Regulation of cholinesterase gene expression affects neuronal differentiation as revealed by transfection studies on reaggregating embryonic chicken retinal cells

Butyrylcholinesterase and Acetylcholinesterase polymorphisms in Multiple Sclerosis patients: implication in peripheral inflammation

Multiple Sclerosis (MS) is an autoimmune disease, having not fully understood aetiology, and both genetic and environmental factors contribute to the pathogenesis of the disease. The cholinergic system has been indicated as a mediator of neuro-immune interactions, as well as an internal regulator of immune responses. The aim of the present research was to assess the associations between BChE and AChE genetic variations and serum cholinergic and inflammatory profiles in 102 Relapsing Remitting-MS patients and 117 healthy controls. An increased frequency of the BChE K-allele in MS patients as compared to controls was found. In addition, data showed that patients had higher BChE enzymatic activity, which is increased by the presence of the polymorphic allele and reduced amounts of circulating ACh. AChE polymorphism was significantly associated to reduced activity in both patients and controls. We propose that serum BChE and AChE activity may be used as a secondary markers to assess the role of non-neuronal cholinergic system in regulating peripheral inflammation via ACh regulation. This pilot study shed light on the role of the non-neuronal cholinergic system in immune cells to better understand MS pathogenesis. The cross-talk between the periphery and the CNS could have a new undescribed crucial role for MS, regarded as a systemic disease.

Cholinesterase and paraoxonase (PON1) enzyme activities in Mexican-American mothers and children from an agricultural community

Exposure to organophosphate and carbamate pesticides can lead to neurotoxic effects through inhibition of cholinesterase enzymes. The paraoxonase (PON1) enzyme can detoxify oxon derivatives of some organophosphates. Lower PON1, acetylcholinesterase, and butyrylcholinesterase activities have been reported in newborns relative to adults, suggesting increased susceptibility to organophosphate exposure in young children. We determined PON1, acetylcholinesterase, and butyrylcholinesterase activities in Mexican-American mothers and their 9-year-old children (n=202 pairs) living in an agricultural community. We used Wilcoxon signed-rank tests to compare enzymatic activities among mothers and their children, and analysis of variance to identify factors associated with enzyme activities. Substrate-specific PON1 activities were slightly lower in children than their mothers; however, these differences were only statistically significant for the paraoxon substrate. We observed significantly lower acetylcholinesterase but higher butyrylcholinesterase levels in children compared with their mothers. Mean butyrylcholinesterase levels were strongly associated with child obesity status (body mass index Z scores >95%). We observed highly significant correlations among mother-child pairs for each of the enzymatic activities analyzed; however, PON1 activities did not correlate with acetylcholinesterase or butyrylcholinesterase activities. Our findings suggest that by age 9 years, PON1 activities approach adult levels, and host factors including sex and obesity may affect key enzymes involved in pesticide metabolism.

Cholinesterases in development: AChE as a firewall to inhibit cell proliferation and support differentiation

Acetylcholinesterase (AChE) is a most remarkable protein, not only because it is one of the fastest enzymes in nature, but also since it appears in many molecular forms and is regulated by elaborate genetic networks. AChE is expressed in many tissues during development and in mature organisms, as well as in healthy and diseased states. In search for alternative, "non-classical" functions of cholinesterases (ChEs), AChE could either work within the frame of classic cholinergic systems, but in non-neural tissues ("non-synaptic function"), or act non-enzymatically. Here, we review briefly some of the major ideas and advances of this field, and report on some recent progress from our own experimental work, e.g. that (i) non-neural ChEs have pronounced, predominantly enzymatic effects on early embryonic (limb) development in chick and mouse, that (ii) retinal R28 cells of the rat overexpressing synaptic AChE present a significantly decreased cell proliferation, and that (iii) in developing chick retina ACh-synthesizing and ACh-degrading cells originate from the same postmitotic precursor cells, which later form two locally opposing cell populations. We suggest that such distinct distributions of ChAT(+) vs. AChE(+) cells in the inner half retina provide graded distributions of ACh, which can direct cell differentiation and network formation. Thus, as corroborated by works from many labs, AChE can be considered a highly co-opting protein, which can combine enzymatic and non-enzymatic functions within one molecule.

