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PubMed2026

Comprehensive analysis of mRNA-microRNA-lncRNA expression profiles in post-traumatic elbow heterotopic ossification using RNA sequencing and experimental validation.

BACKGROUND: This study aimed to profile the molecular signatures of post-traumatic elbow heterotopic ossification (HO) to identify key regulators and potential therapeutic targets. METHODS: Total RNA from post-traumatic elbow HO tissues (n=4) and normal bone tissues (n=6) was subjected to high-throughput sequencing to identify differentially expressed mRNAs (DEGs), microRNAs (DEMs), and lncRNAs (DELs). Bioinformatics analyses included Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, protein-protein interaction network construction, and transcription factor (TF)-microRNA-mRNA network analysis. The expression trends of four most upregulated and four most downregulated DEGs were validated by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). RESULTS: We identified 2,138 DEGs, 40 DEMs, and 905 DELs. DEGs were significantly enriched in biological process "bone mineralization," cellular component "plasma membrane," molecular function "integrin binding," and pathways including PI3K-Akt, NF-κB, JAK-STAT, and TNF signaling pathways. Hub genes with high connectivity included MMP9, IL6, MMP3, CTSK, and BGLAP. Integrated network analysis highlighted the transcription factor JUN and key microRNAs (hsa-miR-124-3p, hsa-miR-548c-3p, and hsa-miR-135b). The qRT-PCR results confirmed the expression trends of selected DEGs. CONCLUSIONS: This study, for the first time, profiled the differentially expressed mRNAs, microRNAs, and lncRNAs in post-traumatic elbow HO using high-throughput RNA sequencing. These findings provide valuable insights into the molecular mechanisms of HO following elbow trauma. The identified hub genes (MMP9, IL6, MMP3, CTSK, and BGLAP), key TF (JUN), and key microRNAs (hsa-miR-124-3p, hsa-miR-548c-3p, and hsa-miR-135b) may serve as potential therapeutic targets for preventing and treating post-traumatic elbow HO.

Humans↗
PubMed2001

Phosphatidylinositol-3-OH kinase regulatory subunits are differentially expressed during development of the rat cerebellum.

Recent evidence implicates a central role for PI3K signalling in mediating cell survival during the process of neuronal differentiation. Although PI3K activity is stimulated by a wide range of growth factors and cytokines in different cell lines and tissues, activation of this pathway by insulin-like growth factor I (IGF-I) most likely represents the main survival signal during neuronal differentiation. IGF-I is highly expressed during development of the central nervous system, and thus is a critical factor for the development and maturation of the cerebellum. Upon ligand binding, the IGF-I receptor phosphorylates tyrosine residues in SHC and insulin receptor substrates (IRSs) initiating two main signalling cascades, the MAP kinase and the phosphatidylinositol 3-kinase (PI3K) pathways. Activated PI3K is composed of a catalytic subunit (p110alpha or beta) associated with one of a large family of regulatory subunits (p85alpha, p85beta, p55gamma, p55alpha, and p50alpha). To evaluate the contributions of these various regulatory subunits to neuronal differentiation, we have used antibodies specific for each of the PI3K subunits. Using these antisera, we now demonstrate that PI3K subunits are differentially regulated in cerebellar development, and that the expression level of the p55gamma regulatory subunit reaches a maximum during postnatal development, decreasing thereafter to low levels in the adult cerebellum. Furthermore, our studies reveal that the distribution of the various PI3K regulatory subunits varies during development of the cerebellum. Interestingly, p55gamma is expressed in both glial and neuronal cells; moreover, in Purkinje neurones, this subunit colocalises with the IGF-IR.

Animals↗
PubMed2006

PI3K is required for insulin-stimulated but not EGF-stimulated ERK1/2 activation.

The Ras/Raf/extracellular signal-regulated kinase 1 and 2 (ERK1/2) signaling pathway is known to cross-talk with other signaling pathways, including phosphatidylinositol 3-kinase (PI3K)/Akt pathway. However, the role of PI3K in ERK-1/2 activation induced by tyrosine kinase receptors was not fully understood. Here, we report that two structurally distinct PI3K inhibitors, wortmannin and LY294002, inhibited insulin-induced activation of ERK1/2 but had no effect on EGF-induced activation of ERK1/2 in hepatocellular carcinoma BEL-7402 and SMMC-7721 cells, breast cancer MCF-7 cells, and prostate cancer LNCaP cells. Although protein kinase C could act as a mediator between PI3K and ERK1/2, protein kinase C inhibitor chelerythrine chloride did not inhibit insulin-induced ERK1/2 activation. Both insulin- and EGF-induced ERK1/2 activation are strictly dependent on Ras activation, however, wortmannin only inhibited insulin-induced, but not EGF-induced Ras activation. These results indicate that PI3K plays different roles in the activation of Ras/ERK1/2 signaling by insulin and EGF, and that insulin-stimulated, but not EGF-stimulated, ERK1/2 and Akt signalings diverge at PI3K.

