Biomedical subjects

M S Sy

Publications and source records attributed to M S Sy.

At least 19 recordsLinked to original sources

PubMed2001

Novel differences between two human prion strains revealed by two-dimensional gel electrophoresis.

The phenotype of human sporadic prion diseases is affected by patient genotype at codon 129 of the prion protein (PrP) gene, the site of a common methionine/valine polymorphism, and by the type of the scrapie PrP (PrP(Sc)), which likely reflects the prion strain. However, two distinct disease phenotypes, identified as sporadic Creutzfeldt-Jakob disease (M/M2 sCJD) and sporadic fatal insomnia (sFI), share methionine homozygosity at codon 129 and PrP(Sc) type 2. One-dimensional gel electrophoresis and immunoblotting reveal no difference between the M/M2 sCJD and sFI species of PrP(Sc) in gel mobility and glycoform ratio. In contrast, the two-dimensional immunoblot demonstrates that in M/M2 sCJD the full-length PrP(Sc) form is overrepresented and carries glycans that are different from those present in the PrP(Sc) of sFI. Because the altered glycans are detectable only in the PrP(Sc) and not in the normal or cellular PrP (PrP(C)), they are likely to result from preferential conversion to PrP(Sc) of rare PrP(C) glycoforms. This is the first evidence that a qualitative difference in glycans contributes to prion diversity.

Electrophoresis, Gel, Two-Dimensional↗

PubMed2001

Differential expression of cellular prion protein in mouse brain as detected with multiple anti-PrP monoclonal antibodies.

The normal cellular prion protein (PrP(C)) plays an essential role in the development of prion diseases. Indirect evidence has suggested that different PrP(C) glycoforms may be expressed in different brain regions and perform distinct functions. However, due to a lack of monoclonal antibodies (Mabs) that are specific for mouse PrP(C), the expression of PrP(C) in the mouse brain has not been studied in great detail. We used Mabs specific for either the N-terminus or the C-terminus of the mouse PrP(C) to study its expression in the mouse brain by immunoblotting and immunohistochemistry. Immunoblotting studies demonstrated that the expression of PrP(C) differed quantitatively as well as qualitatively in different regions of the brain. The anti-C-terminus Mabs reacted with all three molecular weight bands of PrP(C); the anti-N-terminus Mabs only reacted with the 39-42 kDa PrP(C). The results from immunohistochemical staining revealed the spatial distribution of PrP(C) in the mouse brain, which were consistent with that from immunoblotting. Although expression of PrP(C) has been reported to be required for long-term survival of Purkinje cells, we were unable to detect PrP(C) in the Purkinje cell layer in the cerebellum with multiple anti-PrP Mabs. Our findings suggest that PrP(C) variants, i.e. various glycoforms and truncated forms, might be specifically expressed in different regions of mouse brain and might have different functions.

Animals↗

PubMed2001

Prp-c and Prp-Sc at the fetal-maternal interface.

Scrapie is a naturally occurring prion (PrP) disease causing a fatal neurodegenerative disorder in sheep and goats. Previous studies suggest that scrapie is transmitted naturally through exposure to the scrapie agent in wasted placentas of infected ewes. This study determined the distribution and biochemical properties of PrP cellular (PrP-C) and the distribution of PrP scrapie (PrP-Sc) in reproductive, placental, and selected fetal tissues and fetal fluids in sheep. Glycosylated, N-terminally truncated, proteinase K-sensitive PrP-C with apparent molecular masses of 23-37 kDa was present in reproductive, placental, and fetal tissues and fetal fluids. PrP-C was low or undetectable in intercotyledonary chorioallantois, amnion, urachus, amniotic fluid, and fetal urine. In pregnant ewes, cotyledonary chorioallantois, allantoic fluid, and caruncular endometrium contained higher levels of PrP-C than did intercaruncular endometrium, myometrium, oviduct, ovary, fetal bladder, or fetal kidney. Caruncular endometrial PrP-C was up-regulated during pregnancy. Despite the wide distribution of PrP-C in reproductive, placental, and selected fetal tissues and fetal fluid, PrP-Sc was detected only in caruncular endometrium and cotyledonary chorioallantois of pregnant scrapie-infected ewes. The embryo/fetus may not be exposed to scrapie in utero because it is separated physically from PrP-positive allantois and chorioallantois by PrP-negative amnion.

