Expression of porcine complement cytolysis inhibitor mRNA in cultured aortic smooth muscle cells. Changes during differentiation in vitro

Clusterin in Neuroendocrine Epithelial Neoplasms: Absence of Expression in a Well-differentiated Tumor Suggests a Jejunoileal Origin

Clusterin, a widely expressed, tissue-specific glycoprotein, is a diagnostic marker of several tumor types, including anaplastic large cell lymphoma, follicular dendritic cell sarcoma, and tenosynovial giant cell tumor. A recent study has suggested it is highly expressed by well-differentiated neuroendocrine tumors (NET) arising at most anatomic sites, with the exception of jejunoileal tumors, and that it is similarly not expressed by poorly differentiated neuroendocrine carcinomas (NEC). We sought to validate this result in a large cohort of NETs and NECs. Clusterin immunohistochemistry was performed on tissue microarrays of 255 NETs [45 lung, 4 stomach, 8 duodenum, 75 pancreas (62 primary, 13 metastatic), 107 jejunoileum (69 primary, 38 metastatic), 16 appendix] and 88 NECs (43 visceral, 45 Merkel cell). Extent (%) and intensity (0, 1+, 2+, 3+) of staining were assessed and an H-score (extent x intensity) calculated. An average H-score >5 was considered positive. Clusterin expression was noted in 82.4% of 148 nonjejunoileal NETs (average H-score 183) and only 8.4% of 107 jejunoileal NETs (average H-score, 31), as well as 19.3% of NECs (average H-score, 36). Clusterin is frequently, strongly expressed by NETs of diverse anatomic sites, with the exception of jejunoileal tumors, in which it is only rarely, weakly expressed. It is occasionally, weakly expressed by NECs. Most metastatic NETs of occult origin arise in the pancreas or the jejunoileum. For cases in which an initial site of origin immunopanel (eg, islet 1, PAX6, CDX2) is ambiguous, addition of clusterin may be diagnostically useful, with absence of expression suggesting a jejunoileal origin.

Pentosan Polysulfate: Oral Versus Subcutaneous Injection in Mucopolysaccharidosis Type I Dogs

Background

We previously demonstrated the therapeutic benefits of pentosan polysulfate (PPS) in a rat model of mucopolysaccharidosis (MPS) type VI. Reduction of inflammation, reduction of glycosaminoglycan (GAG) storage, and improvement in the skeletal phenotype were shown. Herein, we evaluate the long-term safety and therapeutic effects of PPS in a large animal model of a different MPS type, MPS I dogs. We focused on the arterial phenotype since this is one of the most consistent and clinically significant features of the model.

Methodology/Principal Findings

MPS I dogs were treated with daily oral or biweekly subcutaneous (subQ) PPS at a human equivalent dose of 1.6 mg/kg for 17 and 12 months, respectively. Safety parameters were assessed at 6 months and at the end of the study. Following treatment, cytokine and GAG levels were determined in fluids and tissues. Assessments of the aorta and carotid arteries also were performed. No drug-related increases in liver enzymes, coagulation factors, or other adverse effects were observed. Significantly reduced IL-8 and TNF-alpha were found in urine and cerebrospinal fluid (CSF). GAG reduction was observed in urine and tissues. Increases in the luminal openings and reduction of the intimal media thickening occurred in the carotids and aortas of PPS-treated animals, along with a reduction of storage vacuoles. These results were correlated with a reduction of GAG storage, reduction of clusterin 1 staining, and improved elastin integrity. No significant changes in the spines of the treated animals were observed.

Conclusions

PPS treatment led to reductions of pro-inflammatory cytokines and GAG storage in urine and tissues of MPS I dogs, which were most evident after subQ administration. SubQ administration also led to significant cytokine reductions in the CSF. Both treatment groups exhibited markedly reduced carotid and aortic inflammation, increased vessel integrity, and improved histopathology. We conclude that PPS may be a safe and useful therapy for MPS I, either as an adjunct or as a stand-alone treatment that reduces inflammation and GAG storage.

