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Results for “Colocalization”

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PubMed1993

Absence of estrogen receptor immunoreactivity in somatostatin (SRIF) neurons of the periventricular nucleus but sexually dimorphic colocalization of estrogen receptor and SRIF immunoreactivities in neurons of the bed nucleus of the stria terminalis.

The mechanisms by which somatostatin (SRIF) neurons in the periventricular nucleus and bed nucleus of the stria terminalis (BNST) are differentially regulated by gonadal steroids are unknown. Studies have shown an overlap in the distribution of estrogen receptor and SRIF immunoreactivities in these areas, giving rise to the possibility that SRIF neurons are regulated directly by gonadal steroids. In this study we have used double labeling immunocytochemistry to address the question of whether SRIF neurons in the periventricular region and BNST possess estrogen receptors in male and female rats. Short-term (2- to 4-day) gonadectomized rats with or without colchicine pretreatment for 16-18 h were processed for immunocytochemical staining using monoclonal estrogen receptor (H222) and polyclonal SRIF antisera. Single staining for SRIF and the estrogen receptor in rostral hypothalamic areas showed that the only sites of significant overlap between the two immunoreactivities were in the dorsal half of the periventricular region and posterior BNST. No sex differences were detected in the numbers of SRIF- or estrogen receptor-immunoreactive cells in the dorsal periventricular region. Sequential double-staining techniques demonstrated that periventricular SRIF neurons do not possess estrogen receptor immunoreactivity in either the male or female rat. However, double-labeled cells were readily detected in the posterior division of the BNST in male rats treated with colchicine. No colocalization was detected in the BNST of the female. These results show that the periventricular SRIF neurons controlling GH secretion do not possess estrogen receptor immunoreactivity in either sex and suggest that effects of testosterone and estradiol on SRIF messenger RNA expression in these cells through the estrogen receptor are indirect. In contrast, we provide evidence of a substantial sex difference in the localization of estrogen receptors within SRIF neurons of the BNST.

Animals↗

PubMed1999

Colocalization of neurotensin messenger ribonucleic acid (mRNA) and progesterone receptor mRNA in rat arcuate neurons under estrogen-stimulated conditions.

In the female rat, estrogen and progesterone directly or indirectly regulate the activity of neurotensin (NT)-synthesizing neurosecretory cells located in the hypothalamic arcuate nucleus (ARC). To determine whether these NT neurons are subject to direct regulation by ovarian steroids, estrogen-inducible messenger RNA (mRNA) encoding nuclear progesterone receptor (PR) was used as a cellular marker for nuclear estrogen receptor (ER) as well as PR, and double label in situ hybridization was employed to determine the extent to which NT/neuromedin N mRNA and PR mRNA are colocalized in ARC neurons under estrogen-stimulated conditions. In estradiol-treated ovariectomized rats, approximately 80% of NT/neuromedin N mRNA-expressing cells in sections through the dorsomedial division of the ARC and approximately 60% of such cells in sections through the ventrolateral division of the ARC were found to contain PR mRNA. Depending on the ARC division and rostrocaudal level, double labeled cells accounted for approximately 20-50% of PR mRNA-containing cells. These results indicate that under estrogen-stimulated conditions the majority of NT neurons in the ARC express both PR and ER, as previous studies of this region indicate that estrogen-inducible PR occurs only in cells that also express ER. In the rat, NT neurons appear to be a major ARC cell type subject to direct regulation by estrogen and progesterone.

Animals↗

PubMed1999

Cystatin-related epididymal spermatogenic protein colocalizes with luteinizing hormone-beta protein in mouse anterior pituitary gonadotropes.

