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At least 235 records · Page 13Linked to original sources
PubMed1998

Atypical antineutrophil cytoplasmic antibodies with perinuclear fluorescence in chronic inflammatory bowel diseases and hepatobiliary disorders colocalize with nuclear lamina proteins.

Antineutrophil cytoplasmic antibodies (ANCA) are frequently associated with chronic inflammatory bowel diseases (IBD) and hepatobiliary disorders. However, their target antigens have not been identified yet. Recently, we observed an atypical perinuclear ANCA fluorescence (p-ANCA) together with an intranuclear staining using ANCA-positive sera from patients with IBD and hepatobiliary disorders. This observation suggests that the target antigens are localized within the nucleus of neutrophilic granulocytes. To further investigate this hypothesis, we examined sera from patients with ulcerative colitis, primary sclerosing cholangitis, autoimmune hepatitis or systemic vasculitis on ethanol or formaldehyde-fixed neutrophils using confocal laser scanning microscopy and immunoelectron microscopy. Counterstaining with propidium iodide, a DNA-specific dye, showed that ANCA-positive sera in IBD and heptobiliary disorders react with intranuclear antigens at the nuclear periphery of the neutrophils. Double immunolabeling techniques revealed that nuclear lamina proteins, lamins A, C and B1, and lamin B receptor were colocalized with the antigen(s) recognized by atypical p-ANCA. No colocalization was observed with classical p-ANCA and antibodies against histones (H1-H4). Our study showed that atypical p-ANCA are antinuclear antibodies reactive with granulocyte-specific antigens present in the nuclear lamina.

Adolescent↗
PubMed2002

Association and colocalization of G protein alpha subunits and Purkinje cell protein 2 (Pcp2) in mammalian cerebellum.

Previously, we have demonstrated a novel interaction between Galpha(o) protein and Purkinje cell protein-2 (Pcp2, also known as L7) in vitro and in transfected cells (Luo and Denker [1999] J. Biol. Chem. 274:10685-10688). Pcp2 is uniquely expressed in cerebellar Purkinje cells and in retinal bipolar neurons, and it may function as a cell-type specific modulator for G protein-mediated cell signaling. This interaction has been further evaluated in the present studies. Coimmunoprecipitation experiments reveal that Pcp2 associates with Galpha(o) in vivo in mouse cerebellum and eye extract. Pcp2 also associate with Galpha(i2) in the cerebellum. No detectable associations of Pcp2 with Galpha(z) and Galpha(q) subunits are observed. The association of Galpha(o) and Pcp2 is detected at postnatal day 1 (P1), and the association remains stable from day 3 (P3) until adulthood. Further, immunofluorescent double labeling and confocal microscopy suggest that Pcp2 and Galpha(o) are colocalized in the distal processes of cerebellar Purkinje cells including axonal endings and dendritic spines. Taken together, these findings indicate colocalization and association of Galpha(o) and Pcp2 in cerebellum and suggest a functional role in regions of synaptic activity.

Age Factors↗
PubMed2001

Nitric oxide synthase-positive neurons in the rat superior colliculus: colocalization of NOS with NMDAR1 glutamate receptor, GABA, and parvalbumin.

We analyzed the potential input and output components of nitric oxide synthase (NOS)-containing neurons in the rat superior colliculus (SC). To identify whether NOS-positive neurons receive glutamatergic input we investigated the colocalization of NOS with NMDA receptor subunit R1 (NMDAR1). In addition, to examine whether putative nitric oxide synthesizing neurons represent a neurochemically specific or distinct subpopulation of cells in the SC we studied the colocalization of NOS with the neurotransmitter GABA, the calcium-binding proteins parvalbumin, calbindin and calretinin and with neuropeptides such as somatostatin, substance P and neuropeptide Y. We found that 90% of NOS-positive neurons in the superficial layers of the rat SC express NMDAR1. Nearly 20% of the population of nitridergic neurons also expresses GABA and 15% of them express parvalbumin. NOS-positive neurons in the superior colliculus did not contain calretinin, calbindin or either of the neuropeptides tested. The results of this study show that the capacity for synthesizing NO in the SC is largely restricted to neurons that receive glutamatergic inputs and that some of these neurons express GABA or parvalbumin.

Animals↗
PubMed1990

Evidence for the colocalization of the axonal mitogen for Schwann cells and oligodendrocytes.

