Lymphocyte-specific Protein Tyrosine Kinase Research Articles

The phosphoproteome of human Jurkat T cell clones upon costimulation with anti-CD3/anti-CD28 antibodies

Phosphorylation is a reversible post-translational modification, playing a vital role in protein function. In T cells, protein phosphorylation is the key mechanism regulating T cell receptor-driven signaling pathways. In order to gain insights into the phosphoproteome evolution of T cell activation, we performed a large-scale quantitative phosphoproteomics study of Jurkat E6.1 (wild type) and Jurkat gamma1 (Phospholipase gamma1 null) cell clones upon costimulation with anti-CD3 and anti-CD28 antibodies at times ranging from 15min to as long as 120min. In total, we identified 5585 phosphopeptides belonging to 2008 phosphoproteins from both cell clones. We detected 130 and 114 novel phosphopeptides in Jurkat E6.1 and Jurkat gamma1 clones, respectively. A significantly lower number of proteins containing regulated phosphorylation sites were identified in Jurkat gamma1 in comparison to Jurkat E6.1, reflecting the vital role of Phospholipase gamma1 in T cell signaling. Several new phosphorylation sites from lymphocyte-specific protein tyrosine kinase (Lck) were identified. Of these, serine-121 showed significant changes in JE6.1 while only small changes in the Jgamma1 clone. Our data may contribute to the current human T cell phosphoproteome and provide a better understanding on T cell receptor signaling. Data are available via ProteomeXchange with identifier PXD002871.

T cell receptor signaling pathway is overexpressed in CD4+ T cells from HAM/TSP individuals

Human T-lymphotropic virus type 1 (HTLV-1) is a human retrovirus related to the chronic neuroinflammatory disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). CD4+ T cells activation appears to play a key role on HTLV-1 infection. Here we investigated the expression of genes associated to T cell activation CD3e molecule, epsilon (CD3ɛ), lymphocyte-specific protein tyrosine kinase (LCK), vav 1 guanine nucleotide exchange factor (VAV1), and zeta-chain (TCR) associated protein kinase 70kDa (ZAP70) on T lymphocytes of HTLV-1-infected individuals and compared to healthy uninfected individuals (CT). We observed that CD3ɛ, LCK, ZAP70, and VAV1 gene expression were increased in CD4+ T cells from HAM/TSP group compared to HTLV-1 asymptomatic patients (HAC). Moreover, ZAP70 and VAV1 were also upregulated in HAM/TSP compared to CT group. We detected a positive correlation among all these genes. We also observed that CD3ɛ, LCK, and VAV1 genes had a positive correlation with the proviral load (PVL) and Tax expression. These results suggest that PVL and Tax protein could drive CD3ɛ, LCK, and VAV1 gene expression in CD4+ T cells, and these genes function on a synchronized way on the CD4+ T cell activation. The elucidation of the mechanisms underlying T cell receptor signaling pathway is of considerable interest and might lead to new insights into the mechanism of HAM/TSP.

Retraction Note to: LCK: a new biomarker candidate for the early diagnosis of acute myocardial infarction.

Acute myocardial infarction (AMI) is one of the most common cardiovascular emergencies, of which the molecular pathogenesis is still not fully understood. This study aimed to explore the differentially expressed genes (DEGs) and then identify the critical genes in AMI thus screening out potential biomarkers for the early diagnosis of this serious heart disease. The gene expression data of AMI patients (GSE19339) were downloaded from gene expression omnibus database. After preprocessing with affy package, the DEGs were screened out by significance analysis of microarray (SAM) algorithm within samr package. Then function and pathway enrichment analyses of the DEGs were carried out using DAVID (database for annotation visualization and integrated discovery software) online tools. Further, the relevant genes of AMI were screened out with GENETIC_ASSOCIATION_DB_DISEASE analysis and blastp alignment. Finally, the novel genes were subjected to transcription factor and protein–protein interaction network analyses. A total of 633 DEGs, including 378 up-regulated and 255 down-regulated, were screened out between AMI patients and normal control samples. Among those genes, several important ones such as PPAR, CCL2, HMOX1 and NPR1 were demonstrated to be related to AMI. Most importantly, a novel gene LCK (lymphocyte-specific protein tyrosine kinase) was significantly differentially expressed in AMI. Further analyses showed that LCK was involved in the expression regulation of CXCL12 (chemokine (C-X-C motif) ligand 12) and the expression of LCK can be regulated by different transcription factors. In this study, we provided a new insight into the mechanism of AMI and raised LCK as an attractive marker candidate in the diagnosis of this serious heart disease.