The CRES (cystatin-related epididymal spermatogenic) protein, a member of the cystatin superfamily of cysteine protease inhibitors, exhibits highly restricted expression in the mouse testis and epididymis, suggesting roles in reproduction. Considering the well-established relationship that exists between the gonads and the neuroendocrine system, the present studies were undertaken to determine whether the CRES messenger RNA and protein are expressed in the anterior pituitary gland and, if so, whether the expression is regulated by hormones. RT-PCR analysis of whole pituitary gland RNA preparations, and Northern blot analyses of pituitary gland cell lines, demonstrated that the CRES gene is expressed in the male and female anterior pituitary gland gonadotropes. Furthermore, Western blot analysis demonstrated that CRES protein was present in whole mouse pituitary glands and was synthesized and secreted by the LbetaT2 gonadotrope cell line. Interestingly, whereas the predominant CRES proteins present in epididymal lysates, LbetaT2 secretory granules, and whole pituitary gland lysates were 19 and 14 kDa, the predominant CRES proteins present in the cell culture conditioned media were 17 and 12 kDa. Deglycosylation studies revealed that the higher-molecular-mass CRES proteins (19 and 17 kDa) were the result of N-linked glycosylation, caused by the presence of high mannose residues. Double-label immunofluorescence and confocal microscopic analysis of male and female mouse pituitary gland tissue confirmed the RNA studies and showed that CRES protein colocalized with LHbeta protein in the gonadotropes. Finally, gonadectomy and hormone replacement studies suggest that CRES protein in the gonadotropes is hormonally regulated. These studies suggest that CRES protein may perform a role in the gonadotrope-mediated control of reproduction.

Animals↗

PubMed1999

Colocalization of somatostatin receptor sst5 and insulin in rat pancreatic beta-cells.

Somatostatin, also known as somatotropin release-inhibiting factor (SRIF), is secreted by pancreatic delta-cells and inhibits the secretion of both insulin and glucagon. SRIF initiates its actions by binding to a family of six G protein-coupled receptors (sst1, -2A, -2B, -3, -4, and -5) encoded by five genes. Messenger RNA for both sst2 and sst5 have been reported in the rat pancreas, and the sst2A receptor protein has been localized to rat pancreatic alpha and pancreatic polypeptide-secreting cells in the islets as well as to pancreatic acinar cells. In this study we have used double immunostaining to show that the sst5 protein is expressed exclusively in the beta-cells of rat pancreatic islets and localizes with insulin-secreting alpha-cells. The sst5 receptor is not colocalized with sst2A. Thus, in the rat SRIF inhibits pancreatic insulin and glucagon secretion via different sst receptor subtypes.

Alternative Splicing↗

PubMed1994

Immunocytochemical colocalization of progesterone receptor and prolactin in individual stromal cells of human decidua.

Progesterone stimulates decidual PRL production. However, decidualized tissue, in which a high level of PRL is present, features a relatively low level of progesterone receptor (PR) expression. The discrepancy has to be explored at the individual cell level. The present study employed a double labeling method to colocalize PR and PRL in human decidua to examine the correlation between these two proteins. In frozen sections, decidual stroma presented two kinds of cell, which differed in PRL staining. Decidualized cells were positively stained with PRL in cytoplasm and displayed a large cell size and a clear cell outline. Nondecidualized cells showed no specific PRL staining and no clear cell boundary. In decidual stroma, PR staining was exclusively localized in the nuclei, with variations in intensity. When double staining with PR and PRL was performed, these two types of cells demonstrated diverse staining patterns. The PRL-producing cells exhibited weak PR staining, whereas PRL-negative cells evidenced stronger PR staining. In RU 486-treated samples, decidual stroma became less stained with PRL, compared with the control, and fewer cells displayed typical morphology of decidualization, whereas PR staining in the tissue became more extensive and intensive. Double labeling disclosed that the cells with enhanced PR staining were coupled to weaker PRL immunoreaction. Our data suggested an inverse relationship between PRL and PR in individual stromal cells in vivo, which could be reversed by antiprogestin treatment. A possible autocrine mechanism controlling this phenomenon was proposed and deserves further study.

Cell Nucleus↗

PubMed1996

Steroidogenic factor 1 and Dax-1 colocalize in multiple cell lineages: potential links in endocrine development.