Axons that normally will encounter either CNS or PNS glia have been shown to contain a powerful mitogen for both Schwann cells and oligodendrocytes. The normally nonmyelinated, nonglial ensheathed cerebellar granule cells have been shown to possess a proliferative signal for Schwann cells, suggesting that a glial mitogen is common to all axons. To determine if a glial mitogen capable of stimulating both Schwann cells and oligodendrocytes is colocalized on all types of axons we have (1) cocultured granule cells with oligodendrocytes, (2) incubated oligodendrocytes with granule cell membranes, and (3) evaluated the ability of heparin extracts of granule cell membranes, splenic nerve microsomes, and axolemma-enriched fractions isolated from rat and bovine CNS to stimulate mitosis of cultured oligodendrocytes. Neither the intact granule cells nor the granule cell membrane fraction stimulated cultured oligodendrocytes to divide. However, heparin extracts of the granule cell membranes were significantly mitogenic to the cultured oligodendrocytes. Heparin extracts of splenic nerve microsomes were more mitogenic than the comparable extract obtained from bovine CNS axolemma-enriched fractions. These results suggest that the neuronal mitogen for oligodendroglia is colocalized with the neuronal mitogen for Schwann cells.

Animals↗
PubMed1995

Early neuroblasts are pluripotential: colocalization of neurotransmitters and neuropeptides.

This study was undertaken in order to establish the presence of pluripotential neuroblasts in the developing chick CNS. This has been suggested by our previous observations that expression of emerging neuronal phenotypes in the chick embryo CNS is affected by exposure to neurotrophic substances (i.e., GHRH, SRIF, NGF, EGF, muscle-derived factors) or neurotoxins such as ethanol. We have proposed that one mechanism whereby these substances elicit their effects is by shifting phenotypic expression in populations of pluripotential neuroblasts. In order to establish the presence of significant populations of pluripotential neuroblasts, cultures obtained from 3-day-old whole chick embryos (E3WE) were double-stained with antibodies to markers specific for four neuronal phenotypes in various permutations. Cultures at 6 DIV were tested for the presence of tyrosine hydroxylase (TH), choline acetyltransferase (ChAT), gamma-aminobutyric acid (GABA), and somatostatin (SRIF) alone, and in various combinations. We observed a colocalization of all phenotypic markers within neuronal perikarya and processes in more than fifty percent of neuronal cells in these cultures. These data suggest that developing neuroblasts at this stage of embryogenesis possess the machinery necessary to adopt multiple neuronal phenotypes. The colocalization of neurotransmitter proteins in early neuroblasts (60 hr of embryogenesis) supports the recent concept that these substances themselves may influence phenotypic expression and also supports our idea that microenvironmental factors (i.e., ethanol, growth factors) provide signals which affect emerging phenotypes.

Animals↗
PubMed1990

Immunocytochemical colocalization of progestin receptors and beta-endorphin or enkephalin in the hypothalamus of female guinea pigs.

Double-label immunocytochemistry was used to determine whether estradiol-induced progestin receptors and either beta-endorphin or leucine-enkephalin are colocalized in female guinea pig brain. Ovariectomized, adult guinea pigs were implanted with capsules containing estradiol-17 beta to induce high levels of progestin receptors, and injected intracerebroventricularly with colchicine to improve visualization of the opiate peptides. Sections through the hypothalamus and preoptic area were processed for progestin receptor, followed by beta-endorphin or leucine-enkephalin immunocytochemistry. As reported previously, high concentrations of progestin receptor-immunoreactive (PR-IR) cells were found in the preoptic area (medial and periventricular portions, medial preoptic nucleus) and hypothalamus (anterior hypothalamic and arcuate nuclei, ventrolateral area). Many beta-endorphin-IR cells contained PR-IR in the arcuate nucleus and its surroundings (33%) and in the dorsomedial area of the hypothalamus (64%). Scattered enkephalin-IR cells were found in the septal nucleus, medial and lateral preoptic area, bed nucleus of the stria terminalis, and the arcuate nucleus. The ventromedial nucleus of the hypothalamus and dorsolateral magnocellular nucleus, respectively, contained moderate and heavy concentrations of enkephalin-IR cells. Although some of these areas also contained PR-IR, enkephalin-IR was colocalized consistently with PR-IR only in a small number of cells in the arcuate nucleus and ventromedial/ventrolateral area of the hypothalamus. These data, taken together with earlier observations that virtually all cells containing estradiol-induced PR-IR also contain estrogen receptor-IR, provide neuroanatomical evidence that hypothalamic actions of progesterone and estradiol may be mediated by beta-endorphin and/or enkephalin.