Alkaloids↗
PubMed2006

Caveolae internalization regulates integrin-dependent signaling pathways.

Integrin-mediated adhesion regulates trafficking of cholesterol-enriched membrane microdomains (CEMM). Upon cell detachment from the extracellular matrix (ECM), CEMMs undergo rapid internalization and are cleared from the plasma membrane. This pathway regulates integrin-mediated Rac membrane targeting, allowing coupling of Rac to downstream effectors. Internalization of CEMMs is mediated by Dynamin-2, a regulator of caveolae dynamics, and caveolin-1, an essential caveolae coat protein. Translocation of tyrosine phosphorylated caveolin-1 from focal adhesions to caveolae upon cell detachment induces CEMM internalization. Notably, integrin-mediated regulation of Erk, phosphatidylinositol-3-OH kinase (PI3K) and Rac pathways is dependent on caveolin-1. These results describe a novel pathway in which integrins prevent downregulation of Erk, PI3K and Rac-dependent pathways by inhibiting caveolin-1-dependent endocytosis. This pathway define a novel molecular mechanism for regulated cell growth and tumor suppression by caveolin-1.

Animals↗
PubMed2004

Genetic alterations of phosphoinositide 3-kinase subunit genes in human glioblastomas.

Genetic alterations of PI3K (phosphoinositide 3-kinase) subunits have been documented in a number of tumor types, with increased PI3K activity linked to gene amplification and mutation of catalytic subunits, as well as mutations of regulatory subunits. Among high grade gliomas, activation of the PI3K-AKT signaling pathway through loss of PTEN function is common. We therefore investigated whether genetic alteration of class IA PI3Ks might provide a mechanism for deregulation of this pathway in glioblastomas. We studied a series of glioblastomas with FISH to assess copy number of catalytic subunits (PIK3CA and PIK3CD) and with PCR-SSCP to screen for somatic mutations of conserved regions of both catalytic and regulatory subunits. FISH revealed frequent balanced copy number increases of both PIK3CA and PIK3CD, and one case showed an extra copy limited to PIK3CA. One glioblastoma exhibited a 9-bp deletion that encompassed the exon-intron junction of exon 12 of PIK3R1, documenting for the first time a mutation within a PI3K regulatory subunit in human glioblastoma. This deletion would be predicted to yield a truncated protein that lacks the inhibitory domain, resulting in increased PI3K activity. Furthermore, the case with selected PIK3CA copy number gain and the case with a truncating PIK3R1 mutation both featured AKT activation without PTEN mutation. These results suggest that genetic alterations of class IA PI3K subunit genes can occasionally play a role in human glioblastoma by activating the PI3K-AKT signaling pathway independently of PTEN mutation.

Brain Neoplasms↗
PubMed1995

Activation of pp70/85 S6 kinases in interleukin-2-responsive lymphoid cells is mediated by phosphatidylinositol 3-kinase and inhibited by cyclic AMP.

Activation of phosphatidylinositol 3-kinase (PI3K) and activation of the 70/85-kDa S6 protein kinases (alpha II and alpha I isoforms, referred to collectively as pp70S6k) have been independently linked to the regulation of cell proliferation. We demonstrate that these kinases lie on the same signalling pathway and that PI3K mediates the activation of pp70 by the cytokine interleukin-2 (IL-2). We also show that the activation of pp70S6k can be blocked at different points along the signalling pathway by using specific inhibitors of T-cell proliferation. Inhibition of PI3K activity with structurally unrelated but highly specific PI3K inhibitors (wortmannin or LY294002) results in inhibition of IL-2-dependent but not phorbol ester (conventional protein kinase C [cPKC])-dependent pp70S6k activation. The T-cell immunosuppressant rapamycin potently antagonizes IL-2-(PI3K)- and phorbol ester (cPKC)-mediated activation of pp70S6k. Thus, wortmannin and rapamycin antagonize IL-2-mediated activation of pp70S6k at distinct points along the PI3K-regulated signalling pathway, or rapamycin antagonizes another pathway required for pp70S6k activity. Agents that raise the concentration of intracellular cyclic AMP (cAMP) and activate cAMP-dependent protein kinase (PKA) also inhibit IL-2-dependent activation of pp70S6k. In this case, inhibition appears to occur at least two points in this signalling path. Like rapamycin, PKA appears to act downstream of cPKC-mediated pp70S6k activation, and like wortmannin, PKA antagonizes IL-2-dependent activation of PI3K. The results with rapamycin and wortmannin are of added interest since the yeast and mammalian rapamycin targets resemble PI3K in the catalytic domain.