Immune-Mediated Inflammation May Contribute to the Pathogenesis of Cardiovascular Disease in Mucopolysaccharidosis Type I

Background

Cardiovascular disease, a progressive manifestation of α-L-iduronidase deficiency or mucopolysaccharidosis type I, continues in patients both untreated and treated with hematopoietic stem cell transplantation or intravenous enzyme replacement. Few studies have examined the effects of α-L-iduronidase deficiency and subsequent glycosaminoglycan storage upon arterial gene expression to understand the pathogenesis of cardiovascular disease.

Methods

Gene expression in carotid artery, ascending, and descending aortas from four non-tolerized, non-enzyme treated 19 month-old mucopolysaccharidosis type I dogs was compared with expression in corresponding vascular segments from three normal, age-matched dogs. Data were analyzed using R and whole genome network correlation analysis, a bias-free method of categorizing expression level and significance into discrete modules. Genes were further categorized based on module-trait relationships. Expression of clusterin, a protein implicated in other etiologies of cardiovascular disease, was assessed in canine and murine mucopolysaccharidosis type I aortas via Western blot and in situ immunohistochemistry.

Results

Gene families with more than two-fold, significant increased expression involved lysosomal function, proteasome function, and immune regulation. Significantly downregulated genes were related to cellular adhesion, cytoskeletal elements, and calcium regulation. Clusterin gene overexpression (9-fold) and protein overexpression (1.3 to 1.62-fold) was confirmed and located specifically in arterial plaques of mucopolysaccharidosis-affected dogs and mice.

Conclusions

Overexpression of lysosomal and proteasomal-related genes are expected responses to cellular stress induced by lysosomal storage in mucopolysaccharidosis type I. Upregulation of immunity-related genes implicates the potential involvement of glycosaminoglycan-induced inflammation in the pathogenesis of mucopolysaccharidosis-related arterial disease, for which clusterin represents a potential biomarker.

Chapter 5: Nuclear CLU (nCLU) and the fate of the cell

The possible biological role played by Clusterin (CLU) has been puzzling researchers for a long time since its first discovery and characterization. CLU has been often described as an "enigmatic" gene, a clear indication that too many aspects of this issue have been obscure or difficult to interpret for long. The good news is that this is certainly no longer true. Since the beginning, CLU was believed to play important roles in nearly all most important biological phenomena. The diversity, sometime the contradictions, of its biological action is now likely explained by the existence of different protein products all generated by the same single copy CLU gene. The relatively recent discovery that CLU can be retained inside the cell and targeted to many intracellular sites and organelles, including the nucleus, provided us a very different view from that solely deriving from its possible role in the outer cellular environment. In particular, nuclear localization of CLU (nCLU) was found to trigger cell death in many systems. In this chapter, a critical review of previous work will enable us to reinterpret old data and observations in the attempt to progressively unravelling the CLU "enigma" by considering its localization inside and outside the cell. The final picture would supposedly reconciliate different or alternative hypothesis. Starting with an "historical" approach demonstrating that nCLU was right under our eyes since the beginning, up to the more recent contributions we will describe which stimuli would inhibit secretion and maturation of CLU leading at least one protein product to target the nucleus and kill the cell. A better understanding of this complex issue is not an easy work, considering the thoughtfulness in reviewing the existing literature and the known controversial reports. We hope that the information contained in this article will be useful for the reader to enlighten this field.

Cloning and characterization of two clusterin isoforms in rainbow trout

Clusterin is a broadly distributed glycoprotein constitutively expressed by various tissues and cell types and has been shown to be associated with several physiological and pathological functions. In order to study the molecular evolution of clusterin, here we report the cloning and characterization of two clusterin genes in rainbow trout (Oncorhynchus mykiss). The deduced amino acid sequences of clusterin-1 and a partial clusterin-2 clone are 89% identical to each other, showing 45, 42 and 38% identity with chicken, frog and human orthologs, respectively. Most of the putative N-glycosylation sites, as well as all 10 cysteine residues which are involved in disulfide bond formation in the mature trout clusterin-1 protein, are fully conserved when aligned with its orthologs from various species. Although trout clusterin genes exhibit the same exon-intron organization, in line with that of human clusterin, they show a totally different mRNA expression profile among various trout tissues. Phylogenetic analysis indicates an early segregation of the clusterin ancestral gene within the taxon of fish leading to the formation of a separate subgroup.

