Genetic mapping of the human and mouse phospholipase C genes

Phospholipase Family Enzymes in Lung Cancer: Looking for Novel Therapeutic Approaches

Lung cancer (LC) is the second most common neoplasm in men and the third most common in women. In the last decade, LC therapies have undergone significant improvements with the advent of immunotherapy. However, the effectiveness of the available treatments remains insufficient due to the presence of therapy-resistant cancer cells. For decades, chemotherapy and radiotherapy have dominated the treatment strategy for LC; however, relapses occur rapidly and result in poor survival. Malignant lung tumors are classified as either small- or non-small-cell lung carcinoma (SCLC and NSCLC). Despite improvements in the treatment of LC in recent decades, the benefits of surgery, radiotherapy, and chemotherapy are limited, although they have improved the prognosis of LC despite the persistent low survival rate due to distant metastasis in the late stage. The identification of novel prognostic molecular markers is crucial to understand the underlying mechanisms of LC initiation and progression. The potential role of phosphatidylinositol in tumor growth and the metastatic process has recently been suggested by some researchers. Phosphatidylinositols are lipid molecules and key players in the inositol signaling pathway that have a pivotal role in cell cycle regulation, proliferation, differentiation, membrane trafficking, and gene expression. In this review, we discuss the current understanding of phosphoinositide-specific phospholipase enzymes and their emerging roles in LC.

Distinct Prognostic Values of Phospholipase C Beta Family Members for Non-Small Cell Lung Carcinoma

Background

Non-small cell lung cancer (NSCLC) is a main cause of cancer-related mortality worldwide. The relationships of the phospholipase C beta (PLCB) enzymes, which are encoded by the genes PLCB1, PLCB2, PLCB3, and PLCB4, with NSCLC have not been investigated. Therefore, the aim of the present study was to identify any correlations between NSCLC prognosis and the expression patterns of PLCB family members.

Materials and Methods

The prognostic values of the PLCB gene family members in NSCLC patients were evaluated using the “Kaplan–Meier plotter” database, which includes updated gene expression data and survival information of a total of 1,926 NSCLC patients. The GeneMANIA plugin of Cytoscape software was used to evaluate the relationships of the four PLCB family members at the gene and protein levels. Gene ontology enrichment analysis and KEGG pathway analysis were performed using the Database for Annotation, Visualization, and Integrated Discovery.

Results

High mRNA expression levels of PLCB1, PLCB2, and PLCB3 were significantly associated with poor overall survival (OS) of all NSCLC patients and significantly associated with poor prognosis of adenocarcinoma. In contrast, high mRNA expression of PLCB4 was associated with better OS of adenocarcinoma patients. In addition, the expression levels of the PLCB family members were correlated to smoking status, clinical stage, and patient sex but not radiotherapy and chemotherapy outcomes.

Conclusions

PLCB1, PLCB2, PLCB3, and PLCB4 appear to be potential biomarkers for the prognosis of patients with NSCLC. The prognostic values of the PLCB genes require further investigations.

Molecular basis of P2-receptor-mediated calcium signaling in activated pancreatic stellate cells

OBJECTIVES

There is growing evidence that extracellular nucleotide-induced signaling confers to fibrogenesis in liver and pancreas. Pancreatic stellate cells (PSC) are the most important cell type in pancreatic fibrosis. P2 purine and pyrimidine receptors, again, are pivotal mediators of inflammatory and profibrogenic signals. Our aim was to elucidate the underlying signaling components in activated PSC.

METHODS

We performed expression analysis of calcium ion (Ca(2+)) signaling components and monitored real-time intracellular Ca(2+) responses to nucleotides in rat PSC.

RESULTS

Adenosine monophosphate, adenosine diphosphate, and adenosine-5'-triphosphate elicited detectable rises in intracellular Ca(2+) concentrations. Stimulation of PSC by ATP led to intracellular Ca signals mediated through both P2X and P2Y receptors. Whereas uridine triphosphate-mediated Ca(2+) signals were generated by activation of P2Y receptors only, uridine diphosphate stimulated P2X receptors as well. Of the phospholipase C (PLC)/inositol-1,4,5-trisphosphate pathway, all PLC-facilitating Gα subunits were present in activated cells as were all 3 inositol-1,4,5-trisphosphate receptor isoforms. In addition, transcripts of PLC-β and PLC-δ isoforms were also strongly detectable.

CONCLUSIONS

Activated PSC feature a plethora of elements from the Ca signaling toolkit and functionally express a subset of P2 nucleotide receptors. Purines and pyrimidines elicit robust intracellular Ca(2+) signals likely contributing to the fibrogenetic potential of these cells.

