Alpha-synuclein aggregates are phosphatase resistant.

Alpha-synuclein (αsyn) is an intrinsically disordered protein that aggregates in the brain in several neurodegenerative diseases collectively called synucleinopathies. Phosphorylation of αsyn at serine 129 (PSER129) was considered rare in the healthy human brain but is enriched in pathological αsyn aggregates and is used as a specific marker for disease inclusions. However, recent observations challenge this assumption by demonstrating that PSER129 results from neuronal activity and can be readily detected in the non-diseased mammalian brain. Here, we investigated experimental conditions under which two distinct PSER129 pools, namely endogenous-PSER129 and aggregated-PSER129, could be detected and differentiated in the mammalian brain. Results showed that in the wild-type (WT) mouse brain, perfusion fixation conditions greatly influenced the detection of endogenous-PSER129, with endogenous-PSER129 being nearly undetectable after delayed perfusion fixation (30-min and 1-h postmortem interval). Exposure to anesthetics (e.g., Ketamine or xylazine) before perfusion did not significantly influence endogenous-PSER129 detection or levels. In situ, non-specific phosphatase calf alkaline phosphatase (CIAP) selectively dephosphorylated endogenous-PSER129 while αsyn preformed fibril (PFF)-seeded aggregates and genuine disease aggregates (Lewy pathology and Papp-Lantos bodies in Parkinson's disease and multiple systems atrophy brain, respectively) were resistant to CIAP-mediated dephosphorylation. The phosphatase resistance of aggregates was abolished by sample denaturation, and CIAP-resistant PSER129 was closely associated with proteinase K (PK)-resistant αsyn (i.e., a marker of aggregation). CIAP pretreatment allowed for highly specific detection of seeded αsyn aggregates in a mouse model that accumulates non-aggregated-PSER129. We conclude that αsyn aggregates are impervious to phosphatases, and CIAP pretreatment increases detection specificity for aggregated-PSER129, particularly in well-preserved biological samples (e.g., perfusion fixed or flash-frozen mammalian tissues) where there is a high probability of interference from endogenous-PSER129. Our findings have important implications for the mechanism of PSER129-accumulation in the synucleinopathy brain and provide a simple experimental method to differentiate endogenous-from aggregated PSER129.

Alpha-synuclein aggregates are phosphatase resistant.

Alpha-synuclein (αsyn) is an intrinsically disordered protein that aggregates in the brain in several neurodegenerative diseases collectively called synucleinopathies. Phosphorylation of αsyn at serine 129 (PSER129) was considered rare in the healthy human brain but is enriched in pathological αsyn aggregates and is used as a specific marker for disease inclusions. However, recent observations challenge this assumption by demonstrating that PSER129 results from neuronal activity and can be readily detected in the non-diseased mammalian brain. Here, we investigated experimental conditions under which two distinct PSER129 pools, namely endogenous-PSER129 and aggregated-PSER129, could be detected and differentiated in the mammalian brain. Results showed that in the wild-type (WT) mouse brain, perfusion fixation conditions greatly influenced the detection of endogenous-PSER129, with endogenous-PSER129 being nearly undetectable after delayed perfusion fixation (30-minute and 1-hour postmortem interval). Exposure to anesthetics (e.g., Ketamine or xylazine) before perfusion did not significantly influence endogenous-PSER129 detection or levels. In situ, non-specific phosphatase calf alkaline phosphatase (CIAP) selectively dephosphorylated endogenous-PSER129 while αsyn preformed fibril (PFF)-seeded aggregates and genuine disease aggregates (Lewy pathology and Papp-Lantos bodies in Parkinson's disease and multiple systems atrophy brain, respectively) were resistant to CIAP-mediated dephosphorylation. The phosphatase resistance of aggregates was abolished by sample denaturation, and CIAP-resistant PSER129 was closely associated with proteinase K (PK)-resistant αsyn (i.e., a marker of aggregation). CIAP pretreatment allowed for highly specific detection of seeded αsyn aggregates in a mouse model that accumulates non-aggregated-PSER129. We conclude that αsyn aggregates are impervious to phosphatases, and CIAP pretreatment increases detection specificity for aggregated-PSER129, particularly in well-preserved biological samples (e.g., perfusion fixed or flash-frozen mammalian tissues) where there is a high probability of interference from endogenous-PSER129. Our findings have important implications for the mechanism of PSER129-accumulation in the synucleinopathy brain and provide a simple experimental method to differentiate endogenous-from aggregated PSER129.

Brefeldin A-mediated apoptosis requires the activation of caspases and is inhibited by Bcl-2.

