PLCβ1 Expression Research Articles

The alteration of intracellular signaling on the smooth muscle cells contraction in cat esophagitis

We investigated the alteration of signal transduction after acute esophagitis in cat lower esophageal sphincter (LES). Acute esophagitis (AE) was induced by perfusion with 0.1N HCl at a rate of 1 ml/min for 45 min over three consecutive days. Acetylcholine (ACh)-induced contraction was inhibited by M3>> M1 or M2 antagonists in normal LES. In AE, inhibition by M2 antagonists increased significantly, so that contraction was inhibited by M3> M2> M1 antagonists and the expression of M2 and M3 receptors were increased when compared to normal LES. In normal cells, ACh-induced contractions were antagonized by antibody against G q/11 and the phosphatidylinositol-specific phospholipase C (PI-PLC) antagonist, U73122. The phosphatidylcholine-specific phospholipase C (PC-PLC) inhibitor, D609, or the phospholipase D inhibitor, propranolol had no effects on contraction in normal LES. However, in AE, G q/11, and G i3 antibodies reduced ACh-induced contraction and U73122, propranolol and D609 also reduced the contraction. In AE, we found that the expressions of G protein subtypes were increased but the expression of PLCβ1, and PLCγ1 were decreased when compared to normal LES. In conclusion, experimental esophagitis may alter the signal transduction by ACh in LES. ACh-induced contraction is mediated by M3 receptor, G q/11 and PI-PLC in normal LES. However, in AE, the contractions are mediated by M2, M3 receptor, G q/11 and G i3. PC-PLC and PLD as PI-PLC are also involved in ACh-induced cell contraction in AE.

Dexamethasone decreases phospholipase C β1 isozyme expression in human vascular smooth muscle cells

The molecular characterization of the human PLC β1 gene was just reported by Peruzzi et al. [Biochim. Biophys. Acta 1582 (2002) 46]. This prompted us to investigate the effects of dexamethasone on PLC β1 expression in two types of human vascular smooth muscle cells—coronary artery smooth muscle cells (hCASMC) and aortic smooth muscle cells (hAoSMC), since glucocorticoids are known to affect the signaling pathways of Gprotein coupled receptors. Semi-quantitative RT-PCR was used to analyze mRNA expression and Western-blot for protein expression. Dexamethasone treatment in the two types of cells studied decreased (mRNA and protein) PLC β1 isozyme expression. A rapid (2 h) fall in mRNA occurred in hCASMC after treatment, and hCASMC were more sensitive to dexamethasone (1 nM versus 100 nM) than hAoSMC. The major reduction (80%) was observed after 48 h of exposure in both VSMC. Treatment with mifeprisone, an antagonist of glucocorticoid receptors, blunted the dexamethasone effect on PLC β1 mRNA and showed that this effect was mediated by glucocorticoids receptors.

Disruption of PLC-β1-Mediated Signal Transduction in Mutant Mice Causes Age-Dependent Hippocampal Mossy Fiber Sprouting and Neurodegeneration

Aberrant reorganization of hippocampal mossy fibers occurs in human temporal lobe epilepsy and rodent epilepsy models. We generated a mouse model showing massive late-onset aberrant mossy fiber sprouting in the adult hippocampus. The mutation in this mouse model derives from an intronic insertion of transgene DNA in the mouse PLC-β1 gene (PLC-β1 −/− TC mutation) leading to a splice mutation of the PLC-β1 gene and a complete loss of downstream PLC-β1 expression. PLC-β1 −/− TC mutants develop a loss of NMDA-receptors in the stratum oriens of region CA1, apoptotic neuronal death, and reduced hippocampal PKC activity. The phenotype of these mice further consists of a late-onset epileptiform hyperexcitability, behavioral modifications in a radial maze and in an open field, female nurturing defect, and male infertility. In the present study, we provide evidence that the arising of the behavioral phenotype in PLC-β1 −/− TC mice correlates in time with the development of the aberrant mossy fiber projections and that the disruption of the PLC-β1-mediated signal transduction pathway may lead to a functional cholinergic denervation, which could cause hippocampal remodeling and, in consequence, epileptiform hyperexcitability.

Differential Regulation of Phospholipase C-β Isozymes in Cardiomyocyte Hypertrophy

Cardiac hypertrophy is a major predictor of heart failure and of morbidity and mortality in developed countries. Many hormones and growth factors induce cardiac hypertrophy via activation of members of the phospholipase C (PLC) family. The expression pattern of the PLCβ isozyme subfamily was investigated in neonatal rat cardiomyocytes after stimulation with different hypertrophic stimuli. Under control conditions and after stimulation with norepinephrine, cardiomyocytes expressed similar amounts of PLCβ3 mRNA. In the presence of fetal calf serum (FCS), additional expression of PLCβ1 was induced. Growth hormone (GH) and insulin-like growth factor-I (IGF-I) both induced a substantial increase in PLCβ3 mRNA expression. The response to GH could not be abolished by the IGF-I receptor blocker IGF-I analogue indicating an IGF-I-independent action of GH. The upregulation of PLCβ3 by IGF-I was abolished by preincubation of cardiomyocytes with the IGF-I receptor antagonist IGF-I analogue, the tyrosine kinase inhibitor genistein, the extracellular signal-related kinase (ERK) inhibitor PD 98059, the phosphatidylinositol-3- (PI-3) kinase inhibitor wortmannin and the p70 S6 kinase inhibitor rapamycin. Induction of the immediate early genes c-myc, c-fos, and c-jun by IGF-I was abolished by preincubation with antisense oligos against PLCβ3. It is concluded that the expression of PLCβ isozymes in cardiomyocytes is differentially regulated by different hypertrophic stimuli. The upregulation of PLCβ3 by IGF-I is dependent on the activity of tyrosine kinase, ERK, PI3 kinase, and p70 S6 kinase and PLCβ3 expression seems to be required for the induction of immediate early genes by IGF-I. The involvement of the PLCβ subfamily in signal transduction of receptors other than G-protein-coupled receptors is suggested.