Mutations of the orphan nuclear receptors, steroidogenic factor 1 (SF-1) and DAX-1, cause complex endocrine phenotypes that include impaired adrenal development and hypogonadotrophic hypogonadism. These similar phenotypes suggest that SF-1 and DAX-1 act in the same pathway(s) of endocrine development. To explore this model, we now compare directly their sites of expression. In mouse embryos, SF-1 expression in the urogenital ridge and brain either preceded or coincided with Dax-1 expression, with coordinate expression thereafter in the adrenal cortex, testis, ovary, hypothalamus, and anterior pituitary. The striking colocalization of SF-1 and Dax-1 supports the model that they are intimately linked in a common pathway of endocrine development. The slightly earlier onset of SF-1 expression and its ability to bind specifically to a conserved sequence in the Dax-1 5'-flanking region suggested that SF-1 may activate Dax-1 expression. However, promoter activity of Dax-1 5'-flanking sequences did not require this potential SF-1-responsive element, and Dax-1 expression was unimpaired in knockout mice lacking SF-1, establishing that SF-1 is not required for Dax-1 gene expression in these settings. Although the precise mechanisms remain to be established and may be multifactorial, our results strongly suggest that these two orphan nuclear receptors interact in a common pathway of endocrine development.

Animals↗

PubMed1990

Colocalization of TGF-beta 1 and collagen I and III, fibronectin and glycosaminoglycans during lung branching morphogenesis.

The possible in vivo role of TGF-beta 1 in regulating various proteins of the extracellular matrix, including fibronectin, collagen I and III, and glycosaminoglycans, was examined by immunohistochemical methods during critical stages of lung morphogenesis in the 11- to 18-day-old mouse embryo. Sections of Bouin-fixed, paraffin-embedded whole embryos were exposed to polyclonal antibodies specific to synthetic peptides present in the precursor part of TGF-beta 1 (pro-TGF-beta 1), in the processed TGF-beta 1 (antibody CC), collagen I and III, fibronectin, followed by the PAP or ABC technique to visualize the location of the antibody. GAG were stained with Alcian Blue 8GX. Our results indicate colocalization of TGF-beta 1 expression and that of matrix proteins in the developing lung when branching morphogenesis (cleft formation) and tissue stabilization occur. The presence of TGF-beta 1 at the epithelial-mesenchymal interfaces of stalks and clefts at a time when matrix proteins can first be visualized in these areas, suggests a direct participation of the growth factor in the development of the basic architecture of the lung.

Animals↗

PubMed1991

alpha-Actin proteins and gene transcripts are colocalized in embryonic mouse muscle.

The alpha-actins are among the earliest muscle-specific mRNAs to appear in developing cardiac and skeletal muscle. To determine if there is coexpression of the alpha-actin proteins at early stages of myogenesis, we have used an alpha-actin-specific polyclonal antibody and in situ hybridization with specific cRNA probes to cardiac and skeletal alpha-actin transcripts on serial slides of mouse embryo sections. As soon as we can detect alpha-actin mRNAs in embryonic striated muscle, we also detect the protein suggesting that alpha-actin transcripts are translated very rapidly after transcription during myogenesis. In skeletal muscle, this colocalization of alpha-actin mRNA and protein was observed both in the myotomes of somites and in developing muscles in the limbs. In cardiac muscle, alpha-actin transcripts and proteins are abundantly expressed as soon as a cardiac tube forms.

Actins↗

PubMed2005

Colocalization of muscleblind with RNA foci is separable from mis-regulation of alternative splicing in myotonic dystrophy.

Myotonic dystrophy type I (DM1), which is caused by a non-coding CTG-repeat expansion in the dystrophia myotonica-protein kinase (DMPK) gene, is an RNA-mediated disease. Expanded CUG repeats in transcripts of mutant DMPK form nuclear foci that recruit muscleblind-like (MBNL) proteins, a family of alternative splicing factors. Although transcripts of mutant DMPK and MBNL proteins accumulate in nuclear RNA foci, it is not clear whether foci formation is required for splicing mis-regulation. Here, we use a co-transfection strategy to show that both CUG and CAG repeats form RNA foci that colocalize with green fluorescent protein (GFP)-MBNL1 and endogenous MBNL1. However, only CUG repeats alter splicing of the two tested pre-mRNAs, cardiac troponin T (cTNT) and insulin receptor (IR). Using FRAP, we demonstrate that GFP-MBNL1 in CUG and CAG foci have similar half-times of recovery and fractions of immobile molecules, suggesting that GFP-MBNL1 is bound by both CUG and CAG repeats. We also find an immobile fraction of GFP-MBNL1 in DM1 fibroblasts and a similar rapid exchange in endogenous CUG RNA foci. Therefore, formation of RNA foci and disruption of MBNL1-regulated splicing are separable events.