Iron exposure modifies acetylcholinesterase activity in zebrafish (Danio rerio) tissues: distinct susceptibility of tissues to iron overload

Iron is one the most abundant metals on the earth being essential for living organisms even though its free form can be toxic. The overload of this metal may be related with some disorders, like Alzheimer and Parkinson diseases, and hemochromatosis in the liver. The aim of the present study was to evaluate the effects of iron on acetylcholinesterase (AChE) activity in brain and liver of zebrafish and to investigate the possible correlation with the iron content in these tissues. Different corresponding concentrations of iron were tested using in vitro (0.018, 0.268, and 2.6 mM) and in vivo (1, 15, and 150 mg/l) assays. The in vitro studies showed that iron promoted a significant increase in AChE activity in brain (52%) and liver (53%) at the higher concentration (2.6 mM). In the in vivo assays, a significant increase in this enzyme activity was observed in the presence of 15 mg/l in both, brain (62%) and liver tissue (70%). Semiquantitative RT-PCR did not reveal significant changes in acetylthiocholinesterase mRNA levels. Moreover, we observed that iron content was significantly increased in liver tissue when exposed to 15 (226%) and 150 mg/l (200%). These results indicate that iron can promote significant alterations in AChE activity which probably is not directly related to the iron content in zebrafish tissues.

Counter-regulation of cholinesterases: differential activation of PKC and ERK signaling in retinal cells through BChE knockdown

The ubiquitous cholinesterase (ChE) enzymes, functioning in the termination of acetylcholine mediated neural transmission, are also reported to have additional functions. Through application of siRNAs against butyrylcholinesterase (BChE) in R28 cells, a retinal cell line with pluripotent properties, a counter-regulation between ChEs was revealed. BChE knock down resulted in an up-regulation of not only acetylcholinesterase (AChE), but also altered the signaling status of PKC and ERK. Knockdown of BChE modified ERK signaling most notably through ERK1/2 proteins, together with the transcription activator P90RSK1 and c-fos. Stimulation of the R28 cell line by forskolin revealed that ChEs are involved in an intricate cross talk between different signaling pathways. Forskolin-stimulated R28 cells displayed a robust cholinergic response, as detected by both electrophysiology and ChE expression, and changed the activation status of PKC/ERK signaling pathways. The findings in R28 cells show that ChE expressions are inversely co-regulated and act through the transcription factors c-fos and P90RSK1. Since R28 cells have the capacity to differentiate into different cell types through stimulation of signaling pathways, ChEs are likely to be associated with cell fate determination, rather than just terminating cholinergic responses.

Presenilin 1 interacts with acetylcholinesterase and alters its enzymatic activity and glycosylation

Presenilin 1 (PS1) plays a critical role in the gamma-secretase processing of the amyloid precursor protein to generate the beta-amyloid peptide, which accumulates in plaques in the pathogenesis of Alzheimer's disease (AD). Mutations in PS1 cause early onset AD, and proteins that interact with PS1 are of major functional importance. We report here the coimmunoprecipitation of PS1 and acetylcholinesterase (AChE), an enzyme associated with amyloid plaques. Binding occurs through PS1 N-terminal fragment independent of the peripheral binding site of AChE. Subcellular colocalization of PS1 and AChE in cultured cells and coexpression patterns of PS1 and AChE in brain sections from controls and subjects with sporadic or familial AD indicated that PS1 and AChE are located in the same intracellular compartments, including the perinuclear compartments. A PS1-A246E pathogenic mutation expressed in transgenic mice leads to decreased AChE activity and alteration of AChE glycosylation and the peripheral binding site, which may reflect a shift in protein conformation and disturbed AChE maturation. In both the transgenic mice and humans, mutant PS1 impairs coimmunoprecipitation with AChE. The results indicate that PS1 can interact with AChE and influence its expression, supporting the notion of cholinergic-amyloid interrelationships.

