G4 Acetylcholinesterase Research Articles

Interacting with α7 nAChR is a new mechanism for AChE to enhance the inflammatory response in macrophages

Acetylcholine (ACh) regulates inflammation via α7 nicotinic acetylcholine receptor (α7 nAChR). Acetylcholinesterase (AChE), an enzyme hydrolyzing ACh, is expressed in immune cells suggesting non-classical function in inflammatory responses. Here, the expression of PRiMA-linked G4 AChE was identified on the surface of macrophages. In lipopolysaccharide-induced inflammatory processes, AChE was upregulated by the binding of NF-κB onto the ACHE promotor. Conversely, the overexpression of G4 AChE inhibited ACh-suppressed cytokine release and cell migration, which was in contrast to that of applied AChE inhibitors. AChEmt, a DNA construct without enzymatic activity, was adopted to identify the protein role of AChE in immune system. Overexpression of G4 AChEmt induced cell migration and inhibited ACh-suppressed cell migration. The co-localization of α7 nAChR and AChE was found in macrophages, suggesting the potential interaction of α7 nAChR and AChE. Besides, immunoprecipitation showed a close association of α7 nAChR and AChE protein in cell membrane. Hence, the novel function of AChE in macrophage by interacting with α7 nAChR was determined. Together with hydrolysis of ACh, AChE plays a direct role in the regulation of inflammatory response. As such, AChE could serve as a novel target to treat age-related diseases by anti-inflammatory responses.

Expression and Localization of PRiMA-Linked Globular Form Acetylcholinesterase in Vertebrate Neuromuscular Junctions

Acetylcholinesterase (AChE) is well known to process different molecular forms via the distinct interacting partners. Proline-rich membrane anchor (PRiMA)-linked tetrameric globular AChE (G4 AChE) is mainly found in the vertebrate brain; however, recent studies from our laboratory have suggested its existence at neuromuscular junctions (nmjs). Both muscle and motor neuron express AChE at the nmjs. In muscle, the expression of PRiMA-linked AChE is down-regulated during myogenic differentiation and by motor neuron innervation. As compared with muscle, spinal cord possessed higher total AChE activity and contained PRiMA-linked AChE forms. The spinal cord expression of this form increased during development. More importantly, PRiMA-linked G4 AChE identified as aggregates localized at nmjs. These findings suggest that the restricted localization of PRiMA-linked G4 AChE at the nmjs could be contributed by the pre-synaptic motor neuron and/or the post-synaptic muscle fiber.

Effects of huperzine A on acetylcholinesterase isoforms in vitro: comparison with tacrine, donepezil, rivastigmine and physostigmine

Five inhibitors of acetylcholinesterase, huperzine A, donepezil, tacrine, rivastigmine and physostigmine, were compared with regard to their effects on different molecular forms of acetylcholinesterase in cerebral cortex, hippocampus, and striatum from the rat brain. In general, huperzine A preferentially inhibited tetrameric acetylcholinesterase (G4 form), while tacrine and rivastigmine preferentially inhibited monomeric acetylcholinesterase (G1 form). Donepezil showed pronounced selectivity for G1 acetylcholinesterase in striatum and hippocampus, but not in cortex. Physostigmine showed no form-selectivity in any brain region. In cortex, the most potent inhibitors of G4 acetylcholinesterase were huperzine A ( K i 7×10 −9 M) and donepezil ( K i 4×10 −9 M). The potent inhibitors of cortical G1 acetylcholinesterase were donepezil ( K i 3.5×10 −9 M) and tacrine ( K i 2.3×10 −8 M). In hippocampus, huperzine A and physostigmine were the most potent inhibitors of G4 acetylcholinesterase, while donepezil and tacrine were most potent against G1 acetylcholinesterase. In striatum, huperzine A and donepezil were the most potent against G4 acetylcholinesterase, while again donepezil was the most potent against G1. Although the inhibition constants ( K i) of these acetylcholinesterase inhibitors differed significantly from region to region, the nature of the inhibition did not vary. These results suggest that the use of acetylcholinesterase inhibitors in treatment of Alzheimer's disease must consider both form-specific and region-specific characteristics of acetylcholinesterase inhibition.

