Intracellular colocalization of molecules involved in antigen processing and presentation by B cells.
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Antigen-Presenting Cells↗
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Results for “Colocalization”
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Colocalization of barley lectin and sporamin in vacuoles of transgenic tobacco plants.
Various targeting motifs have been identified for plant proteins delivered to the vacuole. For barley (Hordeum vulgare) lectin, a typical Gramineae lectin and defense-related protein, the vacuolar information is contained in a carboxyl-terminal propeptide. In contrast, the vacuolar targeting information of sporamin, a storage protein from the tuberous roots of the sweet potato (Ipomoea batatas), is encoded in an amino-terminal propeptide. Both proteins were expressed simultaneously in transgenic tobacco plants to enable analysis of their posttranslational processing and subcellular localization by pulse-chase labeling and electron-microscopic immunocytochemical methods. The pulse-chase experiments demonstrated that processing and delivery to the vacuole are not impaired by the simultaneous expression of barley lectin and sporamin. Both proteins were targeted quantitatively to the vacuole, indicating that the carboxyl-terminal and amino-terminal propeptides are equally recognized by the vacuolar protein-sorting machinery. Double-labeling experiments showed that barley lectin and sporamin accumulate in the same vacuole of transgenic tobacco (Nicotiana tabacum) leaf and root cells.
Amino Acid Sequence↗
Colocalization of Polyphenol Oxidase and Photosystem II Proteins.
Polyphenol oxidase (PPO) appears to be ubiquitous in higher plants but, as yet, no function has been ascribed to it. Herein, we report on the localization of PPO based upon biochemical fractionation of chloroplast membranes in Vicia faba (broad bean) into various complexes and immunocytochemical electron microscopic investigations. Sucrose density gradient fractionations of thylakoid membranes after detergent solubilization reveals that PPO protein (by reactivity with anti-PPO antibody) and activity (based upon ability to oxidize di-dihydroxyphenylalanine) are found only in fractions enriched in photosystem II (PSII). Furthermore, of the PSII particles isolated using three different protocols utilizing several plant species, all had PPO. Immunogold localization of PPO on thin sections reveals exclusive thylakoid labeling with a distribution pattern consistent with other PSII proteins (80% grana, 20% stroma). These data strongly indicate that PPO is at least peripherally associated with the PSII complex.
Journal Article↗
Protein-protein interactions between sucrose transporters of different affinities colocalized in the same enucleate sieve element.
Suc represents the major transport form for carbohydrates in plants. Suc is loaded actively against a concentration gradient into sieve elements, which constitute the conduit for assimilate export out of leaves. Three members of the Suc transporter family with different properties were identified: SUT1, a high-affinity Suc proton cotransporter; SUT4, a low-affinity transporter; and SUT2, which in yeast is only weakly active and shows features similar to those of the yeast sugar sensors RGT2 and SNF3. Immunolocalization demonstrated that all three SUT proteins are localized in the same enucleate sieve element. Thus, the potential of Suc transporters to form homooligomers was tested by the yeast-based split-ubiquitin system. The results show that both SUT1 and SUT2 have the potential to form homooligomers. Moreover, all three Suc transporters have the potential to interact with each other. As controls, a potassium channel and a monosaccharide transporter, expressed in the plasma membrane, did not interact with the SUTs. The in vivo interaction between the functionally different Suc transporters indicates that the membrane proteins are capable of forming oligomeric structures that, like mammalian Glc transporter complexes, might be of functional significance for the regulation of transport.
Binding Sites↗
Colocalization of lichen planus and vitiligo.
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Humans↗
AA glomerular amyloid. An ultrastructural immunogold study of the colocalization of heparan sulphate proteoglycan and P component with amyloid fibrils together with changes in distribution of type IV collagen and fibronectin.
An ultrastructural investigation was undertaken on paraformaldehyde-fixed Lowicryl resin-embedded human kidneys of three patients with AA amyloidosis to investigate the association of various basement membrane components with amyloid fibrils. An immunogold technique was used and antibodies to serum amyloid A, heparan sulphate proteoglycan, type IV collagen, P component, and fibronectin were applied to human normal and amyloid glomeruli. The amyloid was identified as AA, and P component was shown to be intimately associated with the fibrils. In addition, heparan sulphate proteoglycan was associated with amyloid in all subendothelial, subepithelial and intramembranous glomerular basement membrane deposits, and those throughout the mesangial matrix. This contrasted with the distribution of the proteoglycan in the normal glomerulus where it was found predominantly on the epithelial aspect of the basement membrane and only in the more peripheral regions of the mesangium. The accumulation of heparan sulphate proteoglycan with amyloid resulted in a marked increase in its amount in the glomeruli. The amyloid deposits contained little or no type IV collagen or fibronectin. These findings demonstrate a strong association of heparan sulphate proteoglycan with amyloid and suggest different roles for the various glomerular basement membrane components in amyloidogenesis.
