The polymorphism of cholinesterase in vertebrates

An in vitro study on the interaction of the anti-Alzheimer drug rivastigmine with human erythrocytes

The inhibition of the enzyme acetylcholinesterase (AChE) is a frequently used therapeutic option to treat Alzheimer's disease (AD). By decreasing the levels of acetylcholine degradation in the synaptic space, some cognitive functions of patients suffering from this disease are significantly improved. Rivastigmine is one of the most widely used AChE inhibitors. The objective of this work was to determine the effects of this drug on human erythrocytes, which have a type of AChE in the cell membrane. To that end, human erythrocytes and molecular models of its membrane constituted by dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were used. They correspond to classes of phospholipids present in the outer and inner monolayers of the human erythrocyte membrane, respectively. The experimental results obtained by X-ray diffraction and differential scanning calorimetry (DSC) indicated that rivastigmine molecules were able to interact with both phospholipids. Fluorescence spectroscopy results showed that rivastigmine produce a slight change in the acyl chain packing order and a weak displacement of the water molecules of the hydrophobic-hydrophilic membrane interface. On the other hand, observations by scanning electron microscopy (SEM) showed that the drug changed the normal biconcave shape of erythrocytes in stomatocytes (cup-shaped cells) and echinocytes (speculated shaped).

Ohm R, Drobne D, Jemec Kokalj A. First evidence of cholinesterase-like activity in Basidiomycota

Cholinesterases (ChE), the enzymes whose primary function is the hydrolysis of choline esters, are widely expressed throughout the nature. Although they have already been found in plants and microorganisms, including ascomycete fungi, this study is the first report of ChE-like activity in fungi of the phylum Basidiomycota. This activity was detected in almost a quarter of the 45 tested aqueous fungal extracts. The ability of these extracts to hydrolyse acetylthiocholine was about ten times stronger than the hydrolytic activity towards butyrylthiocholine and propionylthiocholine. In-gel detection of ChE-like activity with acetylthiocholine indicated a great variability in the characteristics of these enzymes which are not characterized as vertebrate-like based on (i) differences in inhibition by excess substrate, (ii) susceptibility to different vertebrate acetylcholinesterase and butyrylcholinesterase inhibitors, and (iii) a lack of orthologs using phylogenetic analysis. Limited inhibition by single inhibitors and multiple activity bands using in-gel detection indicate the presence of several ChE-like enzymes in these aqueous extracts. We also observed inhibitory activity of the same aqueous mushroom extracts against insect acetylcholinesterase in 10 of the 45 samples tested; activity was independent of the presence of ChE-like activity in extracts. Both ChE-like activities with different substrates and the ability of extracts to inhibit insect acetylcholinesterase were not restricted to any fungal family but were rather present across all included Basidiomycota families. This study can serve as a platform for further research regarding ChE activity in mushrooms.

Differential Expression of Cholinergic System Components in Human Induced Pluripotent Stem Cells, Bone Marrow-Derived Multipotent Stromal Cells, and Induced Pluripotent Stem Cell-Derived Multipotent Stromal Cells

The components of the cholinergic system are evolutionary very old and conserved molecules that are expressed in typical spatiotemporal patterns. They are involved in signaling in the nervous system, whereas their functions in nonneuronal tissues are hardly understood. Stem cells present an attractive cellular system to address functional issues. This study therefore compared human induced pluripotent stem cells (iPSCs; from cord blood endothelial cells), mesenchymal stromal cells derived from iPSCs (iPSC-MSCs), and bone marrow-derived MSCs (BM-MSCs) from up to 33 different human donors with respect to gene expressions of components of the cholinergic system. The status of cells was identified and characterized by the detection of cell surface antigens using flow cytometry. Acetylcholinesterase expression in iPSCs declined during their differentiation into MSCs and was comparably low in BM-MSCs. Butyrylcholinesterase was present in iPSCs, increased upon transition from the three-dimensional embryoid body phase into monolayer culture, and declined upon further differentiation into iPSC-MSCs. In BM-MSCs a notable butyrylcholinesterase expression could be detected in only four donors, but was elusive in other patient-derived samples. Different nicotinic acetylcholine receptor subunits were preferentially expressed in iPSCs and during early differentiation into iPSC-MSCs, low expression was detected in iPS-MSCs and in BM-MSCs. The m2 and m3 variants of muscarinic acetylcholine receptors were detected in all stem cell populations. In BM-MSCs, these gene expressions varied between donors. Together, these data reveal the differential expression of cholinergic signaling system components in stem cells from specific sources and suggest the utility of our approach to establish informative biomarkers.

Hepatic cholinesterase of laying hens naturally infected by Salmonella Gallinarum (fowl typhoid)

Salmonella is a facultative intracellular pathogen that may cause foodborne gastroenteritis in humans and animals consisting of over 2000 serovars. The serovar Salmonella Gallinarum is an important worldwide pathogen of poultry. However, little is known on the mechanisms of pathogenesis of Salmonella in chickens. The aim of this study was to evaluate cholinesterase and myeloperoxidase activities in hepatic tissue of laying hens naturally infected by S. Gallinarum. Twenty positive liver samples for S. Gallinarum were collected, in addition to seven liver samples from healthy uninfected laying hens (control group). The right liver lobe was homogenized for analysis of acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and myeloperoxidase (MPO), and the left lobe was divided into two fragments, one for histopathology and the other for Salmonella isolation. The results showed changes in AChE and BchE activity in the liver of infected laying hens compared to the control group (P < 0.05), i.e. reduced AChE and increased BChE activities in liver samples. Infected animals showed increased MPO activity compared to healthy animals (P < 0.05). Furthermore, the histopathological findings showed fibrinoid necrosis associated to the infiltration of lymphocytes, plasma cells, macrophages,heterophils in the liver of infected hens. These findings suggest that the inflammatory process was attenuated providing a pro-inflammatory action of both enzyme analyzed in order to reduce the free ACh, a molecule which has an anti-inflammatory action. Therefore, our results lead to the hypothesis that cholinesterase plays an important role on the modulation of immune response against S. Gallinarum with an inflammatory effect, contributing to the response against this bacterium. This study should contribute to a better understanding on the pathogenic mechanisms involved in laying hens infected by S. Gallinarum.