Developmental regulation of mouse brain monomeric acetylcholinesterase

Acetylcholinesterase (AChE) molecular forms were studied during mouse brain development. Mouse embryos expressed a monomeric (G1) and a tetrameric (G4) AChE form. Our results indicate that G4 AChE expressed at embryonic day (ED) 9 and ED15 could be purified by acridinium-Sepharose chromatography and shared similar biochemical and kinetic properties with the adult form. However, the G1 form expressed at either embryonic stage did not bind to acridinium, was not inhibited by excess substrate, and possessed higher Km and lower Vmax values than the adult G1 form. Two peripheral anionic binding site inhibitors, fasciculin and propidium, had a significantly lower affinity for the monomeric form at ED9. Results are discussed in terms of the biological significance of the embryonic G1 form, and its resemblance to the AChE activity found, associated with the senile plaques present in the brains of Alzheimerfn2fn2s disease ; FAS : fasciculin ; EDTA : ethylenediaminetetraacetic acid ; TRIS : Tris[hydroxymethyl]aminomethane ; iso-OMPA : tetraisopropyl pyrophosphoramide ; BSA : bovine serum albumin ; PBS : phosphate-buffered saline ; CNS : central nervous system.s patients.

Non‐cholinergic, trophic action of recombinant acetylcholinesterase on mid‐brain dopaminergic neurons

Acetylcholinesterase (AChE) is secreted from various brain regions such as the substantia nigra, where levels of this molecule are disproportionately higher than those of choline acetyltransferase. It is thus possible that AChE may have alternative, non-cholinergic functions, one of which could be in development. Indeed, several recent studies have already demonstrated a neurotrophic action of AChE independent of hydrolysis of acetylcholine. In the developing nervous system the dominant forms of AChE differ from the tetramers (G4) that prevail in maturity, in that they are lower molecular weight monomers (G1) and dimers (G2). Therefore, the aims of this study were to explore the neurotrophic role of AChE by comparing the effects of mouse recombinant G1 and G4 AChE on the survival and development of midbrain tyrosine hydroxylase immunoreactive neurons. Butyrylcholinesterase (BuChE), which also hydrolyses acetylcholine, and basic fibroblast growth factor (bFGF), an established trophic factor for midbrain neurons, were also tested. bFGF had no significant stimulatory effect: moreover, BuChE was also inefficacious, suggesting that the action of AChE was independent of its catalytic site. In contrast, mouse recombinant G1 and G4 AChE both increased the survival as well as the outgrowth of the cultured neurons. However, G1 AChE was more potent than G4 AChE suggesting that developmental forms of AChE exist. The implications of this finding for physiological and pathological functioning of the nervous system are discussed. J. Neurosci. Res. 49:207–218, 1997. © 1997 Wiley-Liss, Inc.

Non-cholinergic, trophic action of recombinant acetylcholinesterase on mid-brain dopaminergic neurons

Acetylcholinesterase (AChE) is secreted from various brain regions such as the substantia nigra, where levels of this molecule are disproportionately higher than those of choline acetyltransferase. It is thus possible that AChE may have alternative, non-cholinergic functions, one of which could be in development. Indeed, several recent studies have already demonstrated a neurotrophic action of AChE independent of hydrolysis of acetylcholine. In the developing nervous system the dominant forms of AChE differ from the tetramers (G4) that prevail in maturity, in that they are lower molecular weight monomers (G1) and dimers (G2). Therefore, the aims of this study were to explore the neurotrophic role of AChE by comparing the effects of mouse recombinant G1 and G4 AChE on the survival and development of mid-brain tyrosine hydroxylase immunoreactive neurons. Butyrylcholinesterase (BuChE), which also hydrolyses acetylcholine, and basic fibroblast growth factor (bFGF), an established trophic factor for midbrain neurons, were also tested. bFGF had no significant stimulatory effect: moreover, BuChE was also inefficacious, suggesting that the action of AChE was independent of its catalytic site. In contrast, mouse recombinant G1 and G4 AChE both increased the survival as well as the outgrowth of the cultured neurons. However, G1 AChE was more potent than G4 AChE suggesting that developmental forms of AChE exist. The implications of this finding for physiological and pathological functioning of the nervous system are discussed.

Tetrameric (G4) Acetylcholinesterase: Structure, Localization, and Physiological Regulation

Acetylcholinesterase (AChE), a highly conserved enzyme in the animal kingdom, is distributed throughout a wide range of vertebrate tissues where it is expressed as multiple molecular forms comprising different arrangements of catalytic and structural subunits. The major AChE form in the CNS is an amphiphilic globular tetramer (G4 AChE) consisting of four identical catalytic subunits attached to cellular membranes by a hydrophobic noncatalytic subunit (P-subunit). This study focuses primarily on current data involving the structure of the G4 AChE P-subunit, the expression and regulation of G4 AChE during development and adulthood, and its role(s) in certain neurological disorders including Alzheimer's disease.