Androstadienes↗
PubMed2003

Protein kinase C-lambda knockout in embryonic stem cells and adipocytes impairs insulin-stimulated glucose transport.

Atypical protein kinase C (aPKC) isoforms have been suggested to mediate insulin effects on glucose transport in adipocytes and other cells. To more rigorously test this hypothesis, we generated mouse embryonic stem (ES) cells and ES-derived adipocytes in which both aPKC-lambda alleles were knocked out by recombinant methods. Insulin activated PKC-lambda and stimulated glucose transport in wild-type (WT) PKC-lambda(+/+), but not in knockout PKC-lambda(-/-), ES cells. However, insulin-stimulated glucose transport was rescued by expression of WT PKC-lambda in PKC-lambda(-/-) ES cells. Surprisingly, insulin-induced increases in both PKC-lambda activity and glucose transport were dependent on activation of proline-rich tyrosine protein kinase 2, the ERK pathway, and phospholipase D (PLD) but were independent of phosphatidylinositol 3-kinase (PI3K) in PKC-lambda(+/+) ES cells. Interestingly, this dependency was completely reversed after differentiation of ES cells to adipocytes, i.e. insulin effects on PKC-lambda and glucose transport were dependent on PI3K, rather than proline-rich tyrosine protein kinase 2/ERK/PLD. As in ES cells, insulin effects on glucose transport were absent in PKC-lambda(-/-) adipocytes but were rescued by expression of WT PKC-lambda in these adipocytes. Our findings suggest that insulin activates aPKCs and glucose transport in ES cells by a newly recognized PI3K-independent ERK/PLD-dependent pathway and provide a compelling line of evidence suggesting that aPKCs are required for insulin-stimulated glucose transport, regardless of whether aPKCs are activated by PI3K-dependent or PI3K-independent mechanisms.

Adipocytes↗
PubMed2004

G protein mediated signaling pathways in lysophospholipid induced cell proliferation and survival.

Agonist activation of a subset of G protein coupled receptors (GPCRs) stimulates cell proliferation, mimicking the better known effects of tyrosine kinase growth factors. Cell survival or apoptosis is also regulated via pathways initiated by stimulation of these same GPCRs. This review focuses on aspects of signaling by the lysophospholipid mediators, lysophosphatidic acid (LPA), and sphingosine 1 phosphate (S1P), which make these agonists uniquely capable of modulating cell growth and survival. The general features of GPCR coupling to specific G proteins, downstream effectors and signaling cascades are first reviewed. GPCR coupling to G(i) and Ras/MAPK or to G(q) and phospholipase generated second messengers are insufficient to regulate cell proliferation while G(12/13)/Rho engagement provides additional complementary signals required for cell proliferation. Survival is best predicted by coupling to G(i) pathways that regulate PI3K and Akt, but other signals generated through different G protein pathways are also implicated. The unique ability of LPA and S1P to concomitantly stimulate G(i), G(q), and G(12/13) pathways, given the proper complement of expressed LPA or S1P receptors, allows these receptors to support cell survival and proliferation. In pathophysiological situations, e.g., vascular disease, cancer, brain injury, and inflammation, components of the signaling cascade downstream of lysophospholipid receptors, in particular those involving Ras or Rho, may be altered. In addition, up or downregulation of LPA or S1P receptor subtypes, altering their ratio, and increased availability of the lysophospholipid ligands at sites of injury or inflammation, likely contribute to disease and may be important targets for therapeutic intervention.

Cell Proliferation↗
PubMed1999

In vivo regulation of protein-serine kinases by insulin in skeletal muscle of fructose-hypertensive rats.