Acetylcholinesterase in Biofouling Species: Characterization and Mode of Action of Cyanobacteria-Derived Antifouling Agents

Effective and ecofriendly antifouling (AF) compounds have been arising from naturally produced chemicals. The objective of this study is to use cyanobacteria-derived agents to investigate the role of acetylcholinesterase (AChE) activity as an effect and/or mode of action of promising AF compounds, since AChE inhibitors were found to inhibit invertebrate larval settlement. To pursue this objective, in vitro quantification of AChE activity under the effect of several cyanobacterial strain extracts as potential AF agents was performed along with in vivo AF (anti-settlement) screening tests. Pre-characterization of different cholinesterases (ChEs) forms present in selected tissues of important biofouling species was performed to confirm the predominance of AChE, and an in vitro AF test using pure AChE activity was developed. Eighteen cyanobacteria strains were tested as source of potential AF and AChE inhibitor agents. Results showed effectiveness in selecting promising eco-friendly AF agents, allowing the understanding of the AF biochemical mode of action induced by different compounds. This study also highlights the potential of cyanobacteria as source of AF agents towards invertebrate macrofouling species.

The effect of temperature on the activity of acetylcholinesterase preparations from rat brain

Homogenization of rat brain with dilute buffer shows that about 15% of the acetylcholinesterase is soluble while the remaining 85% is present in a membrane-bound form which can be brought into solution by extraction with Triton X-100. The effect of temperature on the values of V(max) and K(m) of the buffer-soluble, the membrane-bound and the Triton-soluble forms of acetylcholinesterase have been compared and the results discussed in terms of possible changes in the conformation, dissociation or aggregation of the enzyme molecule. Gradient-gel electrophoresis of the soluble preparations carried out at 4 degrees C or 37 degrees C suggest that the normal tetrameric structure present at 4 degrees C dissociates into monomers and forms some higher molecular weight species at 37 degrees C. The effect of prior storage of the brains in toluene on these properties is also considered.

Species differences in avian serum B esterases revealed by chromatofocusing and possible relationships of esterase activity to pesticide toxicity

Serum cholinesterase (BChE) and carboxylesterase (CbE) activities were investigated in ten species of birds. Multiple forms of serum BChE and CbE were also separated by chromatofocusing. Higher CbE activity and a wider range of CbE and BChE forms were present in the sera of omnivorous/herbivorous birds than carnivores. Omnivores/herbivores studied were the starling, house sparrow, tree sparrow, pigeon, partridge and magpie. Serum CbE activities of these species ranged from 0.46 to 2.93 mumol/min/mL with 2-6 forms separated by chromatofocusing. 0-6 forms of BChE were separated by the same method. The serum CbE activities of the little owl, tawny owl, barn owl and razorbill ranged from 0.19 to 0.58 mumoles/min/mL with 0-2 forms separated by chromatofocusing. No ChE forms were present within the pH gradient. These results may be significant in contributing to the understanding of the selective toxicity of organophosphorus and carbamate pesticides.

Inhibition of acetylcholinesterase and butyrylcholinesterase by the organophosphorus insecticide methylparathion in the central nervous system of the golden hamster (Mesocricetus auratus)

The toxic effects of the organophosphorus pesticide methylparathion are primarily caused by the inhibition of acetylcholinesterase activity in the central nervous system, whereas the relationship between butyrylcholinesterase and poisoning symptoms is unclear. The presumed different effects of methylparathion on acetylcholinesterase in various regions of brain and spinal cord suggest differences in the distribution of molecular enzyme forms. In the present work, the in vitro and in vivo effects of methylparathion on acetylcholinesterase and butyrylcholinesterase were studied in whole brain homogenates of golden hamsters with biochemical methods. Furthermore, acetylcholinesterase activity was determined in regions of the nervous system by quantitative histochemistry (microdensitometry). Biochemically, very low IC50 values of the hydrophilic and lipophilic fractions of both enzymes were measured. Analysis of the time course of enzyme inhibition revealed maximum inhibition 45 min after methylparathion application. Using microdensitometry different degrees of acetylcholinesterase inhibition were found in various areas of the brain. The highest inactivation was observed in the Substantia nigra and in thalamic nuclei; in several regions of the cerebellum, the inhibition rate was comparatively lower. In conclusion, methylparathion acts as an potent inhibitor of acetylcholinesterase and butyrylcholinesterase in the hamster nervous system. The region-specific different inactivation of acetylcholinesterase might be caused by the existence of multiple forms of the enzyme in various brain regions.