Acetylcholinesterase in cell adhesion, neurite growth and network formation

The expression of acetylcholinesterase is not restricted to cholinergically innervated tissues and relates to both neurotransmission and multiple biological aspects, including neural development, stress response and neurodegenerative diseases. Therefore, the classical function of acetylcholinesterase has to be distinguished from its non-classical, e.g. enzymatic from non-enzymatic, functions. Here, the roles of acetylcholinesterase in cell adhesion, promoting neurite outgrowth and neural network formation are reviewed briefly, together with potential mechanisms to support these functions. Part of these functions may depend on the structural properties of acetylcholinesterase, for example, protein-protein interactions. Recent findings have revealed that laminin-1 is an interaction partner for acetylcholinesterase. The binding of acetylcholinesterase to this extracellular matrix component may allow cell-to-cell recognition, and also cell signalling via membrane receptors. Studies using monolayer and 3D spheroid retinal cultures, as well as the acetylcholinesterase-knockout mouse, have been instrumental in elaborating the non-classical functions of acetylcholinesterase.

Artificial design of three-dimensional retina-like tissue from dissociated cells of the mammalian retina by rotation-mediated cell aggregation

The goal of this study was to establish a reliable three-dimensional culture system for the mammalian retina that allows the analysis of retinal function and dysfunction. To produce three-dimensional retinal tissues in vitro, dissociated retinal cells of neonatal rats were maintained in culture dishes on a self-made orbital shaker. On the basis of well-defined rotation conditions, dissociated free-floating cells reaggregate in the center of the culture dish to form a multicellular cluster. Subsequently, cells begin to proliferate, whereby they form spherelike retinal tissues that grow to a size of 180-210 microm. Immunohistochemical characterization of mature retinal spheres revealed the presence of ganglion cells, amacrine cells, Müller cells, and rod photoreceptors, which are arranged in different retina-like layers. Although a small number of cells undergo programmed cell death, retinal spheres remain viable for at least 35 days in culture as revealed by fluorescein diacetate and TUNEL staining. Because most biological processes involved in tissue organization such as proliferation, differentiation, apoptosis, and survival are also observable in retinal spheres, the presented novel mammalian three-dimensional culture system is not only an outstanding model for basic research but may also be of great benefit for stem cell tissue engineering and the pharmaceutical industry.

Bioactivity of a peptide derived from acetylcholinesterase: involvement of an ivermectin-sensitive site on the alpha 7 nicotinic receptor

A peptide fragment of 14 amino acids, derived from the C-terminus of acetylcholinesterase (AChE), might underlie the now well-established noncholinergic effects of the enzyme. This peptide is bioactive in a variety of systems including acute (brain slices) and chronic (organotypic culture) preparations of hippocampus, a pivotal area in Alzheimer's disease (AD); invariably, the action of the peptide is mediated specifically via an as yet unknown receptor. In this study, the allosteric alpha 7 agent, ivermectin (IVM), had a modest inhibitory effect, whilst that of the peptide was significantly more marked. However, ivermectin rendered ineffective the toxicity of high doses of the peptide, that is, when the two were co-applied, only the smaller effects of ivermectin were seen. Ivermectin, therefore, is presumably acting at a site that is identical to, or at least strongly interactive with, the normal binding site for AChE-peptide. This observation could have important implications for eventual therapeutic targeting of the action of AChE-peptide, in neurodegeneration.

Spontaneous Waves in the Ventricular Zone of Developing Mammalian Retina

Spontaneous rhythmic waves in the developing mammalian retina are thought to propagate among differentiated neurons in the inner retina (IR) and play an important role in activity-dependent visual development. Here we report a new form of rhythmic Ca2+wave in the ventricular zone (VZ) of the developing rabbit retina. Ca2+imaging from two-photon optical sections near the ventricular surface of the whole-mount retina showed rhythmic Ca2+transients propagating laterally as waves. The VZ waves had a distinctively slow Ca2+dynamics (lasting ∼20 s) but shared a similar frequency and propagation speed with the IR waves. Simultaneous Ca2+imaging in VZ and multi-electrode array recording in the ganglion cell layer (GCL) revealed close spatiotemporal correlation between spontaneous VZ and IR waves, suggesting a common source of initiation and/or regulation of the two waves. Pharmacological studies further showed that all drugs that blocked IR waves also blocked VZ waves. However, the muscarinic antagonist atropine selectively blocked VZ but not IR waves at this developmental stage, indicating that IR waves were not dependent on VZ waves, but VZ waves likely relied on the initiation of IR waves. Eliciting IR waves with puffs of nicotinic or non- N-methyl-d-aspartate agonists in GCL produced atropine-sensitive waves in the VZ, demonstrating a unique, retrograde signaling pathway from IR to VZ. Thus differentiated neurons in the IR use spontaneous, rhythmic waves to send both forward signals to the central visual targets and retrograde messages to the developing cells in the VZ.