EST-based analysis of gene expression in the porcine brain

Since pig is an important livestock species worldwide, its gene expression has been investigated intensively, but rarely in brain. In order to study gene expression profiles in the pig central nervous system, we sequenced and analyzed 43,122 high-quality 5’ end expressed sequence tags (ESTs) from porcine cerebellum, cortex cerebrum, and brain stem cDNA libraries, involving several different prenatal and postnatal developmental stages. The initial ESTs were assembled into 16,101 clusters and compared to protein and nucleic acid databases in GenBank. Of these sequences, 30.6% clusters matched protein databases and represented function known sequences; 75.1% had significant hits to nucleic acid databases and partial represented known function; 73.3% matched known porcine ESTs; and 21.5% had no matches to any known sequences in GenBank. We used the categories defined by the Gene Ontology to survey gene expression in the porcine brain.

Myc-transformed epithelial cells down-regulate clusterin, which inhibits their growth in vitro and carcinogenesis in vivo

Effective treatment of malignant carcinomas requires identification of proteins regulating epithelial cell proliferation. To this end, we compared gene expression profiles in murine colonocytes and their c-Myc-transformed counterparts, which possess enhanced proliferative potential. A surprisingly short list of deregulated genes included the cDNA for clusterin, an extracellular glycoprotein without a firmly established function. We had previously demonstrated that in organs such as skin, clusterin expression is restricted to differentiating but not proliferating cell layers, suggesting a possible negative role in cell division. Indeed, its transient overexpression in Myc-transduced colonocytes decreased cell accumulation. Furthermore, clusterin was down-regulated in rapidly dividing human keratinocytes infected with a Myc-encoding adenovirus. Its knockdown via antisense RNA in neoplastic epidermoid cells enhanced proliferation. Finally, recombinant human clusterin suppressed, in a dose-dependent manner, DNA replication in keratinocytes and other cells of epithelial origin. Thus, clusterin appears to be an inhibitor of epithelial cell proliferation in vitro. To determine whether it also affects neoplastic growth in vivo, we compared wild-type and clusterin-null mice with respect to their sensitivity to 7, 12-dimethylbenz(a)anthracene /12-Otetradecanoylphorbol-13-acetate (DMBA/TPA)-induced skin carcinogenesis. We observed that the mean number of papillomas/mouse was higher in clusterin-null animals. Moreover, these papillomas did not regress as readily as in wild-type mice and persisted beyond week 35. The rate of progression toward squamous cell carcinoma was not altered, although those developing in clusterin-null mice were on average better differentiated. These data suggest that clusterin not only suppresses epithelial cell proliferation in vitro but also interferes with the promotion stage of skin carcinogenesis.

Apolipoprotein J inhibits the migration, adhesion, and proliferation of vascular smooth muscle cells

PURPOSE

Apolipoprotein J (ApoJ) is expressed during tissue injury and remodeling and has been implicated in vascular smooth muscle cell (VSMC) differentiation. Recently, the gene for ApoJ was identified as upregulated in distal anastomotic intimal hyperplasia after prosthetic arterial grafting. In this study we investigate the effect of ApoJ on VSMC migration, adhesion, proliferation, and gene expression.

METHODS

To study the effect of ApoJ on cell migration, we used a microchemotaxis chamber with an intervening 8-microm pore semipermeable polycarbonate membrane. Assays were performed with ApoJ alone (1-50 microg/mL) or in combination with platelet-derived growth factor homodimer bb (PDGF-bb; 10 ng/mL) or 2% fetal bovine serum (FBS; n = 8) in the lower wells. The influence of extracellular matrix interactions on ApoJ and chemotaxis was studied in a similar way, except membranes were collagen coated. Furthermore, cells were exposed to ApoJ 15 minutes before or after seeding on the coated membrane (n = 10). The influence of ApoJ on cell adhesion to collagen was assessed with cell exposure to ApoJ 15 minutes before or after seeding on a collagen-coated membrane (n = 10). Migration and adhesion were quantified by counting the number of cells per three independent high-power fields with light microscopy. The effect of ApoJ in 0.4% FBS with or without PDGF-bb on VSMC proliferation (n = 12) was assessed by means of [Methyl-(3)H] thymidine incorporation. The transcriptional profile of VSMCs in 2% FBS exposed to ApoJ and a control for 24 hours was analyzed with an oligonucleotide microarray containing 12,560 genes.