Abstract 3041: Lymphocyte-specific protein tyrosine kinase (Lck) interacts with CR6-interacting factor 1 (CRIF1) in mitochondria to repress oxidative phosphorylation

Abstract The purpose of our study is to determine whether and how lymphocyte-specific protein tyrosine kinase (Lck) may exhibit novel functions in cancer cell mitochondria. Mitochondria are responsible for producing cellular energy via oxidative phosphorylation (OXPHOS) of glucose and fatty acids. Compared to normal differentiated cells, cancer cells rely more on aerobic glycosis than mitochondrial OXPHOS. This shift in energy metabolism allows more resources to be converted into biomass for cancer cell's uncontrolled growth and proliferation. Numerous mechanisms contribute to altered mitochondrial activity, including phosphorylation of mitochondrial proteins. Recent studies showed that cytoplasmic protein tyrosine kinases (PTK) also translocate to the mitochondria and regulate mitochondrial functions. It represents an important non-canonical pathway of how PTK modulates mitochondrial activity. As a Src-family PTK, Lck is essential for T cell activation by transmitting signals downstream of cell surface receptors. Overexpression and aberrant activity of Lck have been reported in both blood malignancies and solid tumors. We showed previously that Lck exhibited additional oncogenic property when translocated to the nucleus (BBRC 417:1058). To explore the possibility that Lck may also translocate to mitochondria, we examined human Jurkat T cell leukemia and its Lck-deficient derivative Jcam cell line. Subcellular fractionation and microscopy both confirmed the presence of Lck in Jurkat mitochondria. Compared to Jcam, Jurkat cells exhibit high levels of mitochondrial protein tyrosine phosphorylation, disrupted mitochondrial morphology, and reduced OXPHOS. Subsequent mass spectrometry and in situ proximity ligation assay identified CR6-interacting factor 1 (CRIF1) as a novel Lck-interacting partner in mitochondria. CRIF1 interacts with mitoribosome and Tid1 to facilitate translation and membrane insertion of mitochondrion-encoded proteins, respectively. Compared to Jcam, Jurkat cells express less mitochondrial proteins and show reduced CRIF1-Tid1 interaction. Knocking down CRIF1 in Jcam also results in decreased mitochondrial protein level and mitochondrial dysfunction. Interestingly, CRIF1 is not phosphorylated on tyrosine by Lck, suggesting the presence of other Lck substrates in mitochondria. All together, these results support the role of mitochondrial Lck as a negative regulator of CRIF1 through competitive binding and independent of its kinase activity. Disrupted mitochondrial protein translation and membrane insertion then lead to reduced OXPHOS and abnormal morphology. These findings raise the possibility of targeting mitochondrial Lck to redirect the metabolic shift in cancer cells. Citation Format: Shahrooz Vahedi, Fu-Yu Chueh, Chao-Lan Yu. Lymphocyte-specific protein tyrosine kinase (Lck) interacts with CR6-interacting factor 1 (CRIF1) in mitochondria to repress oxidative phosphorylation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3041. doi:10.1158/1538-7445.AM2015-3041

Nuclear lymphocyte-specific protein tyrosine kinase and its interaction with CR6-interacting factor 1 promote the survival of human leukemic T cells.

Overexpression and hyperactivation of lymphocyte-specific protein tyrosine kinase (Lck) have been associated with leukemia development. We previously showed that, other than its known function as a cytoplasmic signal transducer, Lck also acts as a nuclear transcription factor in mouse leukemic cells. In the present study, we demonstrated the presence of nuclear Lck in human leukemic T cells and in primary cells. We further established a positive correlation between Lck nuclear localization and its kinase activity. Proteomic analysis identified CR6-interacting factor 1 (CRIF1) as one of the Lck-interacting proteins. CRIF1 and Lck association in the nucleus was confirmed both by immunofluorescence microscopy and co-immunoprecipitation in human leukemic T cells. Close-range interaction between Lck and CRIF1 was validated by in situ proximity ligation assay (PLA). Consistent with the role of nuclear CRIF1 as a tumor suppressor, CRIF1 silencing promotes leukemic T cell survival in the absence of growth factors. This protective effect can be recapitulated by endogenous Lck or reconstituted Lck in leukemic T cells. All together, our results support a novel function of nuclear Lck in promoting human leukemic T cell survival through interaction with a tumor suppressor. It has important implications in defining a paradigm shift of non-canonical protein tyrosine kinase signaling.