Animals↗

PubMed2001

Normal cellular prion protein is preferentially expressed on subpopulations of murine hemopoietic cells.

We studied the expression of normal cellular prion protein (PrP(C)) in mouse lymphoid tissues with newly developed mAbs to PrP(C). Most of the mature T and B cells in the peripheral lymphoid organs do not express PrP(C). In contrast, most thymocytes are PrP(C+). In the bone marrow, erythroid cells and maturing granulocytes are PrP(C+). Approximately 50% of the cells in the region of small lymphocytes and progenitor cells also express PrP(C). Most of these PrP(C+) cells are CD43(+), but B220(-), surface IgM(-) (sIgM(-)), and IL-7R(-), a phenotype that belongs to cells not yet committed to the B cell lineage. Another small group of the PrP(C+) cell are B220(+), and some of these are also sIgM(+). The majority of the B220(+) cells, however, are PrP(C-). Therefore, PrP(C) is preferentially expressed in early bone marrow progenitor cells and subsets of maturing B cells. Supporting this interpretation is our observation that stimulation of bone marrow cells in vitro with PMA results in a decrease in the number of PrP(C+)B220(-) cells with a corresponding increase of sIgM(+)B220(high) mature B cells. This result suggests that the PrP(C+)B220(-) cells are potential progenitors. Furthermore, in the bone marrow of Rag-1(-/-) mice, there are an increased number of PrP(C+)B220(-) cells, and most of the developmentally arrested pro-B cells in these mice are PrP(C+). Collectively, these results suggest that PrP(C) is expressed preferentially in immature T cells in the thymus and early progenitor cells in the bone marrow, and the expression of PrP(C) is regulated during hemopoietic differentiation.

Animals↗

PubMed2001

Systemic deficits in transporter for antigen presentation (TAP)-1 or proteasome subunit LMP2 have little or no effect on tumor incidence.

Some tumor cells have deficits in class I MHC antigen processing, suggesting that T cells exert selective pressure on tumor cells. Previous studies have not revealed increased tumor incidence in mice with deficits in T-cell immunity, including mice lacking TAP1 (a subunit of the transporter for antigen presentation) or LMP2 (a regulated subunit of the 20S proteasome). The incidence of spontaneous tumors in these mice, however, is too low to assess differences in host resistance to tumors. To increase tumor incidence and better assess the role of systemic expression of TAP1 and LMP2 in responses to tumors, TAP1-/- and LMP2-/- mice were bred with p53-/- mice to create TAP1-/-p53-/- and LMP2-/-p53-/- double knockout mice. Lymphomas and sarcomas (malignant fibrous histiocytoma and angiosarcoma) occurred with high incidence in all p53-deficient populations. Tumor incidence and death rate were similar in TAP1-/-p53-/- mice and closely matched control TAP1+/+p53-/- mice. Tumor incidence and death rate were slightly accelerated in LMP2-/-p53-/- mice relative to control LMP2+/+p53-/- mice, but the biological significance of this difference was unclear. The relative incidence of lymphomas vs. sarcomas was not significantly altered by variation in TAP1 or LMP2. In conclusion, systemic absence of TAP1 did not alter tumor incidence, while absence of LMP2 was associated with only a slight acceleration of tumor incidence of uncertain significance. These observations are consistent with other evidence that normal T-cell responses do not effectively limit tumorigenesis. Even though T cells can attack some tumor cells, the ability of tumors to alter their immunogenicity and evade T-cell surveillance may render the native immune system ineffective at providing a rate-limiting barrier to tumorigenesis and preventing cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2001

Hyaluronic acid induces survival and proliferation of human myeloma cells through an interleukin-6-mediated pathway involving the phosphorylation of retinoblastoma protein.