Brefeldin A (BFA) has recently been shown to induce apoptosis in human tumor cells in a p53-independent fashion. In this study, BFA-induced apoptosis was analyzed in the human Jurkat T-cell line. Apoptosis occurred 8 h after treatment with BFA and at concentrations as low as 10 ng/ml and increased with the duration of BFA exposure. Forskolin, an inhibitor of BFA-induced deaggregation of the Golgi-microtubular complex in some cell lines, failed to reverse BFA-mediated apoptosis. Further study of the mechanism of BFA-induced apoptosis was conducted by using a series of peptide protease inhibitors. Complete inhibition of cell death was achieved with benzyloxycarbonyl-Val-Ala-Asp-fluromethylketone, a peptide inhibitor of the caspase protease family, and Z-Asp-Glu-Val-Asp-FMK, a specific inhibitor of caspase-3. Both Acetyl-Tyr-Val-Ala-Asp-chloromethylketone and Acetyl-Tyr-Val-Ala-Asp-aldehyde, selective caspase-1 (interleukin-1beta converting enzyme) inhibitors, exerted only partial protection of cells from apoptosis at higher concentrations. Z-Phe-Ala-FMK, a cysteine protease inhibitor lacking aspartate at the P1 position, did not have any impact on BFA-induced apoptosis. Furthermore, Jurkat cells transfected with the proto-oncoprotein Bcl-2, which is able to block various apoptotic conditions, showed remarkable resistance to the apoptotic effect of BFA. Thus, the data indicate that BFA-induced apoptosis requires caspase(s) activation, primarily the activation of caspase-3, and is inhibited by overexpression of Bcl-2.

Expression of the T-cell activation antigen, OX-40, identifies alloreactive T cells in acute graft-versus-host disease.

The OX-40 molecule is expressed on the surface of recently activated T lymphocytes. The presence of OX-40 on CD4+ T cells was analyzed in a rat haplo-identical (parental --> F1) bone marrow transplant model of acute graft-versus-host disease (aGVHD). Increased numbers of activated CD4+ T cells that expressed the OX-40 antigen were detected in peripheral blood soon after transplantation before the earliest sign of disease. The peak of OX-40 expression occurred 12 days posttransplantation with a range of 18% to 36% of circulating T cells and remained 10-fold above background, never returning to baseline. A slight increase in OX-40 expression (range, 1% to 6%) was also detected on peripheral blood lymphocytes from control syngeneic F1 --> F1 recipients. OX-40+ T cells were isolated from spleen, skin, lymph node, and liver tissue of rats undergoing aGVHD, but not in syngeneic transplants. OX-40+ T cells isolated from these tissues were of donor origin and were shown to be alloreactive. These data raise the possibility of using the OX-40 antibody to detect and deplete selectively the T cells that cause aGVHD.

Cloning and characterization of a human cDNA (INPPL1) sharing homology with inositol polyphosphate phosphatases.

We have cloned a novel human cDNA, INPPL1 (GenBank Accession No. L36818), which maps to 11q23. The corresponding mRNA is 4657 nt in length and is widely expressed in both fetal and adult tissues. An open reading frame of 3441 nt encodes a putative polypeptide that shares several domains with inositol triphosphate phosphatases. Several polymorphisms have been mapped to the 3'-untranslated region, yet the putative coding region showed no polymorphisms in nine independent cDNA samples.

Effect of antiepileptic drugs on growth of murine lymphoid tumor cells in single-cell culture.

The effect of three commonly used antiepileptic drugs (AEDs), phenytoin (PHT), carbamazepine (CBZ), and valproate (VPA), on the growth of lymphoid tumor cells was assessed in vitro. A single-cell culture method was used to determine growth rates by direct visualization. The amount of free drug was determined by ultrafiltration to ascertain its correlation to therapeutic drug levels. VPA slowed the growth of B-myeloma (FO) and T-lymphoma (AKR-1) cells significantly within the range of therapeutic drug levels. CBZ and PHT likewise inhibited cell growth in both lineages but at two to four times the therapeutic level of free drug. CBZ was shown to have long-term effects on FO and AKR-1 cells, demonstrated by the reduced growth rates of cloned lines for 2-3 months after drug removal. Cloned sublines of myeloma cells secreting lambda light chain (J558L) treated with CBZ or PHT had a higher frequency of lambda light chain secretion loss mutations than the nontreated parent line.

A micro-enzyme-multiplied immunoassay technique plate assay for antiepileptic drugs.