Adult↗

PubMed1993

Moesin, like ezrin, colocalizes with actin in the cortical cytoskeleton in cultured cells, but its expression is more variable.

The band 4.1 superfamily of proteins show approx. 30% sequence identity in their amino-terminal region to the membrane binding domain of erythrocyte band 4.1. Within this superfamily are three members, ezrin, radixin and moesin, that show approx. 75% overall sequence identity. A comparison of the domain structure and intracellular localization of ezrin and moesin in cultured cells is reported here. Limited proteolytic digestion of ezrin or moesin yields a relatively stable 32 kDa domain derived from the amino-terminal region that is homologous to the protease-resistant membrane binding domain of erythrocyte band 4.1. The remaining regions of the two proteins give rise to very different fragments, suggesting that the secondary/tertiary structures of the two proteins are different in these regions. We have generated polyclonal antibodies that discriminate between ezrin and moesin, and do not react with radixin. All cultured cell lines investigated contain ezrin, whereas moesin is variably expressed. Cells that contain both ezrin and moesin show a very similar pattern: both proteins are enriched and colocalize with actin in cell surface structures. Ezrin is also detected in the cytoplasm. In cells with few or no surface structures, both proteins show a patchy distribution in regions of the cell that contain fine networks of actin filaments. No staining of focal contacts or adherens junctions was observed. These results, together with those of others, lead to the conclusion that, of the members of this protein family, only radixin is an authentic component of adherens junctions and focal contacts. Ezrin and moesin are both found in cell surface structures after treatment of human A431 cells with epidermal growth factor, and ezrin, but not moesin, becomes phosphorylated on tyrosine. This study shows that ezrin and moesin have a similar subcellular distribution in cultured cells, yet are distinguishable in their expression, structure and ability to serve as a kinase substrate.

Actins↗

PubMed1994

A Rab4-like GTPase in Dictyostelium discoideum colocalizes with V-H(+)-ATPases in reticular membranes of the contractile vacuole complex and in lysosomes.

In the course of screening a cDNA library for ras-related Dictyostelium discoideum genes, we cloned a 0.7 kb cDNA (rabD) encoding a putative protein that was 70% identical at the amino acid level to human Rab4. Rab4 is a small M(r) GTPase, which belongs to the Ras superfamily and functions to regulate endocytosis in mammalian cells. Southern blot analysis indicated that the rabD cDNA was encoded by a single copy gene while Northern blot analysis revealed that the rabD gene was expressed at relatively constant levels during growth and differentiation. Affinity-purified antibodies were prepared against a RabD fusion protein expressed in bacteria; the antibodies recognized a single 23 kDa polypeptide on western blots of cell extracts. Density gradient fractionation revealed that the RabD antigen co-distributed primarily with buoyant membranes rich in vacuolar protons pumps (V-H(+)-ATPases) and, to a lesser extent, with lysosomes. This result was confirmed by examining cell lines expressing an epitope-tagged version of RabD. Magnetically purified early endocytic vesicles and post-lysosomal vacuoles reacted more weakly with anti-RabD antibodies than did lysosomes. Other organelles were negative for RabD. Double-label indirect immunofluorescence microscopy revealed that RabD and the 100 kDa V-H(+)-ATPase subunit colocalized in a fine reticular network throughout the cytoplasm. This network was reminiscent of spongiomes, the tubular elements of the contractile vacuole system. Immunoelectron microscopy confirmed the presence of RabD in lysosome fractions and in the membranes rich in V-H(+)-ATPase. We conclude that a Rab4-like GTPase in D. discoideum is principally associated with the spongiomes of contractile vacuole complex.

Amino Acid Sequence↗

PubMed1995

Colocalization of a high molecular mass phosphoprotein of the nuclear matrix (p255) with spliceosomes.