Anticholinesterase treatment of chicken retinal cells increases acetylcholinesterase protein independently of protein kinase C

It has been reported that anticholinesterase exposure, e.g. by environmental toxins or nerve gases, can increase acetylcholinesterase (AChE) protein, possibly as an autoregulatory stress response. We earlier have transfected retinal cells of the chick embryo with a pSVK3-AChE(rab)-cDNA vector to heterologously express rabbit AChE, which concomitantly also increased AChE protein from chick. To analyse further the cell-internal pathways of these different paradigms (anticholinesterase treatment vs. AChE transfection) which both lead to an AChE increase, we here show that AChE overexpression by transfection leads to an increase in protein kinase C (PKC). Most remarkably, when cells independently of, or in addition to their transfection are treated with 10 microM of the AChE inhibitor BW284c51, AChE protein levels are much more dramatically increased up to 20-fold. This treatment, however, does not affect PKC. These data show that (i) retinal cells respond to anticholinesterase insult by a massive increase of AChE protein; (ii) the response to BW284c51 is not PKC-mediated; and (iii) both strategies of AChE increase follow different cell-internal pathways, their effects being additive. The ecological and biomedical implications of these findings are briefly discussed.

A multicellular spheroid-based sensor for anti-cancer therapeutics

The progress in cellular engineering offers novel approaches for anti-cancer therapies. To investigate the effectiveness of potential therapies efficient screening methods are required. We propose an impedance measurement system which enables the use of multicellular spheroid models in bioelectronic screening systems either for non destructive life-time diagnostic or anti-cancer therapies. A biohybrid sensor system is created comprising gene-manipulated T47D clone 11 breast carcinoma spheroids positioned hydrodynamically in a capillary system with electrodes. A novel approach employing an antisense-5'butyrylcholinesterase expression system is probed on reaggregated tumor cells under simulated microgravity, inhibiting the gene transcription and translation of the embryonic proliferation marker butyrylcholinesterase expressed in different tumor types. Alterations in the morphology of cell aggregates e.g. apoptosis or necrosis can be detected by impedance spectroscopy monitoring the electric behavior of membranes and extracellular space with a high resolution and reproducibility. The hydrodynamic positioning of 3D in vitro cell aggregates and the short time for the measurements represent an innovative method for a synchronized multicapillary screening system. The combination of the measuring system with a bioreactor enables cyclic life time recordings of impedance spectra for monitoring the cell aggregate properties for a long period.

Modulation of acetylcholinesterase and voltage-gated Na(+) channels in choline acetyltransferase- transfected neuroblastoma clones

Neurotransmitters appear early in the developing embryo and may play a role in the regulation of neuronal differentiation. To study potential effects of acetylcholine production in neuronal differentiation, we used the FB5 subclone of N18TG2 murine neuroblastoma cells stably transfected with cDNA for choline acetyltransferase. We tested whether the forced acetylcholine production can modify the expression or the cellular localization of different neuronal markers. We studied the activity, localization, and secretion of acetylcholinesterase in view of its possible role in the modulation of the morphogenetic action of acetylcholine and of its proposed role of a regulator of neurite outgrowth. FB5 cells are characterized by a high level of acetylcholinesterase, predominantly released into the culture medium. Acetylcholinesterase secretion into the medium was lower in choline acetyltransferase-transfected clones than in nontransfected and antisense-transfected controls. Moreover, sequential extraction of acetylcholinesterase revealed that detergent-extracted, i.e., membrane-associated, activity was higher in the transfected clones expressing choline acetyltransferase activity than in both control groups. These observations suggest that a shift occurs in the utilization of acetylcholinesterase in choline acetyltransferase-transfected clones from a secretion pathway to a pathway leading to membrane localization. In addition, the choline acetyltransferase-positive clones showed higher densities of voltage-gated Na(+) channels and enhanced high-affinity choline uptake, suggesting the accomplishment of a more advanced differentiated neuronal phenotype. Finally, binding experiments demonstrated the presence of muscarinic acetylcholine receptors in all examined clones. This observation is consistent with the proposed existence of an autocrine loop, which may be important for the enhancement in the expression of neurospecific traits.