Molecular forms of acetyl- and butyrylcholinesterase in normal and dystrophic mouse brain.

In searching for possible differences in the composition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) forms in dystrophic brain, the distribution of various enzyme molecules in normal (NB) and dystrophic (DB) 129B6F1/J mouse brain has been investigated. The tissue was sequentially extracted with saline (S1) and with saline-Triton X-100 buffers (S2) to release soluble and membrane-bound cholinesterases. About 15% of the AChE and 35% of the BuChE activities in NB were recovered in S1, and the rest in S2. G4, G2, and G1 AChE and BuChE forms were identified in the soluble fractions obtained from NB and DB. The shift in sedimentation values of the separated AChE and BuChE species in sucrose gradients made with and without detergents revealed the occurrence of hydrophilic (H) and amphiphilic (A) variants of cholinesterases in the extracts. The amphiphilic properties of the several AChE and BuChE molecules were analyzed by Triton X-114 phase-partitioning and by phenyl-agarose chromatography. A12 (1%), G4A (72%), G4H (8%), and G2A + G1A (19%) AChE molecules, and G4A (34%), G4H (19%), and G2A + G1A (47%) BuChE forms, were identified in NB. The G4A AChE and BuChE isoforms differed in their interaction with Triton X-114 and with a hydrophobic matrix. Neither the extent of cholinesterase solubilization, nor the distribution of individual enzyme forms, was significantly altered in DB. The lack of specific differences in the distribution of AChE and BuChE forms between NB and DB suggests that the biosynthetic pathway leading to the various enzyme forms is altered in muscle but not in dystrophic mouse brain.

Acetyl- and butyrylcholinesterase activities in the rat retina and retinal pigment epithelium.

The acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities in the neural retina and retinal pigment epithelium (RPE) of adult rats were determined. The tissues were extracted with a saline buffer to release the soluble enzymes (S1) and the pellet re-extracted with Triton X-100 to detach the membrane-bound enzymes (S2). Less than 5% of the cholinesterase activity measured in retina and almost 30% of that assayed in RPE was due to BChE. About 20% and 10% of the AChE in retina and RPE was brought into solution with a saline buffer and the rest with a detergent-containing buffer. Main AChE molecular forms of 10.5S (hydrophilic G4H), 9.5S (amphiphilic G4A) and 3.0S (amphiphilic G1A) were identified in retina by subjecting the supernatant S1 to sedimentation analysis in sucrose gradients made with Brij 96. Amphiphilic G4 and G1 AChE were found in S2. Analysis of the soluble fractions obtained from RPE in the gradients made with Brij 96 revealed 16.0S (asymmetric A12), 10.5-10.0S (globular G4H + G4A), 4.5S (G2A), and 3.0S (G1A) AChE forms in S1, whereas G4A, G2A, and G1A enzyme molecules predominated in S2. Our results show that amphiphilic tetramers and monomers of AChE are abundant in neural retina, and enzyme tetramers, dimers, and monomers in RPE. The AChE in the neural retina might be involved in cholinergic actions. The enzyme function in the retinal pigment epithelium remains to be established.

A role for calcitonin gene-related peptide in the regulation of rat skeletal muscle G 4 acetylcholinesterase

Calcitonin gene-related peptide (CGRP) acts as an anterograde trophic agent which regulates skeletal muscle acetylcholine receptor function. We examined whether CGRP also influences other synaptic transmission-related molecules, i.e. acetylcholinesterase (AChE) forms. Results show that: (a) CGRP associated with rat anterior gracilis muscle endplates declines following obturator nerve transection; (b) exogenous CGRP treatment has a selective, innervation-like effect on the globular tetramer (G4) of AChE in gracilis motor endplates; and (c) this effect is reversed by the CGRP receptor antagonist hCGRP8-37. We conclude that exogenous CGRP, and/or a biologically active CGRP fragment(s), influences G4 AChE levels through specific CGRP-CGRP receptor interactions. This conclusion is consistent with the notion that motor nerve-derived CGRP participates in the trophic control of G4 AChE at the neuromuscular junction.

Amphiphilic properties of molecular forms of acetylcholinesterase in normal and dystrophic muscle.

