The mammalian gene of acetylcholinesterase-associated collagen

The collagen-tailed or asymmetric forms (A) represent a major component of acetylcholinesterase (AChE) in the neuromuscular junction of higher vertebrates. They are hetero-oligomeric molecules, in which tetramers of catalytic subunits of type T (AChET) are attached to the subunits of a triple-stranded collagen "tail." We report the cloning of a rat AChE-associated collagen subunit, Q. We show that collagen tails are encoded by a single gene, COLQ. The ColQ subunits form homotrimers and readily form collagen-tailed AChE, when coexpressed with rat AChET. We found that the same ColQ subunits are incorporated, in vivo, in asymmetric forms of both AChE and butyrylcholinesterase. A splice variant from the COLQ gene encodes a proline- rich AChE attachment domain without the collagen domain but does not represent the membrane anchor of the brain tetramer. The COLQ gene is expressed in cholinergic tissues, brain, muscle, and heart, and also in noncholinergic tissues such as lung and testis.

Complex alternative splicing of acetylcholinesterase transcripts in Torpedo electric organ; primary structure of the precursor of the glycolipid-anchored dimeric form

In this paper, we show the existence of alternative splicing in the 3' region of the coding sequence of Torpedo acetylcholinesterase (AChE). We describe two cDNA structures which both diverge from the previously described coding sequence of the catalytic subunit of asymmetric (A) forms (Schumacher et al., 1986; Sikorav et al., 1987). They both contain a coding sequence followed by a non-coding sequence and a poly(A) stretch. Both of these structures were shown to exist in poly(A)+ RNAs, by S1 mapping experiments. The divergent region encoded by the first sequence corresponds to the precursor of the globular dimeric form (G2a), since it contains the expected C-terminal amino acids, Ala-Cys. These amino acids are followed by a 29 amino acid extension which contains a hydrophobic segment and must be replaced by a glycolipid in the mature protein. Analyses of intact G2a AChE showed that the common domain of the protein contains intersubunit disulphide bonds. The divergent region of the second type of cDNA consists of an adjacent genomic sequence, which is removed as an intron in A and Ga mRNAs, but may encode a distinct, less abundant catalytic subunit. The structures of the cDNA clones indicate that they are derived from minor mRNAs, shorter than the three major transcripts which have been described previously (14.5, 10.5 and 5.5 kb). Oligonucleotide probes specific for the asymmetric and globular terminal regions hybridize with the three major transcripts, indicating that their size is determined by 3'-untranslated regions which are not related to the differential splicing leading to A and Ga forms.

Primary structure of a collagenic tail peptide of Torpedo acetylcholinesterase: co-expression with catalytic subunit induces the production of collagen-tailed forms in transfected cells

The asymmetric forms of cholinesterases are synthesized only in differentiated muscular and neural cells of vertebrates. These complex oligomers are characterized by the presence of a collagen-like tail, associated with one, two or three tetramers of catalytic subunits. The collagenic tail is responsible for ionic interactions, explaining the insertion of these molecules in extracellular basal lamina, e.g. at neuromuscular endplates. We report the cloning of a collagenic subunit from Torpedo marmorata acetylcholinesterase (AChE). The predicted primary structure contains a putative signal peptide, a proline-rich domain, a collagenic domain, and a C-terminal domain composed of proline-rich and cysteine-rich regions. Several variants are generated by alternative splicing. Apart from the collagenic domain, the AChE tail subunit does not present any homology with previously known proteins. We show that co-expression of catalytic AChE subunits and collagenic subunits results in the production of asymmetric, collagen-tailed AChE forms in transfected COS cells. Thus, the assembly of these complex forms does not depend on a specific cellular processing, but rather on the expression of the collagenic subunits.