The effects of tail-vein insulin injection (2 U/kg) on the regulation of protein-serine kinases in hindlimb skeletal muscle were investigated in hyperinsulinemic hypertensive fructose-fed (FF) animals that had been fasted overnight. Basal protein kinase B (PKB) activity was elevated about twofold in FF rats and was not further stimulated by insulin. Phosphatidylinositol 3-kinase (PI3K), which lies upstream of PKB, was increased approximately 3.5-fold within 2-5 min by insulin in control rats. Basal and insulin-activated PI3K activities were further enhanced up to 2-fold and 1.3-fold, respectively, in FF rats. The 70-kDa S6 kinase (S6K) was stimulated about twofold by insulin in control rats. Both basal and insulin-stimulated S6K activity was further enhanced up to 1.5-fold and 3.5-fold, respectively, in FF rats. In control rats, insulin caused a 40-50% reduction of the phosphotransferase activity of the beta-isoform of glycogen synthase kinase 3 (GSK-3beta), which is a PKB target in vitro. Basal GSK-3beta activity was decreased by approximately 40% in FF rats and remained unchanged after insulin treatment. In summary, 1) the PI3K --> PKB --> S6K pathway was upregulated under basal conditions, and 2) insulin stimulation of PI3K and S6K activities was enhanced, but both PKB and GSK-3 were refractory to the effects of insulin in FF rats.

Animals↗
PubMed2025

Comparative genomic analysis of key oncogenic pathways in hepatocellular carcinoma among diverse populations.

BACKGROUND/OBJECTIVES: Hepatocellular carcinoma (HCC) is a leading cause of cancer-related mortality, with significant racial and ethnic disparities in incidence, tumor biology, and clinical outcomes. Hispanic/Latino (H/L) patients tend to be diagnosed at younger ages and more advanced stages than Non-Hispanic White (NHW) patients, yet the molecular mechanisms underlying these disparities remain poorly understood. Key oncogenic pathways, including RTK/RAS, TGF-Beta, WNT, PI3K, and TP53, play pivotal roles in tumor progression, treatment resistance, and response to targeted therapies. However, ethnicity-specific alterations within these pathways remain largely unexplored. This study aims to compare pathway-specific mutations in HCC between H/L and NHW patients, assess tumor mutation burden, and identify ethnicity-associated oncogenic drivers using publicly available datasets. Findings from this analysis may inform precision medicine strategies for improving early detection and targeted therapies in underrepresented populations. METHODS: We conducted a bioinformatics analysis using publicly available HCC datasets to assess mutation frequencies in RTK/RAS, TGF-Beta, WNT, PI3K, and TP53 pathway genes. The study included 547 patients, consisting of 69 H/L patients and 478 NHW patients. Patients were stratified by ethnicity (H/L vs. NHW) to evaluate differences in mutation prevalence. Chi-squared tests were used to compare mutation frequencies, while Kaplan-Meier survival analysis assessed overall survival differences associated with pathway-specific alterations in both populations. RESULTS: Significant differences were observed in the RTK/RAS pathway related genes, particularly in FGFR4 mutations, which were more prevalent in H/L patients compared to NHW patients (4.3% vs. 0.6%, p = 0.02). Additionally, IGF1R mutations exhibited borderline significance (7.2% vs. 2.9%, p = 0.07). In the PI3K pathway, INPP4B alterations were more frequent in H/L patients than in NHW patients (4.3% vs. 1%, p = 0.06), while in the TGF-Beta pathway, TGFBR2 mutations were more common in H/L patients (2.9% vs. 0.4%, p = 0.07), suggesting potential ethnicity-specific variations. Survival analysis revealed no significant differences in overall survival between H/L and NHW patients, indicating that molecular alterations alone may not fully explain survival disparities and suggesting a role for additional factors such as immune response, environmental exposures, or access to targeted therapies. CONCLUSIONS: This study provides one of the first ethnicity-focused analyses of key oncogenic pathway alterations in HCC, revealing distinct molecular differences between H/L and NHW patients. The findings suggest that RTK/RAS (FGFR4, IGF1R), PI3K (INPP4B), and TGF-Beta (TGFBR2) pathway alterations may play a distinct role in HCC among H/L patients, while their prognostic significance in NHW patients remains unclear. These insights emphasize the importance of incorporating ethnicity-specific molecular profiling into precision medicine approaches to improve early detection, targeted therapies, and clinical outcomes in HCC, particularly for underrepresented populations.