Acetylcholinesterase (AChE) molecular forms were studied in normal (NM) and in dystrophic (DM) 129B6F1/J mouse muscle. Successive extractions of the tissue with saline and saline-Triton X-100 buffers yielded two soluble fractions, S1 and S2. Forty percent of the AChE in NM was measured in S1 and 60% in S2, and 65% and 35%, respectively, in extracts from DM. A12, A8, G4, G2, and G1 forms of AChE were found in S1 and S2 from NM and DM. A similar content of asymmetric molecules was noticed between NM and DM. G4 AChE was a minor species in DM, and G1 and G2 AChE were more abundant in DM than in NM. The amphiphilic properties of the several molecules were assessed by Triton X-114 phase-partitioning and hydrophobic chromatography. Thirty and 70% of the enzyme in a mixture of S1 and S2 partitioned in the detergent-rich and in the detergent-poor phases, respectively, whether the extracts were obtained from NM or DM. Asymmetric and G4 AChE predominated in the aqueous phase and G1 and G2 in the detergent phase. Ten and 25% of the enzyme in S1 from NM or DM, respectively, was adsorbed to the phenyl-agarose. Elution of the retained enzyme followed by sedimentation analysis revealed that a certain amount of asymmetric and most of the G1 and G2 forms were associated with the matrix. The content of amphiphilic asymmetric and light globular forms was notably higher in DM than in NM. The results suggest that dystrophic muscle produces a specific pattern of molecular forms of AChE.

Expression of dimeric and tetrameric acetylcholinesterase isoforms on the surface of cultured bovine adrenal chromaffin cells

Acetylcholinesterase is a highly polymorphic enzyme, which can be anchored to the cell surface through several different mechanisms. Dimeric (G2) acetylcholinesterase isoforms are attached by a glycosyl-phosphatidyl-inositol (GPI) linkage, whereas tetrameric (G4) forms are linked through a 20 kilodalton hydrophobic subunit. Although cells of haemopoietic origin contain large amounts of G2 GPI-linked acetylcholinesterase, most tissues express only trace amounts of this isoform. We examined the expression of acetylcholinesterase isoforms in cultured bovine adrenal medullary chromaffin cells. Two major isoforms (G2 and G4) were identified on the cell surface. The G2 isoform, which accounted for approximately half the cell-surface enzyme activity, was linked to the membrane through a GPI anchor. After treatment with diisopropylfluorophosphate to completely inhibit cellular acetylcholinesterase, the G4 isoform was found to be resynthesised and transported to the cell surface more rapidly than the G2 isoform. As the addition of GPI anchors is known to be a very rapid step, this finding suggested that the G2 and G4 isoforms might be transported to the cell surface by two different mechanisms. This conclusion was supported by results from subcellular fractionation experiments. The ratio of G4/G2 membrane-bound acetylcholinesterase varied between different subcellular fractions. The membrane-bound G2 isoform was greatly enriched in a high-speed "microsomal" fraction. G4 acetylcholinesterase is known to be actively secreted by chromaffin cells in culture. Although the G4 isoform was present on the cell surface, most of the secreted enzyme was derived from an intracellular pool. Thus, it is unlikely that the cell-surface G4 isoform contributes significantly to the pool of secreted enzyme. Instead, the expression of two different membrane-bound isoforms may provide a means by which chromaffin cells can target the enzyme to different locations on the cell surface.

Acetylcholinesterase adaptation to voluntary wheel running is proportional to the volume of activity in fast, but not slow, rat hindlimb muscles.

Chronic enhancement of neuromuscular activity by forced exercise training programmes results in selective adaptation of the G4 acetylcholinesterase (AChE) molecular form in hindlimb fast muscles of the rat, with only minor and non-selective AChE changes in the soleus. In order to shed further light on the physiological significance of this G4 adaptation to training, we turned to a voluntary exercise model. The impact of 5 days and 4 weeks of voluntary wheel cage running on AChE molecular forms was examined in four hindlimb fast muscles and the slow-twitch soleus from two rat strains. Inbred Fisher and Sprague-Dawley rats, placed in live-in wheel cages, exercised spontaneously for distances which progressively increased up to an average of approximately 3 and 18 km/day, respectively, by the end of week 4. Fast muscles responded to this voluntary activity by massive G4 increases (up to 420%) with almost no changes in A12, so that by week 4 the tetramer became the main AChE component of these muscles. The additional G4 was composed primarily of amphiphilic molecules, suggesting a membrane-bound state. The G4 content of fast muscles was highly correlated with the distance covered by the rats during the 5 days before they were killed (r = 0.850-0.879, P < 0.001 in three muscles). The soleus muscle, in turn, responded to wheel cage activity by a marked selective reduction of its asymmetric forms--up to 45% for A12. This A12 decline, already maximal by day 5 of wheel cage running, showed no relationship with the distance covered.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of denervation on the molecular forms of junctional and extrajunctional acetylcholinesterase in fast and slow muscles of the rat.

