Biosynthesis of calmodulin in normal and virus-transformed chicken embryo fibroblasts

Expression of calmodulin and calmodulin binding proteins in rat fibroblasts stably transfected with protein kinase C and oncogenes

Molecular mechanisms leading to elevated calmodulin (CaM) expression in cancer have not yet been discovered. We have quantitated the levels of transcripts derived from all three CaM genes in a variety of the same origin rat fibroblasts transformed with oncogenes in combination with gene for protein kinase C using Northern blot analysis with three CaM gene specific cDNA probes. Five species of CaM mRNA were detected in all these cells. Surprisingly many of the investigated cell lines exhibited a decreased content of all CaM mRNAs as compared to control cells with CaMI and CaMII transcripts showing the most pronounced alterations. In contrast, CaM protein levels were increased in all these cell lines as determined by a radioimmunoassay. These results suggest that oncogenic up-regulation of CaM synthesis takes place posttranscriptionally. Several CaM binding proteins were found at different concentrations in the studied cell lines depending on the oncogenes used for transformation. However, CaM overexpression does not seem to affect the overall levels of CaM binding proteins.

Expression of calmodulin and calmodulin binding proteins in lymphoblastoid cells

Calmodulin is encoded in vertebrates by three different genes: CALM1, CALM2, and CALM3. We have examined the mRNAs expressed from these three genes in eight lines of human lymphoblastoid cells (Namalwa, Raji, Ramos, JY, Molt-4, Jurkat, CEM, and HPB-ALL). We found that all these cell lines (except Ramos) overexpressed CALM3 transcripts, which led to an increase of total CaM protein with respect to quiescent normal T lymphocytes. The nuclear concentration of calmodulin was measured in two of these lymphoblastoid cell lines (JY and HPB-ALL) and compared to quiescent and phytohemagglutinin-activated T lymphocytes. Activated lymphocytes showed a 2-fold increase of nuclear calmodulin with respect to quiescent cells, whereas in the two lymphoblastoid cell lines, nuclear calmodulin remained similar to that of quiescent cells. The levels of a calmodulin-binding protein of 150 kDa in the homogenates of the eight lymphoblastoid lines was found to be higher than those of quiescent and activated lymphocytes. Likewise, the amount of three calmodulin-binding proteins of 240, 200, and 170 kDa was also increased in several of the cell lines, but not in all of them. The 170-kDa protein was only expressed by activated lymphocytes and lymphoblastoid cells, suggesting that it could be specific for proliferating cells. In the nuclei of activated lymphocytes and lymphoblastoid cells, a decrease of a calmodulin-binding protein of 110 kDa and increases of three other of 240, 180 and 170 kDa were also detected.

The heterodimer calmodulin: myosin light-chain kinase as a prototype vertebrate calcium signal transduction complex

The heterodimer complex of calmodulin (CaM) and the protein kinase catalytic subunit of myosin light chain kinase from vertebrate smooth muscle and non-muscle tissues (sm/nmMLCK) is one of the most extensively characterized CaM-regulated enzyme complexes and it has an established in vivo role in the transduction of calcium signals into biological responses. We have used a combination of approaches to the study of CaM and sm/nmMLCK in order to derive initial insight into the key features of each protein and of the CaM-MLCK heterodimeric complex that are involved in protein-protein and calcium-protein recognition and regulation of enzyme activity. On-going studies are described here that include site-specific mutagenesis, fluorescence spectroscopy, enzymology and peptide analog analysis. These and previous results indicate that: (1), both electrostatic and hydrophobic features are important in the functionally correct interactions between CaM and MLCK; (2), even the interactions between CaM and peptide analogs of the CaM binding site of MLCK are heterogeneous and non-trivial in nature; (3), amino-acid residues that have been conserved in CaM across millions of years of evolution and that are conserved in CaMs with quantitative MLCK activator activity can be mutated without any detectable effect on activity and (4), structures different from the prototypical EF-hand domain of CaM can have similar calcium-binding activity in the presence of a CaM binding structure.

