Novel roles for class II Phosphoinositide 3-Kinase C2 beta in signalling pathways involved in prostate cancer cell invasion

Phosphoinositide 3-kinases (PI3Ks) regulate several cellular functions such as proliferation, growth, survival and migration. The eight PI3K isoforms are grouped into three classes and the three enzymes belonging to the class II subfamily (PI3K-C2a, ß and ?) are the least investigated amongst all PI3Ks. Interest on these isoforms has been recently fuelled by the identification of specific physiological roles for class II PI3Ks and by accumulating evidence indicating their involvement in human diseases. While it is now established that these isoforms can regulate distinct cellular functions compared to other PI3Ks, there is still a limited understanding of the signalling pathways that can be specifically regulated by class II PI3Ks. Here we show that PI3K-C2ß regulates mitogen-activated protein kinase kinase (MEK1/2) and extracellular signal-regulated kinase (ERK1/2) activation in prostate cancer (PCa) cells. We further demonstrate that MEK/ERK and PI3K-C2ß are required for PCa cell invasion but not proliferation. In addition we show that PI3K-C2ß but not MEK/ERK regulates PCa cell migration as well as expression of the transcription factor Slug. These data identify novel signalling pathways specifically regulated by PI3K-C2ß and they further identify this enzyme as a key regulator of PCa cell migration and invasion

Molecular bases of diabetic nephropathy

The determinant of the diabetic nephropathy is hyperglycemia, but hypertension and other genetic factors are also involved. Glomerulus is the focus of the injury, where mesangial cell proliferation and extracellular matrix occur because of the increase of the intra- and extracellular glucose concentration and overexpression of GLUT1. Sequentially, there are increases in the flow by the poliol pathway, oxidative stress, increased intracellular production of advanced glycation end products (AGEs), activation of the PKC pathway, increase of the activity of the hexosamine pathway, and activation of TGF-beta1. High glucose concentrations also increase angiotensin II (AII) levels. Therefore, glucose and AII exert similar effects in inducing extracellular matrix formation in the mesangial cells, using similar transductional signal, which increases TGF-beta1 levels. In this review we focus in the effect of glucose and AII in the mesangial cells in causing the events related to the genesis of diabetic nephropathy. The alterations in the signal pathways discussed in this review give support to the observational studies and clinical assays, where metabolic and antihypertensive controls obtained with angiotensin-converting inhibitors have shown important and additive effect in the prevention of the beginning and progression of diabetic nephropathy. New therapeutic strategies directed to the described intracellular events may give future additional benefits.O principal determinante da nefropatia diabética é a hiperglicemia, mas hipertensão e fatores genéticos também estão envolvidos. O glomérulo é o foco de lesão, onde proliferação celular mesangial e produção excessiva de matriz extracelular decorrem do aumento da glicose intracelular, por excesso de glicose extracelular e hiperexpressão de GLUT1. Seguem-se aumento do fluxo pela via dos polióis, estresse oxidativo intracelular, produção intracelular aumentada de produtos avançados da glicação não enzimática (AGEs), ativação da via da PKC, aumento da atividade da via das hexosaminas e ativação de TGF-beta1. Altas concentrações de glicose também aumentam angiotensina II (AII) nas células mesangiais por aumento intracelular da atividade da renina (ações intrácrinas, mediando efeitos proliferativos e inflamatórios diretamente). Portanto, glicose e AII exercem efeitos proliferativos celulares e de matriz extracelular nas células mesangiais, utilizando vias de transdução de sinais semelhantes, que levam a aumento de TGF-beta1. Nesse estudo são revisadas as vias que sinalizam os efeitos da glicose e AII nas células mesangiais em causar os eventos-chaves relacionados à gênese da glomerulopatia diabética. As alterações das vias de sinalização implicadas na glomerulopatia, aqui revisadas, suportam dados de estudos observacionais/ensaios clínicos, onde controle metabólico e anti-hipertensivo, especificamente com inibidores do sistema renina-angiotensina, têm-se mostrado importantes - e aditivos - na prevenção do início e progressão da nefropatia. Novas estratégias terapêuticas dirigidas aos eventos intracelulares descritos deverão futuramente promover benefício adicional.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)HC Instituto do Coração Unidade de HipertensãoUSP FMUniversidade Federal de São Paulo (UNIFESP), Escola Paulista de Medicina (EPM) Laboratório de NefrologiaFundação Universitária de Cardiologia Instituto de Cardiologia Laboratório de Cardiologia Molecular e CelularUNIFESP, EPM, Laboratório de NefrologiaSciEL

Genotypic variation in response to drought stress is associated with biochemical and transcriptional regulation of ureides metabolism in common bean (Phaseolus vulgaris L.)