Identification of potential therapeutic target genes, key miRNAs and mechanisms in acute myeloid leukemia based on bioinformatics analysis.

The study was aimed to explore the underlying mechanisms and identify the potential target genes and key miRNAs for acute myeloid leukemia (AML) treatment by bioinformatics analysis. The microarray data of GSE9476 were downloaded from Gene Expression Omnibus database. A total of 64 samples, including 26 AML and 38 normal samples, were used to identify differentially expressed genes (DEGs) between AML and normal samples. The functional enrichment analysis was performed, and protein-protein interaction (PPI) network of the DEGs was constructed by Cytoscape software. Besides, the target miRNAs for DEGs were identified. Totally, 323 DEGs were identified, including 87 up-regulated and 236 down-regulated genes. Not only up-regulated genes but also down-regulated genes were related to hematopoietic-related functions. Besides, down-regulated genes were also enriched in primary immunodeficiency pathway. Tumor necrosis factor (TNF), interleukin 7 receptor (IL7R), lymphocyte-specific protein tyrosine kinase (LCK), CD79a molecule and immunoglobulin-associated alpha (CD79A) were identified in these functions. TNF and LCK were hub nodes in PPI networks. miR-124 and miR-181 were important miRNAs in this study. The hematopoietic-related functions and primary immunodeficiency pathway may be associated with AML development. Genes, such as TNF, IL7R, LCK and CD79A, may be potential therapeutic target genes for AML, and miR-124 and miR-181 may be key miRNAs in AML development.

Regulated Expression of miR-155 is Required for iNKT Cell Development.

Invariant natural killer T cells (iNKT cells) are CD1d-restricted, lipid antigen-reactive T lymphocytes with immunoregulatory functions. iNKT cell development in the thymus proceeds through subsequent stages, defined by the expression of CD44 and NK1.1, and is dictated by a unique gene expression program, including microRNAs. Here, we investigated whether miR-155, a microRNA involved in differentiation of most hematopoietic cells, played any role in iNKT cell development. To this end, we assessed the expression of miR-155 along iNKT cell maturation in the thymus, and studied the effects of miR-155 on iNKT cell development using Lck-miR-155 transgenic mice, which over express miR-155 in T cell lineage under the lymphocyte-specific protein tyrosine kinase (Lck) promoter. We show that miR-155 is expressed by newly selected immature wild-type iNKT cells and turned off along iNKT cells differentiation. In transgenic mice, miR-155 over-expression resulted in a substantial block of iNKT cell maturation at Stage 2, in the thymus toward an overall reduction of peripheral iNKT cells, unlike mainstream T cells. Furthermore, the effects of miR-155 over-expression on iNKT cell differentiation were cell autonomous. Finally, we identified Ets1 and ITK transcripts as relevant targets of miR-155 in iNKT cell differentiation. Altogether, these results demonstrate that a tight control of miR-155 expression is required for the development of iNKT cells.

The Src tyrosine kinase Lck binds to CD2, CD4-1, and CD4-2 T cell co-receptors in channel catfish, Ictalurus punctatus