Originating from a post-switch memory B cell or plasma cell compartment in peripheral lymphoid tissues, malignant myeloma cells accumulate in the bone marrow of patients with multiple myeloma. In this favorable microenvironment their growth and survival are dependent upon both soluble factors and physical cell-to-cell and cell-to-extracellular matrix contacts. In this report we show that hyaluronan (HA), a major nonprotein glycosaminoglycan component of the extracellular matrix in mammalian bone marrow, is a survival and proliferation factor for human myeloma cells. The effect of HA is mainly mediated through a gp 80-interleukin 6 (IL-6) receptor pathway by a CD44-independent mechanism, suggesting that HA retains and concentrates IL-6 close to its site of secretion, thus favoring its autocrine activity. In addition, we show that HA-mediated survival and proliferation of myeloma cells is associated with a down-regulation in the expression of p27(kip1) cyclin-dependent kinase inhibitor and a hyperphosphorylation of the retinoblastoma protein (pRb). These data suggest that HA could be an important component in the myeloma cell physiopathology in vivo by potentiating autocrine and/or paracrine IL-6 activities.

Apoptosis↗

PubMed2001

The expression and potential function of cellular prion protein in human lymphocytes.

We examined expression of the normal cellular prion protein (PrP(C)) in human peripheral blood mononuclear cells (PBMC) and in transfected neuroblastoma cells with a panel of six monoclonal antibodies (Mabs). While all six of the Mabs reacted strongly with the neuroblastoma cells, only four of the Mabs reacted with PrP(C) expressed by human PBMC. PrP(C) is expressed at high levels in human T cells, B cells, monocytes, and dendritic cells, but not in red blood cells. Immunoblotting studies revealed that the PrP(C) glycoforms and the composition of the N-linked glycans on PrP(C) in human PBMC are different from those of the brain or the neuroblastoma cells. In human PBMC and the neuroblastoma cell lines the N-terminal portion of the PrP(C) is hypersensitive to proteolytic digestion, suggesting that the N-terminus of the PrP(C) on the surface of a living cell lacks secondary structure. We found that the level of PrP(C) expressed on the surface of human T lymphocytes was up-regulated as a consequence of cellular activation. Accordingly, memory T cells express more PrP(C) than naïve T cells. In addition, the proliferation of human T lymphocytes stimulated with an anti-CD3 Mab was inhibited by anti-PrP(C) Mabs. Collectively, these results suggest that PrP(C) can participate in signal transduction in human T lymphocytes.

Antibodies, Monoclonal↗

PubMed2001

The winged helix/forkhead transcription factor Foxq1 regulates differentiation of hair in satin mice.

Satin (sa) homozygous mice have a silky coat with high sheen arising from structurally abnormal medulla cells and defects in differentiation of the hair shaft. We demonstrate that the winged helix/forkhead transcription factor, Foxq1 (Forkhead box, subclass q, member 1) is mutant in sa mice. An intragenic deletion was identified in the radiation-induced satin mutant of the SB/Le inbred strain; a second allele, identified by an N-ethyl-N-nitrosourea (ENU) mutagenesis screen, has a missense mutation in the conserved winged helix DNA-binding domain. Homozygous mutants of the two alleles are indistinguishable. We show that Foxq1 is expressed during embryogenesis and exhibits a tissue-restricted expression pattern in adult tissues. The hair defects appear to be restricted to the inner structures of the hair; consequently, Foxq1 has a unique and distinct function involved in differentiation and development of the hair shaft. Despite an otherwise healthy appearance, satin mice have been reported to exhibit suppressed NK-cell function and alloimmune cytotoxic T-cell function. We show instead that the immune defects are attributable to genetic background differences.

Amino Acid Sequence↗

PubMed2001

Absence of protease-resistant prion protein in the cerebrospinal fluid of Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob disease (CJD), believed to be caused by a protease-resistant isoform of prion protein (PrP(Sc)), usually manifests itself as a clinically distinctive age-related dementia because of its rapid progression, occasionally accompanied by cerebellar ataxia. Recently, a variant CJD (vCJD) has been described, which has prominent early psychiatric symptoms and an earlier age of death. Although cerebrospinal fluid (CSF) is part of the extracellular fluid of the central nervous system (CNS), the bulk of its proteins are derived from the plasma and there is increasing concern about possible transmission of prion disease by blood. As investigation of CSF has played a significant role in the diagnosis and management of several neurological diseases, it was decided to characterize PrP present in the CSF of CJD individuals. Significant variation was observed in the level of PrP in the CSF from both non-CJD and CJD (including vCJD) patients, and the detected PrP forms are protease-sensitive. Using a conformation-dependent immunoassay, it was further demonstrated that the PrP detected in the CSF from CJD patients was broadly similar in conformation to that found in non-CJD patients. Taken together, the results of this study fail to demonstrate any correlation between the presence of protease-resistant PrP isoform (PrP(Sc)) in the CSF and disease manifestation.