Regulation of the rat oligodendroglia cell line OLN-93 by antisense transfection of butyrylcholinesterase

Butyrylcholinesterase (BChE) is a glial cell marker with unknown function. For neuroepithelial cells, BChE has been shown to regulate cell division and expression of the postmitotic marker acetylcholinesterase (AChE), while similar studies are lacking for glial cells. By transducing an antisense-5'BChE cDNA expression vector via calcium phosphate precipitation, we have analyzed the effect of BChE inhibition on proliferation and differentiation of rat oligodendroglia-derived OLN-93 cells. OLN-93 cells were chosen because they are highly proliferative, while expressing markers of differentiated oligodendrocytes (Richter-Landsberg and Heinrich, 1996). First, we established that OLN-93 cells do express BChE protein, albeit chiefly in an inactive state, and that BChE was decreased by antisense-5'BChE transfection. Cell proliferation was also strongly diminished, protein kinase C (PKCalpha) was upregulated, and expression of cytoskeletal and cell surface proteins was altered. In particular, immunoreactivities of the intermediate filament proteins vimentin and the cell adhesion protein F11 were detected, indicating that BChE-inhibited OLN-93 cells have shifted toward an astrocytic phenotype. These data support a role of the glia marker BChE in CNS glial cell proliferation and differentiation, achieved via a nonenzymatic mechanism. The possible biomedical impact of BChE protein, e.g., on CNS nerve regeneration, is briefly discussed.

Localization of choline acetyltransferase in the developing and adult turtle retinas

Acetylcholine has important epigenetic roles in the developing retina. In this study, cells that expressed choline acetyltransferase (ChAT), the enzyme that synthesizes acetylcholine, were investigated in embryonic, postnatal, and adult turtle retinas by using immunofluorescence histochemistry. ChAT was present at stage 15 (S15) in cells near the vitreal surface. With the formation of the inner plexiform layer (IPL) at S18, ChAT-immunoreactive (-IR) cells were located in the inner nuclear layer (INL) and the ganglion cell layer (GCL). In the INL, presumed starburst amacrine cells were homogenous in appearance and formed a single row next to the IPL: This pattern was conserved until adulthood. In the GCL, however, there were multiple rows of ChAT-IR cells early in development, and this high density of labeled cells continued during the embryonic stages, until around birth. The high density of ChAT-IR cells in the GCL was due in part to a population of cells that expressed ChAT transiently. In postnatal stages and adult retinas, the presumed starburst amacrine ChAT-IR cells formed two mirror-like rows of homogenous cells on both borders of the IPL. Two cholinergic dendritic strata that were continuous with these cells were observed as early as S18, and their depths in the IPL were relatively stable throughout development. A third population of ChAT-IR cells was observed toward the middle of the INL around S25 and persisted into adulthood. Finally, cells in the outer nuclear layer (ONL) were ChAT-IR during the embryonic stages, were less immunoreactive during the postnatal stages, and were not immunoreactive in the adult retinas.

Evidence for the direct role of acetylcholinesterase in neurite outgrowth in primary dorsal root ganglion neurons

Dorsal root ganglion (DRG) neurons show a transient peak expression of acetylcholinesterase (AChE) during periods of axonal outgrowth prior to synaptogenesis, suggesting that AChE has a non-enzymatic role during development. We have previously shown that perturbation of cell surface AChE in cultured embryonic rat DRG neurons results in decreased neurite outgrowth and neurite detachment. In this report, we demonstrate a direct correlation between endogenous AChE content and neurite outgrowth in primary DRG neurons. Adenoviral vectors were constructed using full-length rat AChE(T) cDNA in either the sense or antisense orientations to overexpress or knock down AChE expression, respectively. Treatment with the sense-expressing vector produced a 2.5-fold increase in AChE expression and a 2-fold increase in neurite length compared with either untreated or null virus-treated control cells. Conversely, treatment with the antisense-expressing vector reduced AChE expression by 40% and resulted in a reduction in neurite length of similar magnitude. We also observed that overexpression of AChE resulted in greater branching at the distal tips of each primary neurite as well as an increase in cell body size. These findings further indicate that AChE expressed on the axonal surface of developing DRG neurons may modulate their adhesive properties and thereby support axonal development.