The binding of the lymphocyte specific protein tyrosine kinase (Lck) to T cell co-receptors is required for T cell development and activation. In mammals, Lck initiates signal transduction by binding to CD4 and CD8 co-receptors and phosphorylating ITAMs in the cytoplasmic tail of the CD3 molecules and the ζ chains. In addition, Lck can also bind to the adhesion molecule CD2 and trigger T cell activation. In this study, Lck and CD2 homologs were identified and characterized in channel catfish, Ictalurus punctatus. Lck and CD2 mRNAs were specifically expressed by clonal T cell lines, including both CD4+ and CD4−CD8− CTL lines, and in mixed lymphocyte cultures (MLC). Western blot analyses using anti-trout Lck and anti-human p-Lck antibodies demonstrated that Lck protein is expressed in catfish clonal CTL and is phosphorylated at a conserved tyrosine residue. Because of the lack of CD8+ CTL lines as well as the absence of CD8 message in MLC, we performed magnetic bead binding assays to correlate CD2, CD4, and CD8 co-receptor expression with Lck binding ability. Recombinant Lck reproducibly bound to CD2, CD4-1, and CD4-2, but not to CD8α or CD8β. These data provide one possible explanation for the apparent low numbers of CD8+ CTL and the presence of CD4+ and CD4−CD8−CD2+ CTL in catfish.

Molecular characterization and expression of Lck in Nile tilapia (Oreochromis niloticus) in response to Streptococcus agalactiae stimulus.

Lymphocyte-specific protein tyrosine kinase (Lck) plays a critical role in effective signal transductions that are fundamental to T cell differentiation, proliferation, and effector functions. In this paper, the Lck gene of Nile tilapia, Oreochromis niloticus (designated as On-Lck), was cloned and its expression pattern under the stimulation of Streptococcus agalactiae was investigated. Sequence analysis showed important structural characteristics required for T cell receptor (TCR) signal transduction were detected in the deduced amino acid sequence of On-Lck, and the deduced genomic structure of On-Lck was similar to the known Lck. In healthy Nile tilapia, the On-Lck transcripts were mainly detected in the thymus, spleen, head kidney, and gill. When immunized with inactivated S. agalactiae, the On-Lck mRNA expression was significantly upregulated in the thymus, spleen, and head kidney. Moreover, there was a clear time-dependent expression pattern of On-Lck after immunization, and the expression reached the highest level at 48 h in the spleen and thymus and at 72 h in the head kidney, respectively. This is the first report on the expression of Lck induced by intracellular bacteria vaccination in teleosts. These findings indicated that On-Lck may play an important role in the immune response to intracellular bacteria in Nile tilapia.

Histone deacetylase 6 inhibition impairs effector CD8 T-cell functions during skin inflammation

Broad-spectrum histone deacetylase (HDAC) inhibitors are useful in the treatment of allergic and autoimmune diseases and malignancy. However, use of more specific HDAC inhibitors might limit the toxicities caused by HDAC inhibition. HDAC6, a member of the HDAC family, is highly expressed on CD8 T cells and has been shown to regulate immune responses through interactions between T cells and antigen-presenting cells. However, the mechanism by which HDAC6 inhibition affects the activation and functions of CD8 T cells is unclear. We investigated the role or roles of HDAC6 in CD8 T-cell activation and functions during skin inflammation in vitro and in vivo and examined the mechanism by which HDAC6 inhibition modifies T-cell receptor signaling in vitro. We assessed the clinical and biological effects of ACY-1215, an HDAC6-specific inhibitor, by using murine CD8 T cell-related skin disease models, including contact hypersensitivity (CHS) and experimental graft-versus-host disease (GVHD)-like disease. ACY-1215, an HDAC6 inhibitor, prevented the development of CHS and GVHD-like disease in vivo by modulating CD8 T-cell activation and functions; abrogated the induction of effector T cells from naive CD8 T cells by means of anti-CD3/CD28 antibody- or antigen-specific stimulation in vitro; and enhanced the binding of acetylated heat shock protein 90 to lymphocyte-specific protein tyrosine kinase in vitro, disrupting lymphocyte-specific protein tyrosine kinase phosphorylation and leading to impairment of the mitogen-activated protein kinase pathway. HDAC6, a key modifier of T-cell receptor signaling, might represent a novel target for the treatment of CD8 T cell-related skin diseases, including CHS and GVHD.

LCK: a new biomarker candidate for the early diagnosis of acute myocardial infarction.