Collagens as multidomain proteins

The number of proteins known to contain collagen-like triple helical domains is rapidly increasing. The functions of these domains are to provide molecular rods that separate spatially non-triple helical domains with varied properties and structures and to permit lateral interactions between molecules. Two-thirds of the amino acids of the triple helical domains have their side-chains at the surface of the protein. The triple helix is also a structure that is easily predictable from the primary structure. The structure of several recently discovered collagens are discussed in terms of domains and functions. The triple helical domains have sizes varying from 33 to over 1,000 amino acid residues. The longest uninterrupted triple helices are involved in the formation of the classical quarter-staggered fibrils. Other triple helical domains permit varied molecular aggregates. A very broad spectrum of non-triple helical or globular domains are interspersed by triple helices. Only those located at the extremities of the molecules are large in size, sometimes several hundred kDa, while the domains separating 2 triple helices are small (less than 50 amino acids) and provide the molecules with hinges, proteolytic cleavage sites or other specialized functions like a glycosaminoglycan attachment site. If the assembly of the 3 chains required for the triple helix formation can be controlled in vitro, collagen-like molecules offer an as yet unexploited potential for protein engineering.

Distribution and solubilization of the molecular forms of acetylcholinesterase in rat urinary bladder and sphincter

The distribution and solubility of the molecular forms of acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7) were examined in adult, male rat bladder body and sphincter. Four distinct forms of the enzyme solubilized from bladder body were separated on sucrose density gradients. Two of the forms (A8 and A12) corresponded to asymmetric proteins and were solubilized with high ionic strength buffer. The other two forms represented globular forms. The smallest form (G1) was soluble in low ionic strength buffer without detergent. About 33% of the larger globular form (G4) required detergent for solubilization. There were only minor differences in the distribution of these forms in juvenile rat bladder and adult, female rat bladders. Sphincter tissue lacked one of the asymmetric forms but otherwise resembled the bladder bodies. These results demonstrate that some smooth muscle organs have significant amounts of asymmetric, as well as globular, forms of acetylcholinesterase and suggest that additional studies should be performed to characterize the enzyme in this and other smooth muscle systems.

Characterization of cholinesterase molecular forms in the mucosal cells along the intestine of the chicken

The presence of a butyrylcholinesterase (BuChE, EC 3.1.1.8) in the musocal cells of the chicken intestine was demonstrated by histochemical and biochemical methods. The study of its distribution, along the intestine from duodenum to rectum, showed that the jejuno-ileum possesses the highest activity. Sucrose gradient centrifugation revealed, in all intestinal areas, two globular forms with sedimentation coefficients of 4.3 S (G1 form) and 10.8 S (G4 form). The presence of Triton X-100 in the preparations did not modify the sedimentation profiles of these two forms which can be considered as soluble BuChE. The ratio of G1/G4-forms progressively decreases along the intestine from duodenum to rectum indicating a predominance of the G4 form in the areas where the activity is low. Our results are discussed in relation to other studies of globular forms of chicken BuChE.

Antisera probes to an atypical pseudocholinesterase from surgeonfish reveal immunochemical variability and tissue-specific molecular polymorphism

Polyclonal antisera were raised in rabbits against the purified sialated, presumed-globular tetrameric pseudocholinesterase (pseudo-ChE) from surgeonfish (Leibel: Journal of Experimental Zoology 1988b) and against commercially obtained Electrophorus electroplax AChE. The resulting antisera probes were absolutely specific for their respective antigens and failed to titrate ChE activities heterologously. However, each antisera probe did crossreact with its other respective globular and asymmetric aggregational isozymes. The resultant specific probes were then used to examine interspecific evolutionary conservation of the two ChE activities and, in conjunction with velocity sedimentation analysis and differential paraoxon inhibition, the tissue distribution and molecular polymorphism of these same two enzyme systems in surgeonfish. These experiments suggest the tight evolutionary conservation of AChE in contrast to the apparent high variability of pseudo-ChE amongst the wide range of teleost fishes tested. The native atypical pseudo-ChE was shown to exist, like AChE, as a series of sialated and asialated globular and asymmetric aggregational isozymes whose relative distribution exhibits marked tissue specificity. The extremely high levels of pseudo-ChE characteristic of white skeletal (epaxial) muscle, in particular, was conspicuous, and its occurrence in the sarcolemma is discussed in the context of its possible function and in relation to the apparent lack of evolutionary conservation amongst marine teleosts.

An analysis of esterase activities from surgeonfish tissues yields evidence of an atypical pseudocholinesterase

1. Esterases from tissues of the surgeonfish (Teleostei, Perciformes, Acanthuridae) are characterized electrophoretically and include several carboxylesterases, an acetylesterase, and an atypical pseudocholinesterase (pseudo-ChE). 2. The pseudo-ChE occurs in several isozymic forms including sialated and asialated slightly-anodal forms found principally in liver, and a larger, asialated asymmetric form that barely penetrates the 10% PAGE gel matrix found together with true AChE in epaxial muscle, brain, and eye. 3. Characterization of these three pseudo-ChE activities suggest that they are decidedly atypical in the intermediacy of their substrate and inhibitor specificities relative to classically-defined AChE and pseudo-ChE activities.

Localization of the pool of G4 acetylcholinesterase characterizing fast muscles and its alteration in murine muscular dystrophy