Underutilization of antiepileptic drug monitoring in research situations has made comparison of data difficult to interpret. Experimental animal studies of the effects of antiepileptic drugs are similarly hindered by the lack of methods utilizing small blood samples to determine drug levels. To alleviate both problems, a standard enzyme-multiplied immunoassay technique (EMIT) assay was modified and scaled down. The resulting microEMIT utilizes only a fraction of the costly reagents (5.0 vs. 50.0 microliters) of the original assay and requires only 3-5 microliters of serum, easily obtainable from experimental animals. The method has been successfully tested with three major antiepileptic drugs, phenytoin (PHT), valproic acid (VPA) and carbamazepine (CBZ). The microEMIT assay, utilizing a 96-well plate, displays linear kinetics in the production of reduced nicotinamide adenine dinucleotide (NADH) for at least 8 minutes. The assay is linear from 2 to 100 micrograms PHT/ml, from 2 to 50 micrograms CBZ/ml and from 10 to 150 micrograms VPA/ml. The similarities suggest that a general adaptation for most EMIT drug assays will be possible.

Toxic effects of antiepileptic drugs on immunoglobulin gene expression.

Murine myeloma cells were exposed to toxic, growth-retarding levels of two antiepileptic drugs (AEDs2), phenytoin (PHT) and carbamazepine (CBZ). J558L cells were treated for 12 days, washed free of drug and, upon recovery of growth, cloned to determine the frequency of lambda light chain secreting lines. Our results indicate that short-term exposure to high, toxic levels (5-10 times the therapeutic dose) of PHT and CBZ reduces or eliminates lambda light chain secretion at a high frequency. Furthermore, although most cloned lines tested positive for cytoplasmic lambda light chain, some lines had no detectable cytoplasmic immunoglobulin (Ig). The data are consistent with the hypothesis that long-term changes in fully differentiated B cell function may occur after toxic level AED exposure.

Segregation of the growth slowing effects of valproic acid from phenytoin and carbamazepine on lymphoid tumor cells.

One human and six murine tumor cell lines of lymphoid origin were assessed for growth in the presence of three commonly used antiepileptic drugs (AEDs). All seven lines were sensitive to the growth slowing effects of phenytoin (PHT) and carbamazepine (CBZ). Six lines showed a similar effect when exposed to valproic acid (VPA), while one murine B cell line was resistant to inhibition of growth by VPA.

Characterization of lambda class antibodies from the BALB/c memory response to a [glucosyl-alpha(1----3) glucosyl]-protein conjugate.

Both dextran B-1355 and nigerosyl-KLH (N-KLH) contain alpha(1----3) diglucosyl moieties and both induce lambda class serum antibodies which recognize the alpha(1----3) linkage. However, as shown here, some of the antibodies induced by the thymus-dependent form, N-KLH, have a distinct fine specificity. It is known that B-1355 induces antibodies which resemble the anti-alpha(1----3) myeloma proteins MOPC 104E and J558. The new fine specificity which does not resemble such antibodies is found in the serum of N-KLH primed mice challenged with N-KLH. The two fine specificity types are distinguished by their sensitivity to inhibition by nigerose in ELISA using B-1355 or N-BSA as bound antigen. Twelve hybridomas were produced from N-KLH primed mice boosted with either N-KLH or B-1355. Six of the 12 had the new fine specificity; only two out of the 12 expressed the IdX determinant commonly associated with the B-1355 response and neither of these possessed the new reactivity pattern. Comparative inhibition with the disaccharide nigerose and the tetrasaccharide nigerantetraose indicated that 11 out of the 12 hybridoma proteins have combining sites larger than a disaccharide. Southern and Northern blot analysis of eight hybridomas revealed that all expressed VH genes from the J558 family, but that at least two distinct VH genes from this family were used. The data support the hypothesis that immunization with an alpha(1----3) diglucosyl-protein conjugate alters the composition of the B cell pool capable of producing lambda class antibodies from that ordinarily observed following immunization with B-1355.

Immunochemical analyses of C57BL/6J monoclonal anti-alpha (1----3) dextran antibodies.