PI3K pathway↗
PubMed2003

The role of phosphatidylinositol 3'-kinase and its downstream signals in erbB-2-mediated transformation.

We previously demonstrated that erbB-2-overexpressing human mammary epithelial (HME) cells exhibit several transformed phenotypes including growth factor independence, anchorage-independent growth, motility, and invasiveness. Because phosphatidylinositol 3'-kinase (PI3K) is a major target of erbB-2 activation, we tested the contribution that PI3K and its downstream signaling pathways make to these phenotypes. Utilizing a constitutively active form of PI3K, p110CAAX, we show that PI3K can mediate most phenotypes observed in erbB-2-overexpressing cells. To identify pathways leading from PI3K to specific phenotypes, we expressed constitutively active AKT or PTEN in erbB-2-overexpressing cells or in HME cells. HME cells expressing constitutively active AKT were growth factor independent, anchorage independent and motile, but not invasive. PTEN expression blocked erbB-2-mediated invasion but none of the other phenotypes. Rottlerin blocked invasion induced by p110CAAX and erbB-2, suggesting that protein kinase C delta (PKC-delta) is the downstream effector of PI3K responsible for the invasive capacity of the cells. Consistent with these observations, phospho-AKT remained detectable in erbB-2 cells treated with LY294002 or expressing exogenous PTEN, but was abolished by treatment with the p38MAP kinase inhibitor SB202190. Thus, both PI3K-dependent and p38MAP kinase-dependent pathways lead to activation of AKT, and activation of PKC-delta, via PI3K, mediates invasion.

Cell Line↗
PubMed2005

Basic fibroblast growth factor activates ERK and induces c-fos in human embryonic stem cell line MizhES1.

Human embryonic stem (hES) cells can be maintained in a proliferative undifferentiated state in vitro by growing them on feeder layers of mouse embryonic fibroblast (MEF) cells along with basic fibroblast growth factor (bFGF/FGF-2). To understand the molecular mechanisms involved in the requirement of bFGF in human ES cells, we investigated expression of FGF receptors and intracellular signaling events in response to bFGF in human ES cell line MizhES1. On the basis of the results of RT-PCR, clear expression of FGF receptors FGFR1, FGR2, and FGFR3 was noticed. Because MAPK, PI3K, and PKC pathways are well-known pathways triggered by bFGF in other cells, these pathways were investigated after stimulation with bFGF. bFGF did not induce activation of PI3K or PKC, but induced activation of ERK (extracellular signal-regulated kinase). To monitor the consequences of ERK activation, we examined expression of the immediate early gene c-fos, one downstream target of the MEK1/ERK pathway. mRNA and protein levels of the c-fos gene were increased by bFGF. Induction of c-Fos was dependent on MEKl. Therefore, it is likely that bFGF contributes to maintenance of human ES cells, at least in part, through the MEK1/ERK pathway.

Animals↗
PubMed2004

Role of phosphatidylinositol 3-kinase in the development of hepatocyte preconditioning.

BACKGROUND & AIMS: Ischemic preconditioning has been proved effective in reducing ischemia/reperfusion injury during liver surgery. However, the mechanisms involved are still poorly understood. Here, we have investigated the role of phosphatidylinositol 3-kinase (PI3K) in the signal pathway leading to hepatic preconditioning. METHODS: PI3K activation was evaluated in isolated rat hepatocytes preconditioned by 10-minute hypoxia followed by 10-minute reoxygenation. RESULTS: Hypoxic preconditioning stimulated phosphatidylinositol-3,4,5-triphosphate production and the phosphorylation of PKB/Akt, a downstream target of PI3K. Conversely, PI3K inhibition by wortmannin or LY294002 abolished hepatocyte tolerance against hypoxic damage induced by preconditioning. PI3K activation in preconditioned hepatocytes required the stimulation of adenosine A 2A receptors and was mimicked by adenosine A 2A receptors agonist CGS21680. In the cells treated with CGS21680, PI3K activation was prevented either by inhibiting adenylate cyclase and PKA with, respectively, 2,5-dideoxyadenosine and H89 or by blocking Galphai-protein and Src tyrosine kinase with, respectively, pertussis toxin and PP2. H89 also abolished the phosphorylation of adenosine A 2A receptors. However, the direct PKA activation by forskolin failed to stimulate PI3K. This suggested that PKA-phosphorylated adenosine A 2A receptors may activate PI3K by coupling it with Galphai-protein through Src. We also observed that, by impairing PI3K-mediated activation of phospholypase Cgamma (PLCgamma), wortmannin and LY294002 blocked the downstream transduction of preconditioning signals via protein kinase C (PKC) delta/ isozymes. CONCLUSIONS: PI3K is activated following hepatocyte hypoxic preconditioning by the combined stimulation of adenosine A 2A receptors, PKA, Galphai protein, and Src. By regulating PKC-/delta-dependent signals, PI3K can play a key role in the development of hepatic tolerance to hypoxia/reperfusion.