Animals↗
PubMed1989

Colocalization of taurine- and cysteine sulfinic acid decarboxylase-like immunoreactivity in the hippocampus of the rat.

It is proposed that taurine is an inhibitory neurotransmitter/neuromodulator in the CNS. The present study localized taurine-containing neurons within the rat hippocampus with the use of a monoclonal antibody against conjugated taurine (Tau2) in conjunction with an antiserum against cysteine sulfinic acid decarboxylase (CSADC), a synthesizing enzyme for taurine. Taurine-like immunoreactivity Tau-LI) and CSADC-LI were colocalized in neurons of the dentate gyrus, CA1(/CA2), CA3, and CA4. Of all the cells examined, pyramidal basket cells within the granule cell layer of the dentate gyrus were most intensely stained with both Tau2 and CSADC. Granule cells were also double-labeled with Tau-LI and CSADC-LI. Cell nuclei and dendrites in the CA1 region stained more intensely with Tau2 than somata. CSADC-LI was colocalized with Tau-LI within these neurons. Light staining with both Tau2 and the CSADC antiserum was inconsistently present in CA3 and CA4 neurons and was found to be highly dependent on the type of fixation and delay to fixation. Tau-LI was more consistently present in increased numbers of neurons in CA3 when glutaraldehyde was added to the paraformaldehyde fixative solution. Hippocampi which were immersion-fixed in paraformaldehyde following a 0-, 6-, or 24-hour postmortem delay exhibited a lack of Tau2 staining in the CA3 region in the majority of animals studied, similar to some paraformaldehyde perfusion-fixed rats. These studies suggest that taurine was present in the majority of neurons within the major cell layers of the rat hippocampus, but Tau-LI was more easily lost from neurons in the CA3 region following delay to fixation. The localization of Tau-LI in excitatory neurons such as granule cells and pyramidal cells is not consistent with its proposed inhibitory transmitter role. However, the prominent Tau2 staining in dendrites of the CA1 region provides anatomical support for the hypothesis that taurine may be released from dendrites in the CA1 region and may function as a neuromodulator of calcium flux in these pyramidal neurons.

Animals↗
PubMed1998

Colocalization of emerin and lamins in interphase nuclei and changes during mitosis.

Emerin is a nuclear membrane protein which is affected by mutation in X-linked Emery-Dreifuss muscular dystrophy. We have previously suggested that emerin is a member of a family of type II integral membrane proteins which associate with the nuclear lamina and which include lamina-associated proteins and the lamin B receptor. We now show that emerin in COS cells is not restricted to the nuclear rim but is also found at intranuclear sites, where it colocalizes with nuclear lamins B1, B2 and A/C. During mitosis, emerin is dispersed throughout the cell and then participates in the reconstitution of membranes around the daughter nuclei. Although emerin and lamins do not remain colocalized during mitosis, they all show some association with the midbody of the mitotic spindle.

Animals↗
PubMed2001

Enhanced infection of an X4 strain of HIV-1 due to capping and colocalization of CD4 and CXCR4 induced by capsianoside G, a diterpene glycoside.

We investigated whether capsianosides, diterpene glycosides, extracted from Capsicum plants could affect human immunodeficiency virus type 1 (HIV-1) infection. Significant effect on virus infection in MAGI/CCR5 cells was neither observed for the X4 virus by capsianosides II, XI, and A, nor for an R5 virus by capsianoside G. Apparent enhancement of X4 HIV-1 infection by capsianoside G was observed and exclusively related to the usage of the CXCR4 coreceptor. The capsianoside G-treated cells had no change in the expression level of CD4, CXCR4, and CCR5, however, colocalization and capping of CD4 and CXCR4, but not of CD4 and CCR5 was observed. Our results suggested that capsianoside G enhanced X4 virus infection at the level of viral penetration through the capping and colocalization of receptors needed for infection.

Adsorption↗
PubMed2001

Tartrate-resistant acid phosphatase facilitates hydroxyl radical formation and colocalizes with phagocytosed Staphylococcus aureus in alveolar macrophages.