Creutzfeldt-Jakob Syndrome↗

PubMed2001

Induction of HO-1 and NOS in doppel-expressing mice devoid of PrP: implications for doppel function.

Ectopic expression of the doppel (Dpl) protein, a homologue of the prion protein (PrP), was recently associated with cerebellar Purkinje cell degeneration observed in two aging prion protein knock-out (Prnp(0/0)) mouse lines. We investigated the possible role of Dpl in oxidative metabolism. Two Prnp(0/0) mouse lines of similar genetic background were studied. One line expresses Dpl in the brain and displays Dpl-associated cerebellar abnormalities. The other has no elevated expression of Dpl and no cerebellar abnormalities. We observed a correlation between Dpl expression and the induction of both heme oxygenase 1 (HO-1) and nitric oxide synthase systems (nNOS and iNOS). These responses are suggestive of increased oxidative stress in the brains of the Dpl-expressing Prnp(0/0) mice. No induction was observed with Hsp-60, indicating a specific response by the HO/NOS system. We proposed that Dpl expression exacerbates oxidative damage that is antagonistic to the protective function of wild-type PrP.

Animals↗

PubMed2001

Cellular and subcellular morphological localization of normal prion protein in rodent cerebellum.

Normal cellular prion protein, a necessary protagonist in fatal neurodegenerative prion diseases, was mapped in rodent cerebellum to establish its cellular and ultrastuctural localization. Existing morphological data about native prion protein distribution in brain tissues remain, indeed, contradictory and do not fit with biochemical and cell biological results. Using ultrastructural preembedding immunocytochemistry and a monoclonal anti-mouse prion protein antibody, this report shows that cellular prion protein is present in all cortico-cerebellar and deep nuclei neuronal cell types, as well as in all glial cell types. The heaviest expression appears on parallel fibres and astrocytic processes. The protein is exclusively located on the outer cell membrane and in Golgi and endosomal intracytoplasmic organelles, with no cytoplasmic or synaptic vesicle labelling. Most important, and in contrast with previous ultrastructural data, cellular prion protein is shown to be distributed on all portions of neurons, without any preferential synaptic targeting. The present morphological report shows, for the first time in vivo, that the cellular prion protein is present on the entire cell surface membrane of all neuronal and glial cell types of the rat cerebellum. This ubiquitous presence supports the notion that prion protein has a generalized cellular function in brain tissue rather than a specialized role restricted to synaptic transmission.

Animals↗

PubMed2001

Increased levels of oxidative stress markers detected in the brains of mice devoid of prion protein.

Although minor abnormalities have been reported in prion protein (PrP) knock-out (Prnp-/-) mice, the normal physiological function of PrP, the causative agent implicated in transmissible spongiform encephalopathies (TSE), remains unresolved. Since there are increasing correlations between oxidative stress and amyloidoses, we decided to investigate whether PrP plays a role in oxidative modulation. We found higher levels of oxidative damage to proteins and lipids in the brain lysates of Prnp-/- as compared to wild-type (WT) mice of the same genetic background. These two indicators, protein oxidation and lipid peroxidation, are hallmarks of cellular oxidative damage. Elevated levels of ubiquitin-protein conjugates were also observed in Prnp-/- mice, a probable consequence of cellular attempts to remove the damaged proteins as indicated by increased proteasome activity. Taken together, these findings are indicative of a role for PrP in oxidative homeostasis in vivo.

Aldehydes↗

PubMed2001

Aberrant metal binding by prion protein in human prion disease.