The distributions of acetylcholinesterase and its molecular forms within muscles of normal and dystrophic 129/ReJ mice were established by a concomitant cytochemical and biochemical study performed on 1-mm serial sections of three predominantly fast muscles, i.e., anterior tibialis, extensor digitorum longus, and sternomastoid, as well as the slow-twitch soleus. This comparative study showed the following main findings. 1) In every muscle of both normal and dystrophic mice a) the three asymmetric forms were confined to the motor zone where they systematically codistributed with the endplates, and b) all globular forms, including G4, were concentrated at the motor zone from which they extended over the entire muscle length along a concentration gradient. 2) In the normal muscles, the perijunctional sarcoplasmic cytochemical reaction exhibited by individual fibers was grouped into a well-defined cojunctional acetylcholinesterase compartment in which the endplates were embedded. The overall intensity of the cojunctional cytochemical reaction was either high or low according to whether the muscle was predominantly fast or slow. 3) This cojunctional acetylcholinesterase compartment varied in close parallelism with G4 and thus appeared as the cytochemical correlate of the G4 molecules concentrated around the endplates. In particular, as the shape of the motor zone progressively increased in complexity along with the intricacy of the muscle fiber organization, from sternomastoid to extensor digitorum longus to anterior tibialis, so did both the relative volume occupied by the cojunctional acetylcholinesterase compartment and the proportion of G4. 4) The motor zone of the normal fast-twitch muscles characteristically differed from that of the soleus by the presence of a G4-rich environment around the endplates, which was cooperatively provided by the surrounding fibers. 5) In dystrophic muscles, this cojunctional G4-rich compartment was lost: the cojunctional cytochemical compartment was no longer discernable, while G4 was reduced to a minimal low level similar to that characteristic of the normal soleus.

Solubilization and partial characterization of acetylcholinesterase from the sarcotubular system of skeletal muscle

Attempts were made to solubilize acetylcholinesterase (AChE) from microsomal membranes isolated from rabbit white muscle. The preparative procedure included a step in which the microsomes were incubated in a solution containing high salt concentration (0.6 M KCl). About 15% of the total enzyme activity could be solubilized with dilute buffer. Addition of EDTA (1 mM), EGTA (1 mM) or NaCl (0.5 and 1 M) to the extraction buffer did not improve the solubilization yield. Several non-ionic detergents and biliary salts were then used to bring the enzyme into solution. Triton X-100, C12E9 (dodecylnonaethylenglycol monoether) and biliary salt, above their critical micellar concentration, proved to be very effective as solubilizing agents. The occurrence of multiple molecular forms in detergent-soluble AChE was investigated by means of molecular sieving, centrifugation analysis, and slab gel electrophoresis. Experiments on gel filtration showed that, during the process, half of the enzyme was transformed into aggregates, the rest of the activity appearing as peaks with Stokes radii ranging from 3.7 to 7.9 nm. Both ionic strength and detergent nature modify the number and relative proportion of these peaks. Centrifugation analysis of Triton-saline-soluble AChE yielded molecular forms of 4.8S, 10-11S, and 13.5S, whereas deoxycholate extracts revealed species of 4.8S, 10S, and 15S, providing that gradients were prepared with 0.5 M NaCl. In the absence of salt, forms of 6.5-7.5S, 10S, and 15S were measured. The lightest species was always the predominant form. Slab gel electrophoresis showed several bands (68,000-445,000). The 4.8S component only yielded bands of 65,000-70,000.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracellular acetylcholinesterase of adult rat myofibers is more concentrated in endplate than non-endplate regions

The intracellular distribution of acetylcholinesterase (AChE) was determined in adult rat anterior gracilis muscles. Echothiophate iodide (ECHO), a water-soluble cholinesterase inhibitor, was applied to muscles in situ to eliminate extracellular and/or extracellularly oriented enzyme. Control and ECHO-treated muscles were either cut into 1-mm segments and assayed for AChE activity or cytochemically stained for AChE. Subsequent analysis by light and electron microscopy showed that the AChE stain inside myofibers was highly localized and clearly visible only in the zone immediately underlying the point of nerve-muscle contact. Biochemical assay of muscle segments showed intracellular AChE to be most highly concentrated in regions containing large numbers of endplates (approximately twice the activity of endplate-free areas). Since such "endplate-rich" segments are in fact mostly extra-synaptic tissue, we conclude that intracellular AChE of adult rat gracilis myofibers, although present along the length of the cell, is more than two times as concentrated in sub-synaptic areas as compared to extra-synaptic areas. This result must be carefully considered when attempting to identify "endplate-specific" AChE activity of mammalian muscle, and further points to the importance of neural influences on AChE metabolism/regulation.

Soluble form of acetylcholinesterase from rabbit enterocytes: comparison of its molecular properties with those of the plasma membrane species

A soluble form of acetylcholinesterase was shown to be present in rabbit enterocytes. The enzyme was obtained from a high-speed supernatant (105,000 X g centrifugation) after homogenization of intestinal mucosa without detergent. It was shown to possess no obvious hydrophobic character and could be classified as a low-salt-soluble (LSS) acetylcholinesterase. Sucrose gradient centrifugation revealed a single enzyme species with a sedimentation coefficient of 3.9 +/- 0.2S. By gel filtration performed in HPLC the enzyme was eluted as a protein corresponding to an Mr of 72,000 +/- 3,000. It could be precipitated with concanavalin A by affinoelectrophoresis, but the catalytic activity was not affected by the lectin. Our results are consistent with a G1 globular form for this soluble acetylcholinesterase which differs very clearly from detergent-soluble forms also found recently in the plasma membranes of rabbit enterocytes.

Studies on a possible functional coupling between presynaptic acetylcholinesterase and high-affinity choline uptake in the rat brain

The relationships between presynaptic acetylcholinesterase (AChE) and high-affinity choline uptake (HACU) were investigated using a monolayer of rat cortex synaptosomes in superfusion conditions. The following sets of experiments were performed: determination of [3H]choline ([3H]Ch) uptake during superfusion with [3H]Ch; determination of [3H]Ch uptake during superfusion with acetylcholine (ACh) tritiated in the Ch moiety; evaluation of ACh hydrolysis during superfusion with ACh labelled in the acetate moiety; and comparison of the uptake of [3H]Ch generated by hydrolysis of [3H]ACh with that occurring during superfusion with [3H]Ch. Intact ACh was not taken up by superfused synaptosomes. The uptake of [3H]Ch during superfusion with 1 or 0.1 microM [N-methyl-3H]ACh was two-thirds of that occurring during superfusion with the same concentrations of [3H]Ch. The amount of [3H]Ch produced by hydrolysis during 16 min of superfusion was 1/25 of the amount passing through the synaptosomal monolayer during 16 min of superfusion with [3H]Ch. The results indicate that presynaptic AChE and HACU are located in close proximity to each other on the cholinergic terminal membrane, an observation suggesting the possibility of a functional coupling between the two mechanisms.