Amyloidosis↗
Simultaneous degradation estimation and restoration of confocal images and performance evaluation by colocalization analysis.
A novel method for joint restoration and estimation of the degradation of confocal microscope images is presented. The observed images are degraded due to two sources: blurring due to the band-limited nature of the optical system [modelled by the point spread function (PSF)], and Poisson noise contaminates the observations due to the discrete nature of the photon detection process. The proposed method iterates noise reduction, blur estimation and deblurring, and applies these steps in two phases, i.e. a training phase and a restoration phase. In the first phase, these three steps are iterated until the blur estimation converges. Noise reduction and blur estimation are performed using steerable pyramids, and the deblurring is performed by the Richardson-Lucy algorithm. The second phase is the actual restoration. From then on, the blur estimation is used as a criterion to measure the image quality. The iterations are stopped when this measure converges, a result that is guaranteed. The integrated method is completely automatic, and no prior information on the image is required. The method has been given the name SPERRIL (Steerable Pyramid-based Estimation and Regularized Richardson-Lucy restoration). Compared with existing techniques by both objective measures and visual observation, in the SPERRIL-restored images noise is better suppressed.
Algorithms↗
Vasopressin anti-idiotypic antibody staining in the rat brain: colocalization with [35S] [pGlu4, Cyt6]AVP(4-9) binding sites.
Vasopressin and its fragment peptides such as [pGlu4, Cyt6]AVP(4-9) (AVP(4-9) represent putative neuromodulators within central nervous homeostatic, memory and behavioural circuits. To localize their central receptor systems, the previously characterized monoclonal anti-idiotypic antibody mAb 237 was employed in immunocytological investigations of rat brain tissue sections. This antibody was raised to the monoclonal idiotypic anti-AVP antibody mAb 113 which preferentially binds to the acyclic C-terminal portion of the AVP molecule and is therefore also capable of binding the naturally occurring AVP(4-9) fragment. Immunoreactive magnocellular neurones were detected in the AVP-synthesizing supraoptic but not paraventricular nuclei. Dense staining was observed within circumventricular organs lacking a blood-brain barrier (BBB). These structures include the subfornical organ, the organum vasculosum laminae terminalis, the internal layer of the median eminence, the body of the pineal gland, the choroid plexus and the area postrema, where immunoreactivity was found on capillaries, neurones and fibres. Further staining was found in the nucleus of the solitari tract and the arcuate nucleus, endowed with a leaky BBB. Distinct cell patches in the ependymal lining of the third ventricle as well as dendritic processes of juxtaependymal neurones were labelled by the anti-idiotypic antibody mAb 237. The observed staining pattern did not parallel that obtained in autoradiographic studies performed using either radiolabelled AVP or a V1-receptor antagonist, but that found with the [35S]-labelled AVP(4-9) fragment. Using [35S]-labelled AVP(4-9) fragment, specific high density binding sites could be localized autoradiographically in structures within and outside the BBB, in complete agreement with the anti-idiotypic immunoreactivity. Since the anti-idiotypic methodology is based on transfer of complementary structures, and the epitope recognized by the corresponding idiotypic antibody resembles the sequence of AVP(4-9), the anti-idiotypic antibodies might recognize the AVP(4-9) receptor with high affinity.
Animals↗
Colocalization of natriuretic peptide and estrogen receptor immunoreactivities in preoptic nuclei in the female rat.
Estrogen is known to play an important role in regulating reproductive function in female rats through actions exerted at the preoptic area, a part of the brain that is markedly sexually dimorphic and which contains abundant estrogen receptors. A critical question to our understanding of estrogen's action on the brain is to identify the types of neurons that contain estrogen receptors (ER). Previous studies have shown that atrial natriuretic peptide (ANP) is in abundance in the preoptic area, and that ANP and other natriuretic peptides are capable of regulating gonadotropin secretion. In an effort to determine whether ERs are present in natriuretic peptide-immunoreactive (NP-ir) neurons in the preoptic area of the rat, double label immunocytochemistry was performed. Since ER-ir, as demonstrated with antibody H222 is known to be localized predominantly in cell nuclei, while NP-ir is present in the cytoplasm, single cells can be double labeled. Diaminobenzidine tetrahydrochloride was used for localization of NP-ir neurons, while nickel-enhanced diaminobenzidine tetrahydrochloride was used for localization of ER-ir. The results revealed that many nuclei throughout the preoptic area contained neurons that were ER-ir or NP-ir and that a substantial number were double labeled. Cell counts in selected preoptic nuclei and components, including the anteroventral periventricular nucleus, periventricular preoptic nucleus, medial part of the medial preoptic nucleus, and central part of the medial preoptic nucleus revealed that 13.6%, 11.1%, 13.5%, and 24.4%, respectively, of the NP-ir neurons in these nuclei also contained ER-ir. Collectively, a total of 14.9% of the NP-ir neurons in these nuclei also contained ER-ir.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Helical distribution of the bacterial chemoreceptor via colocalization with the Sec protein translocation machinery.