Synthesis and Accumulation of Calmodulin in Suspension Cultures of Carrot (Daucus carota L.) : Evidence for Posttranslational Control of Calmodulin Expression

The expression of calmodulin mRNA and protein were measured during a growth cycle of carrot (Daucus carota L.) cells grown in suspension culture. A full-length carrot calmodulin cDNA clone isolated from a lambdagt10 library was used to measure steady-state calmodulin mRNA levels. During the exponential phase of culture growth when mitotic activity and oxidative respiration rates were maximal, calmodulin mRNA levels were 4- to 5-fold higher than they were during the later stages of culture growth, when respiration rates were lower and growth was primarily by cell expansion. Net calmodulin polypeptide synthesis, as measured by pulse-labeling in vivo with [(35)S]methionine, paralleled the changes in calmodulin steady-state mRNA level during culture growth. As a consequence, net calmodulin polypeptide synthesis declined 5- to 10-fold during the later stages of culture growth. The qualitative spectrum of polypeptides synthesized and accumulated by the carrot cells during the course of a culture cycle, however, remained largely unchanged. Calmodulin polypeptide levels, in contrast to its net synthesis, remained relatively constant during the exponential phases of the culture growth cycle and increased during the later stages of culture growth. Our data are consistent with increased calmodulin polypeptide turnover associated with periods of rapid cell proliferation and high levels of respiration.

Modulation of calmodulin levels, calmodulin methylation, and calmodulin binding proteins during carrot cell growth and embryogenesis

Carrot cell cultures were used to study the dynamics of calmodulin protein levels, calmodulin methylation, and calmodulin-binding proteins during plant growth and development. Comparisons of proliferating and nonproliferating wild carrot cells show that, while calmodulin protein levels does not vary significantly, substantial variation in post-translational methylation of calmodulin on lysine-115 is observed. Calmodulin methylation is low during the lag and early exponential stages, but increases substantially as exponential growth proceeds and becomes maximal in the postexponential phase. Unmethylated calmodulin quickly reappears within 12 h of reinoculation of cells into fresh media, suggesting that the process is regulated according to the cell growth state. Calmodulin and calmodulin-binding proteins were also analyzed during the formation and germination of domestic carrot embryos in culture. Neither calmodulin methylation nor calmodulin protein levels varied significantly during somatic embryogenesis. However, upon germination of embryos, the level of calmodulin protein doubled. By calmodulin overlay analysis, we have detected a major 54,000 M(r) calmodulin-binding protein that also increased during embryo germination. This protein was purified from carrot embryo extracts by calmodulin-Sepharose chromatography. Overall, the data suggest that calmodulin methylation is regulated depending upon the state of cell growth and that calmodulin and its target proteins are modulated during early plant development.

Association of calmodulin with isolated nuclei from rat hepatocytes

Calmodulin plays an important role in regulating cell proliferation and intranuclear processes (J. Biol. Chem. 265: 18595, 1990). Therefore we studied the association of 125I-calmodulin with highly purified rat hepatocyte nuclear preparations which were characterized by marker enzymes and electron microscopy. Steady-state association of 125I-calmodulin was reached within 5 minutes. Half-maximal binding was achieved at approximately 7.1 microM. This association was partially Ca(2+)-dependent, but was not influenced by ATP, GTP or wheat germ agglutinin. Ultrastructural autoradiography showed specific association of 125I-calmodulin with peripheral and non-peripheral heterochromatin, nuclear membranes, and nucleoli. Specific binding (ratio of the grain density of 125I-calmodulin to Na125I) was greatest in the regions of the nucleoli and non-peripheral heterochromatin. The data indicate that exogenous calmodulin can associate with specific nuclear components in an energy-independent and Ca(2+)-dependent manner.