It was previously demonstrated that monoclonal antibody CC-3 binds to a phosphorylation dependent epitope present on a 255 kDa nuclear protein (p255). We show here that in interphase cells, p255 distributes to typical nuclear speckles that correspond to the localization of spliceosome components as revealed by antibodies to the m3G cap of snRNAs or to the non-snRNP splicing factor SC-35. Immunofluorescence and immunoblot studies indicated that p255 is resistant to extraction with non-ionic detergents, nucleases and high ionic strength buffers and may thus be defined biochemically as a nuclear matrix phosphoprotein. To determine the nature of the association of p255 with the nuclear structure, its distribution was studied at different stages of the cell cycle and after the cells were treated with nucleases or heat shocked. We found that the antigen diffused into the cytoplasm during metaphase but was reorganized into cytoplasmic speckles during anaphase-telophase transition, where it colocalized with SC-35. Nuclear matrix preparations that were digested with DNases and RNases showed that interphasic p255 still localized to nuclear speckles even though snRNA and snRNP antigens were removed. Heat-shocked cells labelled with monoclonal antibody CC-3 exhibited more rounded and less interconnected speckles, identical to those decorated by anti-SC-35 antibody under such conditions. These results indicate that p255 and SC-35 are present in the same nuclear structures, to which they are more tightly bound than the snRNP antigens. They further suggest that both proteins are implicated in spliceosome assembly or attachment.

3T3 Cells↗

PubMed1997

Evidence for colocalization and interaction between 37 and 39 kDa isoforms of secretory carrier membrane proteins (SCAMPs).

Secretory carrier membrane proteins (SCAMPs) are proteins of post-Golgi recycling carriers, including regulated secretory organelles. The two major size variants, SCAMP1 (37 kDa) and SCAMP2 (39 kDa), extensively colocalize in membranes of fibroblasts and parotid acinar cells based on immunocytochemistry and velocity centrifugation, although the relative amounts of each variant may differ in selected organelles. SCAMP1, and to a lesser extent, SCAMP2, are substrates for chemical crosslinking in situ, and the recognizable crosslinking products of SCAMP1 suggest potential formation of homomultimers. SCAMP1 and SCAMP2 can be co-immunoprecipitated following detergent solubilization, using antibodies that specifically react with only one of the variants. Both the localization and interactions of SCAMPs are reiterated using transfected SCAMP1 that is epitope tagged (myc) at either the NH2 or COOH terminus and an anti-myc antibody. Like other transport vesicle membrane proteins, SCAMPs form complexes that apparently include homomultimers. Furthermore, these studies suggest that both SCAMP1 and SCAMP2 may function together in a single protein complex.

Animals↗

PubMed1997

An actin-related protein in Drosophila colocalizes with heterochromatin protein 1 in pericentric heterochromatin.

The actin-related proteins have been identified by virtue of their sequence similarity to actin. While their structures are thought to be closely homologous to actin, they exhibit a far greater range of functional diversity. We have localized the Drosophila actin-related protein, Arp4, to the nucleus. It is most abundant during embryogenesis but is expressed at all developmental stages. Within the nucleus Arp4 is primarily localized to the centric heterochromatin. Polytene chromosome spreads indicate it is also present at much lower levels in numerous euchromatic bands. The only other protein in Drosophila reported to be primarily localized to centric heterochromatin in polytene nuclei is heterochromatin protein 1 (HP1), which genetic evidence has linked to heterochromatin-mediated gene silencing and alterations in chromatin structure. The relationship between Arp4 and heterochromatin protein 1 (HP1) was investigated by labeling embryos and larval tissues with antibodies to Arp4 and HP1. Arp4 and HP1 exhibit almost superimposable heterochromatin localization patterns, remain associated with the heterochromatin throughout prepupal development, and exhibit similar changes in localization during the cell cycle. Polytene chromosome spreads indicate that the set of euchromatic bands labeled by each antibody overlap but are not identical. Arp4 and HP1 in parallel undergo several shifts in their nuclear localization patterns during embryogenesis, shifts that correlate with developmental changes in nuclear functions. The significance of their colocalization was further tested by examining nuclei that express mutant forms of HP1. In these nuclei the localization patterns of HP1 and Arp4 are altered in parallel fashion. The morphological, developmental and genetic data suggest that, like HP1, Arp4 may have a role in heterochromatin functions.

Actins↗

PubMed1999

Rvs167p, the budding yeast homolog of amphiphysin, colocalizes with actin patches.