RESULTS

ApoJ alone was not chemotactic for VSMCs. Without collagen, ApoJ decreased the migration of VSMCs toward 2% FBS by 96% or more starting at 10 microg/mL (P < .05) and toward PDGF-bb by 60.9% or more starting at 25 microg/mL (P < .05) compared with the control. When collagen was introduced, ApoJ (25 microg/mL) decreased migration toward 2% FBS by 64% (P < .01) and toward PDGF-bb by 67.5% (P < .01) and decreased adhesion by 26.8% (P < .01) only when VSMCs in solution were exposed to ApoJ before placement on collagen. ApoJ did not induce VSMC proliferation. ApoJ alone decreased VSMC thymidine incorporation by 41.1% at 25 microg/mL (P < .05). ApoJ decreased thymidine incorporation of PDGF-bb stimulated VSMCs by 42.8% at 50 microg/mL (P < .05). Interleukin-8 and endothelin-1 were demonstrated by means of the microarray to be differentially expressed more than twofold in VSMCs that were exposed to ApoJ.

CONCLUSION

ApoJ is a potent inhibitor of VSMC migration, adhesion, and proliferation. Its genetic targets are linked to cell senescence and differentiation. Therefore, ApoJ may play a role, in part, in modulating the VSMC response to injury.

Apoptotic cell debris and phosphatidylserine-containing lipid vesicles induce apolipoprotein J (clusterin) gene expression in vital fibroblasts

The molecular events in cells undergoing programmed cell death (apoptosis) are well studied; however, the response of the surviving neighbor cells to local cell death is largely uncharacterized. Apolipoprotein J (clusterin) is an 80-kDa glycoprotein that has been implied in cytoprotection of the vital cells, presumably by assisting in the clearance of apoptotic vesicles and membrane remnants. Its mRNA is specifically up-regulated in the vital cells of apoptotic tissues. The molecular mechanisms, however, leading to this response are not known. We here show that exposure of vital fibroblasts to apoptotic vesicles, disrupted vital cells, and trypsin-treated membrane remnants induces apoJ mRNA. Moreover, lipid vesicles consisting of phosphatidylserine (PtSer) and dimyristoylphosphatidylcholine (PC), but not liposomes with PC alone nor with dimyristoylphosphatidylethanolamine or phosphatidic acid, did elevate apoJ mRNA level. These results suggest that, apart from mediating the endocytic uptake of the apoptotic vesicles, PtSer also serves as a trigger to stimulate the expression of genes that might be involved in the cellular clearance process.

Identification of clusterin sequences mediating renal tubular cell interactions

Expression of the glycoprotein clusterin is markedly increased following tissue injury. One function of clusterin is to promote cell interactions which are perturbed in these pathologic settings. Clusterin causes cell aggregation and adhesion in vitro yet the molecular mechanism for this effect is not known. In order to identify the active site(s) of clusterin, 34 peptides, each 15 amino acid residues in length, were synthesized from hydrophilic regions of human clusterin. When studied individually, none of the peptides caused aggregation of LLC-PK1 cells, a porcine renal epithelial cell line. However, two out of the 34 peptides inhibited clusterin-induced cell aggregation in a dose-dependent manner. Scrambled versions of these two 'active' peptides did not inhibit cell aggregation. Seven peptides promoted cell adhesion. In conclusion, these findings provide evidence for novel amino acid sequences mediating clusterin-induced renal cell interactions.