MicroRNA involvement in the pathogenesis and management of breast cancer

MicroRNAs (miRNAs) are a highly abundant class of endogenous small non-coding RNAs (18-25 nucleotides in length) that regulate gene expression by targeting protein-coding mRNAs post-transcriptionally. miRNAs have been implicated in cancer development and progression. As miRNAs and their regulatory functions are further revealed, the more the importance of miRNA-directed gene regulation is emphasised. In the human genome, 695 mature miRNAs have been identified, although computational calculation predicts that this may increase to >1000. Deregulation of miRNA expression profiles is thought to be implicated in the pathogenesis of many human cancers including breast tumours. Breast cancer subtypes are observed to have deranged miRNA expression signatures, which makes miRNAs important targets for developing a novel molecular classification of breast cancer and opening avenues for more individualised treatment strategies for patients with breast cancer.

Endogenous human microRNAs that suppress breast cancer metastasis

A search for general regulators of cancer metastasis has yielded a set of microRNAs for which expression is specifically lost as human breast cancer cells develop metastatic potential. Here we show that restoring the expression of these microRNAs in malignant cells suppresses lung and bone metastasis by human cancer cells in vivo. Of these microRNAs, miR-126 restoration reduces overall tumour growth and proliferation, whereas miR-335 inhibits metastatic cell invasion. miR-335 regulates a set of genes whose collective expression in a large cohort of human tumours is associated with risk of distal metastasis. miR-335 suppresses metastasis and migration through targeting of the progenitor cell transcription factor SOX4 and extracellular matrix component tenascin C. Expression of miR-126 and miR-335 is lost in the majority of primary breast tumours from patients who relapse, and the loss of expression of either microRNA is associated with poor distal metastasis-free survival. miR-335 and miR-126 are thus identified as metastasis suppressor microRNAs in human breast cancer.

Phospholipase C-β1mediates α1-adrenergic receptor-stimulated activation of the sodium–hydrogen exchanger in Chinese hamster lung fibroblasts (CCL39)

The activation of the Na+–H+exchanger 1 (NHE1) and extracellular-signal regulated kinase (ERK) phospho rylation in Chinese hamster lung fibroblasts (CCL39) was characterized in response to the specific α1-adrenergic agonist, phenylephrine (PE). Addition of 100 µmol PE/L increased the steady-state intracellular pH (pHi) by 0.16 ± 0.03 pH units, as well as increasing the phosphorylation of ERK. The response of NHE1 to PE in CCL39 cells was determined by the use of specific antagonists. Use of 2 specific chemical inhibitors of phosphoinositide-specific phospholipase C (PLC) reduced the ability of PE to activate either the exchanger or ERK. Studies were conducted in PLCβ-deficient cell lines derived from parental CCL39 cells. NHE1 activity in both mutant cell lines was increased in response to phorbal esters or lysophosphatidic acid, whereas the addition of PE only caused a minimal change in either pHior ERK phosphorylation. These results, combined with reconstitution experiments with exogenously expressed PLCβ1, PLCβ2, or PLCβ3, revealed that stimulation of NHE1 activity by PE in CCL39 cells is a PLCβ1-coupled event. Furthermore, the data indicate that α1-adrenergic signaling of PLCβ is upstream of ERK activation. These data demonstrate that PLCβ1is primarily involved in the activation of NHE1 in CCL39 fibroblasts.Key words: CCL39, sodium hydrogen exchanger, ERK, α1-adrenergic receptor, phospholipase Cβ.

Phospholipase C delta-type consists of three isozymes: bovine PLCdelta2 is a homologue of human/mouse PLCdelta4

To date, 12 phospholipase C (PLC) isozymes have been identified in mammals, and they are divided into five classes, beta-, gamma-, delta-, epsilon-, and zeta-type. PLCdelta-type is reported to be composed of four isozymes, PLCdelta1-delta4. Here we report that a screening for mouse PLCdelta2 from a BAC library with primers that amplify a specific region of bovine PLCdelta2 resulted in isolation of one clone containing the mouse PLCdelta4 gene. Furthermore, a database search revealed that there is only one gene corresponding to PLCdelta2 and PLCdelta4 in the mouse and human genomes, indicating that bovine PLCdelta2 is a homologue of human and mouse PLCdelta4. However, PLCdelta2 Western blot analysis with a widely used commercial anti-PLCdelta2 antibody showed an expression pattern distinct from that of PLCdelta4 in wild-type mice. In addition, an 80-kDa band, which was recognized by antibody against PLCdelta2, was smaller than an 85-kDa band detected by anti-PLCdelta4 antibody, and the 80-kDa band was detectable in lysates of brain, testis, and spleen from PLCdelta4-deficient mice. We also found that immunoprecipitates from brain lysates with this PLCdelta2 antibody contained no PLC activity. From these data, we conclude that bovine PLCdelta2 is a homologue of human and mouse PLCdelta4, and that three isozymes (delta1, delta3, and delta4) exist in the PLCdelta family.