Human prion diseases are characterized by the conversion of the normal prion protein (PrP(C)) into a pathogenic isomer (PrP(Sc)). Distinct PrP(Sc) conformers are associated with different subtypes of prion diseases. PrP(C) binds copper and has antioxidation activity. Changes in metal-ion occupancy can lead to significant decline of the antioxidation activity and changes in conformation of the protein. We studied the trace element status of brains from patients with sporadic Creutzfeldt-Jakob disease (sCJD). We found a decrease of up to 50% of copper and an increase in manganese of approximately 10-fold in the brain tissues from sCJD subjects. We have also studied the metal occupancy of PrP in sCJD patients. We observed striking elevation of manganese and, to a lesser extent, of zinc accompanied by significant reduction of copper bound to purified PrP in all sCJD variants, determined by the PrP genotype and PrP(Sc) type, combined. Both zinc and manganese were undetectable in PrP(C) preparations from controls. Copper and manganese changes were pronounced in sCJD subjects homozygous for methionine at codon 129 and carrying PrP(Sc) type-1. Anti-oxidation activity of purified PrP was dramatically reduced by up to 85% in the sCJD variants, and correlated with increased in oxidative stress markers in sCJD brains. These results suggest that altered metal-ion occupancy of PrP plays a pivotal role in the pathogenesis of prion diseases. Since the metal changes differed in each sCJD variants, they may contribute to the diversity of PrP(Sc) and disease phenotype in sCJD. Finally, this study also presented two potential approaches in the diagnosis of CJD; the significant increase in brain manganese makes it potentially detectable by MRI, and the binding of manganese by PrP in sCJD might represent a novel diagnostic marker.

Antioxidants↗

PubMed2001

Oxidative impairment in scrapie-infected mice is associated with brain metals perturbations and altered antioxidant activities.

Prion diseases are characterized by the conversion of the normal cellular prion protein (PrP(C)) into a pathogenic isoform (PrP(Sc)). PrP(C) binds copper, has superoxide dismutase (SOD)-like activity in vitro, and its expression aids in the cellular response to oxidative stress. However, the interplay between PrPs (PrP(C), PrP(Sc) and possibly other abnormal species), copper, anti-oxidation activity and pathogenesis of prion diseases remain unclear. In this study, we reported dramatic depression of SOD-like activity by the affinity-purified PrPs from scrapie-infected brains, and together with significant reduction of Cu/Zn-SOD activity, correlates with significant perturbations in the divalent metals contents. We also detected elevated levels of nitric oxide and superoxide in the infected brains, which could be escalating the oxidative modification of cellular proteins, reducing gluathione peroxidase activity and increasing the levels of lipid peroxidation markers. Taken together, our results suggest that brain metal imbalances, especially copper, in scrapie infection is likely to affect the anti-oxidation functions of PrP and SODs, which, together with other cellular dysfunctions, predispose the brains to oxidative impairment and eventual degeneration. To our knowledge, this is the first study documenting a physiological connection between brain metals imbalances, the anti-oxidation function of PrP, and aberrations in the cellular responses to oxidative stress, in scrapie infection.

Animals↗

PubMed2001

Cellular prion protein is expressed on peripheral blood mononuclear cells but not platelets of normal and scrapie-infected sheep.

BACKGROUND AND OBJECTIVES: Transmissible spongiform encephalopathies (TSEs) including sheep scrapie are characterized by the conversion of a normal, cellular prion protein (PrPc) to an abnormal protease-resistant form (PrPSc). Like human peripheral blood, the peripheral blood of scrapie-infected sheep remains one possible source of disease transmission. As a first step in understanding the disease requirements in the natural scrapie host, the presence of PrPc was evaluated in peripheral blood cells from five normal and five scrapie-infected Suffolk sheep. DESIGN AND METHODS: Live peripheral blood cells from normal and scrapie-infected sheep were analyzed for the presence of PrP using flow cytometry and reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: PrP mRNA was detected in peripheral blood mononuclear cells (PBMC) but not in platelets or granulocytes. Consistent with PrP mRNA expression, cell-surface expressed PrP was detected on PBMC, but was not detected on granulocytes, platelets, or erythrocytes. Two-color flow cytometric analysis of PBMC specific phenotypes revealed that regardless of scrapie-status, expression of PrP was significantly higher on B2 positive B-lymphocytes than on CD4, CD8, WC1 positive T-lymphocytes or CD14 positive monocytes. In addition, PrP expressed on PBMC from normal and scrapie-infected sheep was sensitive to proteinase K (PK)and phosphatidylinositol-specific phospholipase C (PIPLC). INTERPRETATION AND CONCLUSIONS: Regardless of the scrapie-status of the sheep, resting PBMC transcribe PrPc and express PrPc as a cell-surface protein sensitive to both PK and PIPLC. Because of the abundance of PrPc on PBMC, future diagnostic tests using PK and PIPLC to discriminate between protease sensitive and resistant PrP must be carefully evaluated.