Acute myocardial infarction (AMI) is one of the most common cardiovascular emergencies, of which the molecular pathogenesis is still not fully understood. This study aimed to explore the differentially expressed genes (DEGs) and then identify the critical genes in AMI thus screening out potential biomarkers for the early diagnosis of this serious heart disease. The gene expression data of AMI patients (GSE19339) were downloaded from gene expression omnibus database. After preprocessing with affy package, the DEGs were screened out by significance analysis of microarray (SAM) algorithm within samr package. Then function and pathway enrichment analyses of the DEGs were carried out using DAVID (database for annotation visualization and integrated discovery software) online tools. Further, the relevant genes of AMI were screened out with GENETIC_ASSOCIATION_DB_DISEASE analysis and blastp alignment. Finally, the novel genes were subjected to transcription factor and protein-protein interaction network analyses. A total of 633 DEGs, including 378 up-regulated and 255 down-regulated, were screened out between AMI patients and normal control samples. Among those genes, several important ones such as PPAR, CCL2, HMOX1 and NPR1 were demonstrated to be related to AMI. Most importantly, a novel gene LCK (lymphocyte-specific protein tyrosine kinase) was significantly differentially expressed in AMI. Further analyses showed that LCK was involved in the expression regulation of CXCL12 (chemokine (C-X-C motif) ligand 12) and the expression of LCK can be regulated by different transcription factors. In this study, we provided a new insight into the mechanism of AMI and raised LCK as an attractive marker candidate in the diagnosis of this serious heart disease.

A novel member of lymphocyte-specific protein tyrosine kinase protein identified in lamprey, Lampetra japonica.

Lymphocyte-specific protein tyrosine kinase p56 (Lck) is a member of the Src family of non-receptor protein tyrosine kinase. Lck plays an important role in mediating T-cell receptor (TCR) signal transduction and the development, differentiation, proliferation, and activation of T-cells [1]. Lck contains N-terminus of myristylation sequence, a unique aminoterminus region, followed by Src homology 3 (SH3) and SH2 domains and a C-terminus of tyrosine kinase catalytic domain [2]. Lck can associate with the inner face of the plasma membrane through its myristoyl glycine and palmitoyl cysteines in the amino-terminus [3].Following the myristylation sequence, there is the unique region, a short region of 80 amino acids. This unique region is involved in the interaction of Lck with specific cellular proteins [4,5]. Downstream of this unique region are SH3 and SH2 domains which are involved in protein–protein interactions [6]. The tyrosine kinase domain is the catalytic domain of Lck catalyzing the transfer of the gamma-phosphate from ATP to tyrosine residues in proteins. The catalytic domain of human Lck contains a site of autophosphorylation (Tyr-394), which plays an important role in regulating the protein kinase activity [7]. Agnathans, represented by lamprey and hagfish, are the oldest vertebrates currently identified possessing the adaptive immune defenses [8]. A recent study of jawless vertebrate has provided a clue for the origin of adaptive immune defense. Though TCR and B-cell receptor system do not exist in jawless vertebrates, lamprey has been confirmed to possess an alternative immune system that could specifically recognize and respond to external pathogens [9]. The handling of lamprey (Lampetra japonica) and all experimental procedures were approved by the Animal Welfare and Research Ethics Committee of the Institute of Dalian Medical University. Adult lampreys were purchased from Tongjiang section of the Heilongjiang River (Tongjiang, China) in December. Adult lampreys (200–220 g in weight) were divided into two groups (20 animals per group); one group of animals was immunized with 0.1 mg of lipopolysaccharide (LPS) (Sigma-Aldrich, St Louis, USA) in 0.1 ml phosphate-buffered saline (PBS), and the control animals were injected with 0.1 ml PBS only. The animals were immunized at 8-day intervals by four intraperitoneal injections. Based on the expressed sequence tag analysis of the cDNA library which was constructed with lamprey lymphocyte-like cells in our laboratory, a Lck homolog was found using Basic Local Alignment Search Tool (BLAST) in the National Center for Biotechnology Information (NCBI; http://www. ncbi.nlm.nih.gov/). Total RNA was isolated from lamprey lymphocyte-like cells [10] using RNAiso (TaKaRa Biotechnology, Dalian, China) reagent following the manufacturer instructions, and dissolved in Diethyl pyrocarbonate-treated water and stored at 2808C. First strand 30and 50-RACEcDNAs were synthesized from 5 mg of total RNA by Reverse Transcriptase M-MLV at 308C for 10 min, 428C for 30 min, 708C for 15 min, 958C for 5 min, 48C for 60 min with the 30-coding sequence primer and 50-coding sequence primer and Random 9-mers primer following the manufacturer instructions (TaKaRa Biotechnology). The 30and 50-end sequences of Lj-Lck were obtained by polymerase chain reaction (PCR) with outer primer, inner primer (TaKaRa Biotechnology), and specific primers (Supplementary Table S1). LA Taq DNA polymerase (TaKaRa Biotechnology) was used for amplification with the following cycling conditions: 948C for 3 min, followed by 40 amplification cycles at 948C for 30 s, 558C for 30 s, 728C for 2 min, and a final extension step at 728C for 10 min. Products were analyzed by electrophoresis in a 2% agarose gel stained with ethidium bromide. The target band of PCR product was isolated and purified, subcloned into Acta Biochim Biophys Sin 2014, 46: 820–825 |a The Author 2014. Published by ABBS Editorial Office in association with Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. DOI: 10.1093/abbs/gmu066. Advance Access Publication 25 July 2014