Cloning and expression of a rat acetylcholinesterase subunit: generation of multiple molecular forms and complementarity with a Torpedo collagenic subunit

We obtained a cDNA clone encoding one type of catalytic subunit of acetylcholinesterase (AChE) from rat brain (T subunit). The coding sequence shows a high frequency of (G+C) at the third position of the codons (66%), as already noted for several AChEs, in contrast with mammalian butyrylcholinesterase. The predicted primary sequence of rat AChE presents only 11 amino acid differences, including one in the signal peptide, from that of the mouse T subunit. In particular, four alanines in the mouse sequence are replaced by serine or threonine. In northern blots, a rat AChE probe indicates the presence of major 3.2- and 2.4-kb mRNAs, expressed in the CNS as well as in some peripheral tissues, including muscle and spleen. In vivo, we found that the proportions of G1, G2, and G4 forms are highly variable in different brain areas. We did not observe any glycolipid-anchored G2 form, which would be derived from an H subunit. We expressed the cloned rat AChE in COS cells: The transfected cells produce principally an amphiphilic G1a form, together with amphiphilic G2a and G4a forms, and a nonamphiphilic G4na form. The amphiphilic G1a and G2a forms correspond to type II forms, which are predominant in muscle and brain of higher vertebrates. The cells also release G4na, G2a, and G1a in the culture medium. These experiments show that all the forms observed in the CNS in vivo may be obtained from the T subunit. By co-transfecting COS cells with the rat T subunit and the Torpedo collagenic subunit, we obtained chimeric collagen-tailed forms. This cross-species complementarity demonstrates that the interaction domains of the catalytic and structural subunits are highly conserved during evolution.

Partial primary deficiency of insulin-like growth factor (IGF)-I activity associated with IGF1 mutation demonstrates its critical role in growth and brain development

CONTEXT

IGF-I is essential for fetal and postnatal development. Only three IGF1 defects leading to dramatic loss of binding to its type 1 receptor, IGF-1R, have been reported.

PATIENT

We describe a very lean boy who has intrauterine growth restriction and progressive postnatal growth failure associated with normal hearing, microcephaly, and mild intellectual impairment. He had markedly reduced concentrations of IGF-I, with IGFBP-3 and ALS serum levels in the upper normal range or above. IGF-I serum concentrations differed according to the immunoassay used. A higher than average GH dose was required for catch-up growth. Given the mismatch between IGF-I and IGFBP-3 levels, we sequenced his IGF1 gene.

RESULT

We identified a homozygous missense IGF1 mutation. This causes the replacement of a highly conserved amino acid (arginine 36) by a glutamine (R36Q) in the C domain of the predicted peptide. We showed that the abnormal IGF-I peptide has reduced mitogenic activity and partial loss of binding to its receptor IGF-1R. The patient's IGF-I level was undetectable in a highly specific monoclonal assay but elevated in a polyclonal assay.

CONCLUSION

This first report of mild deficiency of IGF-I activity demonstrates that the integrity of IGF-I signaling is important for normal growth and brain development. Molecular defects leading to partial loss of IGF-I activity may not be uncommon in patients born small for gestational age. The characterization of this complex phenotype and identification of such molecular defects have therapeutic implications, particularly now that, in addition to GH, recombinant IGF-I is available for clinical use.

Why so many forms of acetylcholinesterase?

Acetylcholinesterase is a key molecule in the control of cholinergic transmission. In the mammalian neuromuscular junction (NMJ), the efficiency of this phenomenon depends on the enzyme location, between the presynaptic site where acetylcholine is released and the postsynaptic membrane where the acetylcholine receptors are packed. Various molecular forms of the enzyme that possess the same catalytic activity are expressed. The relative amounts of these forms are tissue-specific. At the subcellular level, this panoply of forms allows the enzyme to be attached to the membrane or to the basal lamina. Analysis of the forms secreted and their position in the cytoarchitecture of the NMJ is essential to understand the functioning of this synapse. This review will consider the origin of the enzyme polymorphism and its physiological implication.