Clusterin (Apo J) regulates vascular smooth muscle cell differentiation in vitro

Previously we reported a significant and substantial increase in the synthesis and secretion of clusterin in cultured porcine vascular smooth muscle cells (VSMC) during the time when the VSMC culture modulates from a proliferating monolayer morphology to a nodular cell culture morphology. That in vitro process appears to recapitulate some aspects of in vivo vascular remodeling in response to injury and is facilitated by the presence of a well-developed extracellular matrix. To directly test the hypothesis that clusterin regulates VSMC phenotypic modulation, cultured VSMC were stably transfected with an expression plasmid containing the full-length murine clusterin sequence in antisense orientation. Twenty-four clones were selected on the basis of neomycin resistance and characterized for clusterin expression and culture morphology. In contrast to clone SM-CLU18AS, which expresses a high level of clusterin and forms multicellular nodules, clone SM-CLU13AS expresses a low level of clusterin and does not form nodules even in the presence of a preformed collagen gel. Importantly, clusterin-negative SM-CLU13AS retains the ability to form nodules in an environment containing exogenous clusterin. SM-CLU13AS forms nodules when cultured in Matrigel (which contains clusterin) and in the presence of clusterin-containing conditioned media prepared from nodular SMC cultures or SM-CLU18AS cultures. These results demonstrate that clusterin is required for VSMC nodule formation and suggest that it may play a role in smooth muscle cell reorganization in the vascular wall.

Subcellular distribution, secretion, and posttranslational modifications of clusterin in thyrocytes

A prominent secretory glycoprotein was detected in the culture medium of porcine thyrocytes which was identified as clusterin by microsequencing. Treatment of thyrocytes with thyroid stimulating hormone revealed a tight regulation of both synthesis and secretion of clusterin, with a distinct fraction of clusterin being always associated with the cells. At least three N-bound glycans were found on each subunit of clusterin, receiving most of the incorporated [(32)P]phosphate-label. Binding of clusterin to the immobilized cation-independent mannose 6-phosphate (M6P) receptor indicated that part of the phosphate label was contained in M6P moieties. Immunolabeling of cultured thyrocytes and of thyrocytes in situ showed clusterin on the apical cell surfaces where it colocalized with gp330/megalin, which is known to serve as a binding site for clusterin. The association with the apical plasma membrane, which, in thyrocytes, carries the iodinating system, was confirmed by biosynthetic iodination, an as yet unknown posttranslational modification of clusterin. On the basolateral plasma membranes clusterin was found within distinct, bipartite patches, suggesting that it is a constituent of cell-adhesion complexes and that it participates in cell-cell and cell-matrix interactions.

Transforming growth factor beta-1 up-regulates clusterin synthesis in thyroid epithelial cells

Porcine epithelial cells in primary culture seeded on plastic substratum form a monolayer containing pseudo-vesicles. When cultured in the presence of thyreotropin (TSH) thyrocytes adopted a follicular-like structure and formed clusters. Transforming growth factor beta-1 (TGFbeta1) induced a rapid spreading of the TSH-treated cells only. At the same time, TGFbeta1 enhanced clusterin protein and mRNA expression. The increase of clusterin synthesis was proportional to the TGFbeta1 concentration in the culture medium. Tunicamycin abolished the up-regulation of whole clusterin synthesis and morphological changes. The activator protein-1 binding site partly directed the TGFbeta1-stimulated clusterin expression. Phorbol ester caused rapid spreading of the cells with disappearance of vesicular and follicular structures. It decreased clusterin mRNA and protein expression, but increased Mr 45, 000 protein secretion in both TSH-treated and nontreated cells. Up-regulation of clusterin expression may be a marker of TGFbeta-mediated thyrocyte dedifferentiation.

Identification of multiple genes with altered expression at the distal anastomosis of healing polytetrafluoroethylene grafts

PURPOSE

Anastomotic intimal hyperplasia remains a significant cause of delayed prosthetic arterial graft failure. Prior studies have identified several genes with altered expression within the hyperplastic region at the downstream polytetrafluoroethylene arterial anastomosis as compared with normal arteries. The purpose of the current study was to determine the sequence of early gene-related events at the distal anastomosis of an in vivo prosthetic arterial graft model. Messenger RNA (mRNA) differential display was used to screen for alterations in gene expression between anastomotic sites and control arterial segments.