Ablation of reactive oxygen species intensifies diabetogenic CD4 T cell effector responses in type 1 diabetes. (BA14P.210)

Abstract In Type 1 diabetes (T1D), infiltrating leukocytes secrete reactive oxygen species (ROS) and pro-inflammatory cytokines that collectively participate in β-cell destruction and enhance autoreactive T cell responses. Our lab previously demonstrated that superoxide-deficient Non-Obese Diabetic (NOD.Ncf1m1J) mice were T1D-resistant due to skewed T cell responses. To dissect the role of ROS on autoreactive T cells, we generated the NOD.BDC-2.5.Ncf1m1J mouse, possessing diabetogenic, superoxide-deficient CD4 T cells and hypothesized that like NOD.Ncf1m1J, dampening ROS would diminish autoreactive T cell responses. Surprisingly, IFN-γ was upregulated 2-fold by NOD.BDC-2.5.Ncf1m1J T cells compared to NOD.BDC-2.5 with polyclonal stimulation (p=0.0045). Transfer of activated NOD.BDC-2.5.Ncf1m1J T cells was more diabetogenic, as 63% of NOD.scid recipients (n=11, p=0.0662) by 9 days post transfer were hyperglycemic, in contrast to 17% of wild-type recipients (n=7). To mechanistically explain the exacerbated Th1 cytokine response and diabetogenicity, phosphorylation of lymphocyte-specific protein tyrosine kinase (P-Lck (Y505)) and linker for activation of T cells (P-LAT (Y191)), redox-sensitive T cell receptor (TCR) signaling molecules, was enhanced 2-fold by NOD.BDC-2.5.Ncf1m1J CD4 T cells compared to NOD.BDC-2.5. Future experiments will dissect the redox-sensitive cues that control TCR adaptor molecule activation, as unraveling these signals may pinpoint novel targets for T1D prevention.

Leucine-rich repeat containing 8A (LRRC8A) is essential for T lymphocyte development and function.

Lrrc8a is a ubiquitously expressed gene that encodes a leucine-rich repeat (LRR)-containing protein detected at higher levels on the surface of thymocytes than on other immune cells. We generated Lrrc8a(-/-) mice to investigate the role of LRRC8A in lymphocyte development and function. Lrrc8a(-/-) mice had increased prenatal and postnatal mortality, growth retardation, and multiple tissue abnormalities. Lrrc8a(-/-) mice displayed a modest block in B cell development but intact intrinsic B cell function. In contrast, both Lrrc8a(-/-) mice and Lrrc8a(-/-)→Rag2(-/-) bone marrow chimeras exhibited a severe cell-intrinsic block in early thymic development, with decreased proliferation and increased apoptosis of thymocytes, and impaired peripheral T cell function. Thymic epithelial cells expressed an LRRC8A ligand that was critical for double-negative to double-positive thymocyte differentiation and survival in vitro. LRRC8A constitutively associated with the GRB2-GAB2 complex and lymphocyte-specific protein tyrosine kinase (LCK) in thymocytes. LRRC8A ligation activated AKT via the LCK-ZAP-70-GAB2-PI3K pathway, and AKT phosphorylation was markedly reduced in the thymus of Lrrc8a(-/-) mice. These findings reveal an essential role for LRRC8A in T cell development, survival, and function.