Expression of vesicular glutamate transporters, VGLUT1 and VGLUT2, in cholinergic spinal motoneurons

Mammalian spinal motoneurons are cholinergic neurons that have long been suspected to use also glutamate as a neurotransmitter. We report that VGLUT1 and VGLUT2, two subtypes of vesicular glutamate transporters, are expressed in rat spinal motoneurons. Both proteins are present in somato-dendritic compartments as well as in axon terminals in primary cultures of immunopurified motoneurons and sections of spinal cord from adult rat. However, VGLUT1 and VGLUT2 are not found at neuromuscular junctions of skeletal muscles. After intracellular injection of biocytin in motoneurons, VGLUT2 is observed in anterogradely labelled terminals contacting Renshaw inhibitory interneurons. These VGLUT2- and VGLUT1-positive terminals do not express VAChT, the vesicular acetylcholine transporter. Overall, our study establishes for the first time that (i) mammalian spinal motoneurons express vesicular glutamate transporters, (ii) these motoneurons have the potential to release glutamate (in addition to acetylcholine) at terminals contacting Renshaw cells, and finally (iii) the VGLUTs are not present at neuromuscular synapses of skeletal muscles.

Developmental regulation of acetylcholinesterase transcripts in the mouse diaphragm: alternative splicing and focalization

We studied the splicing and compartmentalization of acetylcholinesterase (AchE) mRNAs during muscle differentiation in the mouse, both in vitro and in vivo. We used the polymerase chain reaction (PCR) to analyse AChE mRNAs in cultures of the myogenic C2 and Sol8 cell lines, and in the developing diaphragm, from embryonic day 14 (E14). We characterized three types of alternatively spliced AChE mRNAs, encoding catalytic subunits that differ by their C-terminal regions (R, H and T). The T transcript is predominant in all cases and represents the only AChE mRNA in the adult muscle. We detected the presence of the minor R and H transcripts in the myogenic cell lines, both as myoblasts and differentiated myotubes, and also in the diaphragm from E14 until birth. At E14 the R transcript represents approximately 1% of AChE mRNA and the level of the H transcript is still lower. By in situ hybridization, we found that the T AChE mRNAs begin to preferentially accumulate at the level of the first neuromuscular contacts in the mouse diaphragm and other muscles as early as E14, e.g. concomitantly with mRNAs encoding the receptor subunits. This suggests that a common control mechanism ensures the synaptic focalization of mRNAs encoding the cholinergic proteins AChE and acetylcholine receptor during muscle development.

The polymorphism of acetylcholinesterase: post-translational processing, quaternary associations and localization

The molecular forms of acetylcholinesterase (AChE) correspond to various quaternary structures and modes of anchoring of the enzyme. In vertebrates, these molecules are generated from a single gene: the catalytic domain may be associated with several types of C-terminal peptides, that define distinct types of catalytic subunits (AChE(S), AChE(H), AChE(T)) and determine their post-translational maturation. AChE(S) generates soluble monomers, in the venom of Elapid snakes. AChE(H) generates GPI-anchored dimers, in Torpedo muscles and on mammalian blood cells. AChE(T) is the only type of catalytic subunit that exists in all vertebrate cholinesterases; it produces the major forms in adult brain and muscle. AChE(T) generates multiple structures, ranging from monomers and dimers to collagen-tailed and hydrophobic-tailed forms, in which catalytic tetramers are associated with anchoring proteins that attach them to the basal lamina or to cell membranes. In the collagen-tailed forms, AChE(T) subunits are associated with a specific collagen, ColQ, which is encoded by a single gene in mammals. ColQ contains a short peptidic motif, the proline-rich attachment domain (PRAD), that triggers the formation of AChE(T) tetramers, from monomers and dimers. The critical feature of this motif is the presence of a string of prolines, and in fact synthetic polyproline shows a similar capacity to organize AChE(T) tetramers. Although the COLQ gene produces multiple transcripts, it does not generate the hydrophobic tail. P, which anchors AChE in mammalian brain membranes. The coordinated expression of AChE(T) subunits and anchoring proteins determines the pattern of molecular forms and therefore the localization and functionality of the enzyme.