Presence and characterization of acetylcholinesterase in brush-border and basolateral membranes of rabbit enterocytes

Acetylcholinesterase is found in the brush-border and basolateral membranes purified from rabbit enterocytes. The sedimentation coefficients of the enzymes solubilized from two types of membrane are identical (5.5 +/- 0.2 S) and the apparent molecular weights are not significantly different (154 000 +/- 8000 for the brush-border and 145 000 +/- 8000 for the basolateral membrane enzyme). These results suggest a unique G2 molecular form for acetylcholinesterase from brush-border as well as from basolateral membranes.

Properties of acetylcholinesterase and non-specific cholinesterase in rat superior cervical ganglion and plasma

Amphiphile dependency, solubility in aqueous solutions, and sensitivity to proteolysis of acetylcholinesterase (AChE) and nonspecific cholinesterase (nsChE) in the rat superior cervical ganglion were studied and compared to properties of soluble plasma cholinesterases. Ganglion AChE shows strong amphiphile dependency: an amphyphilic substance must be present in the homogenizing medium in order to obtain maximal apparent enzyme activity. Apparent activity of AChE solubilized in Ringer's solution was also increased after subsequent addition of a detergent. The 4 S molecular form, predominant in this extract (corresponding to the fastest electrophoretic band), is very sensitive to papain proteolysis but can be protected by a detergent. This molecular form therefore carries an important hydrophobic domain and is probably membrane bound in situ. The 10 S form of ganglionic AChE, extracted in Ringer's solution, is probably a soluble enzyme since, like soluble plasma enzymes, it is not amphiphile dependent and is rather resistant to proteolysis. Ganglion nsChE is more water soluble, less amphiphile dependent and more protease resistant than AChE.

Proteolytic digestion patterns of "soluble" and "detergent-soluble" bovine caudate nucleus acetylcholinesterases

The structures of purified "soluble" and "detergent-soluble" bovine caudate nucleus acetylcholinesterases were compared by peptide mapping on polyacrylamide gels. The digestion products generated from the two acetylcholinesterases on proteolysis by a given protease (Staphylococcus aureus V8 protease, alpha-chymotrypsin, or papain) are remarkably similar as judged from the electrophoretic band patterns. We conclude that the "soluble" and "detergent-soluble" acetylcholinesterases from bovine caudate nucleus share a common evolutionary origin.

Rapid axonal transport of three molecular forms of acetylcholinesterase in the frog sciatic nerve

Acetylcholinesterase occurs in the frog sciatic nerve under five stable molecular forms with distinct sedimentation coefficients in sucrose gradients: 3 globular forms (3.6S, 6S and 10.5S) and two asymmetric ones (14S and 18S). Whereas in birds and mammals, the asymmetric tailed forms of acetylcholinesterase are present in trace amounts in peripheral nerves and account for only a small part of the enzyme activity submitted to a rapid axonal transport, the two asymmetric 14S and 18S forms represent nearly 50% of total activity in the frog sciatic nerve and account for 60-70% of the acetylcholinesterase activity accumulated at both sides of a nerve transection, the rest being due to an accumulation of globular molecules. We showed that the three forms, 10.5S, 14S and 18S, are all carried with the fast phase of axonal transport at a velocity of 100-120 mm/day in the anterograde direction and 20-30 mm/day in the retrograde direction. The velocity of transport for the light molecular forms 3.6S and 6S could not be calculated. In addition, we observed that large amounts not only of the 10.5S but also of the asymmetric 14S and 18S forms appear to be stationary along the frog sciatic nerve, contrary to the situation described for peripheral nerves in birds or mammals. Our results thus reveal that some axonal transport parameters for the asymmetric forms of acetylcholinesterase greatly differ in the peripheral nerves of amphibians on the one hand and of birds and mammals on the other, suggesting that these heavy molecular forms might have distinct functions in the nerves of lower and higher vertebrates.

Subcellular localization of acetylcholinesterase molecular forms in endplate regions of adult mammalian skeletal muscle

The characterization of individual acetylcholinesterase (AChE) molecular form subcellular pools in adult mammalian skeletal muscle is a critical point when considering such questions as the origin, assembly, and neurotrophic regulation of these molecules. By correlating the results of differential extraction, in vitro collagenase digestion, and in situ pharmacologic probes of AChE molecular forms in endplate regions of adult rat anterior gracilis muscle, we have shown that: 1) 4.0S (G1) and 6.0S (G2) AChE are predominantly membrane-bound and intracellular; if an extracellular and/or soluble fraction of these forms exists, it cannot be adequately resolved by our methods; 2) 9-11S (globular) AChE activity is distributed between internal and external pools, as well as membrane-associated and soluble fractions; 3) 16.0S (A12) AChE is not an integral membrane protein and exists both intracellularly (25-30%) and extracellularly (70-75%).