The increase of calmodulin in PC12 cells induced by NGF is caused by differential expression of multiple mRNAs for calmodulin

A rat pheochromocytoma cell line (PC12 cells) was used as a model to investigate the role of calmodulin and its multiple mRNAs in NGF-induced neuronal differentiation. The effect of NGF on the degree of differentiation was assayed using a simple differentiation scoring system. Significant increases in the differentiation score were seen by one day, and the scores increased about 10-fold by 8 days of treatment. NGF also increased calmodulin in the PC12 cells; significant increases were seen by 2 days of treatment, and a maximum increase of 3-fold was seen by 4 days. Northern blot analysis using a calmodulin riboprobe revealed that all five calmodulin mRNAs found in rat tissue were present in PC12 cells. The relative abundance of the calmodulin mRNAs was 1.7 greater than 1.4 greater than 2.3 greater than 4.1 greater than 0.9 kb. NGF treatment caused a differential increase in these mRNAs. The 1.4 kb transcript (from Gene II) was increased earlier (at 1 day) and to a greater extent (3-fold) than any of the other mRNAs. Studies of the half-lives (t1/2) of these mRNAs suggested that the t1/2 varied with the mRNA; the smaller the mRNA, the shorter the t1/2. However, there were no significant effects of NGF on the t1/2 of any of the mRNAs. These studies indicate that NGF elevates calmodulin in PC12 cells by causing a differential increase in the multiple mRNAs for calmodulin and that the increase in calmodulin may play some part in NGF-induced neuronal differentiation in PC12 cells.

Decrease of calmodulin and actin in the plasma membrane of rat liver cells during proliferative activation

After proliferative activation of rat liver cells in vivo by a partial hepatectomy a decrease of the calmodulin content in the three plasma membrane domains (blood sinusoidal, canalicular and lateral) was observed. At 24 hours after partial hepatectomy calmodulin was found to be 3 fold lower in the sinusoidal and lateral fractions whereas a 2 fold decrease was detected in the canalicular domain. Decreases on the actin levels have been also detected at 24 hours after a partial hepatectomy. Since at this time after surgery increases on nuclear actin and calmodulin have been reported, these results suggest the possibility that the actin and calmodulin dissociated from the plasma membrane after a partial hepatectomy could subsequently be translocated into the nuclei.

Effects of changes in calmodulin levels on cell proliferation

Calmodulin (CaM) is one of several proteins regulated in a cell cycle-dependent manner. CaM is synthesized at the G1/S boundary and has been implicated in the regulation of cell cycle progression. To elucidate the role of calmodulin in cell cycle control, clonal mouse C127 cell lines transformed with one of four different bovine papilloma virus (BPV)-based vectors were studied. These vectors express a) a chicken CaM gene regulated by its own promoter (CM cells), b) the chicken CaM gene regulated by the inducible human metallothionein-IIa promoter (MCM cells), c) CaM antisense RNA using the Zn2+ inducible mouse metallothionein-I (mMT-I) promoter (AS cells), or d) a rat parvalbumin gene using the chicken CaM promoter (PV cells). C127 cells transformed by BPV-1 alone (BPV cells) are used as a control in each case. Previous studies showed that a 4-fold increase in CaM levels in CM cells shortened the cell cycle by reducing the length of the G1 period. Expression of parvalbumin in PV cells has no effect on cell cycle length, suggesting that increased CAM, and not simply increased Ca2(+)-binding protein, accelerates proliferation. Zn2(+)-induced expression of the chicken CaM gene in MCM cells increased the rate of proliferation, while Zn2(+)-induced expression of high levels of CaM anti-sense RNA stops proliferation at Zn2+ levels that do not affect the growth of BPV cells. In CM cells increased CaM affects cell cycle-dependent level of mRNAs for tubulin, vimentin, and c-myc relative to the levels in BPV cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential calmodulin gene expression in fetal, adult, and neoplastic tissues of rodents

Differential expression during rat development of three genes for calmodulin (CaM I-III) was examined in amnion, decidua, embryo, liver, placenta, parietal and visceral yolk sacs and uterus. CaMI expression was constant except for increasing activity in VYS during gestation. CaMII expression increased in all tissues except for a decrease in embryo. CaMIII did not change dramatically. Differential expression was also found in chemically or virally induced rat tumors, and in metastatic lung nodules of mouse mammary carcinoma. CaMII was the major gene expressed in all these neoplastic tissues.