Acetylcholinesterase: C-terminal domains, molecular forms and functional localization

Acetylcholinesterase (AChE) possesses short C-terminal peptides that are not necessary for catalytic activity. These peptides belong to different classes (R, H, T, S) and define the post-translational processing and targeting of the enzyme. In vertebrates, subunits of type H (AChEH) and of type T (AChET) are the most important: AChEH subunits produce glycolipid (GPI)-anchored dimers and AChET subunits produce hetero-oligomeric forms such as membrane-bound tetramers in the mammalian brain (containing a 20 kDa hydrophobic protein) and asymmetric collagen-tailed forms in neuromuscular junctions (containing a specific collagen, ColQ). The T peptide allows the formation of tetrameric assemblies with a proline-rich attachment domain (PRAD) of collagen ColQ. These complex molecular structures condition the functional localization of the enzyme in the supramolecular architecture of cholinergic synapses.

Expression of a cDNA encoding the glycolipid-anchored form of rat acetylcholinesterase

We amplified by PCR and characterized a fragment of cDNA from rat spleen, encoding the distinctive C-terminal region of the acetylcholinesterase (AChE) H subunit. A recombinant vector encoding this subunit was constructed and expressed in COS cells: the H subunits produced glycophosphatidylinositol (GPI)-anchored dimers, showing that the spleen cDNA fragment contained a functional GPI cleavage/attachment site. Using PCR, we did not detect mRNAs encoding AChE H in rat muscle or hypothalamus. In the liver of 16-day rat embryos, we found both H and T transcripts, in agreement with the presence of both GPI-anchored dimers and amphiphilic monomers of type II. In addition, we detected 'read-through' (R) transcripts, in which regular introns are spliced, but the intervening sequence between the common exon 4 and the alternative exon 5 (H) is maintained.

Development of human single-chain antibodies to the transferrin receptor that effectively antagonize the growth of leukemias and lymphomas

The major route of iron uptake by cells occurs through transferrin receptor (TfR)-mediated endocytosis of diferric-charged plasma transferrin (holo-Tf). In this work, we pursued TfR antibodies as potential cancer therapeutics, characterizing human single-chain variable antibody fragments (scFv) specific for the human TfR isolated from a phage display library. We hypothesized that many of these antibodies would function as ligand mimetics because scFvs from the library were selected for binding and internalization into living cells. In support of this hypothesis, the anti-TfR scFvs identified were antagonists of TfR binding to holo-Tf, particularly two of the most potent antibodies, 3TF12 and 3GH7, which blocked the in vitro proliferation of a number of hematopoietic cancer cell lines. We optimized this activity of 3TF12 and 3GH7 by engineering 55-kDa bivalent antibody formats, namely, F12CH and H7CH, which could block cell proliferation with an IC(50) of 0.1 microg/mL. We found that the mechanism of the scFv antibody cytotoxicity was unique compared with cytotoxic anti-TfR monoclonal antibodies that have been described, causing cell surface upregulation of TfR along with the inhibition of holo-Tf cell uptake and induction of cell death. In a nude mouse model of erythroleukemia, administration of F12CH reduced tumor growth. Together, our findings define a new class of fully human anti-TfR antibodies suitable for immunotherapy against tumors whose proliferation relies on high levels of TfR and iron uptake, such as acute lymphoid and myeloid leukemias.

Coexistence of immunoreactive substance P and serotonin in neurones of the gut

Serotonin (5-HT) and substance P (SP) were visualized by indirect immunofluorescence using two fluorochromes applied sequentially on the same preparation of myenteric plexus from the guinea pig gut. Three groups of labelled neurones were found: (i) neurones with 5-HT-like immunoreactivity only; (ii) neurones with SP-like immunoreactivity only; (iii) neurones with both 5-HT- and SP-like immunoreactivity, which represented approximately one-third of the 5-HT-like immunoreactive neurones.