Denervation induced changes in subcellular pools of 16S acetylcholinesterase activity from adult mammalian skeletal muscle

Acetylcholinesterase (AChE) inhibitors which differ in lipid solubility and thus in their ability to penetrate cell membranes were utilized to study the effects of denervation on discrete pools of 16S AChE from endplate regions of adult rat anterior gracilis muscle. Such pools have been interpreted as extra- and intracellular fractions of endplate 16S AChE activity. Denervation caused an almost immediate decay of intracellular 16S AChE, and a later (12-18 h) but roughly parallel decrease in its extracellular counterpart. Thus, the level at which the motor nerve exerts its primary regulatory influence on adult mammalian skeletal muscle endplate 16S AChE activity appears to be within muscle cells. This influence may affect the molecule's synthesis, assembly, and/or degradation.

Multiple regression analysis of the cholinesterase activity with certain physiochemical factors

Nineteen hundred sixteen agricultural workers who have been living in a rural area in central Japan were studied. Their age, blood pressure, Broca index, hemoglobin content, serum total cholesterol, and activity of serum cholinesterase and transaminase (GOT and GPT) were determined. The relation between the cholinesterase activity and certain physiochemical factors of the subjects was studied. Cholinesterase activity (ChE) is related to certain factors such as age, hemoglobin content (Hb), serum total cholesterol (TCh), transaminase activity (GPT), and Broca index (BI). A multiple regression equation exists between the cholinesterase activity and these factors: ln ChE = a (age) + b (Hb2) + c X ln GPT + d X ln TCh + e BI + f, where a, b, c, d, e, and f are constants. The estimated value of cholinesterase activity agrees with its measured activity. The partial correlation coefficients of the equation can be classified into the following three classes: (1) The partial correlation coefficients of total cholesterol and Broca index are nearly constant without distinction of sex and season. (2) The coefficient of hemoglobin content has a small seasonal and sexual difference. (3) The coefficients of age and GPT have a great seasonal and sexual difference. Using the equation, the most probable value of cholinesterase activity can be estimated. Therefore, the significant changes of its activity may be attributed to the toxic effects of insecticides or the abnormality of liver function.

Asymmetric and globular forms of AChE in slow and fast muscles of 129/ReJ normal and dystrophic mice

Acetylcholinesterase activities and molecular forms were studied in normal and dystrophic 129/ReJ mice, focusing on four predominantly fast-twitch muscles and the slow-twitch soleus. The asymmetric and globular forms were analyzed separately so that the effect of dystrophy on each form could be determined. This comparative study showed the following. (1) In the normal condition, each muscle exhibited a distinct distribution of the molecular forms. (2) The diversity among the fast muscles resulted mainly from variations in the proportions of the three globular forms; in contrast, these muscles showed a constant and precise A12/A8/A4 ratio. (3) The slow-twitch soleus clearly differed from the other muscles in its low acetylcholinesterase activity and distinct distribution of the molecular forms, characterized by a low level of G4 and a peculiar ratio among its asymmetric forms, resulting from a relative increase of the A8 and A4 forms. (4) In dystrophic mice, the diversity of the acetylcholinesterase distribution was lost; all the fast muscles displayed profiles exhibiting the characteristics typical of the soleus. The fast-twitch extensor digitorum longus, sternomastoid, and plantaris converged towards an identical set of acetylcholinesterase molecules. (5) In contrast, the acetylcholinesterase activity and molecular forms of the soleus were only slightly affected by the disease. These results reveal that the dystrophy modifies both categories of molecular forms of acetylcholinesterase in a very precise manner. Such complex changes, which are highly reproducible in a variety of different muscles, are unlikely to result from nonspecific reactions secondary to the disease.

Acetylcholinesterase molecular forms in the fast or slow muscles of the chicken and the pigeon

Molecular forms of acetylcholinesterase (AChE) were examined in various skeletal muscles of the chicken and the pigeon. In chicken pectoralis m., AChE was found to be restricted to endplate containing segments, and no asymmetric form could be detected in aneural samples. In the chicken muscles studied, a relation has been established between globular (G1,G2,G4) forms or asymmetric (A8,A12) forms, and muscle fibre types. Asymmetric forms are preponderant in fast-twitch muscles, whereas in slow tonic muscles 80% of the AChE activity is due to globular forms. However, comparison with pigeon muscles shows that AChE chicken muscle patterns may not be generalized.

Cholinergic traits in the neural crest: acetylcholinesterase in crest cells of the chick embryo

Previous work by our group has demonstrated that mesencephalic neural crest cells at an early stage of migration are able to synthesize acetylcholine (ACh). Acetylcholinesterase (AChE), the enzyme responsible for ACh degradation, was examined in neural crest cells of the chick embryo, using cytochemical and biochemical methods. Observations at the light microscope level showed that cholinesterase activity, identified as true AChE, was present at all axial levels in presumptive crest cells of the neural folds, soon after closure of the neural tube. Subsequently, AChE activity was found in cells of the individualized neural crest and in crest cells migrating at cephalic and trunk levels. Cell counts revealed that 88-94% of the total crest population was AChE-positive. Electron microscope observations indicated that the enzyme was confined to perinuclear and endoplasmic reticulum cisternae. The AChE of migrating mesencephalic neural crest cells was identified as the dimeric form (sedimentation coefficient 6.9 S) of the catalytic subunit. These results indicate that the specific AChE is present in the majority of neural crest cells all along the neural axis. Thus the ability to synthesize and degrade ACh is expressed at least in some neural crest cells at an early stage of development.