LYP's implications cause both increased or decreased susceptibility towards autoimmune and acquired diseases (LB96)

When functioning properly, the immune system protects the body from foreign invaders with the help of T‐cells. An error in the formation of T‐cells in the thymus can lead to autoimmune diseases in which the T‐cells attack normal body tissues. When a T‐cell binds to an antigen, a signal transduction pathway is activated, forming a multimeric signaling complex known as the TCR signalosome. LCK, part of the signalosome, is a lymphocyte‐specific protein tyrosine kinase that phosphorylates a variety of proteins in order to activate the T‐cell receptor pathway. TCR stimulation also leads to the activation of LYP, a lymphoid tyrosine phosphatase that down regulates TCR signaling by removing phosphates from the signaling intermediates of the TCR signalosome. LYP also dephosphorylates Y394 of LCK, thus inactivating the kinase and inhibiting TCR signaling. The LYP R620W mutation prevents LYP from binding to the signalosome, resulting in a gain‐of‐function, leading to increased inhibition of TCR signaling. The LYP R620W mutation has been linked to a wide spectrum of human diseases, including a decreased risk in Crohn’s disease and increased risk to rheumatoid arthritis, and possible links to non‐autoimmune disorders such as cardiovascular disease. The Marshfield SMART (Students Modeling A Research Topic) Team modeled the mutated protein LYP R620W using 3D technology.Grant Funding Source: Supported by grants from NIH‐CTSA and NIH‐SEPA.

Profile of pazopanib and its potential in the treatment of epithelial ovarian cancer.

Epithelial ovarian cancer (EOC) is the most lethal gynecological cancer. Recently, clinical trials have focused on novel antiangiogenic agents in combination with chemotherapy or alone in women with primary and recurrent ovarian cancer. Antiangiogenic agents include monoclonal antibodies, tyrosine-kinase inhibitors, and peptibodies. Many of these agents, including bevacizumab, pazopanib, nintedanib, cediranib, and trebananib, have been evaluated in randomized Phase III clinical trials, and all have demonstrated a progression-free survival (PFS) benefit. Specifically, maintenance pazopanib was shown to improve PFS in women with newly diagnosed EOC. Pazopanib, an oral TKI, inhibits several kinase receptors, including those for vascular endothelial growth factor (-1,-2,-3), platelet-derived growth factor (-α and -β), and fibroblast growth factor. It also targets stem cell-factor receptor (c-kit), interleukin 2-inducible T-cell kinase, lymphocyte-specific protein tyrosine kinase, and colony-stimulating factor 1 receptor. Pazopanib has been investigated in several Phase II and III clinical trials, with results indicating a potential role in the management of EOC. This article provides an overview of pazopanib in the treatment of EOC.

Phosphorylation of FOXP3 by LCK Downregulates MMP9 Expression and Represses Cell Invasion

Forkhead Box P3 (FOXP3) is a member of the forkhead/winged helix family of the transcription factors and plays an important role not only as a master gene in T-regulatory cells, but also as a tumor suppressor. In this study, we identified lymphocyte-specific protein tyrosine kinase (LCK), which correlates with cancer malignancy, as a binding partner of FOXP3. FOXP3 downregulated LCK-induced MMP9, SKP2, and VEGF-A expression. We observed that LCK phosphorylated Tyr-342 of FOXP3 by immunoprecipitation and in vitro kinase assay, and the replacement of Tyr-342 with phenylalanine (Y342F) abolished the ability to suppress MMP9 expression. Although FOXP3 decreased the invasive ability induced by LCK in MCF-7 cells, Y342F mutation in FOXP3 diminished this suppressive effect. Thus we demonstrate for the first time that LCK upregulates FOXP3 by tyrosine phosphorylation, resulting in decreased MMP9, SKP2, and VEGF-A expression, and suppressed cellular invasion. We consider that further clarification of transcriptional mechanism of FOXP3 may facilitate the development of novel therapeutic approaches to suppress cancer malignancy.