METHODS

Six carotid interposition 6-mm expanded polytetrafluoroethylene grafts were placed in mongrel dogs, with the intervening carotid artery segment serving as the baseline control. Five days after graft implantation, the distal anastomotic artery segments were harvested and total RNA was isolated from both the intervening normal arteries and anastomotic segments. Differential mRNA display was used to identify candidate complementary DNA (cDNA) clones with expression that differed in anastomotic segments as compared with normal intervening arteries. Northern blot analysis confirmed alteration of gene expression. The cDNA clones were sequenced, and gene databases were searched. Novel sequences were used as probes for screening human cDNA libraries.

RESULTS

Approximately 7000 mRNA species were screened, and 26 candidate clones were obtained. Northern blot analysis showed altered gene expression in 10 (38%) of the clones, undetectable signals in 13 (50%), and nonregulation in 3 (12%). Seven clones with 92% homology at the nucleotide level to human alpha1 (III) procollagen gene and novel sequence were expressed only at the distal anastomosis. A clone representing apolipoprotein J and a novel sequence had increased expression at the distal anastomosis of 364% +/- 236% and 156% +/- 47%, respectively (mean percentage, control +/- standard deviation).

CONCLUSIONS

These studies identified genes with expressions that increased or were exclusive to the distal anastomosis of healing prosthetic arterial grafts in an in vivo prosthetic arterial graft model. Type III collagen may contribute significantly to the composition of the extracellular matrix associated with intimal hyperplasia by increasing lesion volume. Apolipoprotein J, through its association with proteases, may modulate some of the matrix changes seen early after grafting.

Clusterin protects against oxidative stress in vitro through aggregative and nonaggregative properties

Perturbations of cell interactions, an early event in acute renal injury, have important pathophysiologic consequences. We hypothesized that promotion of cell interactions protects cells from injury. To test this hypothesis, a single cell suspension of LLC-PK1 cells (porcine proximal tubular cell line) treated with albumin (control) was compared to cells aggregated with fibrinogen or purified human clusterin (aggregation graded 0 to 4). Following aggregation, the cells were injured with 1.5 mM hydrogen peroxide (H2O2) for three hours. Cell aggregation induced by clusterin but not fibrinogen protected against oxidant injury by H2O2. Complete abrogation of cytotoxicity occurred at a clusterin concentration of 2.5 micrograms/ml, which resulted in an aggregation score of 1. In the absence of aggregation, clusterin at concentrations of 20 and 50 micrograms/ml, but not lower doses, partially protected against injury induced by H2O2. Cell aggregation induced by both clusterin and fibrinogen partially protected against endogenously generated oxidant stress induced by incubating LLC-PK1 cells with aminotriazole and 1-chloro-2,4-dinitrobenzene (CDNB). In conclusion, clusterin protects against models of oxidant stress in vitro, whether generated by exogenously administered hydrogen peroxide, or from endogenously produced peroxide, and such protective effects can accrue from aggregative and nonaggregative properties of clusterin.

Distribution and synthesis of apolipoprotein J in the atherosclerotic aorta

The distribution of apolipoprotein (apo) J during the development of atherosclerosis in the human aorta was evaluated by immununohistochemical observation, together with the other apolipoprotein A-I, A-II, B, C-III, and E. Although apoJ was never observed in the normal aorta (ie, without any intimal lesions or intimal thickening), it was distributed not only in the intima but also in the media of aortas with diffuse, intimal thickening or atherosclerotic lesions. Double immunostaining with antibodies for apoJ and alpha-smooth muscle actin revealed apoJ deposition in smooth muscle cells (SMCs) or the aortic stroma in the vicinity of SMCs. The extent of apoJ distribution in the aortic wall increased with the degree of atherosclerosis development. In addition, the distribution pattern of apoJ was very similar to that of apoA-I and E. In situ hybridization with human apoJ cDNA demonstrated intense signals in cells scattered within the subendothelial space and medial SMCs of the aorta with advanced atherosclerosis but not in those of the normal aorta without intimal thickening. Furthermore, reverse transcriptase-polymerase chain reaction of the cultured human aortic SMCs revealed apoJ mRNA expression in these cells. The results indicate that apoJ in the aortic wall originates from not only apoJ circulated in the plasma but also apoJ produced by SMCs in the aortic wall. Considering the similarities of the distribution between apoJ and apo-A-I or E, we hypothesize that apoJ possibly has a protective role against human atherosclerosis by its involvement with cholesterol transport from the aortic wall to the liver.