Development of the visual system of the chick. I. Cell differentiation and histogenesis

This review summarizes present knowledge on the embryonic development of the avian visual projections, based on the domestic chick as a model system. The reductionist goal to understand formation and function of complex neuroanatomical systems on a causal level requires a synthesis of classic developmental biology with recent advances on the molecular mechanisms of cell differentiation and histogenesis. It is the purpose of this article. We are discussing the processes underlying patterning of the anterior neural tube, when the retina and optic tectum are specified and their axial polarity is determined. Then the development of these structures is described from the molecular to the anatomical level. Following sections deal with the establishment of secondary visual connections, and the developmental interactions between compartments of the retinotectal system. Using this latter pathway, from the retina to the optic tectum, many investigations aimed at mechanisms of axonal pathfinding and connectivity have accumulated a vast body of research, which will be covered by a following review.

The key role of butyrylcholinesterase during neurogenesis and neural disorders: an antisense-5'butyrylcholinesterase-DNA study

The wide tissue distribution of butyrylcholinesterase (BChE) in organisms makes specific roles possible, although no clear physiologic function has yet been assigned to this enzyme. In vertebrates, it appears e.g. in serum, hemopoietic cells, liver, lung, heart, at cholinergic synapses, in the central nervous system. in tumors and not at least (besides acetylcholinesterase, AChE) in developing embryonic tissues. Here, a functional role of BChE can be found in regulation of cell proliferation and the onset of differentiation during early neuronal development--independent of its enzymatic activity. For studies concerning this point, we have established a strategy for a specific and efficient inhibition of BChE to investigate how the expected decrease of enzyme and, therefore, the manipulation of cellular cholinesterase-equilibrium influences embryonic neurogenesis--among others to gain information about the significance of noncholinergic, activity-independent and cell growth functions of BChE. The antisense-5'BChE-DNA strategy is based on inhibition of BChE mRNA transcription and protein synthesis. For this, the BChE gene is cloned into a suitable vector system; this is done in antisense-orientation, so that a transfected cell will produce their own antisense mRNA to inhibit gene expression. For such investigations in neurogenesis, the developing retina is a good model and we are able to create organotypic, three-dimensional retinal aggregates in vitro (retinospheroids) using isolated retinal cells of 6-day-old chicken embryos. Using this in vitro retina and "knock out" of BChE gene expression, we could show a key role of BChE during neurogenesis. The results are of great interest because in tumorigenesis and some neuronal disorders, the BChE gene is amplified or abnormally expressed. It has to be discussed how the antisense-5'BChE strategy can play a role in the development of new and efficient therapy forms.

Activation of neurospecific gene expression by antennapedia homeobox peptide

Antennapedia homeobox peptide has been reported to enhance neurite outgrowth and branching. Thus it is of interest to investigate whether antennapedia peptide is capable of modulating the expression of genes related to different events of neuronal development. In this paper we report the enhancement of a 68 KDa neurofilament subunit, choline acetyltransferase and acetylcholinesterase expression in spinal cord neurons, elicited by antennapedia peptide. Modulation of gene expression is different with respect to each gene product analyzed, suggesting a specific action of the peptide on diverse genes controlling different events of neuronal differentiation.

Structural roles of acetylcholinesterase variants in biology and pathology

Apart from its catalytic function in hydrolyzing acetylcholine, acetylcholinesterase (AChE) affects cell proliferation, differentiation and responses to various insults, including stress. These responses are at least in part specific to the three C-terminal variants of AChE which are produced by alternative splicing of the single ACHE gene. 'Synaptic' AChE-S constitutes the principal multimeric enzyme in brain and muscle; soluble, monomeric 'readthrough' AChE-R appears in embryonic and tumor cells and is induced under psychological, chemical and physical stress; and glypiated dimers of erythrocytic AChE-E associate with red blood cell membranes. We postulate that the homology of AChE to the cell adhesion proteins, gliotactin, glutactin and the neurexins, which have more established functions in nervous system development, is the basis of its morphogenic functions. Competition between AChE variants and their homologs on interactions with the corresponding protein partners would inevitably modify cellular signaling. This can explain why AChE-S exerts process extension from cultured amphibian, avian and mammalian glia and neurons in a manner that is C-terminus-dependent, refractory to several active site inhibitors and, in certain cases, redundant to the function of AChE-like proteins. Structural functions of AChE variants can explain their proliferative and developmental roles in blood, bone, retinal and neuronal cells. Moreover, the association of AChE excess with amyloid plaques in the degenerating human brain and with progressive cognitive and neuromotor deficiencies observed in AChE-transgenic animal models most likely reflects the combined contributions of catalytic and structural roles.