Tartrate-resistant acid phosphatase (TRAP) is an enzyme expressed specifically in osteoclasts and activated macrophages, two phagocytosing cell types originating from the same hematopoietic stem cells. TRAP contains a binuclear iron centre which has been shown to generate reactive oxygen species (ROS). In this study murine macrophage like cell line RAW-264 overexpressing TRAP was shown to produce elevated levels of hydroxyl radicals compared to parental cells. TRAP transfected cells also had reduced growth rate indicating harmful effects of excessive intracellular ROS levels. Using TRAP specific antibody TRAP protein was shown in alveolar macrophages partially colocalize with late endosomal/lysosomal markers Rab7, Lamp 1 and MHC II molecules that bind antigenic peptides. TRAP also colocalized into compartments where Staphylococcus aureus were phagocytosed. These results suggest that TRAP may have an important biological function in the defence mechanism of macrophages by generating intracellular ROS which would be targeted to destroy phagocytosed foreign material.

Acid Phosphatase↗
PubMed1993

43K protein and acetylcholine receptors colocalize during the initial stages of neuromuscular synapse formation in vivo.

The 43K protein is a cytoplasmic peripheral membrane protein concentrated subsynaptically in skeletal muscle. Recombinant 43K has been shown to cause clustering of acetylcholine receptors (AChRs) in cultured cells. However, the role of 43K in vivo is disputed, because in some cases it appears only after AChRs have clustered. We therefore examined the expression and distribution of 43K and AChRs during synapse formation in embryonic mouse muscles. Messenger RNA for 43K was detected on Embryonic Day (E) 12, a day prior to the first AChR clusters. Immunofluorescence showed that both AChRs and 43K were colocalized in patches by E13, the stage at which intramuscular nerves were first detected. The AChR/43K patches were nerve associated, and more than 98% of AChR patches were accompanied by 43K. The precise colocalization of 43K and AChRs persisted through development. These results are consistent with 43K being involved in the nerve-induced clustering of AChRs during synapse formation.

Animals↗
PubMed1995

Chromatin assembly factor 1 (CAF-1) colocalizes with replication foci in HeLa cell nuclei.

In the S-phase of the eukaryotic cell cycle, newly replicated DNA is assembled into chromatin. I used indirect immunofluorescence microscopy to localize the sites of chromatin assembly in respect to DNA replication. Replication foci in the nuclei of permeabilized HeLa cells were labeled by incorporation of biotin-16-dUTP and detected by fluorescent streptavidin. Prelabeling of replication foci in vivo with bromodeoxyuridine showed that replication in permeabilized cells proceeds at preexisting replication forks. The localization of chromatin assembly factor 1 (CAF-1) was determined with subunit-specific monoclonal antibodies. CAF-1 is not detectable in mitotic cells and is detectable only at background levels in about 60% of all interphase nuclei. The other interphase nuclei show an intense punctate immunostaining of CAF-1. These sites of CAF-1 colocalize with replication foci during all stages of the S-phase. No other discrete sites of CAF-1 are observed. Human replication protein A (RPA) colocalizes with these replication/chromatin assembly sites. In addition, extra nuclear sites of RPA are observed that probably represent prereplication foci, poised for initiation of DNA replication.

Antibodies, Monoclonal↗
PubMed1997

The activation domain of a hormone inducible HTLV-1 Rex protein determines colocalization with the nuclear pore.

Human T-cell leukemia/lymphoma virus type 1 (HTLV-1) Rex is an essential regulatory protein that acts at the posttranscriptional level to promote expression of unspliced and singly spliced genes of the virus. Rex functions have been attributed to at least three separate domains of the protein determining nuclear/nucleolar accumulation and RNA binding (overlapping), multimerization, and nuclear export of Rex-responsive RNA. The steady-state intracellular localization of functional Rex molecules is mainly nucleolar. Fusions of wild-type Rex and the ligand binding domain of human estrogen receptor (ER) produced conditional molecules (ERRex and ERalaRex), which remained cytoplasmic in the absence of hormone and in response to hormone colocalized with the nuclear pore complex (NPC). These molecules induced in a hormone-dependent manner the expression of a Rex reporter plasmid and of the HTLV-1 Env protein and fusion of Env expressing cells. In contrast, activation domain mutants (ERRex delta and ERRexGly) translocated from the cytoplasm and acquired a diffuse nuclear localization. These mutants did not associate with the NPC and failed to show any of the expected Rex functions. Rex functions were perturbed by inactivating the RNA binding domain (mutant ERM2) or the oligomerization domain (mutant ERM7). However, these two mutant fusion proteins exhibited a hormone-dependent NPC colocalization. These observations provide in vivo evidence that intranuclear translocation of intact Rex to the NPC is dependent exclusively on a functional activation domain and is not influenced by binding to the target RNA.