Twelve C57BL/6J anti-B-1355S monoclonal antibodies (five IgM lambda and seven IgM kappa) were characterized immunochemically by binding and inhibition ELISA. All 12 were negative for the expression of the cross-reactive idiotype (IdX) of BALB/c mice, as expected from previous work; no kappa IdX+ antibodies have been reported and IdX- lambda class antibodies were observed in B-1355-Con A induced immune sera [Geckeler W., Blomberg B., dePreval D. and Cohn M. (1977) Cold Spring Harb. Symp. quant. Biol. 41, 743-748]. The antibodies studied bind to B-1355 coated plates and this binding is inhibited by B-1355 but not by dextrans B-512 (F) or B-742S; the latter two have no linear alpha (1----3; 1) linkages. The nomenclature of Jeanes is used [Jeanes A. (1986) Molec. Immun. 23, 999-1028]; alpha (1----3; 1) refers to glucosyl diose residues linked alpha (1----3) linearly. In the case of B-1355 these linear stretches alternate with alpha (1, 6) linkages and are non-contiguous; alpha (1----3; b) refers to the linkage at a branching residue, e.g., a 1,3,6 linked moiety. The IgM kappa class antibodies are not inhibited by nigerose or nigerantetraose, suggesting that they have binding site sizes which are unusually large for B-1355 specific antibodies. The five IgM lambda antibodies are inhibited identically by equimolar amounts of nigerose and nigerantetraose, suggesting that their binding sites accommodate a disaccharide epitope. These antibodies are also inhibited by the alpha (1----6), alpha (1----4) triose, panose. The kappa class antibodies do not bind to alpha (1----3)-diglucosyl-(nigerosyl; N)-BSA. Four of the five lambda class antibodies show weak binding to N-BSA, while the fifth binds N-BSA better but less well than MOPC 104E (the BALB/c myeloma protein). All 12 antibodies are unique when compared to BALB/c antibodies derived from B-1355 immunization. The primary response of 15 C57BL/6J mice to B-1355 was re-assessed for kappa and lambda class antibody contribution. A patchy lambda class response was observed suggesting that previous lambda class responses may have been overlooked.

A characterization of the BALB/c lambda and kappa class antibodies to alpha (1,3) glycosidic linkages.

The avidity relationships of kappa and lambda antibodies with specificity for the glucosyl-alpha (1,3)-glucose disaccharide epitope were compared using a solid-phase hapten inhibition assay. The kappa class antibodies, induced by the T-cell-dependent antigen, nigerosyl-keyhole limpet hemocyanin (N-KLH), and the lambda class antibodies, induced by the T-cell-independent antigen, Dextran B1355, were only marginally distinguishable (approximately equal to 10-fold) on the basis of hapten inhibition using the free disaccharide, nigerose, as inhibitor. Analysis of the binding site sizes of antibodies induced by N-KLH through inhibition with oligosaccharides of different sizes showed that the disaccharide protein antigen did not select for antibodies with smaller binding site sizes. The cellular basis for these findings is discussed.

Immunogenicity of a synthetic glucosyl-alpha(1,3)-glucosyl protein conjugate.

We compare antibody responses to nigerose [alpha(1,3) diglucoside] when it is presented as a hapten linked to keyhole limpet hemocyanin (N-KLH) or as a native constituent of dextran (B1355). In classic terms, N-KLH is thymus dependent (TD), whereas B1355 is thymus independent (TI). N-KLH only induced an in vitro antibody response in T-depleted splenic B cells when syngeneic, KLH-specific T helper cells (TH) were supplied. This need for H-2-restricted TH could not be supplanted by the addition of lymphokines (LK). In contrast, the response to B1355 only required the addition of LK. In vivo, N-KLH induced both kappa class and lambda class antibodies, unlike B1355, which induced a response that was restricted to the lambda class. N-KLH induced a substantial IgG response in vivo, with IgG1, IgG2a, and IgG2b subclasses increasing by two to three orders of magnitude over preimmunization levels. These isotypes were not found in the in vivo response to B1355. This is consistent with the TD and TI classifications of these immunogens. Antibodies induced by N-KLH were totally inhibited by the free alpha(1,3)-linked diglucosyl hapten, nigerose, as were those induced by B1355. In vitro, B1355 also induced a lambda predominant response in naive splenic B cells. However, prepriming with N-KLH resulted in a dramatic kappa class response to B1355. The data suggest that B cells can become responsive to TI antigens after TD activation.

In vivo maturation of pre-B cells derived from long-term cultured bone marrow.