In Escherichia coli, chemoreceptor clustering at a cell pole seems critical for signal amplification and adaptation. However, little is known about the mechanism of localization itself. Here we examined whether the aspartate chemoreceptor (Tar) is inserted directly into the polar membrane by using its fusion to green fluorescent protein (GFP). After induction of Tar-GFP, fluorescent spots first appeared in lateral membrane regions, and later cell poles became predominantly fluorescent. Unexpectedly, Tar-GFP showed a helical arrangement in lateral regions, which was more apparent when a Tar-GFP derivative with two cysteine residues in the periplasmic domain was cross-linked to form higher oligomers. Moreover, similar distribution was observed even when the cytoplasmic domain of the double cysteine Tar-GFP mutant was replaced by that of the kinase EnvZ, which does not localize to a pole. Observation of GFP-SecE and a translocation-defective MalE-GFP mutant, as well as indirect immunofluorescence microscopy on SecG, suggested that the general protein translocation machinery (Sec) itself is arranged into a helical array, with which Tar is transiently associated. The Sec coil appeared distinct from the MreB coil, an actin-like cytoskeleton. These findings will shed new light on the mechanisms underlying spatial organization of membrane proteins in E. coli.
Bacterial Outer Membrane Proteins↗
Colocalization of the dihydropyridine receptor, the plasma-membrane calcium ATPase isoform 1 and the sodium/calcium exchanger to the junctional-membrane domain of transverse tubules of rabbit skeletal muscle.
The subcellular distribution of the calmodulin-stimulated plasma-membrane Ca(2+)-ATPase (PMCA) has been studied in rat and rabbit skeletal muscle cells by indirect (calmodulin gel overlays) and direct (Western blotting with specific antibodies) methods. It has also been studied in situ in immunocytochemistry experiments. The distribution of PMCA has been compared with that of the NA+/Ca2+ exchanger and of the dihydropyridine receptor, which has been studied by Western blotting with specific antibodies. Both PMCA and the Na+/Ca2+ exchanger had a dual localization, i.e., they were found in the plasma membrane and in the transverse-tubule fractions of the two main types of skeletal muscles studied. The pump and the exchanger were not diffusely distributed in the transverse-tubule-membrane system, but specifically confined to the membrane domain where the dihydropyridine receptor was also localized, i.e., the junctional membrane. Experiments with isoform-specific antibodies have shown that the pump isoform expressed in skeletal muscle is PMCA 1.
Animals↗
Immunohistochemical colocalization of serotonin, substance P and Met-enkephalin-Arg6-Gly7-Leu8 in the endocrine cells of the ruminant duodenum.
The duodenum of various ruminants was examined by immunohistochemical staining for serotonin, substance P and Metenkephalin-Arg6-Gly7-Leu8 (MENK8). Serotonin- and substance P-immunoreactive endocrine cells were detected in samples from cow, calf, sheep, goat, and barbary sheep, MENK8-immunoreactive endocrine cells were detected exclusively in samples from cow and calf. Substance P and MENK8 immunoreactivity was found in serotonin-immunoreactive endocrine cells of cattle. Substance P- and MENK8-immunoreactive nervous elements were detected in all ruminants examined. The present results suggest that the expression and/or the mechanism that controls the expression of each peptide might differ between endocrine cells and nerve cells and might also depend on animal species.
Aging↗
Colocalization of oestrogen receptor immunoreactivity and preproenkephalin mRNA expression to neurons in the superficial laminae of the spinal and medullary dorsal horn of rats.
A double-labelling procedure combining immunohistochemical staining with in situ hybridization using a radiolabelled cRNA probe was employed to demonstrate oestrogen receptor-like immunoreactivity and preproenkephalin-A mRNA in the medullary and spinal dorsal horn of female rats. Both markers labelled large numbers of neurons in the substantia gelatinosa and its trigeminal homologue. Many of these neurons were double-labelled, displaying both oestrogen receptor-like-immunoreactivity and preproenkephalin-A mRNA; cell counts showed that 40-60% of the of the oestrogen receptor-like-immunoreactive cells in the superficial laminae also were labelled for preproenkephalin-A mRNA, and that 60-70% of the preproenkephalin-A mRNA-labelled neurons in the same laminae displayed oestrogen receptor-like immunoreactivity. Previous studies have shown that oestrogen receptors can bind to the promoter region of the preproenkephalin-A gene, and studies on the hypothalamus have demonstrated that oestrogen regulates enkephalin expression in select neuronal populations. The present results demonstrate that enkephalinergic neurons in the superficial dorsal horn contain oestrogen receptors and suggest that oestrogen may play an important role in the modulation of sensory and nociceptive processing in the lower medulla and spinal cord.