Manipulations of ACHE gene expression suggest non-catalytic involvement of acetylcholinesterase in the functioning of mammalian photoreceptors but not in retinal degeneration

To explore role(s) of acetylcholinesterase (AChE) in functioning and diseased photoreceptors, we studied normal (rd/+) and degenerating (rd/rd) murine retinas. All retinal neurons, expressed AChEmRNA throughout fetal development. AChE and c-Fos mRNAs peaked at post-natal days 10-12, when apoptosis of rd/rd photoreceptors begins. Moreover, c-Fos and AChEmRNA were co-overexpressed in rd/rd mice producing transgenic human (h), and host (m) AChE, but not in rd/+ mice. However, mAChE overexpression also occurred in transgenics expressing human serum albumin. Drastic variations in AChE catalytic activity were ineffective during development. Neither transgenic excess nor diisopropylfluorophosphonate (DFP) inhibition (80%) affected the rd phenotype; nor did DFP exposure induce photoreceptor degeneration or affect other key cholinergic proteins in rd/+ mice, unlike reports of adult mice and despite massive induction under DFP of c-Fos70 years). Therefore, the extreme retinal sensitivity to AChE modulation may reflect non-catalytic function(s) of AChE in adult photoreceptors. These findings exclude AChE as causing the rd phenotype, suggest that its primary function(s) in mammalian retinal development are non-catalytic ones and indicate special role(s) for the AChE protein in adult photoreceptors.

Osteoblast-derived acetylcholinesterase: a novel mediator of cell-matrix interactions in bone?

The adhesive interactions that occur between bone cells and the developing matrix during bone formation help guide coupled remodeling and the maintenance of bone mass. Here, we provide evidence that acetylcholinesterase (AChE) is a novel osteoblast-derived mediator of cell-matrix interactions in bone. These findings complement an increasing body of evidence which suggests that AChE, in addition to its role in terminating cholinergic signaling, may be instrumental in regulating cellular differentiation and adhesion. We have shown, using RT-PCR, that osteosarcoma cell lines and primary cultures of osteoblasts express AChE mRNA. Expression appeared to be differentiation-dependent, and restricted to AChE splice variants containing the T subunit (exon 6). Immunofluorescent localization demonstrated that these osteoblastic cells expressed protein for AChE with an intracellular vesicular distribution. Immunohistochemistry on tissue sections confirmed AChE expression by osteoblasts in vivo, and revealed the presence of AChE along cement lines, also identified by enzyme histochemistry. In vitro functional studies indicated that osteoblast-like cells adhered specifically to and spread on AChE substrates, but did not interact with butyrylcholinesterase, a closely related protein. Our evidence strongly implicates AChE as a novel bone matrix protein, capable of mediating cell-matrix interactions, and as such may be a principal participant in organized bone formation and the regulation of remodeling.

Butyrylcholinesterase is complexed with transferrin in chicken serum

The function of the enzyme butyrylcholinesterase (BChE) both in serum and in brain is unclear. In serum, BChE has been found complexed with several biomedically relevant proteins, with which it could function in concert. Here, the existence of a similar complex formed between BChE and sero-transferrin from adult chicken serum was elucidated. In order to identify both proteins unequivocally, we improved methods to highly purify the 81-kDa BChE and the coisolated 75-kDa transferrin, which then allowed us to tryptically digest and sequence the resulting peptides. The sequences as revealed for BChE peptides were highly identical to mammalian BChEs. A tight complex formation between the two proteins could be established (a) since transferrin is coisolated along with BChE over three steps including procainamide affinity chromatography, while transferrin alone is not bound to this affinity column, and (b) since imunoprecipitation experiments of whole serum with a transferrin-specific antiserum allows us to detect BChE in the precipitate with the BChE-specific monoclonal antibody 7D11. The possible biomedical implications of a complex between transferrin and BChE which here has been shown to exist in chicken serum are briefly discussed.