Identification of genetic loci associated with paralysis, inflammation and weight loss in mouse experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE), a model for human multiple sclerosis, is an inducible inflammatory and demyelinating disease of the central nervous system (CNS). Susceptibility to this disease is heritable and is demonstrated by the development of an ascending paralysis accompanied by a loss in body wt 2-3 weeks following immunization with proteins derived from CNS myelin. In a previous genetic analysis of susceptibility to EAE in a cross between susceptible SJL/J mice and resistant B10.S mice, we found suggestive evidence of linkage with disease susceptibility at the telomeric end of chromosome 2 and in the central region of chromosome 3. To define these associations more precisely and to investigate the genetic factors controlling measurable phenotypes of EAE, we performed a new analysis with a larger number of mice. The results now indicate that the chromosome 2 locus significantly influences EAE-related weight loss (P = 6.7 x 10(-5)) and that the chromosome 3 locus is linked with the development of paralysis. In addition, an intriguing inheritance pattern was revealed in which female backcross mice generated from B10.S female x (B10.S x SJL/J)F(1) male parents experienced significantly more EAE-related weight loss (P = 1.2 x 10(-4)) than females generated from F1 female x B10.S male parents. After controlling for this inheritance, a new locus at the centromeric end of chromosome 8 was identified that significantly influences both the development of paralysis (P = 8.2 x 10(-6)) and the incidence of CNS inflammation (P = 7.0 x 10(-5)) in EAE.

Evidence for two alternatively spliced forms of phospholipase C-beta2 in haematopoietic cells

Alternatively spliced forms have been reported for several phospholipase C (PLC) isozymes, but not for PLC-beta2, the most abundant PLC-beta in platelets. PLC-beta2 cDNA cloned from the HL-60-cell cDNA library is 3543 bases long, coding for 1181 amino acids. Compared with the published sequence, a deletion of 45 nucleotides (2755-2799 nt, amino acids 864-878) was detected in platelet and leucocyte mRNA amplified by reverse transcription (RT) polymerase chain reaction (PCR) using primers corresponding to 1814-1838 nt (forward) and 3328-3352 nt (reverse). Amplification of genomic DNA using primers corresponding to 2575-2596 nt and 2864-2885 nt yielded a approximately 750 bp product; restriction analysis and sequencing revealed the 45-bp exon flanked by introns of 198 bp and 118 bp. Amplification of leucocyte and platelet cDNA using the same primers yielded products of approximately 310 nt and approximately 265 nt, with (PLC-beta2a) and without (PLC-beta2b) the 45-nt sequence. Thus, two alternatively spliced forms (1181 and 1166 amino acids) of PLC-beta2 are generated in haematopoietic cells. They differ in the carboxyl terminal sequence implicated in interaction of PLC-beta enzymes with Galphaq, particulate association and nuclear localization. We propose that the PLC-beta2 splice variants may be regulated differentially with distinct roles in signal transduction.

Identification and chromosomal localisation by fluorescence in situ hybridisation of human gene of phosphoinositide-specific phospholipase C beta(1)

Members of phosphoinositide-specific phospholipase C (PLC) families are central intermediary in signal transduction in response to the occupancy of receptors by many growth factors. Among PLC isoforms, the type beta(1) is of particular interest because of its reported nuclear localisation in addition to its presence at the plasma membrane. It has been previously shown that both the stimulation and the inhibition of the nuclear PLCbeta(1) under different stimuli implicate PLCbeta(1) as an important enzyme for mitogen-activated cell growth as well as for murine erythroleukaemia cell differentiation. The above findings hinting at a direct involvement of PLCbeta(1) in controlling the cell cycle in rodent cells, and the previously reported mapping of its gene in rat chromosome band 3q35-36, a region frequently rearranged in rat tumours induced by chemical carcinogenesis, prompted us to identify its human homologue. By screening a human foetal brain cDNA library with the rat PLCbeta(1) cDNA probe, we have identified a clone homologous to a sequence in gene bank called KIAA 0581, which encodes a large part of the human PLCbeta(1). By using this human cDNA in fluorescence in situ hybridisation on human metaphases, it has been possible to map human PLCbeta(1) on chromosome 20p12, confirming the synteny between rat chromosome 3 and human chromosome 20 and providing a novel locus of homology between bands q35-36 in rat and p12 in man. Since band 20p12 has been recently reported amplified and/or deleted in several solid tumours, the identification and chromosome mapping of human PLCbeta(1) could pave the way for further investigations on the role exerted both in normal human cells and in human tumours by PLCbeta(1), which has been shown to behave as a key signalling intermediate in the control of the cell cycle.

