The family of voltage-gated potassium Kv2 channels consists of the Kv2.1 and Kv2.2 subtypes. Kv2.1 is constitutively highly phosphorylated in neurons and its function relies on its phosphorylation state. Whether the function of Kv2.2 is also dependent on its phosphorylation state remains unknown. Here, we investigated whether Kv2.2 channels can be phosphorylated by protein kinase C (PKC) and examined the effects of PKC-induced phosphorylation on their activity and function. Activation of PKC inhibited Kv2.2 currents and altered their steady-state activation in HEK293 cells. Point mutations and specific antibodies against phosphorylated S481 or S488 demonstrated the importance of these residues for the PKC-dependent modulation of Kv2.2. In layer II pyramidal neurons in cortical slices, activation of PKC similarly regulated native Kv2.2 channels and simultaneously reduced the frequency of action potentials. In conclusion, this study provides the first evidence to our knowledge that PKC-induced phosphorylation of the Kv2.2 channel controls the excitability of cortical pyramidal neurons.
Action Potentials ; HEK293 Cells ; Humans ; Protein Kinase C/metabolism* ; Pyramidal Cells/enzymology* ; Shab Potassium Channels/genetics*

Animals ; Humans ; Models, Biological ; Oxidative Stress ; genetics ; physiology ; Phosphorylation ; Protein Kinase C ; genetics ; metabolism ; physiology ; Signal Transduction ; genetics ; physiology

Calcitonin (CT), a polypeptide hormone, plays important roles in a variety of physiological processes. CT has been used clinically to treat osteoporosis and humoral hypercalcemia of malignancy. In order to clarify the pharmacological effects of CT in the kidney, we identified potential downstream genes induced by CT in the renal cells. Using a cDNA subtraction hybridization method, we identified connective tissue growth factor (CTGF) as a CT-induced gene in the porcine renal cell line, LLC-PK1. Furthermore, we found that CT-mediated induction of the gene was not inhibited by cycloheximide, which suggests that CTGF gene was not induced by an increased synthesis of regulating proteins. Therefore, CTGF is an immediate early gene. We further demonstrated that the regulation of CTGF gene expression by CT involved the ERK1/2 pathway, because PD98059, a MEK1 inhibitor, partially inhibited the mRNA expression of CTGF induced by CT. CT-induced CTGF protein expression was also observed in vivo. Our present findings suggest that CT induces the transcription of CTGF through ERK1/2 phosphorylation. We also identified twelve other genes induced by CT that, like CTGF, were related to wound healing. These results suggest that CT may have an effect on renal differentiation and wound healing in the kidney.
Animals ; Calcitonin/*pharmacology ; Cell Line ; Connective Tissue Growth Factor/*genetics/metabolism ; Female ; Kidney Tubules, Proximal/*enzymology/metabolism ; *MAP Kinase Signaling System ; Mice ; Mice, Inbred BALB C ; Mitogen-Activated Protein Kinase 1/*metabolism ; Mitogen-Activated Protein Kinase 3/*metabolism ; Phosphorylation ; Swine

Calcitonin (CT), a polypeptide hormone, plays important roles in a variety of physiological processes. CT has been used clinically to treat osteoporosis and humoral hypercalcemia of malignancy. In order to clarify the pharmacological effects of CT in the kidney, we identified potential downstream genes induced by CT in the renal cells. Using a cDNA subtraction hybridization method, we identified connective tissue growth factor (CTGF) as a CT-induced gene in the porcine renal cell line, LLC-PK1. Furthermore, we found that CT-mediated induction of the gene was not inhibited by cycloheximide, which suggests that CTGF gene was not induced by an increased synthesis of regulating proteins. Therefore, CTGF is an immediate early gene. We further demonstrated that the regulation of CTGF gene expression by CT involved the ERK1/2 pathway, because PD98059, a MEK1 inhibitor, partially inhibited the mRNA expression of CTGF induced by CT. CT-induced CTGF protein expression was also observed in vivo. Our present findings suggest that CT induces the transcription of CTGF through ERK1/2 phosphorylation. We also identified twelve other genes induced by CT that, like CTGF, were related to wound healing. These results suggest that CT may have an effect on renal differentiation and wound healing in the kidney.
Animals ; Calcitonin/*pharmacology ; Cell Line ; Connective Tissue Growth Factor/*genetics/metabolism ; Female ; Kidney Tubules, Proximal/*enzymology/metabolism ; *MAP Kinase Signaling System ; Mice ; Mice, Inbred BALB C ; Mitogen-Activated Protein Kinase 1/*metabolism ; Mitogen-Activated Protein Kinase 3/*metabolism ; Phosphorylation ; Swine

OBJECTIVETo observe the effect of chronic lead contaminant on mRNA expression of protein kinase C (PKC) and calmodulin (CaM) in hippocampus of baby rats.