Axonal transport of the molecular forms of acetylcholinesterase in developing and regenerating peripheral nerve

In chick sciatic nerve, acetylcholinesterase (AChE) occurs in four main molecular forms characterized by their sedimentation coefficients in sucrose gradients, referred to as G1 (5S), G2 (7.5S), G4 (11S), and A12 (20S). Under normal conditions, we previously showed by accumulation technique that the G4 and A12 forms are rapidly transported along the axons, whereas G1 and G2 are carried much more slowly. Here, we used to the same technique to study the anterograde axonal transport of these different AChE forms during normal axonal growth and experimental regeneration. During the first 2 months after hatching, G4 and A12 transport virtually doubled, whereas G1 + G2 transport increased only slightly. After nerve cutting, crushing, or freezing, the flow rates of G1 + G2 and G4 in the regenerating proximal stump decreased by 75% at 4 to 7 days compared with control values and that of A12, by 90 to 95%. In crushed and frozen nerves the transport of all four AChE forms slowly recovered thereafter, but failed to attain control values even after 7 weeks. In cut nerves, on the contrary, no significant recovery of G1 + G2, or G4 transport occurred, but A12 transport began to recover by day 7. Taken together, our results show that axonal transport of G1 + G2, G4, and A12 is selectively regulated in chick sciatic nerve, and suggest that the A12 form of AChE might have a special role and/or destination in regenerating axons.

Comparative affinity chromatography of acetylcholinesterases from five vertebrate species

The efficacy of N-methylacridinium affinity chromatography in the purification of acetylcholinesterases from chicken, rat, calf and human brain and from the electric organ of the electric fish Torpedo marmorata has been investigated. Retention of the enzymes on the N-methylacridinium columns exceeded 90% in all instances except for the chicken enzyme, where 40-80% retention was observed depending on the acridinium concentration. Sucrose density gradient centrifugation profiles revealed no difference between the distribution of molecular forms in the crude extracts and in the partially purified fractions eluted from the columns by decamethonium iodide.

Acetylcholinesterase content in both motor nerve and muscle is correlated with twitch properties

The activity and molecular forms of acetylcholinesterase (AChE) were studied in the rat soleus muscle and its nerve, as compared to their fast-twitch counterparts. The soleus muscle and its nerve exhibited both significantly lower AChE activity and less of the G4 (10S) molecular form. In addition, the soleus muscle displayed a specific increase in the A8 (13S) and A4 (8.8S) asymmetric forms, not seen in any of the fast-twitch muscles examined. These results indicate that the AChE content of a muscle and its nerve are linked and depend on the twitch properties, and that the slow-twitch muscle is characterized by a specific set of AChE molecular forms.

Serotonin-sensitive aryl acylamidase activity of platelet acetylcholinesterase

Serotonin-sensitive aryl acylamidase (AAA, EC 3.5.1.13) was purified to apparent homogeneity from sheep platelets by affinity chromatography and it was shown to be associated with the platelet acetylcholinesterase (AChE, EC 3.1.1.7). The basis for the association of the two enzymes was the following. Both enzyme activities co-eluted from the affinity columns with constant ratios of specific activities and percentage recoveries. Both enzymes co-migrated on gel electrophoresis. Both enzymes co-eluted during sepharose 6B gel filtration. Potent inhibitors of AChE such as bis(4-allyldimethyl ammoniumphenyl) pentan-3-one dibromide (BW 284C51), neostigmine and eserine also inhibited AAA potently. Both enzymes lost significant activity on treatment with deoxycholate or taurodeoxycholate and the loss could be partly restored by a mixture of phospholipids. The platelet AAA was specifically inhibited by serotonin and to a lesser extent by tryptamine but not by several other amines. It was also inhibited by acetylcholine and several of its analogues and homologues. It is suggested that in the platelets the two enzymes (AAA and AChE) are probably identical.

Divergent regulation of acetylcholinesterase and butyrylcholinesterase in tissues of the rat

Investigating the possibility that acetylcholinesterase (AchE) and butyrylcholinesterase (BuChE) are regulated in a coordinated manner, we have examined the natural variation in activity of these two enzymes in several tissues of adult male Sprague-Dawley, Fischer-344, and Wistar-Furth rats. Both enzymes varied greatly in mean activity among brain, diaphragm, atria, serum, superior cervical ganglia, and liver. In Sprague-Dawley rats there were also large individual variations with up to a fivefold range of AChE activities and up to a 100-fold range of BuChE activities in a given tissue. Individual variations in cholinesterase activities appeared to be smaller in the inbred Fischer-344 or Wistar-Furth rats. Experiments with internal standards of partially purified AChE and BuChE indicated that the individual variations probably reflected differences in the intrinsic content or specific activity of the tissue enzymes. Comparison of the AChE activities in different tissues of a given group of rats failed to reveal statistically significant correlations in any strain (i.e., the relative activity of any one tissue was no guide to the relative activity of any other tissue in the same rat). This result indicates that the regulation of AChE is tissue-specific. By contrast, BuChE activity showed highly significant correlations among the majority of the tissues examined in the Sprague-Dawley rats, implying that widely dispersed factors can affect the regulation of this enzyme. Body-wide regulation is not necessarily the rule, however, since only a single tissue pair in the inbred Fischer rats and none of the pairs in the Wistar-Furth rats showed significant correlations of BuChE activity. In general, AChE and BuChE activities were not correlated with each other to a statistically significant degree. We conclude that the control of these enzymes normally involves different mechanisms and is strongly affected by the genetic background of the sample population.