Molecular cloning and expression analysis of a mouse phospholipase C-delta1

We describe here the molecular cloning and expression analysis of mouse PLC-delta1 (mPLC-delta1), a key enzyme in cell signal transduction. A mouse brain cDNA library was screened in order to isolate the mPLC-delta1 cDNA. The mPLC-delta1 cDNA was 2660 bp in length. The predicted open reading frame encodes a protein of 756 amino acids with an estimated molecular mass of 85 kDa. The deduced amino acid sequence exhibits 96.9% and 92.7% identity with the sequence of rat and human PLC-delta1, respectively. The mPLC-delta1 mRNA was highly expressed in brain, heart, lung, and testis. We found that transcripts of mPLC-delta1 are present in almost all regions of mouse brain examined, implying that the enzyme may play a role in some fundamental cellular process in brain. In male reproductive tract, mPLC-delta1 mRNA was widely expressed in the epididymis as well as in the testis. In situ hybridization studies indicate that distribution of mPLC-delta1 mRNA in mouse testis is discrete and unique. The expression of mPLC-delta1 mRNA was defined in the periphery of each seminiferous tubule, especially in spermatogonia, which might imply that mPLC-delta1 plays a role in proliferation of spermatogonia. To the best our knowledge, this is the first report to demonstrate the high expression of mPLC-delta1 mRNA in spermatogonia of testis. Taken together, these results suggest that mPLC-delta1 may carry out fundamental roles in almost all of mouse tissues, especially in brain and specific roles in testis.

A phenotype-based screen for embryonic lethal mutations in the mouse

The genetic pathways that control development of the early mammalian embryo have remained poorly understood, in part because the systematic mutant screens that have been so successful in the identification of genes and pathways that direct embryonic development in Drosophila, Caenorhabditis elegans, and zebrafish have not been applied to mammalian embryogenesis. Here we demonstrate that chemical mutagenesis with ethylnitrosourea can be combined with the resources of mouse genomics to identify new genes that are essential for mammalian embryogenesis. A pilot screen for abnormal morphological phenotypes of midgestation embryos identified five mutant lines; the phenotypes of four of the lines are caused by recessive traits that map to single regions of the genome. Three mutant lines display defects in neural tube closure: one is caused by an allele of the open brain (opb) locus, one defines a previously unknown locus, and one has a complex genetic basis. Two mutations produce novel early phenotypes and map to regions of the genome not previously implicated in embryonic patterning.

The mouse genome encodes a single homolog of the antimicrobial peptide human beta-defensin 1

The cysteine-rich beta-defensin peptides are broad-spectrum bactericidal agents expressed in epithelial and myeloid tissues. The human beta-defensin-1 (hBD-1) gene maps adjacent to the human alpha-defensin cluster and is expressed in the respiratory, gastrointestinal and genitourinary tracts. Here, we characterize a mouse beta-defensin gene (mBD-1) which is: (1) closely related to hBD-1 both in sequence and gene organization; (2) expressed at high levels in the mouse kidney and at lower levels in brain, heart, lung, uterus, spleen, skeletal muscle, stomach, and small intestine; and (3) maps to mouse chromosome 8 at or near the location of the mouse alpha-defensin genes. These data indicate that mBD-1 is a close homolog of hBD-1, and suggest that analysis of its role in mouse host defense may provide significant insights into human epithelial innate immunity.

Characterization of the mouse dihydrolipoamide dehydrogenase (Dld) gene: genomic structure, promoter sequence, and chromosomal localization

The mouse dihydrolipoamide dehydrogenase (Dld) gene has been cloned, characterized, and mapped. This nuclear gene encodes a mitochondrial protein that is shared among several alpha-keto acid dehydrogenase complexes and the glycine cleavage system. The Dld gene is contained within an approximately 21-kb region and consists of 14 exons ranging in size from 69 to 521 nucleotides. The open reading frame codes for a preprotein of 509 amino acids with a predicted mature protein of 474 amino acids that is highly conserved among mammalian species (> 90% identical). Primer extension analyses have shown the gene to have transcription initiation sites with tissue-specific differences in relative utilization. The 5' flanking region is G-C rich and lacks a TATA box, but does contain initiator element and multiple transcription factor-binding consensus sequences. Northern blot analysis shows that the Dld mRNA in various tissues is approximately 2.4 kb in size. The Dld gene has been localized to the proximal region of chromosome 12, approximately 21 cM from the centromere.