METHODSThe Wistar pregnant rats were randomly divided into 3 groups fed with distilled water and lead contained water (0.2% and 1.0% lead acetate) respectively. The lead exposure period was from the 0 day of pregnancy to the day when the offspring weaned. Then the baby rats were fed with lead water the same as their mothers. The cliff avoidance reflex within postnatal day 8 and step down test at postnatal day 50 were performed. Then pups were killed at postnatal day 8 and 50 respectively. Atomic absorption spectrometry was used to determine lead content of rats' brain. RT-PCR was used to observe mRNA expression of PKC and CaM in hippocampus of baby rats.

RESULTSThe brain lead content of test groups were much higher than that of the control group. The completion rate of cliff avoidance reflex and the score of step down test of test groups were lower than those in the control group (P < 0.05). Compared with control group, PKC and CaM mRNA expression of chronic lead exposure baby rats in the hippocampus had the down trend (P < 0.05).

CONCLUSIONThe decrease of PKC and CaM mRNA expression level in hippocampus has a great link with the impairment of learning and memory induced by lead in baby rats, which might be one of the molecule mechanisms of lead induced impairment of learning and memory.

Animals ; Calmodulin ; genetics ; metabolism ; Female ; Hippocampus ; drug effects ; metabolism ; Lead ; toxicity ; Learning ; drug effects ; Male ; Memory ; drug effects ; Protein Kinase C ; genetics ; metabolism ; RNA, Messenger ; genetics ; Rats

The previous study indicated that aquaporin 4 (AQP4) deficiency attenuated opioid physical dependence. However, the underlying mechanism remains unknown. In the present study, the effects of AQP4 deficiency on the expression of three factors, protein kinase C (PKC) α, PKCγ and c-Fos in the spinal cord, which are known to be concerned with spinal neuronal sensitization and opiate dependence, were investigated in AQP4 knockout mice using Western blotting analysis. It was observed that AQP4 deficiency reduced the score of naloxone-precipitated abstinent jumping after repeated morphine administration compared with wild-type (P < 0.001). Meanwhile, the protein levels of PKCα and c-Fos in the spinal cord of AQP4 knockout mice were significantly higher than those in the wild-type mice; while the expression of PKCγ was decreased remarkably by AQP4 knockout during the withdrawal (P < 0.01). These data suggest that AQP4 deficiency-attenuated morphine withdrawal responses may be partially attributed to the changes in the spinal expression of PKCα, PKCγ or c-Fos.
Analgesics, Opioid ; pharmacology ; Animals ; Aquaporin 4 ; deficiency ; genetics ; Mice ; Mice, Knockout ; Morphine ; pharmacology ; Naloxone ; pharmacology ; Protein Kinase C ; metabolism ; Protein Kinase C-alpha ; metabolism ; Spinal Cord ; metabolism ; Substance Withdrawal Syndrome ; metabolism

OBJECTIVETo investigate the effects of antisense oligonucleotides (ASODN) targeting protein kinase C alpha (PKCalpha) on the proliferation of A549 cells.

METHODSPKCalpha ASODN and random oligonucleotides (RODN) were transfected into A549 cells mediated by polyethyleneimine, and the proliferation and clone formation of A549 cells were detected by CCK-8 and clone formation assay, respectively. The expression of PKCalpha in the transfected cells was analyzed by RT-PCR and Western blotting.

RESULTSCompared with those in the control group, PEI group and PEI-RODN group, the proliferation and clone formation of A549 cells treated with ASODN targeting PKCalpha were significantly inhibited (P<0.05). The expressions of PKCalpha mRNA and protein in PKCalpha ASODN-transfected A549 cells were significantly lower than those in the other 3 groups (P<0.05).

CONCLUSIONThe PKCalpha ASODN mediated by PEI down-regutates the expression of PKCalpha gene and suppress the proliferation and clone formation of A549 cells.

Cell Line, Tumor ; Cell Proliferation ; drug effects ; Humans ; Lung Neoplasms ; enzymology ; pathology ; Oligonucleotides, Antisense ; genetics ; pharmacology ; Protein Kinase C-alpha ; genetics ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Transfection