Identification and characterization of tumor antigens by using antibody phage display and intrabody strategies

To generate a panel of antibodies binding human breast cancers, a human single chain Fv phage display library was selected for rapid internalization into the SK-BR-3 breast cancer cell line. Thirteen unique antibodies were identified within the 55 cell binding antibodies studied, all of them showing specific staining of tumor cells compare to normal epithelial cells. Two of the antibodies bound the ErbB2 oncogene while 6 bound the tumor marker transferrin receptor (TfR). By developing a scFv immunoprecipitation method, we were able to use LC-MS/MS to identify the antigen bound by one of the antibodies (3GA5) as FPRP (prostaglandin F2alpha receptor-regulatory protein)/EWI-F/CD9P-1 (CD9 partner 1) an Ig superfamily member that has been described to interact directly with CD9 and CD81 tetraspanins and to be overexpressed in adherent cancer cell lines. Although the 3GA5 scFv had no direct anti-proliferative effect, intracellular expression of the scFv was able to knockdown CD9P-1 expression and could be used to further define the role of the tetraspanin system in proliferation and metastasis. Moreover, the 3GA5 scFv was rapidly internalized into breast tumor cells and could have potential for the targeted delivery of cytotoxic agents to breast cancers. This study is the proof of principle that the direct selection of phage antibody libraries on tumor cells can effectively lead to the identification and functional characterization of relevant tumor markers.

Protein kinase D1 stimulates proliferation and enhances tumorigenesis of MCF-7 human breast cancer cells through a MEK/ERK-dependent signaling pathway

Protein kinase D1, PKD1, is a novel serine/threonine kinase whose altered expression and dysregulation in many tumors as well as its activation by several mitogens suggest that this protein could regulate proliferation and tumorigenesis. Nevertheless, the precise signaling pathways used are still unclear and the potential direct role of PKD1 in tumor development and progression has not been yet investigated. In order to clarify the role of PKD1 in cell proliferation and tumorigenesis, we studied the effects of PKD1 overexpression in a human adenocarcinoma breast cancer cell line, MCF-7 cells. We demonstrated that overexpression of PKD1 specifically promotes MCF-7 cell proliferation through accelerating G0/G1 to S phase transition of the cell cycle. Moreover, inhibition of endogenous PKD1 significantly reduced cell proliferation. Taken together, these results clearly strengthen the regulatory role of PKD1 in cell growth. We also demonstrated that overexpression of PKD1 specifically diminished serum- and anchorage-dependence for proliferation and survival in vitro and allowed MCF-7 cells to form tumors in vivo. Thus, all these data highlight the central role of PKD1 in biological processes which are hallmarks of malignant transformation. Analysis of two major signaling pathways implicated in MCF-7 cell proliferation showed that PKD1 overexpression significantly increased ERK1/2 phosphorylation state without affecting Akt phosphorylation. Moreover, PKD1 overexpression-stimulated cell proliferation and anchorage-independent growth were totally impaired by inhibition of the MEK/ERK kinase cascade. However, neither of these effects was affected by blocking the PI 3-kinase/Akt signaling pathway. Thus, the MEK/ERK signaling appears to be a determining pathway mediating the biological effects of PKD1 in MCF-7 cells. Taken together, all these data demonstrate that PKD1 overexpression increases the aggressiveness of MCF-7 breast cancer cells through enhancing their oncogenic properties and would, therefore, define PKD1 as a potentially new promising anti-tumor therapeutic target.

Influence of matricial molecules on growth and differentiation of entrapped chondrocytes

Primary cultures of rabbit articular chondrocytes have been cultivated normally and within three-dimensional systems using different alginate matrices. The in vitro proliferation capacity of the cells immobilized in the calcium alginate beads was investigated. The growth curve showed that chondrocytes are able to grow and to divide for several days inside the beads; in parallel an increase in protein contents was also measured. The differentiated phenotype of rabbit articular chondrocytes consists of cartilage-specific proteoglycans. During serial monolayer cultures this phenotype was lost and replaced by a low level of proteoglycan synthesis. On the contrary when cultivated in beads, entrapped cells maintained their differentiated phenotype over time; the rates of proteoglycan were similar to those of primary chondrocytes. All these parameters were tested comparatively using different substrata in monolayer cultures and in alginate gels. Assays were carried out to assess the influence of type I collagen, type IV collagen, and of fibronectine on the growth as well as on the differentiation phenotype. The encapsulation methodology is readily applicable to the culture of chondrocytes in single beads, in multiwell dishes, or to mass culture for a bioproduction of extracellular matrix components.