In this report, we have shown that the yeast amphiphysin-like protein Rvs167p was localized mainly in small cortical patches throughout the cell in unbudding cells. During budding, the patches were polarized at bud emergence site. During mating, Rvs167p was concentrated at the tip of the shmoo. Rvs167p colocalized with actin patches during yeast vegetative growth and mating. Complete disruption of the actin cytoskeleton using Latrunculin-A did not affect Rvs167p localization in patches throughout the cell. In rvs167 mutant cells, actin patches are mislocalized and in rvs161 or abp1 mutant cells, Rvs167p localization is not affected. These observations suggest that Rvs167p may localize the actin cortical complex properly. Finally, the amphiphysin-conserved N-terminal domain of Rvs167p, called the BAR domain, was required but not sufficient for the correct localization of the protein.

Actins↗

PubMed1999

Colocalization of intranuclear lamin foci with RNA splicing factors.

The lamins form a fibrous network underlying the inner nuclear membrane termed the nuclear lamina. In order to gain insights into the role of lamins in nuclear organization, we have characterized a monoclonal antibody (LA-2H10) raised against recombinant rat lamin A that labels nuclei in a speckled pattern in all cells of unsynchronized populations of HeLa and rat F-111 fibroblast cells, unlike the typical nuclear periphery staining by another monoclonal antibody to lamin A, LA-2B3. In immunolocalization studies the lamin A speckles or foci were found to colocalize with the RNA splicing factors SC-35 and U5-116 kD, but not with p80 coilin found in coiled bodies. Lamin B1 was also associated with these foci. These foci dispersed when cells entered mitosis and reformed during anaphase. The differential reactivity of LA-2H10 and LA-2B3 was retained after nuclei were extracted with detergents, nucleases and salt to disrupt interactions of lamins with chromatin and other nuclear proteins. Using deletion fragments of recombinant lamin A, the epitope recognized by LA-2H10 was located between amino acids 171 and 246. Our findings are consistent with a structural role for lamins in supporting nuclear compartments containing proteins involved in RNA splicing.

Animals↗

PubMed2000

Colocalization of chaperone Cpn60, proinsulin and convertase PC1 within immature secretory granules of insulin-secreting cells suggests a role for Cpn60 in insulin processing.

Many of the mechanisms that control insulin processing and packaging by interaction with different elements along the secretory pathway remain poorly understood. We have investigated the possibility that Cpn60, a member of the heat shock protein family, may be present in rat insulin-secreting cells, participating in the proinsulin-insulin maturation process. Immunofluorescence and high resolution immunocytochemical studies revealed the presence of the Cpn60 protein all along the insulin secretory pathway, being particularly abundant over the proinsulin-containing immature secretory granules. Double-labeling experiments showed associations between Cpn60 and proinsulin, as well as between Cpn60 and PC1 convertase, with a preferential binding to proinsulin. These findings paralleled those of coimmunoprecipitation studies showing the Cpn60 chaperone and the mature form of the PC1 convertase in proinsulin immunoprecipitates, as well as the PC1 in Cpn60 immunoprecipitates from total islet cell extracts. In vitro binding of Cpn60 to proinsulin, insulin and glucagon was also documented. Cpn60, significantly abundant in proinsulin-containing secretory granules where conversion of proinsulin to insulin takes place, and the colocalization of the chaperone with proinsulin and PC1 convertase suggest that the Cpn60 protein may play a role directing precise molecular interactions during insulin processing and/or packaging.

Animals↗

PubMed2002

The plant Spc98p homologue colocalizes with gamma-tubulin at microtubule nucleation sites and is required for microtubule nucleation.

The molecular basis of microtubule nucleation is still not known in higher plant cells. This process is better understood in yeast and animals cells. In the yeast spindle pole body and the centrosome in animal cells, gamma-tubulin small complexes and gamma-tubulin ring complexes, respectively, nucleate all microtubules. In addition to gamma-tubulin, Spc98p or its homologues plays an essential role. We report here the characterization of rice and Arabidopsis homologues of SPC98. Spc98p colocalizes with gamma-tubulin at the nuclear surface where microtubules are nucleated on isolated tobacco nuclei and in living cells. AtSpc98p-GFP also localizes at the cell cortex. Spc98p is not associated with gamma-tubulin along microtubules. These data suggest that multiple microtubule-nucleating sites are active in plant cells. Microtubule nucleation involving Spc98p-containing gamma-tubulin complexes could then be conserved among all eukaryotes, despite differences in structure and spatial distribution of microtubule organizing centers.

Arabidopsis↗