Acetylcholinesterase (AChE) molecular forms in denervated rat muscles, as revealed by velocity sedimentation in sucrose gradients, were examined from three aspects: possible differences between fast and slow muscles, response of junctional vs extrajunctional AChE, and early vs late effects of denervation. In the junctional region, the response of the asymmetric AChE forms to denervation is similar in fast extensor digitorum longus (EDL) and slow soleus (SOL) muscle: (a) specific activity of the A12 form decreases rapidly but some persists throughout and even increases after a few weeks; (b) an early and transient increase of the A4 AChE form lasting for a few weeks may be due to a block in the synthetic process of the A12 form. In the extrajunctional regions, major differences with regard to AChE regulation exist already between the normal EDL and SOL muscle. The extrajunctional asymmetric AChE forms are absent in the EDL because they became completely repressed during the first month after birth, but they persist in the SOL. Differences remain also after denervation and are, therefore, not directly due to different neural stimulation patterns in both muscles: (a) an early but transient increase of the G4 AChE occurs in the denervated EDL but not in the SOL; (b) no significant extrajunctional activity of the asymmetric AChE forms reappears in the EDL up till 7 wk after denervation. In the SOL, activity of the asymmetric AChE forms is decreased early after denervation but increases thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Trophic regulation of acetylcholinesterase isoenzymes in adult mammalian skeletal muscles

This work addresses the physiological regulation of skeletal muscle acetylcholinesterase (AChE) isoforms by examining endplate-enriched samples from adult rat gracilis muscles 48 h after: low-intensity treadmill exercise; obturator nerve transection; nerve impulse conduction blockade by tetrodotoxin; acetylcholine (ACh) receptor (AChR) inactivation by alpha-bungarotoxin; and, addition of obturator nerve extracts to muscles in organ culture. Results document the important role(s) of functional AChRs and ACh-AChR interactions in the differential control of individual AChE isoenzymes. A theoretical model based on these and other findings considers that: AChR activation by spontaneously released ACh is the only neural factor required for the maintenance of G1 + G2 AChE; the amount of A12 AChE is determined by the combined effects of ACh and another neurogenic substance; although mechanisms intrinsic to myofibers control normal levels of G4 AChE, enhanced production of this isoform is initiated through increasing the frequency of ACh-AChR interactions.

Plasma and Serum G4 Isoenzyme of Acetylcholinesterase in Patients with Alzheimer-Type Dementia and Vascular Dementia

We developed a new assay for plasma or serum G4 acetylcholinesterase (AChE) activity. There was no difference in G4 AChE activity between serum and plasma. Plasma AChE activity in control subjects (8-92 years) was independent of age. Serum G4 AChE activity was significantly increased in patients with vascular dementia (P less than 0.01), compared with age-matched control, and significantly decreased in those with probable Alzheimer-type dementia (P less than 0.02). The difference between VD and ATD was significant (P less than 0.001), and thus the measurement of plasma or serum G4 AChE activity would be helpful in the differential diagnosis of dementia.

Regulation by exercise of the pool of G4 acetylcholinesterase characterizing fast muscles: opposite effect of running training in antagonist muscles

Fast muscles of rodents characteristically differ from their slow-twitch counterparts by exhibiting high levels of G4, i.e., the tetrameric acetylcholinesterase (AChE) molecular form. Converging evidence suggests that this additional G4 pool is specifically regulated by the type of activity actually performed by the muscle. This hypothesis was tested by studying the effect of a chronic increase in neuromuscular activity on the AChE content and distribution of molecular forms of functionally antagonist rat hindlimb muscles. They included the fast ankle extensors gastrocnemius (GAST) and plantaris (PL), the fast ankle flexors tibialis anterior (TA) and extensor digitorum longus (EDL), as well as the slow-twitch soleus (SOL). Neuromuscular activity was enhanced by subjecting the rats to a 12-week training program consisting of repeated sessions of prolonged endurance running on a rodent treadmill. This exercise regimen preferentially affected the G4 pool characterizing fast muscles which exhibited marked and opposite changes according to the functional role of the muscles. The amount of G4 was increased by more than 50% in the ankle extensors GAST and PL, which play a dynamic role, and reduced by about 40% in the ankle flexors TA and EDL, which exhibit a predominant tonic activity during running. The asymmetric forms A12 and A8 were slightly elevated in the fast muscles. In the case of the slow-twitch SOL, running training resulted in a small, nonspecific decrease in AChE content which affected most of the molecular forms. These data indicate that the size of the G4 pool characteristic of fast muscles depends on the type, dynamic or tonic, of activity actually performed. The present results support the conclusion that this G4 pool fulfills a specific and essential function, distinct from that of A12.