Animals↗
PubMed2002

Requirement of phosphoinositide 3-kinase and Akt for interferon-beta-mediated induction of the beta-R1 (SCYB11) gene.

We previously reported (Rani, M. R., Asthagiri, A. R., Singh, A., Sizemore, N., Sathe, S. S., Li, X., DiDonato, J. D., Stark, G. R., and Ransohoff, R. M. (2001) J. Biol. Chem. 276, 44365-44368) that IFN-beta induction of beta-R1 in fibrosarcoma cells required transcription factors ISGF-3 and NF-kappa B. IFN-beta treatment did not augment the abundance of NF-kappa B, but led to phosphorylation of the NF-kappa B subunit p65 and induced a nuclear activity capable of phosphorylating a p65-GST fusion construct in the carboxy-terminal transactivation domain (TAD), residues 354-551. We now present evidence for the involvement of phosphoinositide 3-kinase (PI3K) in this pathway. Pretreatment of HT1080-derived fibrosarcoma cells with pharmacological inhibitors of PI3K (wortmannin or LY294002) selectively inhibited IFN-beta-induced beta-R1 mRNA accumulation in a dose-dependent manner. In stably transfected cell lines, bovine p85, the regulatory subunit of PI3K, functioned as a dominant-negative inhibitor of interferon (IFN) signaling via PI3K and selectively suppressed IFN-beta-mediated induction of beta-R1. Overexpression of PTEN (phosphatase and tensin homologue mutated on chromosome ten), an antagonist of PI3K, blocked induction of a beta-R1 promoter-reporter construct. Studies with PTEN mutants suggested that the lipid kinase activity of PI3K was essential for IFN-beta-induced transcription of beta-R1. Consistent with this finding, a dominant-negative mutant of the serine-threonine kinase Akt, a downstream effector of PI3K, selectively blocked IFN-beta-mediated induction of the beta-R1 promoter reporter. Furthermore, IFN-beta-mediated phosphorylation of GST-p65 was blocked by pretreatment with LY294002. These data suggest that IFN-beta acts through PI3K to enhance the transactivation competence of NF-kappa B complexes through phosphorylation of p65 within the TAD. The results provide novel insight into the role of PI3K in the transcriptional response to IFN-beta.

Animals↗
PubMed2005

Gene expression profiling of mantle cell lymphoma cells reveals aberrant expression of genes from the PI3K-AKT, WNT and TGFbeta signalling pathways.

Microarray studies have revealed the differential expression of several genes in mantle cell lymphoma (MCL), but it is unknown which of these differences are dependent on the transformed MCL cell itself or on the tumour microenvironment. To investigate which genes and signalling pathways are aberrantly expressed in MCL cells we used oligonucleotide microarrays to perform gene expression profiling of both purified leukaemic MCL cells and their normal counterparts, the naive B cells. A total of 106 genes were differentially expressed at least threefold in MCL cells compared with naive B cells; 63 upregulated and 43 downregulated. To validate the microarray results in a larger set of samples, we selected 10 differentially expressed genes and quantified their expression by real-time polymerase chain reaction in peripheral blood of MCL patients (n=21), purified MCL cells (n=6) and naive B cells (n=4), obtaining fully concordant results. A computer-assisted approach was used to procure specific molecular signalling pathways that were aberrantly expressed in MCL cells. Several genes related to apoptosis and to the PI3K/AKT, WNT and tumour growth factor beta signalling pathways were altered in MCL cells when compared with naive B cells. These pathways may play a significant role in the pathogenesis of MCL and deserve further investigation as candidates for new therapeutic targets.