Long-term culture of a nonadherent pre-B cell line was established from BALB/c bone marrow by the method of Whitlock and Witte. Adherent filler cells, also derived from bone marrow, were required for the growth of such pre-B cells. The surface phenotypes of the nonadherent cells determined by FACS analysis were negative for mu-chain, kappa-chain, and Ia, but 50% of nonadherent cells expressed a marker recognized by the monoclonal 14.8. Analysis of cytoplasmic immunofluorescent staining revealed the presence of cytoplasmic mu-chain but absence of kappa-chain. These pre-B cells did not respond in vitro to such mitogens as LPS or DxSO4 and were not stimulated by allospecific helper T cells. However, when such BALB/c derived pre-B cells were transferred to irradiated BDF1 mice, recovered spleen cells expressed mu-chain as well as the marker recognized by 14.8. Such in vivo passaged pre-B cells were able to respond to LPS in vitro. Moreover, the response observed was diminished markedly by anti-H-2d antiserum and complement (C) but not anti-H-2b and C, indicating that the responder cells were of donor rather than host origin. Because the reconstitution of irradiated mice was limited to cells of the B lymphocyte lineage, it would appear that cells recovered from in vivo passage are the progeny of in vitro cultured pre-B cells and not that of in vitro contaminating stem cells.

Synthesis of DNA by Micrococcus luteus is resistant to 6-(p-hydroxyphenylazo)uracil.

The DNA synthesis inhibitor 6-(p-hydroxyphenylazo)uracil (HPUra), at concentrations ranging from 0.2 to 2000 micro M, had essentially no effect on DNA synthesis in Micrococcus luteus strain ML-1. Seven other M. luteus strains were unaffected by 200 micro M HPUra. In vitro DNA synthesis in toluene-treated M. luteus strain ML-1 ws resistant to both HPUra and reduced HPUra.

IgG B memory cell subpopulations: differences in susceptibility to stimulation by TI-1 and TI-2 antigens.

Spleen cells from mice primed with the thymus dependent (TD) antigen trinitrophenyl keyhole limpet hemocyanin several months earlier can be stimulated in vitro to produce an IgG anti-hapten response to TD as well as thymus independent (TI) forms of the hapten. Selective killing of TD or TI-2 responding B cells can be accomplished with the corresponding antigen by bromouridine deoxyribose (BUdR) and light treatment without affecting the other population. In contrast, we show here that selective killing with TI-1 antigens does not occur. Rather, the TI-1 antigens, TNP-Brucella abortus or TNP-lipopolysaccharide, eliminate both TD and TI-2 responding IgG memory B cells. All TNP-responding B cells are similarly eliminated if cultures are challenged simultaneously with TD and TI-2 antigens before BUdR and light but not when they are challenged with either a TD or TI-2 antigen separately. We conclude that IgG memory B cell precursors stimulated to produce anti-TNP by TD or TI-2 forms of the hapten are defined by only two functionally distinct subpopulations and that TI-1 antigens can stimulate both of these populations at least to divide.

Distinct subpopulations of IgG memory B cells respond to different molecular forms of the same hapten.

Spleen cells from mice primed with the thymus-dependent antigen trinitrophenyl keyhold limpet hemocyanin several months earlier can be cultured in vitro to give vigorous IgG antihapten PFC responses to thymus-dependent (TD) and thymus-independent (TI) forms of the same hapten. Here we show that the IgG memory precursors that respond to these two forms of the hapten constitute functionally distinct subpopulations. We have designated these subpopulations as B1gamma and B2gamma to represent secondary precursor cells responding to TI and TD antigens, respectively. Three types of evidence for these subpopulations are presented: 1) In vitro secondary IgG responses to TD and TI forms of the TNP hapten are additive when both forms are added to the same culture. 2) The precursor frequencies for the TD and TI antigens are additive, but addition is not observed between two TD or two TI antigens. 3) Each population can be selectively eliminated by BUdR and light treatment without affecting the other population. The ontogenetic relationships between these subpopulations are discussed in relation to all presently proposed subpopulations B1mu, B2mu, B1gamma, and B2gamma.

Independent precursors for thymus dependent and thymus independent IgG memory B cells.

Spleen cells from mice primed with the thymus dependent antigen trinitrophenyl keyhole limpet hemocyanin several months earlier can be cultured in vitro to give vigorous IgG antihapten PFC responses to thymus dependent and thymus independent forms of the hapten. The IgG memory precursors responding to these two forms of the hapten constitute functionally distinct subpopulations which we have designated as B1gamma and B2gamma to represent the precursor cells responding to the thymus independent and thymus dependent antigens respectively. Four types of evidence for these subpopulations are presented 1) the responses to the two types of antigen are additive when both forms are added to the same culture; 2) the precursor frequency for the thymus dependent and thymus independent populations is different although expansion over primary IgM precursor frequencies was not detectable; 3) the avidities of the PFC elicited by each antigen are distinct; the thymus independnet antigens elicit lower avidity PFC; 4) selective killing of one population can be accomplished by BUdR and light treatment without affecting the other population.