The glycoproteins that occur in the colloids of senescent porcine pituitary glands are clusterin and glycosylated albumin fragments

Periodic acid-Schiff-positive colloids occur in the pituitary glands of many vertebrates. These colloids are surrounded by folliculo-stellate (FS) cells and increase dramatically in number and size with age. The characterization of these colloidal substances is necessary for the establishment of FS cell function. In a previous study we showed that these colloids in the senescent pituitary contain a number of glycoproteins; however, the characterization of these glycoproteins has not yet been carried out. To characterize the pituitary colloid, we purified the colloids by centrifugation and Percoll gradient. The isolated colloids were unable to be solubilized in a regular buffer since they were very dense. However, solubilization was accomplished in sodium dodecyl sulfate (SDS) lysis buffer following treatment with exoglycosidase. Analysis using SDS-polyacrylamide gel electrophoresis showed that the porcine pituitary colloids contain four proteins, CP26, CP40, CP48 and CP60, whose estimated molecular weights were 26 kD, 36-43 kD, 48 kD, and 60 kD, respectively. Staining with concanavalin A (ConA) showed that both CP26 and CP40 were glycoproteins. Moreover, N-terminal amino acid sequencing and Western blot analysis revealed CP26, CP48 and CP60 to be porcine albumin while CP40, the major protein in the colloids, proved to be clusterin. Therefore we report here that the glycoproteins that occur in senescent porcine pituitary colloids are of two types, namely, albumin fragments and clusterin.

Clusterin: a role in cell survival in the face of apoptosis?

Clusterin is a multifunctional glycoprotein complex found in virtually all body fluids and on the surface of cells lining body cavities. Demonstrated and proposed functions include the transport of lipoproteins, the inhibition of complement-mediated cell lysis and the modulation of cell-cell interactions. On the basis of its elevated expression in apoptotic tissues, it was originally proposed that the protein might be casually involved in apoptosis. Here, we discuss the recent data that, in contrast to the earlier notion, suggest that clusterin expression is not enhanced, but rather is down-regulated in the cells undergoing apoptosis and that its expression in the apoptotic tissue is restricted to the vital neighboring cells. These results led to the proposal that rather than being a cell death gene, clusterin is a cell survival gene, exerting a protective function on the surviving bystander cells.

Identification of a 38-kDa heparin-binding glycoprotein (gp38k) in differentiating vascular smooth muscle cells as a member of a group of proteins associated with tissue remodeling

Cultured aortic smooth muscle cells (SMC) exhibit morphological and phenotypic modulation characterized by a change from a substrate attached monolayer culture to a multilayered nodular cell culture in which SMC are imbedded into the extracellular matrix. Associated with nodule formation is a change in the pattern of SMC gene expression including increased expression of a well characterized marker of smooth muscle cell differentiation, SM alpha-actin, and a 38-kDa glycoprotein (gp38k). gp38k has sequence homology with proteins reported to be correlated with tissue remodeling. To characterize the gp38k mRNA we designed degenerate oligonucleotides based on partial polypeptide sequencing to select a cDNA encoding the full-length gp38k. Southern analysis indicates that porcine gp38k is present as a single copy gene. Northern analysis indicates that the increase in gp38k is correlated with an increase in the steady state level of gp38k mRNA; and is present in cultures that have initiated the formation of multilayered foci and nodules. The correlation between SMC differentiation and gp38k expression is further established by using culture conditions that facilitate SMC differentiation. Cultures seeded onto reconstituted extracellular matrix show rapid formation of nodules and increased expression of gp38k mRNA. Comparison of the gp38k and cDNA sequences with nucleotide and protein sequences available through GenBank and SwissProt data banks revealed that molecules homologous to gp38k were present in human, mouse, bovine, and Drosophila tissues, suggesting that the gp38k may be a member of a gene family. Although a function for gp38k has not been identified, this report represents the first report of its correlation with a specific process important in phenotypic and morphological modulation of vascular SMC.