Slow axonal transport of the molecular forms of butyrylcholinesterase in a peripheral nerve

Butyrylcholinesterase was found in chick sciatic nerve in four main molecular forms--G1, G2, G4 and A12--distinguishable by thier sedimentation coefficients in sucrose gradients (4.2S, 6.4S, 11.3S and 19S, respectively). Axonal transport of butyrylcholinesterase was studied by measuring the accumulation of its molecular forms on each side of a transected sciatic nerve. Twenty-four hours after transection, butyrylcholinesterase activity had risen by about 32% at the extremity of the proximal stump, and by 20% at the extremity of the distal stump. Proximal accumulation was due to a two-fold rise in G4 activity and to a six-fold rise in A12 activity, whereas distal accumulation was exclusively due to a 50% increase in G4 activity, accompanied by the complete loss of A12. The activities of G1 and G2 remained stable in both directions. Under our experimental conditions, the accumulation of butyrylcholinesterase activity cannot be attributable to local protein synthesis, cross-contamination with accumulated acetylcholinesterase or the presence of plasma butyrylcholinesterase. Hence we conclude that all A12 butyrylcholinesterase molecules were carried in the anterograde direction, moving at 11.6 +/- 4.2 mm/day, and that probably some of the G4 molecules were slowly transported in both directions. These findings suggest that some of the butyrylcholinesterase is located in the axonal mitochondria and/or axolemma.

Acrylamide neuropathy and changes in the axonal transport and muscular content of the molecular forms of acetylcholinesterase

Acetylcholinesterase (AChE) is present in nervous and muscular tissues of normal chickens in four main molecular forms (G1, G2, G4, and A12), distinguishable by sedimentation analysis. In the sciatic nerve of acrylamide-poisoned chickens, the anterograde axonal transport of A12 AChE was reduced by 60%, and that of G4 by 21%, compared to control values whereas the slow axoplasmic transport of G1 and G2 was unaffected. Regarding the leg muscles, only the tibialis anterior revealed dramatic alterations in the distribution of it AChE forms coinciding with a large reduction in the number of nerve endings. In acrylamide poisoning, the AChE molecular forms were considered as very sensitive markers of both axonal transport phases and of the innervation state. Our results support the hypothesis that a defect in the fast axonal transport of proteins might be involved in the degeneration process of the disease.

Solubilization of collagen-tailed acetylcholinesterase from chick retina: effect of different extraction procedures

We have extracted acetylcholinesterase from young chick retinas by homogenization in different solutions combining high salt concentration, ionic and nonionic detergents, and EDTA, looking for an optimum procedure for the solubilization of collagen-tailed, asymmetric structural forms of the enzyme. High salt and EDTA seem to be the only necessary requirements for the solubilization of acetylcholinesterase as the A12 form (20S), and the presence of detergent in the homogenization medium does not significantly improve the yield of tailed enzyme. Extraction in the absence of detergent has the potential advantage of a threefold enrichment of tailed enzyme, because only about one-third of the total retinal acetylcholinesterase activity is solubilized. Divalent cations, especially Ca2+, seem to be involved in the attachment of the tailed enzyme to the retinal membranes, at the tail level. High salt-EDTA-extracted 20S acetylcholinesterase (without detergent) aggregates in the presence of exogenous Ca2+ and becomes "insoluble." However, the aggregated 20S acetylcholinesterase can be completely recovered and brought back into solution by further addition of EDTA. Besides, the aggregation can be prevented by the inclusion of Triton X-100 in the homogenization buffer or by adding the detergent concurrently with Ca2+. It is postulated that the acetylcholinesterase collagenous tail is coated by acidic lipid molecules hydrophobically bound to the tail protein so that Ca2+ ionic bridges would actually link these lipid molecules (and consequently the tail) to the membrane matrix. Removal of the lipid coat (e.g., by Triton X-100) produces tailed acetylcholinesterase molecules that no longer aggregate in the presence of Ca2+ and are fully accessible to collagenase digestion.

Properties of 16S acetylcholinesterase from rat motor nerve skeletal muscle

Rat obturator nerve 16S acetylcholinesterase (16S AChE) was separated by sucrose gradient velocity sedimentation and compared to the 16S form of AChE similarly derived from endplate regions of anterior gracilis muscles. The 16S AChE from both tissues could only be extracted in high ionic strength buffer; as it aggregated under low ionic strength conditions. Treatment of nerve and muscle 16S AChE with purified collagenase, in the presence of calcium, caused an identical "shift" in the enzyme's sedimentation coefficient to 17.5S. Other properties which were also equivalent for 16S AChE from both tissue sources included: an excess substrate inhibition above 2 x 10(-3) M acetylcholine and Km of 1.6 x 10(-4) M, relative sensitivity to the specific inhibitors BW284C51 (I50 of 5 x 10(-8) M) and Iso-OMPA (I50 of 5 x 10(-4) M), and a half maximal thermal inactivation at 62.5 degrees C. These and additional results indicate that the 16S forms of AChE in both tissues are analogous molecules, which have a highly asymmetric conformation probably containing a collagen-like domain. The present findings are also consistent with the view that motor neurons provide at least a fraction of the 16S AChE present at the neuromuscular junction.

Acetylcholinesterase aggregates in a newly formed motor nerve-smooth muscle junction

We have studied the changes in acetylcholinesterase (AChE) molecular forms during cross-innervation of the inferior smooth muscle of the cat nictitating membrane by the hypoglossal nerve. One month after functional cross-innervation AChE activity increases by two-fold above control values, and a new high molecular weight AChE form (A12) is detected, BW284c51, an anti-AChE, potentiates the contraction of the cross-innervated smooth muscle. Three months later, AChE activity has raised six-fold above normal values. At this time, half of the activity sediments to the bottom of the sucrose gradient and a time-dependent dissociation occurs in lighter AchE forms, reminiscent of AChE aggregates observed in the electric eel. We discuss the possibility that the multimolecular aggregates are involved in the immobilizatin of AChE at the neuromuscular junction of a motor nerve and a smooth muscle.