Ureidic legumes such as common bean (Phaseoulus valgaris L.) plants export nitrogen from the nodules to shoots and leaves as ureides during symbiotic biological nitrogen fixation. Common bean gene encoding allantoinase (allantoin amidohydrolase, EC 3.5.2.5), is a key enzyme that catalyses the hydrolysis of allantoin to allantoic acid. It plays a role in ureide generation for export and ureide catabolism to generate a nitrogen source in sinks tissues. As such, one of the adaptive mechanisms of plants to drought stress, is associated with ureides accumulation. To identify genetic variation of common bean in response to drought stress, changes in the expression of ALLANTONAISE (PvALN) gene and ureides content were examined in the leaf tissues of the three common bean genotypes (CAL96, DAB514 and DAB541) and one tepary bean genotype (Phaseolus acutifolius A.Gray). Amongst all the genotypes, the suggested drought susceptibility in DAB514 common bean genotype, was probably attributed to a repressed PvALN expression rate which were corroborated by an impaired ureides levels, and reduced plant growth. On contrary, drought stress induced an upregulated relative expression of PvALN coupled with an increase in allantoin and allantoate in DAB541 common bean genotype. In addition, the sustained plant growth in CAL96 was probably attributed to a steady amount of allantoin synthesized under drought stress. Taken together, DAB541 and CAL96 common bean genotypes are the promising genotypes with an induced upregulated transcriptional control of catabolism and/or biosynthesis of ureides, hence potential genotypes for selection and introduction under Botswana semi-arid conditions

Induction of Central Host Signaling Kinases during Pneumococcal Infection of Human THP-1 Cells

Streptococcus pneumoniae is a widespread colonizer of the mucosal epithelia of the upper respiratory tract of human. However, pneumococci are also responsible for numerous local as well as severe systemic infections, especially in children under the age of five and the elderly. Under certain conditions, pneumococci are able to conquer the epithelial barrier, which can lead to a dissemination of the bacteria into underlying tissues and the bloodstream. Here, specialized macrophages represent an essential part of the innate immune system against bacterial intruders. Recognition of the bacteria through different receptors on the surface of macrophages leads thereby to an uptake and elimination of bacteria. Accompanied cytokine release triggers the migration of leukocytes from peripheral blood to the site of infection, where monocytes differentiate into mature macrophages. The rearrangement of the actin cytoskeleton during phagocytosis, resulting in the engulfment of bacteria, is thereby tightly regulated by receptor-mediated phosphorylation cascades of different protein kinases. The molecular cellular processes including the modulation of central protein kinases are only partially solved. In this study, the human monocytic THP-1 cell line was used as a model system to examine the activation of Fcγ and complement receptor-independent signal cascades during infection with S. pneumoniae. Pneumococci cultured either in chemically defined or complex medium showed no significant differences in pneumococcal phagocytosis by phorbol 12-myristate 13-acetate (PMA) differentiated THP-1 cells. Double immuno-fluorescence microscopy and antibiotic protection assays demonstrated a time-dependent uptake and killing of S. pneumoniae 35A inside of macrophages. Infections of THP-1 cells in the presence of specific pharmacological inhibitors revealed a crucial role of actin polymerization and importance of the phosphoinositide 3-kinase (PI3K) and Protein kinase B (Akt) as well during bacterial uptake. The participation of essential host cell signaling kinases in pneumococcal phagocytosis was deciphered for the kinase Akt, ERK1/2, and p38 and phosphoimmunoblots showed an increased phosphorylation and thus activation upon infection with pneumococci. Taken together, this study deciphers host cell kinases in innate immune cells that are induced upon infection with pneumococci and interfere with bacterial clearance after phagocytosis

CIIA functions as a molecular switch for the Rac1-specific GEF activity of SOS1

CIIA mediates the TGF-β–induced activation of SOS1–Rac1 signaling and cell migration