Binding Sites↗
PubMed2001

Dynamic nuclear localization of the baculovirus proteins IE2 and PE38 during the infection cycle: the promyelocytic leukemia protein colocalizes with IE2.

The early gene products IE2 and PE38 of Autographa californica multicapsid nuclear polyhedrosis virus localize to distinct nuclear domains after transient expression. Here, the nuclear localization pattern and the putative association with cellular proteins have been determined during virus infection to shed light on the functional significance of the nuclear domains. IE2 was always localized to distinct nuclear structures while PE38 was partly present in nuclear dots. Confocal imaging indicated colocalization of PE38 and IE2 to common domains, prominently at 2 h p.i. The nuclear dot localization of PE38 in infected cells was different from that in transfected cells. Hence, we have performed cotransfection experiments that suggested that a viral factor influences the nuclear distribution. Since the promyelocytic leukemia protein (PML) that localizes to distinct nuclear multiprotein complexes termed ND10/PODs in mammalian cells functions as a target for some immediate early viral proteins, we have investigated whether baculovirus proteins act similarly. Transiently expressed IE2 and PE38 were found to be associated with endogenous PML in the mammalian cell line BHK21. Infection with a recombinant virus that expresses the human pml gene in insect cells reveals IE2 and PML to be colocalized during the early phase of infection followed by a redistribution of both proteins. Taken together our results provide first evidence that the early baculovirus protein IE2 associates at least with one component of mammalian PODs during virus infection, suggesting that POD-like structures can be formed in insect cells.

Animals↗
PubMed2001

Colocalization prostacyclin (PGI2) synthase--caveolin-1 in endothelial cells and new roles for PGI2 in angiogenesis.

In vascular cells, prostacyclin (PGI2) synthase (PGI2s) has been localized in the endoplasmic reticulum of endothelial cells and in the nuclear and plasma membrane of smooth muscle cells. In human umbilical vein endothelial (HUVE) cells, we detected the enzyme in abundant cytoplasmic vesicles apparently originating from the plasma membrane and similar to those stained by gold-albumin, which interacts with a caveolar receptor. This prompted us to try a direct confocal microscopy approach aimed at colocalizing gold-albumin, caveolin-1, and PGI2 synthase. Moreover, the staining of HUVE cells with an anti-BiP7Grp78 antibody (a marker of endoplasmic reticulum) shows a perinuclear localization, sharply separated from PGI2 synthase localization. The results indicate that more than 80% of the enzyme resides in cellular sites costaining with caveolin-1 antibody and gold-albumin. This evidence was confirmed by the demonstration that PGI2 synthase and caveolin-1 coimmunoprecipitate in HUVE cell lysates and that they are associated to detergent-insoluble membrane domains in the same low-density fractions of a sucrose gradient. In addition, depletion of cellular cholesterol by mevalonate and methyl-beta-cyclodextrin leads to the shift of PGI2 synthase and caveolin-1 to higher density fractions of the gradient. Biochemical evidence about colocalization was supported by the use of a fusion protein glutathione S-transferase (GST)/caveolin-1, which retained either PGI2s purified from ram seminal vesicles or PGI2s present in HUVE cell lysates. Binding of PGI2s to caveolin "scaffolding domain" and to C-terminal region was deduced by using full-length GST--Cav-1, GST--Cav 61--101, and GST C- and N-terminal fusion proteins. A double approach based on the usage of filipin as a specific caveolae-disrupting agent and antisense oligonucleotides targeting PGI2 synthase mRNA suggests that the production of PGI2 in caveolae is likely to be connected to the regulation of angiogenesis, at least in vitro.

6-Ketoprostaglandin F1 alpha↗
PubMed1997

Expression of NMDA receptor-1 (NR1) and huntingtin in striatal neurons which colocalize somatostatin, neuropeptide Y, and NADPH diaphorase: a double-label histochemical and immunohistochemical study.

