The activity of Src-related protein-tyrosine kinses is repressed by the phosphorylation of a conserved carboxyl-terminal tyrosine by another cytoplasmic proteintyrine kinase termed p50c*. In this study, we characterize Ntk, a protein-tyrouine kinase bering king smities to pO=c. Like p5Oi, Ntk Src homology 3 and Src homology 2 doma and lacks the consensus tse phosphorylation and myristoylation sites found in members of the Src family. Expression ofntk transcripts was m in brain, and was observed at signint levels in thymus and spleen. ntk RNA levels were dramatically reduced upon mitogenic stimulation of normal T lymphocytes and were minimal in transformed T-cell populations. Firm evidence that Ntk is a Cskrelated enzyme was provided by the observation that it phosphorylated a Src-related polypeptide on the inhibitory carboxyl-terminal tyrosine. These indigs indicate that Ntk is a Csk-related enzyme that may play an inhibitory role in the control of T-cell proliferation.Members of the Src family of protein-tyrosine kinases participate in a variety of signal transduction responses (for reviews, see refs. 1-3). The most convincing illustration of this role is perhaps provided by studies of intracellular signaling in T lymphocytes. In mature T cells, antigen receptor stimulation is associated with a rapid rise in intracellular protein-tyrosine phosphorylation, which is critical for subsequent T-cell mitogenesis. Because the T-cell antigen receptor lacks intrinsic catalytic properties, this biochemical signal must involve coupling to other protein-tyrosine kinases. From biochemical and genetic evidence, it is now clear that T-cell receptor signaling requires the action of Lck and FynT, two Src-related enzymes abundantly expressed in T lymphocytes.The activity of Src-related enzymes is repressed by phosphorylation of a conserved carboxyl-terminal tyrosine residue (4,5). This inhibitory phosphorylation is not a consequence of autophosphorylation but is mediated (at least in part) by a 50-kDa cytoplasmic protein-tyrosine kinase termed Csk or p5ocsk (6)(7)(8). pSOcsk is ubiquitous, but is most abundant in thymus and spleen, as well as in neonatal brain (9,10).The importance ofp5ocsk in normal cellular physiology has been documented in at least two independent systems. First, mutant mice lacking Csk have significantly altered development of the nervous system, which is associated with early embryonic lethality (11,12). Second, in antigen-specific T-lymphocyte lines, overexpression of Csk negatively regulates T-cell responsiveness following antigen receptor stimulation (13).The exon-intron structure of the csk gene differs significantly from that of other protein-tyrosine kinase genes (14).Based on this finding, as well as on the unique structural and biochemical properties of its product, the csk gene has been considered to be the sole member of a distinct family. This view is further supported by the fact that previous attempts to identify additional csk-like genes by cross hybridization under low-stringency cond...

Oral bacteria, including Streptococcus mutans and Streptococcus salivarius, contribute to tooth decay and plaque formation; therefore, it is essential to develop strategies to prevent dental caries and plaque formation. We recently showed that organo-selenium compounds covalently attached to different biomaterials inhibited bacterial biofilms. Our current study investigates the efficacy of an organo-selenium dental sealant (SeLECT-Defense TM sealant) in inhibiting S. mutans and S. salivarius biofilm formation in vitro. The organo-selenium was synthesized and covalently attached to dental sealant material via standard polymer chemistry. By colony-forming unit (CFU) assay and confocal microscopy, SeLECT-Defense TM sealant was found to completely inhibit the development of S. mutans and S. salivarius biofilms. To assess the durability of the anti-biofilm effect, we soaked the SeLECT-Defense TM sealant in PBS for 2 mos at 37°C and found that the biofilm-inhibitory effect was not diminished after soaking. To determine if organoselenium inhibits bacterial growth under the sealant, we placed SeLECT-Defense sealant over a lawn of S. mutans. In contrast to a control sealant, SeLECTDefense TM sealant completely inhibited the growth of S. mutans. These results suggest that the inhibitory effect of SeLECT-Defense TM sealant against S. mutans and S. salivarius biofilms is very effective and durable.

BackgroundAlthough inflammation and prostate cancer (PCa) have been linked, the molecular interactions between macrophages and PCa cells are poorly explored. Pigment Epithelium-Derived Factor (PEDF) is an anti-angiogenic and anti-tumor factor. We previously showed that PEDF induces macrophages recruitment in vitro, correlates with macrophages density in human prostate, and stimulates macrophages polarization towards the classically activated pathway. Here, we demonstrate that PEDF modulates the interaction between macrophages and PCa cells through a bidirectional signalling leading to tumor cell apoptosis and phagocytosis.MethodsRAW 264.7 and THP-1 cells, and BMDMs were grown in vitro as mono- or co-cultures with PC3 or CL1 tumor cells. The effects of PEDF and its derived P18 peptide were measured on macrophages differentiation, migration, and superoxide production, and tumor cell apoptosis and phagocytosis. PEDF receptors (ATP5B, PNPLA2, and LRP6) and CD47 mRNA and protein expression were quantified in macrophages and tumor cells by quantitative RT-PCR, western blot, immunofluorescence and flow cytometry.ResultsWe found that PEDF induced the migration of macrophages towards tumor 3D spheroids and 2D cultures. In co-culture, PEDF increased PCa cells phagocytosis through an indirect apoptosis-dependent mechanism. Moreover, PEDF stimulated the production of superoxide by macrophages. Conditioned media from macrophages exposed to PEDF induced tumor cells apoptosis in contrast to control conditioned media suggesting that ROS may be involved in tumor cells apoptosis. ATP5B and PNPLA2 PEDF receptors on macrophages and CD47 on tumor cells were respectively up- and down-regulated by PEDF. As PEDF, blocking CD47 induced phagocytosis. Inhibiting ATP5B reduced phagocytosis. Inversely, PNPLA2 inhibition blocks differentiation but maintains phagocytosis. CD47-induced phagocytosis was partially reverted by ATP5B inhibition suggesting a complementary action. Similar effects were observed with P18 PEDF-derived peptide.ConclusionsThese data established that modulating the molecular interactions between macrophages and PCa cells using PEDF may be a promising strategy for PCa treatment.

Our findings highlight the great promise of cabazitaxel drug and predict a possible move of cabazitaxel forward within the therapeutic sequence of prostate cancer.