-Multiple Reaction Monitoring, (LC-MRM) to provide simultaneous quantification of expression and post-translational modification of SFKs. Results: Src family members have been screened using SDS-PAGE coupled to LC-MRM to identify specific peptides that can be used to monitor the expression of each individual protein (e.g. Src peptides containing amino acids 164-172 and 472-480: LLLNAENPR and EVLDQVER). The activation of each SFK will also be assessed using a ratio of tyrosine phosphorylated and unmodified peptides. Assays have already been developed to measure the following tryptic peptides containing a tyrosine phosphorylation site (underlined residue): LIEDNEYTAR (Src, Fyn, Yes, Lck) and VIEDNEYTAR (Lyn, Hck). Further, we have also identified a longer LysC peptide corresponding to amino acids 383-404 of Src (IADFGLARLIEDNEYTARQGAK) that is unique among each of seven SFKs expressed in hematopoietic cells. This peptide and the corresponding sequences in other SFKs may be used as an alternative method to simultaneously quantify tyrosine phosphorylation of individual SFKs. Conclusions: This work will establish a new LC-MRM peptide based method to simultaneously measure both the activity and abundance of specific SFKs in very small sample sizes that are not amenable to analysis by other methods. As such, this technique will have a broad range of experimental applications and will be particularly useful in future studies that validate results from cell line models with patient specimens, which inherently contain a very low number of cells. This presenting student is supported by an ARRA supplement to the NCI Cancer Center Support Grant awarded to Moffitt (3P30 CA076292-11S6 PI WS Dalton) to create a training program for underrepresented undergraduate students in clinical proteomics, Project LINK (Leaders In New Knowledge-Emerging Technologies), that also emphasizes education in health disparities and community outreach. Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):A67.

Activation of src-family tyrosine kinases by LPS regulates cytokine production in dendritic cells by controlling AP-1 formation.

The role of src-family tyrosine kinases in LPS-induced DC maturation has not been fully addressed. We show that LPS induces activation of c-Src and Lyn in human DC. Inhibition of these kinasesby PP1 uncoupled LPS-induced cytokine production from the up-regulation of costimulatory molecules, resulting in DC still capable of stimulating T cell proliferation but much less efficient in inducing Th1 differentiation. This is the first example of a pharmacological inhibitor able to modulate the capacity of DC to induce a particular type of immune response. Inhibition of src-family kinases impaired phosphorylation and accumulation of c-Jun, leading to reduced formation of AP-1 complexes upon LPS stimulation. Thus, src-kinases control cytokine production in LPS-induced DC maturation through a timely formation of AP-1.