Mutations of PIK3CA in gastric adenocarcinoma

BACKGROUND: Activation of the phosphatidylinositol 3-kinase (PI3K) through mutational inactivation of PTEN tumour suppressor gene is common in diverse cancer types, but rarely reported in gastric cancer. Recently, mutations in PIK3CA, which encodes the p110α catalytic subunit of PI3K, have been identified in various human cancers, including 3 of 12 gastric cancers. Eighty percent of these reported mutations clustered within 2 regions involving the helical and kinase domains. In vitro study on one of the "hot-spot" mutants has demonstrated it as an activating mutation. METHODS: Based on these data, we initiated PIK3CA mutation screening in 94 human gastric cancers by direct sequencing of the gene regions in which 80% of all the known PIK3CA mutations were found. We also examined PIK3CA expression level by extracting data from the previous large-scale gene expression profiling study. Using Significance Analysis of Microarrays (SAM), we further searched for genes that show correlating expression with PIK3CA. RESULTS: We have identified PIK3CA mutations in 4 cases (4.3%), all involving the previously reported hotspots. Among these 4 cases, 3 tumours demonstrated microsatellite instability and 2 tumours harboured concurrent KRAS mutation. Data extracted from microarray studies showed an increased expression of PIK3CA in gastric cancers when compared with the non-neoplastic gastric mucosae (p < 0.001). SAM further identified 2910 genes whose expression levels were positively associated with that of PIK3CA. CONCLUSION: Our data suggested that activation of the PI3K signalling pathway in gastric cancer may be achieved through up-regulation or mutation of PIK3CA, in which the latter may be a consequence of mismatch repair deficiency

Topographical expression of class IA and class II phosphoinositide 3-kinase enzymes in normal human tissues is consistent with a role in differentiation

BACKGROUND: Growth factor, cytokine and chemokine-induced activation of PI3K enzymes constitutes the start of a complex signalling cascade, which ultimately mediates cellular activities such as proliferation, differentiation, chemotaxis, survival, trafficking, and glucose homeostasis. The PI3K enzyme family is divided into 3 classes; class I (subdivided into IA and IB), class II (PI3K-C2α, PI3K-C2β and PI3K-C2γ) and class III PI3K. Expression of these enzymes in human tissue has not been clearly defined. METHODS: In this study, we analysed the immunohistochemical topographical expression profile of class IA (anti-p85 adaptor) and class II PI3K (PI3K-C2α and PI3K-C2β) enzymes in 104 formalin-fixed, paraffin embedded normal adult human (age 33–71 years, median 44 years) tissue specimens including those from the gastrointestinal, genitourinary, hepatobiliary, endocrine, integument and lymphoid systems. Antibody specificity was verified by Western blotting of cell lysates and peptide blocking studies. Immunohistochemistry intensity was scored from undetectable to strong. RESULTS: PI3K enzymes were expressed in selected cell populations of epithelial or mesenchymal origin. Columnar epithelium and transitional epithelia were reactive but mucous secreting and stratified squamous epithelia were not. Mesenchymal elements (smooth muscle and endothelial cells) and glomerular epithelium were only expressed PI3K-C2α while ganglion cells expressed p85 and PI3K-C2β. All three enzymes were detected in macrophages, which served as an internal positive control. None of the three PI3K isozymes was detected in the stem cell/progenitor compartments or in B lymphocyte aggregates. CONCLUSIONS: Taken together, these data suggest that PI3K enzyme distribution is not ubiquitous but expressed selectively in fully differentiated, non-proliferating cells. Identification of the normal in vivo expression pattern of class IA and class II PI3K paves the way for further analyses which will clarify the role played by these enzymes in inflammatory, neoplastic and other human disease conditions

Mutation of the PIK3CA oncogene in human cancers

It is now well established that cancer is a genetic disease and that somatic mutations of oncogenes and tumour suppressor genes are the initiators of the carcinogenic process. The phosphatidylinositol 3-kinase signalling pathway has previously been implicated in tumorigenesis, and evidence over the past year suggests a pivotal role for the phosphatidylinositol 3-kinase catalytic subunit, PIK3CA, in human cancers. In this review, we analyse recent reports describing PIK3CA mutations in a variety of human malignancies, and discuss their possible implications for diagnosis and therapy

The coordination of signaling during Fc receptor‐mediated phagocytosis

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141562/1/jlb1093.pd