Animals↗

PubMed2001

A Yin-Yang role for metals in prion disease.

Prion diseases are not only genetic or sporadic neurodegenerative disorders, but more important, they are transmissible diseases. The etiological agent in these unprecedented diseases is believed to be prion protein (PrP), which undergoes post-translational conversion from the predominant a-helical conformation known as PrP(C), to a b-sheet rich abnormal isoform called scrapie PrP (PrP(Sc)). Accumulating evidence has shown PrP(C) to be a copper-binding antioxidant in vivo. The prevailing view that PrP binds copper weakly is based on in vitro observations using peptides or short fragment of recombinant PrP. However, recent in vitro evidence indicates human PrP has significantly higher affinity for copper, similar to other copper-binding proteins and copper uptake experiments show that PrP expressed by cells has a Km in the nanomolar range. Besides binding copper within the octarepeats region along the N-terminus, PrP can also binds copper at a second site further upstream. More importantly, PrP also binds other metals such as zinc and manganese at these two sites albeit at a lower affinity. This is important because there is evidence that native PrP in prion diseases binds not only copper, but also zinc. This abnormal metal binding probably resulted in the loss of its anti-oxidation function, and together with impairment in the cellular antioxidant mechanisms, contributed to the increased oxidative stress, and possibly trigger neurodegeneration.

Animals↗

PubMed2000

Expression and structural characterization of the recombinant human doppel protein.

The doppel protein (Dpl) is a newly recognized prion protein (PrP)-like molecule encoded by a novel gene locus, prnd, located on the same chromosome as the PrP gene. To study the structural features of Dpl, we have expressed recombinant human Dpl corresponding to the putative mature protein domain (residues 24-152) in Escherichia coli. The primary structure of the recombinant Dpl 24-152 was characterized using gel electrophoresis, N-terminal Edman sequencing, matrix-assisted laser desorption ionization mass spectrometry, and electrospray ionization mass spectrometry. Dpl 24-152 was shown to contain two disulfide bonds (Cys94-Cys145 and Cys108-Cys140). The secondary structure of Dpl was analyzed using far-UV circular dichroism spectroscopy. Dpl 24-152 was found to be an alpha-helical protein having a high helical content (40%). Dpl 24-152 exhibited characteristics of a thermodynamically stable protein that undergoes reversible and cooperative thermal denaturation. In addition, Dpl was found to be soluble and sensitive to proteinase K digestion. Therefore, Dpl 24-152 possesses biochemical properties similar to those of recombinant PrP. This study provides knowledge about the molecular features of human Dpl that will be useful in further investigation into its normal function and the role it may play in neurodegenerative diseases.

Amino Acid Sequence↗

PubMed2000

Copper refolding of prion protein.

We have shown previously that normal mouse prion protein (MoPrP) binds copper ions during protein refolding and acquires antioxidant activity. In this report, we probe the structure of the copper refolded form of MoPrP to determine how copper binding alters the secondary and tertiary features of the protein. Circular dichroism showed that recombinant MoPrP prepared in the presence of copper (as Cu(++)) showed an increased signal in the 210-220 nm range of the spectrum. Changes in protein conformation were localised to the N-terminal region of MoPrP using a panel of antibodies to assess epitope accessibility. The copper refolded recombinant prion protein had reduced proteinase K (PK) sensitivity when compared to the non-copper liganded form. Reduced PK sensitivity was not due to aggregation however as high resolution electron microscopy showed a homogenous preparation with little aggregate when compared to the non-copper form. Finally, disruption of the single disulphide linkage in MoPrP significantly diminished the antioxidant activity of the copper refolded form suggesting that activity was not solely dependent on bound copper but also on a conformation enabled by the formation of the disulphide bond.

Animals↗