Molecular forms of acetylcholinesterase in subcortical areas of normal and Alzheimer disease brain

We have previously reported that the 10s molecular form (G4) of acetylcholinesterase (AChE) is selectively lost from several cortical areas of Alzheimer's disease (AD) brain. In the current follow-up study, we microdissected several areas of nondemented and AD brain, including the hippocampus, amygdala, and cingulate gyrus. Tissue homogenates were separated on sucrose density gradients and the resulting fractions were analyzed for AChE activity in order to define the ratios of the predominant AChE molecular forms (G4/G1). Both the hippocampus and amygdala exhibited distinct patterns of alterations in the G4/G1 ratio which correlate with the known distribution of histopathological changes in AD brain. In order to further define the major pool of AChE that is depleted in AD, we separated fractionated tissue homogenates into salt-soluble and detergent-soluble fractions. The G4/G1 ratios were only altered in the detergent-soluble fractions, indicating that the loss of the G4 AChE molecular form involves a selective depletion of the membrane pool. Available evidence would suggest that this form is the AChE molecular form physiologically relevant at the cholinergic synapse.

Coated vesicles from developing and adult rat skeletal muscles contain multiple molecular forms of acetylcholinesterase

The main purpose of this work was to determine which of the multiple isoforms of acetylcholinesterase (AChE) are associated with clathrin-coated vesicles (CVs) from developing and adult rat skeletal muscles. CV-enriched preparations were obtained by subcellular fractionation/equilibrium sedimentation and further purified by immunoadsorption to anti-clathrin IgG-coated Staphylococcus aureus cells. Analysis of individual AChE isoforms by velocity sedimentation ultracentrifugation showed that a) while both globular (G-forms) and asymmetric (A-forms) AChE were detected in all subcellular fractions evaluated, the CV-enriched fraction contained a higher proportion of A-forms (mainly the A12 species); b) most of the AChE activity contained in such a CV fraction was recovered following immunoadsorption; c) alkaline extraction conditions (pH 8.5) which depolymerize clathrin were necessary to detect a large proportion of A-forms in both the CV-enriched and immunoprecipitated preparations, while most of the G-forms (especially G1 + G2 AChE) were detected following extraction at pH 6.8; and d) comparison of AChE isoform profiles from neonate and adult muscle CV-enriched fractions showed a greater concentration of A-forms in the former. These data suggest that considerable amounts of A12 and, to a lesser extent, G4 AChE are sequestered within muscle CVs which may be destined for the plasmalemma. Our findings also indicate that the relative proportions of AChE isoenzymes in rat muscle CVs vary according to the extent of muscle development and lend support to the contention that CVs participate in the externalization of functionally important AChE isoenzymes.

Regional distribution of the molecular forms of acetylcholinesterase in adult rat heart.

Acetylcholinesterase (AChE), the enzyme that degrades acetylcholine, exists as a multiple molecular forms that differ in their quaternary structure and mode of attachment to the cell surface. The distribution of the individual molecular forms of AChE in various cardiac regions with distinct anatomical characteristics was investigated. The results confirmed those of others by showing that the total pool of cardiac AChE had a nonuniform distribution in heart that paralleled the distribution of choline acetyltransferase. The rank order of this distribution was right atrial appendage greater than interatrial septum greater than left atrial appendage = right ventricle = interventricular septum greater than left ventricle. Velocity sedimentation in sucrose gradients of extracts from selected cardiac areas showed that four molecular forms were present in all areas but that the proportions of these forms differed as a function of area. The right and left ventricular walls, the apical portion of the interventricular septum, and the left atrial appendage contained G1 and G4 (globular) AChE in near-equal proportions, but in the basal portion of interventricular septum, the contribution of G4 AChE was greater than that of G1 AChE. The right atrial appendage and the interatrial septum had the largest amount of activity attributable to G4 AChE and the lowest amount attributable to G1 AChE. In all cardiac regions, A12 (asymmetric) AChE comprised 8-10% of the total AChE pool.(ABSTRACT TRUNCATED AT 250 WORDS)