Anatomical analysis of the neurons expressing the acetylcholinesterase gene in the rat brain, with special reference to the striatum

The localization of the neurons expressing the acetylcholinesterase gene in the rat central nervous system was studied by in situ hybridization. The striatal and nigral neurons containing acetylcholinesterase messenger RNA were especially identified. Acetylcholinesterase messenger RNA was detected in numerous areas of the central nervous system, including cholinergic areas, like striatum, nucleus basalis of Meynert, septum and diagonal band of Broca, but also non-cholinergic areas, like the cerebral cortex, the hippocampus, the cerebellum and the raphe dorsalis. In the striatum, 75% of the neurons expressing the acetylcholinesterase gene were identified as cholinergic neurons and 25% as somatostatin-producing neurons. All dopaminergic neurons of the substantia nigra pars compacta and ventral tegmental area were demonstrated to express the acetylcholinesterase gene. Our results suggest that several neuronal populations could contribute to the presence of acetylcholinesterase in the striatum: the striatal cholinergic and somatostatin-containing interneurons, the nigral dopaminergic neurons and other neurons that may be the corticostriatal, thalamostriatal and raphe-striatal neurons. This demonstrates that, especially in the striatum, acetylcholinesterase is not a specific marker of the cholinergic neurons. The diversity of the origins of striatal acetylcholinesterase suggests a multiplicity of functions for this enzyme: besides its cholinolytic actions, it may also possibly play a non-cholinolytic role in neuromodulation.

Selection of cytotoxic responses to maitotoxin and okadaic acid and evaluation of toxicity of dinoflagellate extracts

The cytotoxicity of maitotoxin (MTX) and okadaic acid (OA) was studied on three mammalian fibroblast cell lines. Neutral red uptake (NRU), which measures cell viability, and morphological alterations were selected as rapid suitable responses. NRU allowed a precise toxicity quantification while the observations of morphological damage revealed differences specific to MTX (cell blebbing) and OA (cell rounding). BHK21 C13 fibroblasts, although less sensitive to MTX than the other cell lines, were chosen since they gave stable information and a two-stage morphological response with OA ("square"-shaped cells, then round cells). When NRU and morphology alterations were studied with crude extracts of Gambierdiscus toxicus and Prorocentrum lima, responses were typical of the dominant toxins, MTX and OA or related toxins respectively. Applied to several dinoflagellate extracts, the two tests revealed no toxicity for Amphidinium carterae, Ostreopsis siamensis, O. ovata and Coolia monotis (from La Réunion) and toxicity for A. carterae and A. operculatum (from Saint Barthélémy). When toxic, A. carterae extracts showed blebbing similar to that caused by MTX. Morphology alterations caused by A. operculatum crude extracts, different from those corresponding to MTX or OA, were also observed.

Estradiol regulates the insulin-like growth factor-I (IGF-I) signalling pathway: A crucial role of phosphatidylinositol 3-kinase (PI 3-kinase) in estrogens requirement for growth of MCF-7 human breast carcinoma cells

Estrogens can stimulate the proliferation of estrogen-responsive breast cancer cells by increasing their proliferative response to insulin-like growth factors. With a view to investigating the molecular mechanisms implicated, we studied the effect of estradiol on the expression of proteins implicated in the insulin-like growth factor signalling pathway. Estradiol dose- and time-dependently increased the expression of insulin receptor substrate-1 and the p85/p110 subunits of phosphatidylinositol 3-kinase but did not change those of ERK2 and Akt/PKB. ICI 182,780 did not inhibit estradiol-induced IRS-1 and p85 expression. Moreover, two distinct estradiol-BSA conjugate compounds were as effective as estradiol in inducing IRS-1 and p85/p110 expression indicating the possible implication of an estradiol membrane receptor. Comparative analysis of steroids-depleted and steroids-treated cells showed that IGF-I only stimulates cell growth in the latter condition. Nevertheless, expression of a constitutively active form of PI 3-kinase in steroid-depleted cells triggers proliferation. These results demonstrate that estradiol positively regulates essential proteins of the IGF signalling pathway and put in evidence that phosphatidylinositol 3-kinase plays a central role in the synergistic pro-proliferative action of estradiol and IGF-I.