Elevated complement activities of sera from patients with high density lipoprotein deficiency (Tangier disease): the presence of normal level of clusterin and the possible implication in the atherosclerosis

Clusterin (apolipoprotein J, SP-40,40), as well as apolipoprotein A-I (apo A-I) and apolipoprotein A-II (apo A-II), are apolipoprotein components of high density lipoprotein (HDL), but not of low density lipoprotein. In spite of the deficiencies of apo A-I, apo A-II and HDL in the sera of patients with Tangier disease, clusterin was found in them at normal level. While clusterin was present as the component of HDL with apo A-I in sera of normal donors, it was present as a protein which did not form a complex in sera of Tangier patients. SC5b-9 made from the sera of Tangier patients contained normal amounts of clusterin and was deficient in apo A-I, indicating that clusterin could be incorporated into the SC5b-9 complex without apo A-I. The complement activities of the sera of the patients were higher than those of normal donors. These results may be explained by the deficiencies of apo A-I, apo A-II and HDL in the patients, because they were suggested to be the inhibitors of the reactive haemolysis of complement. The elevated complement activities of the patients might be related to the severe atherosclerotic lesions in Tangier disease.

Isolation of heparin-insensitive aortic smooth muscle cells. Growth and differentiation

Previous work has shown heparin and heparan sulfates to be potent inhibitors of vascular smooth muscle cell (VSMC) growth. This laboratory has previously isolated a VSMC line insensitive to the antiproliferative action of heparin by subjecting VSMCs that grew out from rat aortic medial explants to continuous passage in media containing heparin at 200 micrograms/mL. In the present study, we have isolated two additional heparin-resistant (HR) cell lines and have used the HR cells to investigate cellular mechanisms responsible for the potent antiproliferative activity of heparin. In contrast to normal heparin-sensitive VSMCs, the HR cells were smaller, displayed elongated processes, and possessed altered growth characteristics; however, both HR and normal cells bound and internalized comparable amounts of heparin. Immunohistochemical detection of smooth muscle cell-specific actin in growth-arrested cells showed staining of nearly all normal VSMCs and of a much smaller percentage of HR cells; heparin treatment caused a marked increase in the percentage of HR cells expressing smooth muscle cell alpha-actin, indicating that the antiproliferative and differentiation-promoting actions of heparin are independent. Proteins from control VSMCs and HR cells were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and heparin affinity chromatography. Several proteins were expressed preferentially by either HR cells or normal VSMCs, with the most significant difference being the secretion of a high-affinity, heparin-binding protein (M(r), 38,000) by control VSMCs but not by HR cells. We conclude that the aortic VSMC population may give rise to HR cells under selective conditions and that their unique characteristics, such as alterations in their ability to produce heparin-binding proteins, will prove useful in deciphering the cellular mechanisms involved in heparin's regulation of VSMC growth and differentiation.

Sulfated glycoprotein 2: new relationships of this multifunctional protein to neurodegeneration

Sulfated glycoprotein 2 (SGP-2) from rat, and similar molecules from cow, dog, human, pig, ram and quail are known by 11 or more acronyms. SGP-2 is associated with the responses of brain and other tissues to injury; it and related molecules are also normally secreted by the adrenal gland, the liver and the testes. The mRNA of this protein is found in increased levels in Alzheimer's disease. In rats, after perforant path or excitotoxin lesions, levels of the protein or mRNA are elevated in astrocytes, and also in neurons. In rats, brain SGP-2 is regulated by gonadal and adrenal steroids. However, these increases after brain lesions may relate to a function that is associated with the human protein, namely that of inhibiting complement-mediated cell lysis. Other activities suggested for SGP-2 are lipid transport and cell-cell interactions, which are consistent with sequence data that predict binding of dinucleotides, heparin and lipids. The emerging neurobiology of SGP-2 encompasses the subjects of cell death, synaptic remodelling, neuroendocrinology and neurodegenerative diseases.