New synthesis of cyclic AMP-dependent protein kinases during liver regeneration

As has been previously reported one surge in cytosolic calmodulin is produced between 4 and 12 h after a partial hepatectomy. Moreover, a surge in cytosolic cyclic AMP and another in cyclic AMP-dependent protein kinase activity can be detected during the late period of the prereplicative phase of liver regeneration after a partial hepatectomy. It is known that these three surges are involved in triggering DNA synthesis. By kinetic studies and by injecting transcription (actinomycin D) and translation (cycloheximide) inhibitors into hepatectomized rats we have demonstrated that the cyclic AMP-dependent protein kinase surge is produced by new synthesis of the enzyme. In thyroparathyroidectomized rats subjected to a partial hepatectomy the calmodulin surge was similar to that observed in normal hepatectomized rats whereas the surge in cyclic AMP-dependent protein kinase activity was strongly decreased suggesting that the cyclic AMP-dependent protein kinase surge is not generated by the previous surge in calmodulin.

Possible cyclic AMP-dependence of the prereplicative surge of cytosolic calmodulin in proliferatively activated rat liver cells

The infusion of a solution containing triiodothyronine, amino acids, glucagon, and heparin (TAGH solution) triggered rat liver cell proliferation. It also induced a transient prereplicative surge of cytosolic calmodulin (between 6 and 20 hr postinfusion) similar to that observed in liver cells proliferatively activated by partial hepatectomy. The injection of the beta-adrenergic blocker dl-propanolol (20 mg/kg of body weight) at the time of the infusion prevented this transient rise of cytosolic calmodulin and also inhibited the early prereplicative surge of total liver cyclic AMP, which usually occurred between 1 and 4 hr after infusion. Propanolol also inhibited the early prereplicative surge of cyclic AMP and the increase of calmodulin in liver cells proliferatively activated by partial hepatectomy. The infusion of a solution containing cyclic AMP (5 mumoles) and theophylline (10 mg) into normal rats produced an increase of cytosolic calmodulin similar to that observed after infusion of TAGH solution or after partial hepatectomy. Thus it seems that the prereplicative rise of cytosolic calmodulin observed in proliferatively activated liver cells may be regulated by the early prereplicative surge of cyclic AMP.

Calmodulin mRNA in Barley (Hordeum vulgare L.) : Apparent Regulation by Cell Proliferation and Light

Calmodulin is encoded by a 650-nucleotide mRNA in higher plants. This messenger was identified in barley and pea by a combination of in vitro translation and blot hybridization experiments using anti-sense RNA produced from an eel calmodulin cDNA probe. In all plant tissues tested, calmodulin mRNA represents between 0.01 and 0.1% of the total translatable mRNA population. Calmodulin mRNA levels are three- to fourfold higher in the meristematic zone of the first leaf of barley. At all other stages of leaf cell differentiation, calmodulin mRNA levels are nearly identical. During light-induced development in barley leaves, the relative proportion of translatable calmodulin mRNA declines about twofold. Cytoplasmic mRNAs that may encode calmodulin-like proteins were also detected. The levels of several of these putative Ca(2+)-binding protein mRNAs are modulated during the course of light-induced barley leaf cell development.

Calmodulin in lymphocyte mitogenic stimulation and in lymphoid cell line growth

Calmodulin levels are elevated three- to fourfold in the dividing cells, resulting from the lectin-induced stimulation of fresh human lymphocytes. This increase in calmodulin appears to be related mainly to progression into S phase and supports the hypothesis that calmodulin might be crucial in regulating the progression of lymphoblasts through their division cycle. Calmodulin levels are higher in a lymphoid cell line derived from human acute lymphoblastic leukemia blood cells than in a lymphoid cell line derived from normal human blood cells, suggesting that calmodulin could be an important mediator of the leukemogenetic process.