The role of membrane rafts in Lck transport, regulation and signalling in T-cells

Tyrosine phosphorylation is one of the key covalent modifications that occur in multicellular organisms. Since its discovery more than 30 years ago, tyrosine phosphorylation has come to be understood as a fundamentally important mechanism of signal transduction and regulation in all eukaryotic cells. The tyrosine kinase Lck (lymphocyte-specific protein tyrosine kinase) plays a crucial role in the T-cell response by transducing early activation signals triggered by TCR (T-cell receptor) engagement. These signals result in the phosphorylation of immunoreceptor tyrosine-based activation motifs present within the cytosolic tails of the TCR-associated CD3 subunits that, once phosphorylated, serve as scaffolds for the assembly of a large supramolecular signalling complex responsible for T-cell activation. The existence of membrane nano- or micro-domains or rafts as specialized platforms for protein transport and cell signalling has been proposed. The present review discusses the signals that target Lck to membrane rafts and the importance of these specialized membranes in the transport of Lck to the plasma membrane, the regulation of Lck activity and the phosphorylation of the TCR.

Main Histologic Types of Non–Small-Cell Lung Cancer Differ in Expression of Prognosis-related Genes

BackgroundThere is increasing evidence that suggests that particular histopathologic types of non–small-cell lung cancer (NSCLC) display distinct molecular characteristics. We analyzed, in lung squamous cell carcinoma (SCC) and adenocarcinoma (AC), the expression of 8 genes that constitute 2 previously reported prognostic expression signatures in NSCLC. MethodsFresh-frozen tumor and normal lung samples were obtained at surgery from 135 patients with stage I-III NSCLC (89 (65.9%) SCC, 46 (34.1%) AC). Expression of CSF1 (colony stimulating factor for macrophages), carbonic anhydrase 9 (CA9), epithelial growth factor receptor (EGFR), dual specificity phosphatase 6 (DUSP6), v-erb-b2 erythroblastic leukemia viral oncogene homolog 3 (ERBB3), monocyte to macrophage differentiation-associated (MMD), lymphocyte-specific protein tyrosine kinase (LCK) and signal transducer and activator of transcription 1 (STAT1) was assessed in SCC, AC, and in normal lung by quantitative reverse transcriptase - polymerase chain reaction (qRT-PCR). Metastasis-free survival was analyzed according to the median value of gene expression in the entire NSCLC cohort and separately in SCC and AC. ResultsExpression of CA9, CSF1, DUSP6, STAT1, and MMD differed between NSCLC and normal lung. EGFR was more abundant in SCC compared with AC, whereas the reverse was true for DUSP6 and ERBB3. A high expression of CSF1 correlated with shorter metastasis-free survival in the entire NSCLC group (P = .016) and in SCC (P = .049) and AC (P = .034) cohorts. ConclusionsSeveral genes considered prognostic in NSCLC showed significantly different expression in SCC and AC, and thus should be analyzed separately in these 2 subtypes for their prognostic significance. CSF1 is similarly expressed in SCC and AC, and portends a poor outcome in the entire group of patients with NSCLC, and in SCC and AC when considered separately.

LCK Is an Important Mediator of B-Cell Receptor Signaling in Chronic Lymphocytic Leukemia Cells

B-cell receptor (BCR) signals promote survival of chronic lymphocytic leukemia (CLL) cells, and it is believed that overexpressed and constitutively active Lyn mediates this signaling. Here, we show that CLL cells express lymphocyte-specific protein tyrosine kinase (LCK) and that inhibition of this Src family tyrosine kinase with the specific inhibitor [4-amino-5-(4-phenoxyphenyl)-7H-pyrrolo[3,2-d]pyrimidin-7-yl-cyclopentane (Lck-i)], or reduction of its expression with siRNA, blocks the induction of CD79a, Syk, inhibitor of IκB kinase (IKK), Akt, and extracellular signal-regulated kinase (ERK) phosphorylation by BCR cross-linking in these cells. Furthermore, we show that CLL cells with high levels of LCK expression have higher levels of BCR-mediated IKK, Akt, and ERK phosphorylation as well as cell survival than CLL cells with low levels of LCK expression. We also show that treatment of CLL cells with Lck-i inhibits BCR cross-linking-induced cell survival. Taken together, these data show a major role for LCK in proximal and distal BCR-mediated signaling in CLL cells and suggest that LCK expression is important in the pathogenesis of this disease. On a clinical level, these studies advocate the use of specific LCK inhibitors in the treatment of progressive CLL.