Phospholipase Cgamma1 (PLCgamma1) plays an important role in controlling cellular proliferation and differentiation. PLCgamma1 is overexpressed in some tumors, and its overexpression induces solid tumors in nude mice. However, the regulatory mechanisms underlying PLCgamma1-induced cell proliferation are not fully understood. Here we show that overexpression of PLCgamma1 highly phosphorylated glycogen synthase kinase-3beta (GSK-3beta) at serine-9 in 3Y1 fibroblasts. Inhibition of protein kinase C (PKC)s with GF109203X abrogated GSK-3beta phosphorylation by PLCgamma1. We also found that steady-state level of cyclin D1 protein, but not cyclin D1 mRNA, was highly elevated in response to serum stimulation in PLCgamma1-transfected cells as compared with vector-transfected cells. Since GSK-3beta is involved in cyclin D1 proteolysis in response to mitogenic stimulation, PLCgamma1-mediated GSK-3beta phosphorylation may function as a regulation of cyclin D1 accumulation in PLCgamma1-overexpressing cells.
Animals ; Cyclin D1/metabolism ; Epidermal Growth Factor/pharmacology ; Fibroblasts ; Gene Expression ; Glycogen Synthase Kinase 3/chemistry/*metabolism ; Mitogens/pharmacology ; Phospholipase C/genetics/*metabolism ; Phosphorylation/drug effects ; Phosphoserine/*metabolism ; Protein Kinase C/antagonists & inhibitors/*metabolism ; Rats ; Signal Transduction

Mer is one member of Axl receptor tyrosine kinase family, and its ligand Gas6 can stimulate activity of Mer receptor tyrosine kinase after binding it, and then activate the downstream signal transduction pathway, Mer participates in cell inflammation, apoptosis, tumorigenesis, thrombosis and hemostasis. Rencet advances of study on Mer function were reviewed, and its potential prospects of antithrombosis and antitumor were discussed in this article.
Animals ; Fibrinolytic Agents ; Humans ; Intercellular Signaling Peptides and Proteins ; metabolism ; Proto-Oncogene Proteins ; genetics ; metabolism ; Receptor Protein-Tyrosine Kinases ; genetics ; metabolism ; Signal Transduction ; c-Mer Tyrosine Kinase

OBJECTIVETo study the molecular mechanisms of nm23-H1 for regulating PKC signal pathway before and after transfection with nm23-H1 gene.

METHODSUsing Western-blot, Boyden-chamber, MTT and laser scanning confocal microscopy (LSCM) techniques to detect the distribution of PKC in cytosol and plasma membrane, changes of invasion and proliferation activity, PKC translocation status and changes of intracellular Ca(2+) concentration among different human pulmonary carcinoma cells with transfected or untransfected nm23-H1 gene, and changes of the three cell lines after treatment with Calphostin C, a PKC inhibitor.

RESULTS(1) The expression of PKCalpha, PKCbeta II on L9981 and L9981-pLXSN cell membrane, which was in activated status, was remarkably higher than those in L9981-nm23-H1 cell line (P < 0.001). The expression of PKCalpha, PKCbeta II in cytosol in L9981 and L9981-pLXSN cell lines, which was in inactivated status, was lower than those in L9981-nm23-H1 cell line (P < 0.001). It means that the PKC signal pathway was activated in L9981 and L9981-pLXSN cell lines. (2) PKCalpha and PKCbeta II mainly located in nuclei and perinuclear area in L9981 and L9981-pLXSN cells, which were in active status, and the Ca(2+) concentration in these cells was obviously higher than that in L9981-nm23-H1 cell line (P < 0.01). In L9981-nm23-H1 cell line, which was transfected with nm23-H1 gene, PKCalpha and PKCbeta II mainly located in soluble cytosolic section, in an inactive status. (3) The invasion and proliferation ability of L9981 and L9981-pLXSN lung cancer cells was higher than that of L9981-nm23-H1 cell line (P < 0.001). There was no statistically significant difference between L9981 and L9981-pLXSN cell lines (P > 0.05). (4) After treated with PKC inhibitor Calphstin C, the expression of PKC and PKCbeta II in membrane in L9981 and L9981-pLXSN cell lines was down-regulated (P < 0.001), PKCalpha and PKCbeta II were mainly located in cytosolic area, mainly in an inactive status, and the Ca(2+) concentration was found to be decreased in all the three cell lines. The invasion and proliferation ability of the three lung cancer cell lines were obviously decreasing (P < 0.001). However, the invasion and proliferation ability of L9981-nm23-H1 lung cancer cell line was still lower than that of L9981 and L9981-pLXSN lung cancer cell lines (P < 0.001). There was also no significant difference between L9981 and L9981-pLXSN cell lines (P > 0.05).

CONCLUSIONThe results of this study suggest that nm23-H1 gene might inhibit the invasion and metastasis of lung cancer cells by down-regulating PKC signaling pathway. The Ca(2+) in cells might be involved in this process.

Calcium ; metabolism ; Cell Line, Tumor ; Cell Membrane ; metabolism ; Cell Proliferation ; drug effects ; Cytosol ; metabolism ; Down-Regulation ; Humans ; Lung Neoplasms ; enzymology ; metabolism ; pathology ; NM23 Nucleoside Diphosphate Kinases ; genetics ; Naphthalenes ; pharmacology ; Neoplasm Invasiveness ; Protein Kinase C ; antagonists & inhibitors ; metabolism ; Protein Kinase C beta ; Protein Kinase C-alpha ; metabolism ; Signal Transduction ; Transfection