Adult↗
PubMed2005

The Jak/Stat pathway: a novel way to regulate PI3K activity.

Phosphoinositide 3-kinases (PI3Ks) have been grouped into three major classes that have different substrate specificities. Class IA PI3Ks consist of a catalytic and a regulatory subunit and have multiple isoforms that arise from different subunit combinations. The role of two of the small regulatory subunits, p55alpha and p50alpha, is poorly understood. We have now identified a novel function for these subunits and have shown that their expression is specifically induced in the involuting mouse mammary gland where they are involved in the downregulation of PI3K signalling and Akt/PKB activity. This abrogation of survival signalling thru Akt/PKB and its downstream targets is essential for the induction of apoptosis. The switch from lactation to involution is associated with activation of the transcription factor Stat3, by the cytokine LIF. Stat3 is essential for the induction of apoptosis and, in the absence of Stat3 or LIF, expression of the p55alpha and p50alpha subunits is abrogated. Surprisingly, Stat3 is a direct regulator of p55alpha and p50alpha expression, as demonstrated using ChIP assays, and therefore these subunits are not splicing isoforms as previously thought. An important implication of our results is that the p55alpha and p50alpha small regulatory subunits are regulated independently of the larger p85alpha subunit, and have an essential role in Stat3-mediated apoptosis in mammary gland.

Animals↗
PubMed2003

Role of ephrin B2 in human retinal endothelial cell proliferation and migration.

This study was designed to determine the presence of Eph B4 or ephrin B2 in human retinal endothelial cells (REC) and their signal transduction. Human retinal endothelial cells were stimulated with an Eph B4/Fc chimera and probed for phosphorylation of phosphatidylinositol-3-kinase (PI3K), Src, and mitogen-activated protein kinase (MAPK) pathways. Proliferation and migration were investigated after Eph B4/Fc stimulation in the presence of various pathway inhibitors. Human retinal endothelial cells express ephrin B2, with little expression of Eph B4. Treatment with EphB4/Fc chimera resulted in activation of PI3K, Src, and MAPK pathways. Eph B4-stimulated endothelial cell proliferation was mediated via PI3K, nitric oxide synthase, and extracellular signal-regulated kinase 1/2 (ERK1/2). Blockade of Src-PI3K pathways produced significant attenuation of Eph B4/Fc-stimulated migration. These results demonstrate for the first time that ephrin B2 is present in human retinal endothelial cells. Additionally, it appears that vascular growth may be modulated in the retina through activation of the PI3K pathway and its downstream components.

Cell Division↗
PubMed2004

Extracellular ATP-induced proliferation of adventitial fibroblasts requires phosphoinositide 3-kinase, Akt, mammalian target of rapamycin, and p70 S6 kinase signaling pathways.

Extracellular nucleotides are increasingly recognized as important regulators of growth in a variety of cell types. Recent studies have demonstrated that extracellular ATP is a potent inducer of fibroblast growth acting, at least in part, through an ERK1/2-dependent signaling pathway. However, the contributions of additional signaling pathways to extracellular ATP-mediated cell proliferation have not been defined. By using both pharmacologic and genetic approaches, we found that in addition to ERK1/2, phosphatidylinositol 3-kinase (PI3K), Akt, mammalian target of rapamycin (mTOR), and p70 S6K-dependent signaling pathways are required for ATP-induced proliferation of adventitial fibroblasts. We found that extracellular ATP acting in part through G(i) proteins increased PI3K activity in a time-dependent manner and transient phosphorylation of Akt. This PI3K pathway is not involved in ATP-induced activation of ERK1/2, implying activation of independent parallel signaling pathways by ATP. Extracellular ATP induced dramatic increases in mTOR and p70 S6K phosphorylation. This activation of the mTOR/p70 S6 kinase (p70 S6K) pathway in response to ATP is because of independent contributions of PI3K/Akt and ERK1/2 pathways, which converge on the level of p70 S6K. ATP-dependent activation of mTOR and p70 S6K also requires additional signaling inputs perhaps from pathways operating through Galpha or Gbetagamma subunits. Collectively, our data demonstrate that ATP-induced adventitial fibroblast proliferation requires activation and interaction of multiple signaling pathways such as PI3K, Akt, mTOR, p70 S6K, and ERK1/2 and provide evidence for purinergic regulation of the protein translational pathways related to cell proliferation.

Adenosine Triphosphate↗