Calcium-binding proteins in carcinoma, neuroblastoma and glioma cell lines

Antisera against the Ca2+-binding proteins parvalbumin, calbindin D-28K, and the S-100 proteins were used to study the distribution of their target proteins in selected human carcinoma (LICR-HN6;Caco-2), mouse neuroblastoma (clone NB-2a), and rat glioma cell lines (clone C-6). Pronounced staining with anti-parvalbumin was observed in the cytosol of all cells as well as in some nuclei, in particular, mitotic nuclei were highly immuno-reactive. Applying light and immune-electron microscopy (colloidal gold labelling) the parvalbumin-fluorescence was associated with filaments in the LICR-HN6 cells. However, this immunoreactivity was not a result of the presence of parvalbumin itself--as shown by biochemical analyses (HPLC, 2D-PAGE)--but was due to the presence of a Ca2+-binding and tumour-associated protein with similar biochemical and immunological properties. S-100 proteins were present in all tumour cell lines but their intracellular distribution was different from calbindin D-28K. Calbindin-immunoreactivity was found on the membranes of the carcinoma cell lines whereas neuroblastoma and glioma cells remained unlabelled. It is suggested that these proteins might be involved in the modulation of the enhanced stimulation of Ca2+-dependent processes occurring in tumour cells.

Structure of rat calmodulin processed genes with implications for a mRNA-mediated process of insertion

Two distinct processed calmodulin genes of rat (lambda SC8 and lambda SC9) were identified, cloned and their DNA sequences determined. The existence of direct repeats of 19 base-pairs for lambda SC8 or 9 base-pairs for lambda SC9 at both ends of the coding plus non-coding regions suggested a possible involvement of a mRNA-mediated process of insertion. Total genomic Southern hybridization suggested the existence of at least three different calmodulin-related genes in the rat genome. The other gene was the bona fide calmodulin gene (lambda SC4) which was split into at least five exons. lambda SC9 contained insertions of one nucleotide and two 17 base-pair direct repeats in the coding region. These insertions cause frameshift mutations probably preventing it from encoding a functional calmodulin. It also carried an insertion of a rat middle repetitive sequence, identifier sequence (IDS: Sutcliffe et al., 1982) in the 3'-non-coding region. Otherwise, it consisted of an almost identical DNA sequence to that of the bona fide calmodulin gene (lambda SC4), including the 3'-non-coding region down to the poly(A) recognition signal, A-A-T-A-A-A. On the other hand, lambda SC8 did not possess frameshift mutations in the coding region, and hence was capable of encoding a functional protein. In fact, a probe specific to the lambda SC8 sequence identified a band in Northern blotting whose size was 300 nucleotides smaller than that of authentic calmodulin mRNA. Comparison of the nucleotide sequences showed that only the coding regions of these two processed genes were homologous, indicating that the divergence of these two processed genes from the common ancestor calmodulin was an ancient event.

An investigation of the ability of antipsoriatic drugs to inhibit calmodulin activity: a possible mode of action of dithranol (anthralin)

Epidermal calmodulin (CaM) has been reported to be elevated in psoriasis and to decrease following clearance of psoriasis with treatment. We set out to investigate whether any of the principle drugs used in the treatment of psoriasis had inherent CaM antagonist activity. Utilizing a CaM-activated phosphodiesterase we have demonstrated that even at very high concentrations, the systemic drugs etretinate, methotrexate, and 8-methoxypsoralen, and the topical agents hydrocortisone and crude coal tar showed minimal CaM inhibitory activity. Dithranol (anthralin), however, whether freshly prepared or oxidized, produced substantial inhibition of CaM activity and was demonstrated to be a potent competitive antagonist of CaM, suggesting another possible therapeutic mode of action of dithranol in psoriasis.

Elevation of calmodulin in avian muscular dystrophy

In an attempt to understand the mechanism of calcium accumulation in myopathies, changes in the major calcium-binding protein, calmodulin, was studied in genetically dystrophic chickens. Measurements by radioimmunoassay revealed an increase in the calmodulin concentration of dystrophic chicken muscles. Poly A-containing RNA(s) of fast and slow muscles from the normal and dystrophic chicks were hybridized with [32P]-labeled calmodulin cDNA probe by the dot-hybridization technique. Densitometric scan of the autoradiogram showed that the calmodulin mRNA levels of dystrophic fast muscles (pectoralis and posterior latissimus dorsi) were approximately two-fold higher than those of the corresponding normal muscles. No significant change in calmodulin and calmodulin messenger RNA of slow muscle (ALD) was found in dystrophic chickens. Our results suggest that increased calcium flux within the dystrophic muscle may be modulated by calmodulin.