Protein kinase D1 regulates ERα-positive breast cancer cell growth response to 17β-estradiol and contributes to poor prognosis in patients

About 70% of human breast cancers express and are dependent for growth on estrogen receptor α (ERα), and therefore are sensitive to antiestrogen therapies. However, progression to an advanced, more aggressive phenotype is associated with acquisition of resistance to antiestrogens and/or invasive potential. In this study, we highlight the role of the serine/threonine-protein kinase D1 (PKD1) in ERα-positive breast cancers. Growth of ERα-positive MCF-7 and MDA-MB-415 human breast cancer cells was assayed in adherent or anchorage-independent conditions in cells overexpressing or depleted for PKD1. PKD1 induces cell growth through both an ERα-dependent manner, by increasing ERα expression and cell sensitivity to 17β-estradiol, and an ERα-independent manner, by reducing cell dependence to estrogens and conferring partial resistance to antiestrogen ICI 182,780. PKD1 knockdown in MDA-MB-415 cells strongly reduced estrogen-dependent and independent invasion. Quantification of PKD1 mRNA levels in 38 cancerous and non-cancerous breast cell lines and in 152 ERα-positive breast tumours from patients treated with adjuvant tamoxifen showed an association between PKD1 and ERα expression in 76.3% (29/38) of the breast cell lines tested and a strong correlation between PKD1 expression and invasiveness (P < 0.0001). In tamoxifen-treated patients, tumours with high PKD1 mRNA levels (n = 77, 50.66%) were significantly associated with less metastasis-free survival than tumours with low PKD1 mRNA expression (n = 75, 49.34%; P = 0.031). Moreover, PKD1 mRNA levels are strongly positively associated with EGFR and vimentin levels (P < 0.0000001). Thus, our study defines PKD1 as a novel attractive prognostic factor and a potential therapeutic target in breast cancer.

Development of 5-hydroxytryptamine-like immunoreactive neurones in cultures of the myenteric plexus from the guinea-pig caecum

5-Hydroxytryptamine (5-HT)-like immunoreactive neurones were studied during the development of myenteric plexus explant cultures from the guinea-pig taenia coli over a period of 3 weeks in vitro, using immunofluorescence histochemistry. Brightly fluorescent 5-HT-like immunoreactive neuronal cell bodies and fibres were found in all ages of cultures examined. In mature cultures, where the histotypic organization resembles that of the plexus in vivo, the pattern of immunoreactivity was strikingly similar to that previously described for in situ preparations. These culture preparations may therefore be useful models for the study of the development of putative serotonergic neurones. High-performance liquid chromatography was used to measure 5-HT levels in fetal calf serum, a supplement of the culture medium used in this study. 5-HT levels of 0.48 X 10(-5) M to 1.74 X 10(-4) M were found in 4 batches of this serum, indicating that some of the immunoreactive neurones observed in the cultures may have selectively taken up 5-HT during development in vitro.

Acetylcholinesterase and molecular interactions at the neuromuscular junction

The efficiency and the tight control of neurotransmission require the accumulation of synaptic proteins in discrete domains. In neuromuscular junctions, the main form of acetylcholinesterase (AChE) is a hetero-oligomer in which the catalytic subunits are associated to a specific collagen, ColQ. This structural protein is responsible for the insertion and the accumulation of AChE in the synaptic basal lamina. We have analyzed the time-course of acetylcholinesterase and acetylcholine receptors (AChR) mRNAs during mouse muscle cell differentiation in culture. In parallel, we have visualized the formation of AChE and AChR aggregates. We show that AChR clusters form first which correlates with high gamma-subunit mRNA levels. Then, AChE clusters appear with the onset of contraction and correlate with a dramatic increase in AChE, ColQ1 and ColQ1A mRNA levels in muscle cells. At that stage, AChR gamma-subunit levels drop while the expression level of epsilon-subunits increase. AChE aggregates are organized by a ternary complex, which involves direct interactions between ColQ, perlecan and MuSK.