The subset of striatal neurons which colocalize SS/NPY/NADPH-d are selectively resistant to neurodegeneration in Huntington's Disease (HD) and to excitotoxic cell death induced experimentally with NMDA receptor (NMDAR) agonists. Here we have analyzed the expression of immunoreactive NMDAR-1 (NR1) subunit (as an index of NMDAR protein) and of huntingtin (the normal product of the HD gene) in primary cultures of rat striatum to see if differential expression of the two antigens in the subset of SS/NPY/NADPH-d and other striatal neurons can explain their selective resistance or vulnerability. Double-label histochemical and immunocytochemical studies were carried out using conventional and confocal laser scanning microscopy to characterize the cellular and subcellular expression of NR1 and SS, or NPY or bNOS, together with NADPH-d histochemistry. The percentages of cultured striatal neurons that were positive for NADPH-d, SS, NPY, bNOS, and NRI were, respectively, 3.8, 8.4, 10.2, 5.1, and 80%. The majority of striatal NADPH-d neurons coexpressed SS and NPY; 17% of SS-producing neurons were strongly positive for NR1; the remaining cells (approximately 80%) exhibited only weak NR1 expression. Comparable data were obtained for NPY-positive neurons, 15% of which colocalized NR1 strongly and 70-80% weakly. By double-label immunofluorescence, huntingtin was nonselectively expressed in virtually all striatal neurons including SS/NPY/NADPH-d neurons. These results show that the majority of striatal SS/NPY/NADPH-d neurons express NR1. The relative abundance of NR1 in SS/NPY/NADPH-d neurons, however, varies between a small subset of neurons that are receptor rich and the remainder that express low levels only and may determine susceptibility to NMDAR-mediated neurotoxicity. Huntingtin is nonselectively expressed in virtually all striatal neurons and does not appear to be a determinant of the selective resistance of normal striatal SS/NPY/NADPH-d neurons to NMDA toxicity.

Animals↗
PubMed1995

Ligation-induced acute pancreatitis in opossums: acinar cell necrosis in the absence of colocalization.

Acute necrotizing pancreatitis in opossums after bile and pancreatic duct ligation (BPDL) is a useful experimental corollary of gallstone-induced acute pancreatitis in humans. In experimental and human acute pancreatitis, a loss of segregation of the lysosomal enzyme cathepsin B and the zymogen proenzyme trypsinogen (colocalization) is implicated as the triggering event of disease pathogenesis, as cathepsin B can activate trypsinogen. The object of this study was to quantitate acinar cell necrosis and to study subcellular distribution of cathepsin B in BPDL-induced acute necrotizing pancreatitis in opossums. Bile and pancreatic ducts were ligated separately (no bile reflux) in four opossums while ducts were dissected in four sham controls. Opossums were killed 24 hr after operation. Three equidistant cross-sectional portions of each opossum pancreas were submitted to histologic examination. In blinded fashion, each focus of acinar cell necrosis was photographed and quantitated with digitizing morphometry. Numerical density (foci/cm2) and areal density (x10(3) micron 2/cm2) of focal acinar cell necrosis were determined. Differentially centrifuged pancreatic homogenates were assayed for cathepsin B, the lysosomal marker enzyme N-acetylglucosaminidase, and amylase. Morphometric quantitation of acinar cell necrosis confirmed development of acute necrotizing pancreatitis after 24 hr of BPDL in opossums. However, colocalization was not observed after BPDL, as evidenced by an absence of subcellular shift of cathepsin B activity (and N-acetyl-glucosaminidase activity) from the lysosome-enriched to the zymogen-enriched subcellular fraction. Amylase activity was increased in subcellular fractions after BPDL.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylglucosaminidase↗
PubMed1996

Agrin is synthesized by retinal cells and colocalizes with gephyrin [corrected].

At the neuromuscular junction, motoneuron-derived agrin is concentrated in the basal lamina of the synaptic cleft where it is responsible for the formation of the postsynaptic apparatus. As a step toward understanding agrin's role in the developing central nervous system, we have characterized agrin in retinal cell cultures as well as in the intact retina. Agrin was synthesized and secreted by cultured retinal cells and at least part of this agrin was active in acetylcholine receptor aggregation. Punctate anti-agrin immunoreactivity was associated with the cell bodies and processes of retinal neurons. Double labeling with antibodies against agrin and against the synapse-associated molecule gephyrin demonstrated that approximately half of the gephyrin clusters colocalized with the punctate agrin immunoreactivity in vitro. In the in vivo retina, more than 80% of the gephyrin clusters colocalized with extracellular agrin. These data indicate that agrin is concentrated at synapses in the retina as it is at the neuromuscular junction.

Agrin↗