Animals↗
Identification of a novel brain-specific and Reelin-regulated gene that encodes a protein colocalized with synapsin.
We carried out a screening of genes that are differentially expressed in normal mice and reeler mutants and are characterized by abnormal neuronal migration and neurite deployment due to defective Reelin signalling. A novel gene, provisionally named C61, was overexpressed in Reelin-deficient embryonic mouse brain RNA. C61 encodes a 3.7 kb mRNA that is brain specific and developmentally regulated, with predominant expression in differentiating neurons. The predicted protein is 664 amino acids long, and contains LAG1 and Ezrin/Radixin/Moesin-Myosin-Filament motifs, suggesting that it may function as an intracellular adaptor. From E14.5 to birth, C61 was highly expressed in all neuronal differentiation fields, with the highest signal in the telencephalic cortical plate and mitral cells in the olfactory bulb. When expressed as a GFP fusion protein in transfected non-neuronal cells and primary neurons, this protein localizes, respectively, to the nuclear membrane or axonal outgrowths, indicating a function in axonal traffic or signalling.
Amino Acid Motifs↗
Expression of A-type K channel alpha subunits Kv 4.2 and Kv 4.3 in rat spinal lamina II excitatory interneurons and colocalization with pain-modulating molecules.
Voltage-gated K(+) channel alpha subunits Kv 4.2 and Kv 4.3 are the major contributors of somatodendritic A-type K(+) currents in many CNS neurons. A recent hypothesis suggests that Kv 4 subunits may be involved in pain modulation in dorsal horn neurons. However, whether Kv 4 subunits are expressed in dorsal horn neurons remains unknown. Using immunohistochemistry, we found that Kv 4.2 and Kv 4.3 immunoreactivity was concentrated in the superficial dorsal horn, mainly in lamina II. Both Kv 4.2 and Kv 4.3 appeared on many rostrocaudally orientated dendrites, whereas Kv 4.3 could be also detected from certain neuronal somata. Kv 4.3(+) neurons were a subset of excitatory inerneurons with calretinin(+)/calbindin(-)/PKCgamma(-) markers, and a fraction of them expressed micro-opioid receptors. Kv 4.3(+) neurons also expressed ERK 2 and mGluR 5, which are molecules related to the induction of central sensitization, a mechanism mediating nociceptive plasticity. Together with the expression of Kv 4.3 in VR 1(+) DRG neurons, our data suggest that Kv C4 subunits could be involved in pain modulation.
Animals↗
Conversion of neuropeptide K to neurokinin A and vesicular colocalization of neurokinin A and substance P in neurons of the guinea pig small intestine.
The highest concentration of neurokinin A-like immunoreactivity and substance P-like immunoreactivity in the guinea pig small intestine was associated with the myenteric plexus-containing longitudinal muscle layer. Chromatographic analysis of extracts of this tissue demonstrated the presence of neurokinin A and neuropeptide K but the probable absence of neurokinin B. A fraction of synaptic vesicles of density 1.133 +/- 0.003 g/ml was prepared from the myenteric plexus-containing tissue by density gradient centrifugation in a zonal rotor and was enriched 29 +/- 12-fold in the concentration of neurokinin A-like immunoreactivity and 43 +/- 13-fold in the concentration of substance P-like immunoreactivity. This fraction was separated from the fraction of vasoactive intestinal peptide-containing vesicles (density, 1.154 +/- 0.009 g/ml). Chromatographic analysis of lysates of the vesicles indicated the presence of neurokinin A but not neuropeptide K. It is postulated that beta-pre-protachykinin is processed to substance P, neurokinin A, and neuropeptide K in the cell bodies of myenteric plexus neurons but that conversion of neuropeptide K to neurokinin A takes place during packaging into storage vesicles for axonal transport. The data are consistent with the proposal that neurokinin A and substance P are stored in the same synaptic vesicle, but the possibility of cosedimentation of different vesicles of very similar density cannot be excluded.
Animals↗
Colocalization of vitiligo and alopecia areata.
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Alopecia Areata↗
Colocalization of alopecia areata and lichen planus.
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Alopecia Areata↗